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Home My WebLink About821085002 Drainage Report DRAINAGE & EROSION CONTROL REPORT FOR PARCEL 10# 821085002 JEFFERSON COUNTY, WASHINGTON MLA #: MLA04-00401; CASE #: BL004-00446 LOCATEOIN SECTION 8, TOWNSHIP 28 NORTH, RANGE 1 EAST, W.M. Prepared for Todd & Cindy Colebrook. ". 0/ APPROVED STORMW A TER PLAN Prepared by SEP 1 0 2004 Robert A. Leach, P.E. NTI Engineering & Land Surveying 717 South Peabody Port Angeles, WA 98362 (360) 452-8491 Voice (360) 452-8498 Fax www.nti4u.com f5) [E(ClEOWre 1m ru SEP - 7 2004 lW August, 2004 JEFFERSON COUNTY DEPT. OF COMMUNITY DEVELOPMENT . :-,' C-':,'" <,"/':.';'" , ~ ,.-.--:.~..- -,' , I ;:"l..,.:' ',:..;:,"-"'. '. -.'" ,,; -," 'E o 1 () '5 E 0> i2 ~ \; ! ~ 2:- '" " ~iil ::< " :r: @ '" .~ .~ .c "5 " C <0 U <0 C <0 () E ,g c o .~ ~~ Q) 0- E ~~ C <0 "" 2! c ~Q ro E 5 1; '" Q) '0 ::J " ~S <0 ro '0 '" ~ . . " ".,.~,;:,."~ ;, . :;' ~.;- .' .......;:.y....'. ~'" .:7~ N ,~:.~.B"" . OljS""er0A'0Jn: :". ....,,,_pn~~ /"'=. ,,' J Ii ,'.' -r-:.:r~ (f ,;;,~,'~;;,;, ~1 . ." ...,.. i(,~,-.-/'f'\Yi ",'" ~ f_F " ""\ .r o /r~~11 --L~ :?i~ "~..""'~' dt,~~_~,~l .S'" 0... ='/}./~ ~ ~~ 1\~2L~~~ C /" " SJ ~ ,"",_~U ,_ / ' .' "-- ~" yW'''''' iU' o/~ ~ ~.................l~~~ 5: ~\ ~u~'1'" ,'t n If'.r,i,J ill .~q,Qj!\I~~' ~~u4i \~1~1\J vii '2,~ r ~ ~ I' \2 uJ J (II ~'-- .JL. /,"'C:__ -~ '" Qua; f\ I ,=,,"",CC\.\" "> ~ ~S--d \\ : ~- " /;- >!! \ \'\ ','" ~''''',,-,jL!:/ c 'iI "'" \'\ ,'" lf1rJ '0 ~~' -~ \\' ~ ,/" ~ ~~~>, ~ i '~ o "'- IF'!> ,,\ ~ """ 1f~ '2f'=~~ \ I 0... ,,"""'" ' " .. 'il ~~ ~ >> I' ) -'-~.. " . . ' / ' "",", ." #0"--- /=' ~ =~~~y~~~)/'eJ~~, ". '--=:~ o ,r--' o --: ? u I~ ~ ~) ,/ ~ ~ ! i .', .,c:":' ';:~':::::-::';::':'" :-_,..--:>,:~?;:.:'f~:r,~.;;;/ .--:' /:'..;t:>\"-;::-::""C :::,'c':':' 0, l{) ~ ~ l{) ci U <D C: <D ~ '" E Cf).Q'J l~ ~r.ti E'~ 8~ -' 0 O,E ~g .Q r- ~6 ~'g ~~~ .s.Z :Co .0 'ON ~@ ~-g Lt il~ ~ .' i. ~ , .. a. I' ' " ~(~! z~A'~ =mJ".jfI~ ~S~~JI / (:? ~r~ ~ ~ ~I ~~br~ ~ V~~ {7Y' \.1 SEP -7 2004PI~h O<>JOU~ L"u. P /;/ L · L.. .. -"".~/'" // . 'jf''"''''--- !'~ //", Dff'T. or r!;'~"sor.! CO;,;7'V"" _..._.. .:<~::'!',;~ji i~~'r'_ Q':JA~~}~~ ~~ T " ~ fE<<:/EUIW/E r JU1 SfP - 7 2004 Lll L__._ North.western Territ~ries, Inc. (NTI) was hired by !odd and Cind~ COI~b_~!~~~~f~~~~rro 1;'1 a drainage and erosion control plan for the of their proposed residential home site 6n-----~---~-~ Parcel #821-085-002 at lot 2, Section B of Port Ludlow #6 (revised) in Section 8, Township 28 North, Range 1 East. As part of this analysis, a storm water collection and dispersion system has been designed and a temporary / permanent erosion and sediment control plan has been prepared for the construction of a private single family residence and driveway. I. INTRODUCTION II. PROJECT OVERVIEW Proposal: This project proposes the construction of a single family home upon an "l" shaped wooded 5.1 acre site (221,067 sf). The home and ancillary buildings will have approximately 7409 sf of roof area (home, garage and shop) with 565 sf wood deck at the house, approximately 1197 net sf in concrete aprons for the garage and shop (note that approximately 171 sf is under the structure's eave line) and approximately 12,900 sf of 15' wide gravel driveway and parking (recommend a narrower, 12' wide drive where possible). A small yard area of approximately 1065 sf is envisioned along with an allocation of about 500 sf of site disturbance for the installation of a well and sewer line. The total disturbed area will be approximately 23,636 sf and the total impervious surface (post restoration) will be 7409 + 12,900 +1200 +65 = 22,071 = 9.98% of the site. A preliminary analysis of this proposal by Jefferson County (July 2, 2004 -see appendix) has indicated that a "Medium Project Storm Water Plan" is required. With the total site impervious area being less than 10%, full dispersion disposal is allowed without triggering flow control facility requirements. This will be accomplished by use of BMP T5.30 (dispersion) in accordance with BMPs T5.1 0, T5.11 and T5.12 which are included in total in Appendix 3 for reference. Drainage dispersion per BMP T5.1 0 will be used for the roof/deck/cone pad drainage and BMP T5.12 will be used for the gravel driveway drainage. III. EXISTING CONDITIONS SUMMARY 1. Existing Topography: The property slopes to the south and has a slight ridge line running in a north south direction along the west property which causes the contours to be curved convex to the south and to shed water both easterly and westerly from the crown of the ridge (westerly flow is on the adjacent property with little or no runoff from this property). The slopes along the N-S ridge line begin at about 2% at the north for about 1/4 of the site and then moderate to about 5% - 6% for the majority of the site (through the building zone). The E-W slope from the ridge line is Page 1 of 12 approximately 5% for the majority of the site until reaching the base of the site's "L" shape when the slope steepens and varies from approximately 15% to over 25% indicating the change in soil type from AIC to AID. No off-site runoff enters this property from the east, west or south and the Walden Lane access intercepts runoff from the north. 2. Existing Vegetation: The site is partially treed per the County's web site photo of 2000 (see Appendix 2) and the Architect's site plan shows a tree line to the southwest of the home site. On-site observations reveal that the shallow slope upland area is predominantly grass with treed areas while the steeper slope downhill areas is treed. The Jefferson County Drainage Regulations (DOE 2001) require that the storm drainage plan consider the site to be vegetated as it was before European contact (early-mid 1800s) which would, likely, have been totally forested. All calculations for project related disturbances have been made with a forested condition. No significant removal of trees is required for this home's construction. 3. Existing Soils: The site soils are mapped by the USDA Soil Conservation Service (SCS) at AIC or Alderwood Gravelly, Sandy, Loam (0% - 15% slope) which is a hydrologic type "C" family of soils. Further inspection resulting from an analysis of the site topographic information obtained from the Jefferson County web site indicates that portion of the site are AID or Alderwood Gravelly, Sandy, Loam (15% - 30% slope). This is significant only in that the potential for erosion is greater in the AID soils than in the AIC soils. All work on-site is confined to the AIC soil area and 50' setbacks for storm drainage dispersion facilities is required by BMP T5.10, T5.11, T5.12 and T5.30 4. Existing Site Hydrology: A site contour map and a regional contour map obtained from the Jefferson County web site (see appendix) indicated the general lay of the land for approximately 500' east and south of the site and clearly show the drainage way that exists approximately 250' east of this site's east property line. The dominant grade leads to this drainage way and suggests that natural drainage leaves the site in a southwesterly direction. The Alderwood soils are gravelly but shallow and drain moderately well for their depth with infiltration rates ranging from 2.0 - 6.0 in/hr in the upper strata and less than 0.6 in/hr in the deeper strata. 5. Noise Production: Once construction is completed, there will be no significant sources of noise at this site. 6. Significant Geological Features or Critical Areas: The portion of the property located in the base of the "L" (southeast of property) where the slope increases beyond 15% is classified as a "type one landslide hazard area. A minimum buffer of 30' is required by the landsl'~~Bat~Q~--~~~_~~.. and a minimum of 50' setback is required by the storm I "I~rl!lis~~/Jio~ Wi [; rn)<) Page 2 of 12 ~[~~p <~-;-~o~JllJ I .IFr-I=r-{~<:rlhl r'n, "'~-V I i I I I ! regulations from a steep slope (40%+) which may include any buffers. This site's slopes do not reach 40% and only the 30' buffer is required. Note that the 30' buffer can be reduced to a minimum of 15' if supported by the recommendation of a geo-technical analysis and report. A geological site evaluation was prepared by NTl's staff Geologist, Bill Payton, and is included in Appendix 2 for reference. 7. Description of General Vicinity: The general vicinity is characterized by larger parcels (5+ acre) for secluded residential development. This subdivision is a part of the overall Port Ludlow development. IV. PERMANENT STORM WATER CONTROL PLAN 1. Developed Site Hydrology: The developed parcel will behave much like the undeveloped parcel in that drainage will flow down hill to the southeast following the full dispersion of all collected runoff. 2. Storm Water Treatment: The water from the composition roofs of the three buildings will not require any treatment. The water from the gravel driveway upstream of the home site will be controlled and diverted into the area east of the driveway for sheet flow vegetation treatment and adsorption in accordance with BMP T5.30which references BMP 5.10, BMP 5.11 and BMP T5.12 (see appendix) 3. Performance Goals & Standards: Not applicable. 4. Flow Control System: None required since this is a rural residential site with less than 10% total impervious surface. 5. Water Quality System: Full dispersion filtration in forest and/or native vegetation per BMP T5.30 6. Conveyance System: The conveyance system(s) will vary across the site depending upon where you are. a. The downhill driveway will have two dispersion units to serve its approximately 475 lineal feet. periodic dispersion units. The driveway will be sloped transversely at 2% in addition to its longitudinal slope (2% - 6%) and a shallow ditch will be installed to collect the runoff after 3500 SF of surface. This 3500 SF will be piped to a dispersion unit of 3500/700 = 50' in length located such that downstream building development is not in the direct path of the resulting surface flow. Although the current plan is for a 15' wide driveway, a recommendation has been madert9_-GO~id~r-a._,lZ~-;--~~_ facility to reduce the runoff. I rr)~ !L!;L a~_ u ~.7 ffio r ~..~;\ 1 lru L SEP - ;-;o4--j~1 JEFFEf1S0N COUN1Y I DEPT. OF COMMUNI1Y DEVELOPMENT Page 3 of 12 7. 8. 9. 10. 11. 12. 13. b. The parking area from the last catch basin along to the parking area and up to the two concrete pads will sheet flow to the southeast and filter through the native vegetation. The 60' of width will require 25' for the first 20' and 5' each for the second and third 20' for a total of 30' minimum distance; several times this distance is available. c. The roof, deck and concrete pads will be connected through a series of down spouts, pipes and catch basins (with SC oil/water separators) and transport the collected storm water to three (3) dispersion units located downstream of the collected facilities. A maximum of 3500 SF is allowed in each of these units. The area calculations show that the two units serving the home, deck and garage will serve slightly more area than this by approximately 100 SF, but, the 565 SF of deck will likely not be impervious and not need to be included. The deck is included in these calculations to provide a contingency. d. Landscaped yard will filter through native vegetation. A maximum of 150' of landscaping flow length is allowed. More space exists than this maximum but less space will actually be required. Source of Fill Material: Unknown Soil Placement: Minimal import soil will be needed. The building site will be "balanced" to the degree possible and landscaped areas may have imported topsoil. The most critical soil to be placed is the backfill in utility trenches which should be compacted to 95% of optimum and bedded with sand per the manufacturer's recommendation. Surfacing: The paving surfaces planned for this project include a gravel access driveway and parking area and a concrete access pad for the garage and for the shop. All other surfaces will be vegetative with the exception of the home roof (composition) and two wooden decks. Site Restoration: Disturbed areas will be either paved, roofed, landscaped or restored to natural vegetation. Hydro-seeding of cut slopes and fills as soon as possible is highly recommended even if the area is to be fully restored to native vegetation at a later date Operations Manuals: None required Special Reports Generated: A site evaluation of the landslide hazard area was made by Bill Payton, NTl's staff Geologist. His letterrr;.eRe~~~--=-- included in Appendix 2 of this report forreference < i I D) ,Jt rc; ~ u WiJ~ I Other Permits or Approvals; Jefferson County Building per~'ni I SEP -] 200411 Page 4 of 12 I L~,".",_._..~_ ---.J r:: . JEf-FEf1S0N COUNTY _.0.~P1 OF COMMUNITY DEVELOPMI V. CONSTRUCTION STORM WATER POLLUTION PREVENTION PLAN (SWPPP) A. Required 12 Elements 1. Clearing Limits: No additional clearing is needed to construct the home beyond the removal of site grasses for the site grading necessary to construct the home and driveway. Construction limits are shown on the plans and will be marked in the field with orange construction and/or silt fencing to provide a strong visual reference for equipment operators. 2. Construction Access: Construction access will be provided along the driveway leading from Walden Lane. Walden Lane is a private road and not subject to the County's regulation. However, site access roads should be protected from the effects of mud being tracked off-site on tires. This is, typically, vehicle accomplished with a crushed rock or quarry spall paved section of driveway to help knock any mud from the vehicle's tires. (see appendix for DOE's recommended BMP) 3. Control Flow Rates: Full dispersion disposal requires no flow control. 4. Install Sediment Controls: Erosion and sediment control facilities should be among the first activities on site to ensure that a sudden storm event will not catch the project by surprise. 5. Stabilize Soils: Stabilization of site soils can be accomplished by minimizing the area of clearing to that area being actively worked upon and by expediting the restoration process upon completion. Proper scheduling of the tasks to be performed for sequence as well as for time of year is essential. To minimize the soil erosion forces of raindrop impact, flowing water and wind erosion during construction, the contractor will follow the exposed and unworked soil schedule set by DOE for all soils on site. From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days, and from May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. 6. All exposed soils shall be stabilized and hydroseeded or sodded upon completion of the project. "~..,____.._.~_~ Protect Slopes: Slopes are, typically, protected by ) i1~stf~e ([; .} fi~=rr:: setbacks and by sediment control/filtering from silt fe ~e'p1]\1 straw . 111 ! U L/ SEP - 7 2004 IlL.! Page 5 of 12 L__~. . r '''<' . r ) . J EFf:E!iS orTCOiJNfY-l _ Den OF COfvlivlUNJTY Df:VElOO"E.' "" ------ ~ ~ I lvt I,! ...." --.....--- bale barriers or straw mulch. The use of silt fencing is recommended for this project down stream of all construction activities because the site impact is small and they can be easily removed and recycled upon project completion. 7. Protect Drain Inlets: Drain inlets are, typically, protected in a construction area by wrapping with silt fence filter material or by lining the inside of the unit with filter fabric if a barrier fence is an obstruction. Other techniques are available including gravel filters which are equally as effective an provide the owner and/or contractor with options. 8. Stabilize Channels and Outlets: The existing drainage path upon this property beyond disturbed areas will be maintained during and after construction with native vegetation. 9. Control Pollutants: All chemicals, liquid products, petroleum products and non-inert wastes present on site shall be covered, contained and protected from vandalism and handled in a manner to minimize contamination of storm water. To minimize pollutants generated by heavy equipment and vehicles, all maintenance and repairs shall be conducted using spill prevention measures such as drip pans. 10. Control De-Watering: If de-watering is required during construction and the de-watering water has similar characteristics to storm water runoff, it is to be directed across the nature vegetative buffer at a minimal velocity. If the de-watering water contains contaminants, the de-watering water should be directed to a sanitary sewer as permitted by the sewer utility. 11. Maintain Best Management Practices (BMPs): It is the contractor's responsibility to maintain the temporary erosion and sediment control measures and to install the permanent erosion and sediment control measures set forth in this report and plan. After construction is complete, maintenance of permanent erosion and sediment control measures are the owner's responsibility. All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization is achieved or as needed if longer.) If[":)"') -r~'~<(f;:;-~if~::,.'"'11~\\,-,:,-j-'rr~;-'r"':'::.:.~1,' II I /1" ,J,!J L~~ U .;if lf~: I I,' c\ I" ; , '..( I~-""~"-"-~->'~~'>-'::>'i!: I' Page 6 of 12 Ilflll SEP - 7 2004 Ill)')! L !'=~ ~~".~--,~>~.~>--~ JEHERSO!-J COUNTY DEPT or COMMIItJI1Y [\1:\"", rom w..~ 12. Manage the Project: Management of this project can best be conducted in accordance with DOE if the guidelines set forth in this report and plan are followed to ensure that the long term goals of environmental protection and site stability are achieved. B. Adjacent Areas 1. Adjacent Areas Description: The immediate adjacent area is the downhill property to the southeast which contains the local drainage route. 2. Downstream Drainage Path: The downstream drainage path is a forested depression (see photo in appendix) C. Environmentally Sensitive Areas: The portion of the property located in the base of the "L" (southeast of property) where the slope increases beyond 15% is classified as a "type one landslide hazard area. A minimum buffer of 30' is required by the landslide designation and a minimum of 50' setback is required by the storm water dispersion regulations from a steep slope (40%+) which may include any buffers. This site's slopes do not reach 40% and only the 30' buffer is required. Note that the 30' buffer can be reduced to a minimum of 15' if supported by the recommendation of a geo-technical analysis and report. A geological site evaluation was prepared by NTl's staff Geologist, Bill Payton, and is included in Appendix 2 for reference. D. Erosion Problem Areas: The only potential erosion problem is the relatively steep slope below the home site. Full dispersion techniques should insure that the runoff is fully spread and adsorbed. It is prudent site stewardship to periodically inspect the downstream conditions to ensure that the facilities are working as designed and that the site remains stable for the structures above. E. Construction Phasing: 1. Construction Sequence: Specific plans for construction phasing are not known. It is likely that the complete access will be constructed along with the home and garage and the shop deferred. Another possibility is to build the access and shop, live in the shop during home/garage construction. The plan developed is modular and can be adapted to cover any phasing plan developed. Page70f 12 'L=:-)\','-Ir; 'a~;'~wr"IT"\\ir~U:~~~-'r~;:-:.l r~ (~,~.:~~C:~"_~.~I' i I !) I !1 U! ,) t r .. 7 1.004 I L.J j . ! ',,;,j i L___._~ ,>'0 '''u -'---(;5Li'iJl:y,,~_1 ~~::~.Qf___,~,_",__~',!2!:_\(5LOPfV~tli T I 2. Phasing (if proposed): Not applicable at this ti F. Construction Schedule: None exists at this time G. Financial/Ownership Responsibilities: The contractor is responsible for the maintenance of all temporary drainage, erosion and sediment control features during construction and, possibly, through the construction warranty period. Following construction and final restoration, the owner is responsible for all permanent drainage, erosion and sediment control features. H. Engineering Calculations 1. Sediment Ponds & Traps: Not applicable 2. Diversions: Not applicable 3. Waterways: Not applicable 4. Runoff/Storm Water Detention Calculations: None required I. Monitoring Locations: Not applicable VI. EROSION & SEDIMENT CONTROL PLAN REQUIREMENTS (a check list) 1. General a. b. c. 2. Site Plan a. b. c. d. e. f. g. Vicinity Map: See narrative Jefferson County Approval Block: On drawings Erosion & Sediment Control Notes: On drawings Legal Description of Property: See Appendix 2 North Arrow: On drawings Boundary of Existing Vegetation: On drawings Label Potential Erosion Problems: On drawings Show FEMA Flood or Shorelines Management Boundaries (if applicable): Not applicable I~~~ ..._~~-~-._~'.....~- .....'~~~~CL~~~~_~____ _ Show Existing & Proposed Contours: On draWiHt:)) r.l~~~~~...J~_.n~\~~:j~~~'rrS] Indicate Drainage Basins & Direction of Flow: ~I' fl~tawipg,$ 7 20r! I i.IJ i I I J ll, j vEr"~ UI'I '.,..l..J. I I' .- .4'1 '.~ Page 8 of 12 ! L_~,...,"....~..~_.:_~,,~.~._._~..__J I JUFf:);SiJi'! COUN1Y J L DEPT. OF COfY':iViUi~ny'~ DE~ELOfJM~!~ h. Label Final Grade Contours & Show Developed Condition Drainage Basins: On drawings I. Delineate Clearing & Grading Limits: On drawings, see narrative j. Show Cut & Fill Slopes (Top & Bottom): See note on drawings 3. Conveyance Systems a. Designate Swales, Interceptor Trenches & Ditches: On drawings b. Show Temporary & Permanent Pipes, Ditches & Trenches: On drawings c. Provide Minimum Slope & Cover Data For Pipes: On drawings d. Show Grades, Dimensions & Direction of Slope: On drawings e. Provide Details of By-passing Off-Site Runoff: Not applicable f. Indicate Locations of Outlets & De-Watering Systems: Not applicable 4. Location of Detention BMPs: Not applicable 5. Erosion & Sediment Control Facilities a. Dimensions of Traps, Ponds & Pipes: On drawing b. Dimensions of Pond Berms: Not applicable c. Pond Volume and Dimensions: Not applicable d. Typical Pond Cross-sections: Not applicable e. tails of Filter Facilities: Not applicable f. Outlet Stabilization Techniques: Not applicable g. Control I Restriction Details: Not applicable h. Mulch Specifications & Check Dam Details:!~r:.:::\~-~:;~~; .,~~~-.,.~.,--~"-.-._--.--." I "-, I I' - (,-) > J \; ,t~ Lt.}:; it Rock Specifications for Check Dams: Not a :~tf9~5Te~:'.""" l f 'I i I~rD . . il ;; 0CI l Check Dam Spacing: Not applicable " "I ' Page 9 of 12 L L",,,,,", . .-.~.- OEr'1 OF --.._-~-~---"'.. >,- ---'--, .. -..----____..-1 ---~~><<.~--..--lr:SI '-"'-.-'--; I, I if /' f [ i i I It; ^e--' r, i jf {;(JLi II J./ ! -_~"-",,,,J i. J. k. Front & Side Cross-sections of Check Dams: Not applicable I. Locations for Silt Fencing: On drawings m. Construction Entrance Details: On drawings 6. Detailed Drawings: See the end of the narrative section of this report and BMP details in Appendix 3 7. Other Pollutant BMPs: A variety of BMPs apply to this project including construction barrier fence, silt fence, catch basin protection, straw bales for ditches, construction access and full dispersion techniques for both roofs and driveways. All BMPs are detailed Appendix 3. 8. Monitoring Locations: Not applicable VII. METHODOLOGY As of December 20, 2002, Jefferson County requires the use of the Department of Ecology (DOE) August 2001 Storm Water Management Manual for Western Washington. Based an analysis of this site's characteristics made by Jefferson County and noted in their July 2, 2004 letter, has been determined that a "medium" plan is needed where the first five of the ten minimum requirements for new and replaced impervious surfaces apply to this property. . ~/. To support runoff volume amounts for energy dissipation method determination, an analysis was performed using the SBUH technique as allowed by the DOE 2001 manual. This exercise was performed to estimate the amount of runoff in cfs produced by the 15' driveway per 100' length (0.02 cfs) and 200' length (0.04 cfs) and to estimate the amount of runoff produced by the roof/deck/concrete pad system per 1500 SF unit (0.03 cfs). VIII. CONCLUSIONS The development and implementation of the storm water drainage system and erosion and sediment control plan are both a temporary and permanent part of the construction phase and the long term maintenance of the completed project. The first step in implementing this plan is readying the site in accordance with DOE guidelines. A temporary construction fence shall be placed marking the clearing limits, and trees within the clearing limits that are to remain shall be clearly marlre:Gi..n~S-i':\E-f'l~-;,'~:-"~'-~~"-::::"~'--:::--' I. .." 'if tf1~9' II; 11 \V tl'" r '" for locati?n of fence. In addition prior to sta~ing land disturbing activities,! !~})litlf~n~~..~~'-_l!....~'l_~.X;'.II'\ shall be I~stalled down sl~pe of all constru.ctlon and a quarry spall or cru1~~Pi f?ck 1- i i access dnveway shall be Installed at the site entrance. The 50 foot long'lr)5L~ldeSEP = 7 2004 IlL i t L~'-~"'~"T~'''-'''__'_'''_''_....._.mJ : Jl:iFEHSIJN COUNTl LC:.~,f'L?r ~-2r'IiMl!~iITY DEVtLO~rvH"2~_. Page100f 12 ..,-- access driveway should provide the necessary debris and sediment trap for protecting the private roadway from the construction equipment leaving the site. It is the contractor's responsibility to maintain a clean roadway in accordance with the county Public Works Department regulations. The standard silt fence, catch basin filter and access driveway details are provided with the drawings at the end of this section of this document and again in this document's Appendix 3 in full BMP format. The next steps are installation and minimizing erosion caused by the construction. This can be minimized by sustaining the access driveway, silt fence, natural vegetative buffer, limiting the exposure of soils and installing check dams, as needed, in sloped trenches. The drainage system is limited to collection and disposal, no detention or treatment is required. The system consists of a 12" ADS or equivalent traffic bearing catch basins in the concrete pads for the garage and shop, WSDOT type 1 catch basins along the driveway entrance, gutters and downspouts to collect roof runoff, underground 6" diameter ADS or equivalent PVC or HOPE pipe collection lines and a discharge via dispersion trenches meeting the BMP T5.1 0 and BMP T5.12 designs in Appendix 3. Since grading of the site will cause runoff to collect in the drainage system, filter fabric should be placed over or around all drains and/or catch basins until the driveway is stabilized. The final steps are stabilizing the site and long term maintenance. Before leaving the site the contractor is responsible for stabilizing all soils disturbed during construction, hydro-seeding or landscaping exposed soils. All temporary erosion and sediment control measures shall be removed from the site and the drainage system shall be cleaned of debris and sediment to allow runoff to flow freely. Long term maintenance of the system is the owner's responsibility. All ditches, drains, catch basins and down spouts should be checked regularly for debris and/or blockages and cleaned out if necessary. Long term erosion control on the site can be controlled by minimizing exposed soils and maintaining a vegetative buffer between this property and its neighbors!. The site geo-tech report has specific recommendations for the long term stability of the bluff and is included in the appendix for reference. IX. LIMITATIONS This report has been prepared for the exclusive use of Todd and Cindy Colebrook for their proposed construction of a private home. The recommendations in the report apply only to the property that was examined and they are not applicable to other locations. The investigation and recommendations contained in this report are based upon site conditions as they existed at the time of our site inspections. During construction, if subsurface or other conditions are discovered that are significantly different from those described in the report, NTI should be advised at once so that we can review the conditions and reconsider our recommendations, where necessary. Unanticipated soil conditions are commonly encountered on const .~. '~Frfil \VI. [f \~ especially when the topography has been altered years ago. Sue . _ e~~__u... Ll ~ Page 11 of 12 nJ SEP -- 7 20011 ...J L___.._____- JEFFERSOI~ COUNTY nFPT OF CmJJMU:~:TY DEVELOPMENT conditions frequently require that additional expenditures be made to attain a properly constructed project. We recommend that a contingency be established in the project budget and schedule to cover unexpected conditions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted professional engineering principles and practice. This warranty is in lieu of all others, either expressed or implied. Sincerely NTI Engineering & Land Surveying Robert A. Leach, P.E. Principal Engineer 08-23-04 attachment: appendicies EXPIRES 12/30/2004 E:\Colebrook\Colebrook drainage plan 2.wpd Page 12 of 12 l~.' ',._.._~._--~-- I ri".:J"') n~ ((:;If:Tqir~Wl' ~ T~~:'J I i L,) I-':::'~':::._"~:::_"~"":~~~::"l I \ \ II' \ [ I i I : I ) i : . I ' i . 1') (} C J ""' r Il . 1 I l ,I - "' _=, 1.). I ) - L l \ I .,J...f 7 200 f I ~j / I " "'.. . I I L.......-... .. .' J ...., jri!'Eiis()~i(':curJ"lY J l_E.~~~.gl~~_~_~;~'~~.j rYQ.~~~~OPM~~~ L\~T OF ISt:IT HNJAGCf1C7J( P~CTICGS C eM P ~ ') f:. \<os I 0;0 g S t:D / /vi 6VT CQ/JTk-O L ... 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Land Surveyors. Geologists. Materials Testing 717 SOUTH PEABODY. PORT ANGELES, WASHINGTON 98362. (360) 452.8491 www.nti4u.cominfo@nli4u.com '---' "--/ ~ I'~' '----./ y ".'-.~/ ~, WALDEN LANE PR P RTY LINE 230.01 TO SMfTARY E8 SEWER ?" ~ !'- Y' N z: r- ;] 0 (") (") r- 0 -i U1 0 CO f"Tl ~ ~ -i ~ s:: -l C) ~ ro II I I ~ ;? 3' f"Tl 0 f"Tl "2, -0 ::> (/) r'l r- z: 1 0 (') 3 3 ""Tl 0 (") (") .." -0 ('5 ~ rT1 ...., -6' -0 ::;,- c: c: )> ~ 0 r- ~ CJ ;I: CD 3 3 ""T1 ~ ~ 0 CD (') r- r'l :z: (") '" ~ 0- -0 0 -i ::0 :z: :r: N r-+ -6' 3 (') U) x: ~ 0 CD 0 <5 ::E Vl 0 CO r- cr -0 < -0 ...., -0 -0 ~ C )> 0" CD 0 <1> 0 ~~~:::J< 0 CD 0- n ..... 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I GC)t 1""--._, l .y-.'jI r,) ~; : c:S I 12:::; r-:n ..: ~ 1 S-;:) I S-<l.r' 'm ;l2 L._.~-j ~ ~J -i _ ft NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY. PORT ANGELES. WASHINGTON 98362, (360) 452-8491 PROPER1Y LINE 230.01 TO SANITARY SEWER @~ 1~ ,.." ~ :;00'> o . ~~ 00 zg N 0, '"c.o ~z ,"'" ~ 0 fT1 0 q ~ 0 l.I) :;0 ~ -r] ,-,>0 C') ,# ~ .jy ~ rT1 ~ r- CJ :;0 Q) <: . -...J rT1 0 ::E; 0 ~ ~ ~ . .--.. l~ !I: <.n. 0 -0 ~ :;0 ::E; ... ;>I , 0 6 fT1 -0 c;, rT1 rT1 ~ :;0 =<! 3:: ~ )> c: f :z: rrl '~ ~-_/\ WALDEN LANE EB @ @ r- o Ii: ~I~ @) rI ~C5~~ 08 C) rI !:"1c::r-.. ~ t z: ::t:i"-il::) D $ CJ ~Cj~ CJ ~ + :t ~ ~~ r- 8 -( . x (") (") S:Q ~ ~~~ . ~ 0 r- r- rT1 :z: -j -j :-;:-1 0 :z: !I: ~)>:~ :z: -j (") <./J ""T1 ~ ()~);: :;0 ::c -j .., I'T'1 :;0 rT1 CjYi~ <./J )> ~ c :z: :z: , ::c :z: (") (") (") ,.., 'J::t~ rT1 ('") -j I'T'1 I'T'1 c;, I'T'1 I'T'1 ~ tl\;'J -j :z: i5 0 :;0 :z: :;0 ~ O:l ....( 0 ::E; . )> =i c: OJ -( 0 ::c s::: :;0 -j =i 0 :;0 ~ ^ ?B c:j -r] I'T'1 I'T'1 :z: rT1 :z: s:: :;0 Q <./J rT1 -j :z: ::E; :z: ~ -j :;0 C') )> -0 -0 :;0 ~ 0 r- -0 I'T'1 r'l :;0 s::: -j c -< r- c: (") I: :z: r'l :;00'> o . ~~ 0 ~:::! z~ o;::J F~ @) fT1 08 q 0 SI en 11 ~ r'l <./J r'l ! ~ ~ )> I'T'1 :::0 n ~ :::c . ---1 II r'l crl n o. ---1 en u s;: Z :;00> o . ~ ~~ 00 :::0 $!:::! -c;, Z:J: o;::J IT) F~ r- ,.., CJ q C) 0 :;0 r- ;,o';:j\o, 0 8 ;.~ n :;00'> \ )> 8' ---1 .. ..,~ 0 0 ~:::! Z ~ a; zg en ~ 0, , 1~ ! 0 ~~ "U ~ .., 1 fT1 q 0 .... ;0 N rJf OF IIISPERSAL '6f OF ~ 1IINCH 20' 50' @) 00 o m -.J o ""T1<.... om 0"'" s;:g ~8 g:\gM \ boO \coIebr<>ok\flflQI,"omncon/r on.dwg PLOTTED: 8/30/04 (> NORTHWESTERN TERRITORIES. I . 2004 SCALE: 1" = 60' DRAWN BY: PROJECT: FOR: FINAL REVIEW: SHEET 2 OF 10 Dol nlCj <~, m 'I ' -<- o -0 :s; 0...- m z -i Cf) rTI '~D ffi g ffi '-,_I = --( ) c;g; ffi ~ "') c-' c;; -~ ~ NORT~::,:~~~~s",:,~~I:'~'~i;:S, INc. 't:!:I Construction Inspection - Materials Testing NT I 717 SOUTH PEABODY. PORT ANGELES. WASHINGTON 98362. (360) 452-8491 ONE IJ BAR HOOP FOR 6" TWO J BAR HOOP FOR 12" FRAME AND VANED GRA TE (SEE STANDARD PLAN FOR DETAIL) 12" RISER SECTION (RECTANGULAR ADJUSTMENT SECTION) 6" REDUCING SECTION #J BAR EACH WAY , ~ ~ PRECAST BASE SECTION (MEASUREMENT A T THE TOP) OF THE BASE #J BAR EACH CORNER #J BAR EACH SIDE SCALE: DRAWN BY: PROJECT: DRA 1 N 1\6 f plJ\p FOR: -rODD (OLEBROo FINAL REVIEW: Robert A. Leach, PE SHEET 3 or 10 DATE: r-.-:\ lE ..(Cv~.... [Efl WI ~ rrn I Dj r---------, n CA TCH ~~~~CAL'!PE 1 tfi\l_<~f:~-:___J1l JLr-f-l:f~SOr~ COUN-IY l_;.~._.:._~__~:.~.":~~~i~',i I '( UiVi:UWMHn ft NORTHWESTERN TERRITORlrS",-'-lflc-.~ Engineers - Land Surveyors - Geologists . Construction Inspection - Materials Testing NT I 717 SOUTH PEABODY, PORT ANGELES. WASHINGTON 98362. (360) 452.8491 G: \ Prod \ DelaH. \Munic;pol\ NTI\REPORT DETAlLS\ PLOTTED: iD NORTHWf:STERN TERRITORIES. INC. 2004 ~~ 4-" pEri piP3 -j Iii' . '3lf"'!iashed rock TRENCH X-SECTION flITS slcpe - :3 me<. II catch basin or '1arel clrai n ! - 2' ~; 10' IfNEi trench-::s :5 700 sq. ft. :> 700 sq. ft. Typ~ I CB / st3Jlchn:J di3p~r:3ion tn:.nch wi n:rtct-ed '=-lmre bo&d lerryh I [j pEr 700 sq ft of mof atea. Figure 5.1 Typical Dispersion Trench , ~ S~P~. :04~1~ I f L__~_.~.~__~___ J J FH Hi eJ) N (' () ;I"':'Y~' DEPT OF f~)~~;/"~~,;il:ri'~';"~!.OPMENT PLAN VIEW OF ROOF NTS G: \Prod\Oeloils \Municipol\NTI\REPORT OETAlLS\ PLOTTED: lid NORTHWESTERN TERRITORIES. INC. 2004 SCALE: DATE: DRAWN BY: PROJECT: D RA I fJ " G t Pl11 f-I FOR: TOb D COLE BROOK FINAL REVIEW: Roberl A. Leach, P.E. SHEET 1 OF Ie, fj NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors -- Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362. (360) 452-8491 noo:hed gra::le board 2"x 2' nm) tel> 1S"0.C. o U) l' p'pe 0 [! I 1':0 I l~.:~ I ~ ,.erdcaporplU] . -. '7" ~ cean ou~w~ flDm pipe t ........ inflU2nl pipe (ma:x: desgn tbw ~. 0.5 G FS per trenc h) PLAN NTS 9i:>h8.nired bolts \ x 15% B"R'\fcr 11m' ccrrtro['wcler q.1Blily treatrrert in rural areas. SECTION A-A NTS [5) liE CG [i; U[rrrr~1 I Ii j I I: i I i iJ L: 1--1 .. ..IEFFEf~SDf',) C-U\.!;)rY DEPl or CO\!,r,~l';'J:iY iY\TlCH vi[in- flON 10 second dispersal ~rero::h it necessary t ....- . fb.vtootrer brar,)hing CB's as necessary I 18' 0.(; I -~~~ --i 4-2" T- .----~/"':.'---':t: v~ 2" grade board rc.~tes NOTES: i. This tremh shan b: construct:d 'SO as b prevent point discha'ge and.or elOsbn. 2. Trencres n"\=o/ be pieced no cb=~r than 50 fee~ bone an:ltter. (100 feet abrg fbwlir.:) 3. Trench ard grad; beaId mlJst be P-~1. Align to to/bo.... cori1oursoi si~. 4. SuProrl post spacing ilS required by soil oorditbns to ensure gl<l.de boOfd remains level. Figure 5.2 Standard Dispersion Trench with Notched Grade Board G: \Prod\Oelo;ls \Mun;c;pal\Nn\REPORT OETAlLS\ PLOTTED: lid NORTHWESTERN TERRITORIES. INC. 2004 SCAlE: DATE: DRAWN BY: PROJECT: DRA uJ /\ G ~ pLl1 W FOR: TOCt> cOU:. BRC\OK FINAL REVIEW: Robert A. Leach, P.E. SHEET 5 OF /b fj NORTHWESTERN TERRITORIES, INC. EngineeTs - Land SurveyoTs - Geologists Construction Inspection - MateTials Testing NTI 717 SOUTH PEABODY, PORT ANGELES. WASHINGTON 98362. (360) 452.8491 REPLACE WITH EXISTING SURFACE COVER OR REPAIR W/ CDF BACKFILL ~) [E_~]fif)r ~l I' II .J j SEP --. 7 200!!. I! r , n L_.--:;:;:"::,:,._,,: ._--~-~...~_J . .JllrUiSON CUUNTY ..Q~.c'~:.2.~.~!?~~)~~~~l!!l.i~~~~:~r~~!.'!!. RESEED, REPLACE EXISTING ~ - - SOD, OR RE-LANDSCAPE AS NECESSARY ASPHALT OR GRAVEL AS APPROPRIA TE .,.c- . .; ~ . ///g :::~ 1I1t-:/fl,t' =//// . :. . !(/liSi: m ~ .--:..:::=; . - .;:..'?:... TRACER TAPE WITH WIRE TRACER <: ~ COMPACT SELECT SITE BACKFILL (SEE NOTE BELOW) ..;.:..:..".:. . a "1 # 12 DETECTOR WIRE AND BL UE TAPE @ WA TERLlNES BRING UP INTO VAL VE BOXES . ...;:... :wi;;: ~. ,. >j/!i~j!l: >:. !/I!!!IJ.'I.~ fA t.:> PIPE BEDDING PER WSDOT/APWA 9-03.16 FOR FLEX AND 9-03.15 FOR RIGID PIPE (Q . "I' SEWER/WA TER PIPE PER PLANS 24" MAX. NOTE: BACKFILL TO BE COMPACTED TO 95% MODIFIED PROCTOR DENSITY IN 12" LIFTS IN ALL AREAS REQUIRING PAVING. COMPACTION SHALL BE 90 % ELSEWHERE. TYPICAL PIPE TRENCH DETAIL NO SCALE G: \ Prod \ De/oils \Municipal\ NTI\ REPORT DETAlLS\ PLDTrED: 10 NORTHWESTERN TERRITORIES. INC. 2004 SCALE: NOT TO SCALE DATE: DRAWN BY: PROJECT: D RA I JAG E ?lh"j FOR: TOi)~) e.o LE ?"PJ)OI<, FINAL REVIEW: Robert A. Leach, PE SHEET ~ OF I 0 ~ NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362. (36G) 452-8491 [E T~ LE ~J~ \VI IE --- -"---=""-'~~~O=-----'~_~~T SEP ", 7 2004 l__._...~.~..~_._~ JEfTEfiSON COWi1Y DEPT. OF COMf"'1UNI1Y Di:VEl.OPMENT ------------~,~-~-- NOTE: PROVIDE A CLEAN, HARD SURFACE TO ELlMINA TE TRACKING OF SOIL ONTO STREET. SURFACE MATERIALS MAY INCLUDE QUARRY SPALLS, CRUSHED ROCK, OR OTHER NON-SOIL OR NON-SOUND MATERIALS. / / ,/ / ,/ ~OP' ~\~G /<(,-j.\J ,/ 4" TO 8" QUARRY SPALLS OR APPROVED EQUAL MAINTENANCE: THE ENTRANCE SHALL BE MAINTAINED IN A CONDITION WHICH WILL PREVENT TRACKING OR FLOW OF MUD ONTO PUBLIC RIGHTS-OF-WAY. THIS MAY REQUIRE PERIODIC TOP DRESSING WITH 2-INCH STONE OR OTHER APPROVED MATERIAL AS CONDITIONS DEMAND, AND REPAIR AND/OR CLEANOUT OF ANY STRUCTURES USED TO TRAP SEDIMENT. ALL MATERIALS SPILLED, DROPPED, WASHED, OR TRACKED FROM VEHICLES ONTO ROADWA YS OR INTO STORM DRAINS MUST BE REMOVED IMMEDIA TEL Y. PROVIDE FULL WIDTH OF INGRESS/EGRESS AREA SITE ACCESS DETAIL G: \ Prod\ De/oils \ Mun;c;pol\ N17\ REPORT OErAlLS\ SlrtAGGESS.OWG PLD rrED: q;) NORTHWESTERN TERRITORIES. INC. 2004 SCALE: NOT TO SCALE DATE: DRAWN BY: PROJECT: 0 R fll [.J 1\ G t PLI\1J FOR: 10DP CuLE- ,R\:lOK FINAL REVIEW: Robert A. Leach, PE SHEET 7 OF 10 O NORTHWESTERN TERRITORIES, INC. [ngineers - Land Surveyors - Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98382. (380) 452-8491 STAKES ------...... ---~"-~~_..._~_.~--~'<.~-~~.>>._~~." I<'~. If: f0\L' !T~; 1'1' \\1 rf; f"r~''\ I [) I.G l~9 ,,," --, ':.' Ilocr ,\ ; I _ I__'_~_._m_...,___._.__.., I I ! i n~ !ii Ii! ! [I c'r.D ' I! f; i U\ I\)[ r ; : '. / : l " L"j[:f'::.'~.'...' . -. - -- -- -'.' i DEPT or' ~:\,)/., , 'L..' i , -~'-'---" .---.--- ~-.- _ . 0.._ ___.._~_.l '"FILTER F~ MIRAFlC 100 NS OR EQUIVALENT 2''><2'' WOOD~ F1L~R ~Bmc~ ~ RUNOFF WA TER~ ""- WITH SEDIMENT \ q- ~~~~~~~d~~~~i~~~ BURIED F1L TER ~ FABRIC DROP INLET WITH GRA TE WHERE CATCH BASIN LIES IN ROUTE OF ACCESS USE SIL T SACK MANUFACTURED BY ACF, INC. OR EQUAL. CLEAN AFTER EACH RUN-OFF EVENT. FILTER FABRIC FENCE INLET FIL TER DETAIL NOT TO SCALE G: \ Prod\ Detoils \ Municipal\ NT!\ Report details \ CB-FF. dW9 PLOTTED: iD NORTHW[STfRN TfRRITORlfS. INC. 2004 SCALE: NOT TO SCALE DATE: DRAWN BY: PROJECT: 0 1< f\ ! rJ A., G 1-::: PL'V} FOR: TOD D COL", 1::00\< FINAL REVIEW: Robert A. Leach, P.E. SHEET 8 OF ID ft NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 -.j; rr(~. fE . 0)'l~-n- WI rc: ~;::'l I'. [1 lt~ ll!J .E u \v ~ 1,\ '. J I -~.'-~-"--'--'~' I ' ~.., ~'l I I ." \ I i \' 'I If l\l SFP 7 \L}!i. d \.-! . '.. .m_i i I L._..~....~..~__._.."._.._, i j[HU1.s0U CQUNTY . DE t)"f. OF C Of~i: r'.,'~ l ff--~~TY DF\'ELOPMFNT BACKFILL AGAINST FABRIC 6" MIN. DEPTH WITH PROPER COMPACnON -.j; -.j; GROUND ~ .;:: or -.j; ,\\o~ Q\'r-t-G -.j; MIRAFI (OR APPROVED EQUAL) WOVEN SIL T FENCE FABRIC STAPLE TO POST AT 6" O. C. -.j; KEY 8" OVERLAP OF FABRIC INTO EXISnNG GROUND WITH 6" DEEP TRENCH SILT FENCE DETAIL NOT TO SCALE C: \ Prod\ Deto;'. \ Municipal\ Nn\ Reporl de to;'. \ CB - FF.dwg PLOTTED: o NORtHWESTERN tERRitORIES. INC. 2004 SCALE: NOT TO SCALE DATE: DRAWN BY: PROJECT: D R A I 10 ""G E- f.; Lf') iJ FOR: \0 DD CO\...L 81->00\< FINAL REVIEW: Robert A. Leach, P.E. SHEET q OF 10 O NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors - Geologists Construction Inspection- Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES. WASHINGTON 98362, (360) 452-8491 ~[l~')" ~r [~. frflr \\jJ ~~r~"~ I, II ! ,-~-- . b Is I' II i:~i'1 i (' ~--~::~-~I i I : 1 j U .: ' ) !dJU4 .Il. I ' ~_.' ;,: !... ',iT". EfiSiSrrCr)ur.iiy-- f-\f-"~--l lr0'\~;>'ll.t.- (", ;:.<::~'" ,i'n iY bL'VELOiJrvIU!" -.....-.__.....~_.__.. .'. SILTATION FENCE STANDARD NOTES ,. THE FlL TER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF THE BARRIER TO AVOID USE OF JOINTS. WHEN JOINTS ARE NECESSARY, FlL TER CLOTH SHALL BE SPLICED TOGUHER ONLY AT A SUPPORT POST, WITH A MINIMUM 6 INCH OVERLAP, AND BOTH ENDS SECUREL Y FASTENED TO THE POST. 2. THE FILTER FABRIC SHALL BE INSTALLED TO FOLLOW THE CONTOURS (WHERE FEASIBLE). THE FENCE POSTS SHALL BE SPACED A MAXIMUM OF 5 FEU APART AND DRIVEN SECUREL Y INTO THE GROUND (MINIMUM OF 18 INCHES). 3. A TRENCH SHALL BE EXCA VA TED, ROUGHL Y 6 INCHES WIDE AND 6 INCHES DEEP, UPSLOPE AND ADJACENT TO THE WOOD POST TO ALLOW THE FILTER FABRIC TO BE BURIED. 4. SILTATION FENCES SHALL BE INSPECTED IMMEDIATELY AFTER EACH RAINFALL AND AT LEAST DAILY DURING PROLONGED RAINFALL. ANY REQUIRED REPAIRS SHALL BE MADE IMMEDIA TEL Y. 5. SILTATION FENCES SHALL BE REMOVED WHEN THEY HAVE SERVED THEIR USEFUL PURPOSE, BUT NOT BEFORE THE UPSLOPE AREA HAS BEEN PERMANENTL Y STABILIZED. STIL FENCE DETAIL NOT TO SCALE G: \ Prod\Delo;!s \ Mun;c;pol\ NTI\ Reporl delo;ls \ C8 -FF.dw'l PLOrTEO: <Id NORrHWf:STERN rERRlroRIES. INC. 2004 SCALE: NOT TO SCALEI DATE: DRAWN BY: PROJECT: oRA [rJ PI (:> E fLl\lJ FOR: TO 1)\) CO LE B1?OO 1< FINAL REVIEW: Robert A. Leach, PE SHEET 10 OF 10 fJ NORTHWESTERN TERRITORIES, INC. Engineers - Land Surveyors - Geologists Construction Inspection - Materials Testing NTI 717 SOUTH PEABODY, PORT ANGELES, WASHINGTON 98362, (360) 452-8491 '.. _-./ rFr:::~ fE:-~R:,)" ..[ f "'; -<r~' - ..~ :: Illl ) I ,. ~[; _li!/ ~_!~~ I i Vi I ,~, j r -- H II r" \ i Ill! i! ';, it t t I - ). '! II, :-j .": 3 o ("l --- \0 ...... --- 00 It.~-- ~--'-I , ) , , j , I .J '+-< o ~'~' 0.. 2 E-< II E o ~ 0<3 o ~ II ~ .8 (J) I-< Q) :> ...... ~ ] u 0<3 Q) '1::l "(il ..... ;::l o I g. S >- o II Q) ~ Z Q) u 't Q) if) c--. g. S .- I-< (J) J:.il g. S ...... I-< (J) ~ ...... I-< U'l Q) a o u ':;:;, Q) "E Q) (J) --- (J) ;::l d ~ d o (J) .1-< ~ tH Q) .? o ~ (J) g. s --- "";-; 0.. t:: ..c: j!J .;; <0 ..... ..... tig> ~<( w C ~ 0 ..c~ ..... . .~ 5 ~+:l cU co~ t:o coU ~ w - 0'- c'O w> O>u ~~ E~ -oU C co CO-o C C 'Q) co Q)g ..c..c -0..... 0> 0> C E '(ij 0> 'E-.5 0>- U.o 2-0 co 0> -o:!::: 0> E ..c= .:: .!!2 00. >co ~E :;.!!2 u..c z~~ 0<1>:0 (I):SO> UJ o.!:: (I)"'" co Oti'E 0-0>0 o:::t:U :Jcoco O-oro '" -' cO ,,<(w. ~z~~ ~ O-o:-Q S i=~(ij <(c> ~::J...."<t ?>o:::ooo 8 00::l~ jLLCQ)r-- zOEI.O W U .. 0:: Q> Q) "<t 0l:=1::~ LLQ)go :I: "'0 [ ~:E e e "' O>~ i l!.! .~ III ~ ro -l ::l <J <J '0 R ~ ~ ~ .9 ~ ~ c: C ::l ~ ~ ~ III 8 '" '" 0 ~ fil 0 a.. (lJ ~ <J DO \ ODD ", i i Q.9~ o,;>e i \. .. '.. .. .. -'-. .. . .' i ~",'fJ ~ "',-.__.r ~ CI) ~ CI) > -I :!: I- J: (J) ~ (J ~ <( ---- -----:--=---- -=:. ~ -= -=---~=---=----==-=--~----~7 .,,<'" -......-- __--~. 0 ~-~------o:.---~1 O~e -~--~L --f..---- O(J~ -. ~------ I . I ~ , '. ------- . .---~-- ~ ~ "~S: " g. ~ "-..--/ Appendices '" ------ APPENDIX 1 - Jefferson County Strom Water Forms & Communications "'jr[\i e-frT~fc~e_---,(t'",\1 II ,.,< r--"-':='" M...._.__ ! i j II 'r-U' I Ii 111 II 1 I (,C" ! I I J I I I" ,') 1-.....1..' ,. ( , , J' I ' . ' <, f " J I ,.-" ! I) L-Jf.Ti~:}~S,0:/~~():}, ,Y,. '" _. I DE, T. qr COfl'ir"lili~.1~!,~:i:'l.i~~i!~~r1.d JEFFERSON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street Port Townsend, WA 98368 AI Scalf, Director July 2, 2004 TODD N COLEBROOK CYNTHIA F COLEBROOK 21 BARQUE LN PORT LUDLOW WA 98365-9729 RE: SITE ADDRESS: WALDEN LN ------- \~~,,,<.-c'-"'" II r<\ 1\\ \ 1\ 1\ ,: ~ \ -..' ...,. \ I f"-\'\ \' I ! '. \ \ \\ \,,1 .' '\ '-'.'-. ......... '.' ~. . '. " L~1:-; \ [" I,T f1\ Cc.;,,, L~_~_~-_:~~~__~~_~r- .:.--=-..-----.- ,. \1 ."" i~:; .-;.:..:-\ \~.., \ r \\ ,I....j . \ I \ .....\ I .'. .-- '\ \ \ \ \ \ \ \ t:~!) \ \. \ . .\ \ , I __,,___~l :., .-' .. MLA #: MLA04-00401 CASE #: BLD04-00446 Dear TODD N COLEBROOK: The Department of Community Development is in the process of reviewing your application. The following information is needed to continue review of your project. Consistent with the Department of Ecology 2001 Stormwater Management Manual, the proposal is subject to a Medium Project stormwater plan due to the proposed 6141 square feet of impervious surface and 7700 square feet of land disturbing activity. Enclosed is a Stormwater Site Plan. Please fill it out completely and submit original to me for review. 1 can be reached at 360-379-4457 if you have any questions or concerns. Please submit the above information to the Department of Community Development by September 30,2004. Pursuant to Unified Development Code Section 8.2.3.c and f., if the applicant refuses to submit the additional information or does not request additional time to submit the required information within the ninety (90) calendar day period, the application will be mnsidered abandoned and therefore withdrawn and the applicant shall forfeit the application fee. The Department of Community Development shall not be responsible for notifying the applicant of an impending expiration. c: File LINDBERG & SMITH ARCHITECTS Building Permits/Inspections Development Review Division Long Range Planning FAX: (360) 379-4451 (360) 379-4450 JEFFERSON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street Port Townsend, WA 98368 AI Scalf, Director July 2, 2004 ( ~_n'_._~~.~._~~___~.,-"" IIIY~). J~_ OC~ [E fVIE -- ~~~~ ' II L,J. r _.~~..~~.__.~o_~ ~ I if") \ , )111111. snl .~. 7 ?tll)".'./i]/1 tf. I_~ t,..1 J ~ -- I .' ~t)L -y L:::J I I I L~_......_.~ I <r ~ J[?TE~SON'COUN1Y CASE #: MLA04-G0401 L.~~:.~~9L~:.Q!~~~~ifY DfVEl.OPMENT LOCATION: Parcel Number 821 085002 Port Ludlow No 6, Lot 2, in Section 8, Township 28, Range 01 East, WM, Located on Walden Ln, Port Ludlow, WA 98365-9729 TODD N COLEBROOK CYNTHIA F COLEBROOK 21 BARQUE LN PORT LUDLOW W A 98365-9729 RE: Dear TODD N COLEBROOK: Jefferson County Department of Community Development staff have received the application materials for the above project proposal and have assigned your case to: Michelle Farfan (360) 379-4457 E-mail: mfarfan@Co.jefferson.wa.us Fax: (360) 379-4473 Please direct all questions to Michelle Farfan and refer to MLA04-00401. If you need to speak with Michelle Farfan in person, please call to schedule an appointment in order to ensure availability. Review times vary depending on the type of application and how complete the application is upon submittal. For more information, please visit the Jefferson County Department of Community Development web page at www.co.iefferson.wa.us/commdevelopment/. Thank you. mmunity Development Staff c: File LINDBERG & SMITH ARCHITECTS 319 S PEABODY ST STE B PORT ANGELES WA 98362 . . LIND-BERG. & SMITH ARCHITECTS 31.9 S PEABODY ST SIE B PORI fflGELES WA 9836? BUilding fJermrts/ Inspections uevelopment Heview ulvision Long Range Planning (360) 379-4450 FAX: (360) 379-4451 JEFFERSON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT ~lEa:IEOWIE Ln.!! I I nrJ)j L... . .,' )(1! il! ~I L, 621 Sheridan Street. Port Townsend' Washington 98368 360/379-4450.360/379-4451 Fax http://wwvv.co.jefferson.wa.us/commdevelopment/ I L. --ir;~~:';~:-;;-'~"'~---_, J ..... .. ,.. . "1,1..:; V' -"(11 "~7Y~-- (X ri:':~-,/tl?/!.\'> r)i~~rr:~9!~r~'in:i" STORMWATER SITE PLAN SUBMITTAL TEMPLATE I MLA# N'\LALl4 '~l PROJECT/APPLlCANTNAME: ~ Todd Coltb[QQJ( Please answer all of the following questions to the best of your ability. Where the question calls for depiction on a site map, the applicant may choose to either incorporate the elements into the general plot plan for the Master Land Use Application or to submit a separate stonnwater site plan map. Project Overview 1. Describe the proposed developed conditions of the site. Indicate position and relative size of proposed improvements on the site map. .. Existing Conditions Summary 2. Describe the existing topography. Indicate contours on the site map. 3. Describe the existing vegetation. Indicate native vegetation areas on the site map. 4. Describe the existing soils. Indicate soil type on the site map. . 5. Describe the existing site hydrology (Le., drainage; behavior of water on the site-above, below, and on the ground). Indicate existing stonnwater drainage to and from the site on the site map. Depict separate drainage basins on the site map, if applicable, and indicate acreage of each. 6. Describe any excess levels of noise generated by the proposed use or activity: slormwnl&' aHa plonl&rrplale - '0_. Hl'll2003 5 Project Overview ~-~~-~'~---~-'-~l ~ [E (G n~: n \V7 l'~ ~.\ r~~r~--~.- -~~ _L..~. :;l.... ~...! ' In, n 'J' j. u \__~:____'cJ-/ JEFFEflSON COUNTY DEPT. OF corv1MUi~ir::~)_i:~~~~~pr,.~[~~~~ Proposal (MLA #: MLA04-00401; CASE #: BLD04-00446): This project proposes the construction of a single family home upon an "L" shaped wooded 5.1 acre site (221,067 sf). The home and ancillary buildings will have approximately 7409 sf of roof area (home, garage and shop) with 565 sf wood deck at the house, approximately 1197 net sf in concrete aprons for the garage and shop (note that approximately 171 sf is under the structure's eave line) and approximately 12,900 sf of 15' wide gravel driveway and parking (recommend a narrower, 12' wide drive where possible). A small yard area of approximately 1065 sf is envisioned along with an allocation of about 500 sf of site disturbance for the installation of a well and sewer line. The total disturbed area will be approximately 23,636 sf and the total impervious surface (post restoration) will be 7409 + 12,900 +1200 +65 = 22,071 = 9.98% of the site. General Project Information 1. A preliminary analysis of this proposal by Jefferson County (July 2, 2004 -see appendix) has indicated that a "Medium Project Storm Water Plan" is required. With the total site impervious area being less than 10%, full dispersion disposal is allowed without triggering flow control facility requirements. This will be accomplished by use of BMP T5.30 (dispersion) in accordance with BMPs T5.1 0, T5.11 and T5.12. Drainage dispersion per BMP T5.1 0 will be used for the roof/deck/cone pad drainage and BMP T5.12 will be used for the gravel driveway drainage. Existing Conditions Summary 2. Existing Topography: The property slopes to the south and has a slight ridge line running in a north south direction along the west property which causes the contours to be curved convex to the south and to shed water both easterly and westerly from the crown of the ridge (westerly flow is on the adjacent property with little or no runoff from this property). The slopes along the N-S ridge line begin at about 2% at the north for about 1/4 of the site and then moderate to about 5% - 6% for the majority of the site (through the building zone). The E-W slope from the ridge line is approximately 5% for the majority of the site until reaching the base of the site's "L" shape when the slope steepens and varies from approximately 15% to over 25% indicating the change in soil type from AIC to AID. No off-site runoff enters this property from the east, west or south and the Walden Lane access intercepts runoff from the north. 3. Existing Vegetation: The site is partially treed per the County's web site photo of 2000 (see Appendix 2) and the Architect's site plan shows a tree line to the southwest of the home site. On-site observations reveal that the shallow slope Page 1 of 9 upland area is predominantly grass with treed areas while the steeper slope downhill areas is treed. The Jefferson County Drainage Regulations (DOE 2001) require that the storm drainage plan consider the site to be vegetated as it was before European contact (early-mid 1800s) which would, likely, have been totally forested. All calculations for project related disturbances have been made with a forested condition. No significant removal of trees is required for this home's construction. 4. Existing Soils: The site soils are mapped by the USDA Soil Conservation Service (SCS) at AIC or Alderwood Gravelly, Sandy, Loam (0% - 15% slope) which is a hydrologic type "C" family of soils. Further inspection resulting from an analysis of the site topographic information obtained from the Jefferson County web site indicates that portion of the site are AID or Alderwood Gravelly, Sandy, Loam (15% - 30% slope). This is significant only in that the potential for erosion is greater in the AID soils than in the AIC soils. All work on-site is confined to the AIC soil area and 50' setbacks for storm drainage dispersion facilities is required by BMP T5.10, T5.11, T5.12 and T5.30 5. Existing Site Hydrology: A site contour map and a regional contour map obtained from the Jefferson County web site (see appendix) indicated the general lay of the land for approximately 500' east and south of the site and clearly show the drainage way that exists approximately 250' east of this site's east property line. The dominant grade leads to this drainage way and suggests that natural drainage leaves the site in a southwesterly direction. The Alderwood soils are gravelly but shallow and drain moderately well for their depth with infiltration rates ranging from 2.0 - 6.0 in/hr in the upper strata and less than 0.6 in/hr in the deeper strata. 6. Noise Production: Once construction is completed, there will be no significant sources of noise at this site. 7. Significant Geological Features or Critical Areas: The portion of the property located in the base of the "L" (southeast of property) where the slope increases beyond 15% is classified as a "type one landslide hazard area. A minimum buffer of 30' is required by the landslide designation and a minimum of 50' setback is required by the storm water dispersion regulations from a steep slope (40%+) which may include any buffers. This site's slopes do not reach 40% and only the 30' buffer is required. Note that the 30' buffer can be reduced to a minimum of 15' if supported by the recommendation of a geo-technical analysis and report. A geological site evaluation was prepared by NTI's staff Geologist, Bill Payton, and is included in Appendix 2 for reference. 8. Description of General Vicinity: The general vicinity is characterized by larger parcels (5+ acre) for secluded residential development. ThiS"'~~~: d~S}. /.~: f1..~[~-'tt.-..'jcf1.-.a....,.lr. ...-.-[i~~I'[-~:"- of the overall Port Ludlow development IJ lhc<.lc~,,-~~.'.'.~.~. fli U uL S!:[1 - i iilu4 1.0 -~-------1 JEFFEnSON COUN'lY DEPT. OF COMMUNITY DEVELOPMENT Page 2 of 9 ~( 8~' ~;~:lrm ; fl Permanent Storm Water Control Plan L, ____ : 1 _ _ (1' )).~-i.\;-:!/Ii',:--'r;;!'~/f\~,"~i 9. Developed Site Hydrology: The developed parcel will behave muchlike-the " i undeveloped parcel in that drainage will flow down hill to the southeast following the full dispersion of all collected runoff. 10. Storm Water Treatment: The water from the composition roofs of the three buildings will not require any treatment. The water from the gravel driveway upstream of the home site will be controlled and diverted into the area east of the driveway for sheet flow vegetation treatment and adsorption in accordance with BMP T5.30 which references BMP 5.10, BMP 5.11 and BMP T5.12. 11. Performance Goals & Standards: Not applicable. 12. Flow Control System: None required since this is a rural residential site with less than 10% total impervious surface 13. Water Quality System: Full dispersion filtration in forest and/or native vegetation per BMP T5.30 14. Conveyance System: The conveyance system(s) will vary across the site depending upon where you are. a. The downhill driveway will have two dispersion units to serve its approximately 475 lineal feet. periodic dispersion units. The driveway will be sloped transversely at 2% in addition to its longitudinal slope (2% - 6%) and a shallow ditch will be installed to collect the runoff after 3500 SF of surface. This 3500 SF will be piped to a dispersion unit of 3500/700 = 50' in length located such that downstream building development is not in the direct path of the resulting surface flow. Although the current plan is for a 15' wide driveway, a recommendation has been made to consider a 12' facility to reduce the runoff. ., ,./ b. The parking area from the last catch basin along to the parking area and up to the two concrete pads will sheet flow to the southeast and filter through the native vegetation. The 60' of width will require 25' for the first 20' and 5' each for the second and third 20' for a total of 30' minimum distance; several times this distance is available. c. The roof, deck and concrete pads will be connected through a series of down spouts, pipes and catch basins (with SC oil/water separators) and transport the collected storm water to three (3) dispersion units located downstream of the collected facilities. A maximum of 3500 SF is allowed in each of these units. The area calculations show that the two units serving the home, deck and Page 3 of 9 garage will seNe slightly more area than this by approximately 100 SF, but, the 565 SF of deck will likely not be impervious and not need to be included. The deck is included in these calculations to provide a contingency. d. Landscaped yard will filter through native vegetation. A maximum of 150' of landscaping flow length is allowed. More space exists than this maximum but less space will actually be required. 15. Source of Fill Material: Unknown 16. Soil Placement: Minimal import soil will be needed. The building site will be "balanced" to the degree possible and landscaped areas may have imported topsoil. The most critical soil to be placed is the backfill in utility trenches which should be compacted to 95% of optimum and bedded with sand per the manufacturer's recommendation. 17. Surfacing: The paving surfaces planned for this project include a gravel access driveway and parking area and a concrete access pad for the garage and for the shop. All other surfaces will be vegetative with the exception of the home roof (composition) and two wooden decks. 18. Site Restoration: Disturbed areas will be either paved, roofed, landscaped or restored to natural vegetation. Hydro-seeding of cut slopes and fills as soon as possible is highly recommended even if the area is to be fully restored to native vegetation at a later date 19. Operations Manuals: None required 20. Special Reports Generated: None 21. Other Permits or Approvals: Jefferson County Building Permit Construction Storm Water Pollution Prevention Plan (SWPPP) Section I - Construction SWPPP Narrative 1. Required 12 Elements 1. Clearing Limits: No additional clearing is needed to construct the home beyond the removal of site grasses for the site grading necessary to construct the home and driveway. Construction limits are shown on the plan~ and will ~e marked in t~e field with orange co.nst ~:fe~aAq+e~m'~~\'t7'f;-'~i;:;.:~:;'l fencing to provide a strong visual reference for equlpm ~j)~ ~r~r~; U \\/ .h~ II i.,...\.... '.'. Page 4 of 9 ~l8_~~7-~0~~-1~!\ ____ _)Ef~~~.~9,t,L~fllLt~.l'r M. "'''T I 2. Construction Access: Construction access will be provided along the driveway leading from Walden Lane. Walden Lane is a private road and not subject to the County's regulation. However, site access roads should be protected from the effects of mud being tracked off-site on tires. This is, typically, vehicle accomplished with a crushed rock or quarry spall paved section of driveway to help knock any mud from the vehicle's tires. (see appendix for DOE's recommended BMP) 3. Control Flow Rates: Full dispersion disposal requires no flow control. 4. Install Sediment Controls: Erosion and sediment control facilities should be among the first activities on site to ensure that a sudden storm event will not catch the project by surprise. 5. Stabilize Soils: Stabilization of site soils can be accomplished by minimizing the area of clearing to that area being actively worked upon and by expediting the restoration process upon completion. Proper scheduling of the tasks to be performed for sequence as well as for time of year is essential. To minimize the soil erosion forces of raindrop impact, flowing water and wind erosion during construction, the contractor will follow the exposed and unworked soil schedule set by DOE for all soils on site. From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days, and from May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. All exposed soils shall be stabilized and hydroseeded or sodded upon completion of the project. 6. Protect Slopes: Slopes are, typically, protected by vegetative setbacks and by sediment control/filtering from silt fences, straw bale barriers or straw mulch. The use of silt fencing is recommended for this project down stream of all construction activities because the site impact is small and they can be easily removed and recycled upon project completion. All sloped trenches shall include check dams placed at 50 foot intervals 7. Protect Drain Inlets: Drain inlets are, typically, protected in a construction area by wrapping with silt fence filter material or by lining the inside of the unit with filter fabric if a barrier fence is an obstruction. Other techniques are available including gravel filters which are equally as effective an provide the owner and/or contractor with options. 8. Stabilize Channels and Outlets: The existing drainage ~.9Jb__ld_QQllJb_i~__~_~~~x__ property ?eyo~d dist~rbed area~ will be maintained during 'i'~QJi~ f~e~~ lG II WI It: constructIon with natIve vegetation. b>~[~-'-' ~_d__~.__._... - i lnl SEP ~ 7 200~- ! Page 5 of 9 L__~~__~_._J JEFFEfiSON cournv OEPT. OF COMMUNI1Y DEVELOPMHFr 9. rl'OO":')--[E Q~~LE_ ~~WW. [E. II~f\11 - r-. ""------- I ", r"\"11 II' :; ; , ! I . " i ! I (1 E p -~ 7 ?0(1) I I J d Lt I 0 -I ! i.l) J4 II "-', j jl.,.. Control ~ollutants: All chemical~. liquid products, JI:trolbu.1f1.['[f.7f.l:~..,ttt~iN"r~"-".J and non-Inert wastes present on sIte shall be covereql.1'~~hr~If-l5l9!9.~'di protected from vandalism and handled in a manner to minimize -.. "'--'-"~"-_. contamination of storm water. To minimize pollutants generated by heavy equipment and vehicles, all maintenance and repairs shall be conducted using spill prevention measures such as drip pans. 10. Control De-Watering: If de-watering is required during construction and the de-watering water has similar characteristics to storm water runoff, it is to be directed across the nature vegetative buffer at a minimal velocity. If the de-watering water contains contaminants, the de-watering water should be directed to a sanitary sewer as permitted by the sewer utility. 11. Maintain Best Management Practices (BMPs): It is the contractor's responsibility to maintain the temporary erosion and sediment control measures and to install the permanent erosion and sediment control measures set forth in this report and plan. After construction is complete, maintenance of permanent erosion and sediment control measures are the owner's responsibility. All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization is achieved or as needed if longer. 12. Manage the Project: Management of this project can best be conducted in accordance with DOE if the guidelines set forth in this report and plan are followed to ensure that the long term goals of environmental protection and site stability are achieved. 2. Adjacent Areas a. Adjacent Areas Description: The immediate adjacent area is the downhill property to the southeast which contains the local drainage route. b. Downstream Drainage Path: The downstream drainage path is a forested depression (see photo in appendix) 3. Environmentally Sensitive Areas: The portion of the property located in the base of the "L" (southeast of property) where the slope increases beyond 15% is classified as a "type one landslide hazard area. A minimum buffer of 30' is required by the landslide designation and a minimum of 50' setback is required by the storm water dispersion Page 6 of 9 ',~ regulations from a steep slope (40%+) which may include any buffers. This site's slopes do not reach 40% and only the 30' buffer is required. Note that the 30' buffer can be reduced to a minimum of 15' if supported by the recommendation of a geo- technical analysis and report. A geological site evaluation was prepared by NTl's staff Geologist, Bill Payton, and is included in Appendix 2 for reference. 4. Erosion Problem Areas: The only potential erosion problem is the relatively steep slope below the home site. Full dispersion techniques should insure that the runoff is fully spread and adsorbed. It is prudent site stewardship to periodically inspect the downstream conditions to ensure that the facilities are working as designed and that the site remains stable for the structures above. 5. Construction Phasing: a. Construction Sequence: Specific plans for construction phasing are not known. It is likely that the complete access will be constructed along with the home and garage and the shop deferred. Another possibility is to build the access and shop, live in the shop during home/garage construction. The plan developed is modular and can be adapted to cover any phasing plan developed. b. Phasing (if proposed): Not applicable at this time. 6. Construction Schedule: None exists at this time 7. Financial/Ownership Responsibilities: The contractor is responsible for the maintenance of all temporary drainage, erosion and sediment control features during construction and, possibly, through the construction warranty period. Following construction and final restoration, the owner is responsible for all permanent drainage, erosion and sediment control features. a. Sediment Ponds & Traps: Not applicable --r::--~rp;'~'-~-:~~"~~~>';:"~;-~~i:C.--- ~~;-~I:-~~"-' ~/_~;""-__~~~J,:~~ ---1 [")~ It; U,lj lt~ tl Vi l.~ Ilire'i' i f' V) 1--.....- '. --.",...-..."'."...."......'..--1'1. III L ld SEP -. 7 ! I J) I , i ".Op~ I I I I L..__"._,___".~._,. __'n., . ....j I ,Ii Cfi'i1':C:" ';1'y J L_~ ~T ~_~:_r_ _~ n ~'~,:~;~ . ____:!~~-:_~~!!~~'..L~ 8. Engineering Calculations b. Diversions: Not applicable c. Waterways: Not applicable d. Runoff/Storm WaterDetention Calculations: None required Page 7 of 9 Section II - Erosion and Sediment Control Plan Requirements 1. General a. b. c. 2. Site Plan a. b. c. d. e. Vicinity Map: See narrative Jefferson County Approval Block: On drawings Erosion & Sediment Control Notes: On drawings rl,::',DJ", ~I' 1E~~-lU .W= [E ~1~::~\1.1 Ilr\'\' jUli Ii, i I ',rn - I I U U i,' Str'~ 7 2004 .,,~j: I ! I ! L______:~-_ I : _, JUIUiSCN COUN1Y I L2~!~~.~~~ r.crYl~NITY DEVELOPM~~ Legal Description of Property: See narrative North Arrow: On drawings Boundary of Existing Vegetation: On drawings Label Potential Erosion Problems: On drawings Show FEMA Flood or Shorelines Management Boundaries (if applicable): Not applicable / f. Show Existing & Proposed Contours: On drawings g. Indicate Drainage Basins & Direction of Flow: On drawings h. Label Final Grade Contours & Show Developed Condition Drainage Basins: On drawings I. Delineate Clearing & Grading Limits: On drawings, see narrative J. Show Cut & Fill Slopes (Top & Bottom): See note on drawings 3. Conveyance Systems a. Designate Swales, Interceptor Trenches &Ditches: On drawings b. Show Temporary & Permanent Pipes, Ditches & Trenches: On drawings c. Provide Minimum Slope & Cover Data For Pipes: On drawings d. Show Grades, Dimensions & Direction of Slope: On drawings ". ..-/ e. Provide Details of By-passing Off-Site Runoff: Not applicable Page 8 of 9 f. Indicate Locations of Outlets & De-Watering Systems: Not applicable '. -~ 4. Location of Detention BMPs: Not applicable 5. Erosion & Sediment Control Facilities a. Dimensions of Traps, Ponds & Pipes: On drawings b. Dimensions of Pond Berm: Not applicable c. Pond Volume and Dimensions: Not applicable d. Typical Pond Cross-sections: Not applicable e. Details of Filter Facilities: Not applicable f. Outlet Stabilization Techniques: Not applicable g. Control I Restriction Details: Not applicable h. Mulch Specifications & Check Dam Details: Not applicable '--_./ I. Rock Specifications for Check Dams: Not applicable j. Check Dam Spacing: Not applicable k. Front & Side Cross-sections of Check Dams: Not applicable I. Locations for Silt Fencing: On drawings m. Construction Entrance Details: On drawings 6. Detailed Drawings: See report and appendicles 7. Other Pollutant BMPs: A variety of BMPs apply to this project including silt fence, catch basin protection, straw bales for ditches, construction access and full dispersion, All BMPs are detailed in the report and appendicies. 8. Monitoring Locations: Not applicable "W'~"'~'_....""__~~~.' ~"-. -..' --<--------0 'I '~_'~-' 'P (..,) .." '-j ~w - rE r'm I [" ~ 1-" r Ie , .\ ['~ [J '\ 1-;; ,~.;;r If; t ~. L; Ill)~ r----.---.~.~~-.-1 ! , I ,.. , I I . II I ~\ \ ' j : iU U! SEP ~ 7 2004 L)l l L__._~__~~..___._. .~~~ I, JUHf1SQ[~ COUNTY DEPT. OF COM MUf'H1Y DE\jEl.O~,./1ENT I Page 9 of 9 $tormwater SIte Plan Changes Ii the designer wishes to make changes or revisions to the originally approved Stormwater Site Plan, the proposed revisions shall be "- -' submitted to OeD prior to construction. The submittal shall include substitute pages that Include all proposed changes, revised drawings showing any structural changes, and any other supporting Information that explains and supports the reason for the change. FInal Corrected Plan SubmIttal If the project included construction of conveyance systems, treatment facilities, flow control facilities, or structural source control BMPs (not standard on-site stormwater management BMPs), the applicant shall submit a final corrected plan {"as-buiUsj when the project is completed. These should be engineering drawings (stamped by a licensed civil engineer) that accurately represent the project as constructed. APPLICANT SIGNATURE By signing the Construction SWPPP worksheet, , as the applicanVowner atlest that the information provided herein is true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners of the affected property. (lANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) THIS SPACE MAY BE USED FOR ADDITIONAL NOTES, IF NEEDED: " ---- .~~---- r.;:.;-'~'-~-fi;;~'l~\;:.--~"",",.'r::-~"'\ r[J~ If, IT 1"0' II ,J7 If; I r'" \ lb, -19 J;" L I:; .h I j .. I r---~---~'~--'-'---'.-~-'-'ll i 1...1 "\ ! I I! I rl \ I' n r-p "7 'l('() A II L' ) j ! [I \1 ,,' ,..~. I I 1.1. I f I 1 'd L . / ..,.. J II j I ) ... I.m.- 1 I I I ~f PT~~?[J~;J:i,~tIX~~Yu>lY;;~~::d olormwalor olio pion torrplolo - rov, HVII200J 12 APPENDIX 2 - Calculations, Etc. r'~:~:::~:_'~~---~-' j n"__~__ _r~_~- .-.- >.". 11 'It r"\ \ , 'I il i j I II ,~, j Ii r\"\ \11 \ \ II.. ,,' i lDEPf 01 " , , ...! It,",' 'I' I \ i ! \ \! I \' II \ ILl1 L_"i \ , I I I"~, CO[ii!/uIJn~(t;-N\:iUJWMl-Jn ! U~__~ ."r_. .-r..'~_ ~"~,. ~~ ~~--------~,~--~-' EJf::P i )004 .M'- . y(~A . ~,.. "V NTI NORTHWESTERN TERRITORIES, INC. 717 SOUTH PEABODY STREET, PORT ANGELES, WA 98362 Engineers. Land Surveyors. Geologisls Construction Inspection. Materials Testing (360) 452.8491 1.800.654-5545 FAX 452.8498 E-Mail: info@nli4u.com H'WW.IJ{j-lll.C()1JI August 27, 2004 i-!;::::~----;{;"-';;'\.)"";~~;-r~1 ~ii':;-'\-E-~-r;;:-] I'rk \ k' Ii ," li~' I \li 'Ie; - 11.1 )'/"'" '.. _:'~:~ ..\;'.'J.'-.'.'_::::~:.:'~":----~2.1~ ,. ""'< i \ ' r"\' i II, \' 1\ \ It cr:p'/ Il ILl \\: .)f. / L.:. , , 1 j' L._ .,....._'..__..__. .-,,,.- ..~.--,,.----.---- JEFFUiS()l>J COUNTY L~~E:L9~!!~,!)!,1~~:_~)i.:yE~.Q~~~~NT Todd and Cindy Colebrook 21 Barque Ln Port Ludlow, W A 98365 Subject: Geotechnical Assessment of Lot 2, Port Ludlow #6, Tax Parcel #821085002, Located in Section 8, Township 28 North, Range 1 East, W.M., Jefferson County, Washington Dear Mr. And Mrs. Cole brook: Bill Payton of NTI Engineering and Surveying completed a geotechnical assessment of the above referenced property consisting of research of available literature and geologic maps of the area, and a site visit for visual observations. This assessment was in response to the eastern portion of the parcel being listed as a landslide hazard area 1 by the Jefferson County Department of Community Development, specifically a ravine that runs southward along the eastern side of the property. The USDA Soil Survey maps the soils in the area of the property as the Alderwood gravelly sandy loam (0%-15% slopes), a silty sand or silty gravel soil that formed in glacial till. The Washington State Department of Ecology's Geology and Ground-Water Resources of Eastern Jefferson County, Washington maps the soils in the area of the subject property as Lodgement till (Qvt), a glacially derived soil. This same soil is mapped by Ecology's Coastal Zone Atlas as Vashon Lodgement till (Qvt1). For comparison purposes, this is the same soil that comprises the steep bluffs along Water Street in Port Townsend. The Atlas states that this soil stands in steep natural and cut slopes for long periods (as evidenced by the vertical cliffs in Port Townsend). Visual observations of the surface soils at the property match the above soil descriptions. The property is well vegetated predominantly in grass with young to mature native trees and shrubs along the gully. No springs or seeps observed, and it appears that no water flows in the gully except storm runoff. Likewise, no water loving plants such as horsetail ferns were present in the gully. There was no evidence of past slide activity observed in the gully or elsewhere on the property. A few of the trees in the west side of the gully had slightly curved trunks indicating that minor down slope creep of the surface soils is occurring. The slope of the gully at the subject property is approximately 14 to 16 degrees (25%-28%), and is approximately 40 to 50 feet high. The typical angle of repose for loose cohensionless material ranges from 33 to 37 degrees. The angle of repose is considered the maximum slope that a loose cohesionless material remains stable. The slopes at the subject property are well below this angle. This office is providing an engineered drainage and erosion control plan for the development. As part of the development, a series of infiltration/dispersion units are proposed along the southern portion of the property and along the eastern portion of the property at least 30 feet west of the top of the gully. Based upon our assessment of the property, we anticipate that the proposed drainage system will not destabilize the gully slope and further that the ravine does not pose a landslide risk to the development. If you have any questions regarding this matter or need further assistance, please feel free to contact us. Sincerely, NORTHWESTERN TERRITORIES, INC. Bill Payton, L.E.G. Engineering Geologist G:\Gen\Bill\Reports\Colebrook.8(28.1 E). Geolech review. PI Ludlow.doc r;.::::-"': ~ . -- - " - - - - .. " -::'1 Ii rl' \ ~..\ \ 1\ " ",) II i I il: I":" i I I, ! i i Ii; IU ~\" . :;'J 1 _ __ J( 1.; L'~L:)U;J CC \ 0< ''/ ~1-Q~ c J'"' ~~f j_~.'::_ [-~: _~ ,_:_~~J~~~rn 2 {glO 5/1 /.JQPy 2bP ~z9T %/-----<;~ L I 0 "]3>>" ~ 10,3 s 0 S 17 ~ I, (,2- Ace I .1'// 3> 35 I ,(g2-+ II S4 -=- "3, /1'0 I .' I / Vt~ecl O,f(;' !\C:::o G 9 70 s {=' \ 235 1.----- ~ - -I LUU (/ /, ( I ( // ./ ( -4'~ 735 G SC;>o -=- S ,3 2 s :?_cJu '1-""3 ~.s ~ G, 70008":-"=' (, 5 'i A-0 \ LV I 5> 2.\0 '1-33 'S: -= 70) '550 SF";::: l ,02 AG \ , f / 53'S / / / ( / /, I I ,/ I _ ~-L---, - I 2.00, /~ ,,_-!~3.~? / If Co2'ti,7'3 f>C-:: 3,s s ;.c! ].321.C - - \ C <. ~sPcJ 0\ ~tol ) S?,S ~O;2~)-C:S:SS =75) 37 ~ 'h!::::~ ~ l {$ AC bS <10 V/J DISTUR 12~ C0,1J 6E S T DESIGNED BY: PROJECT: FOR: SHT: R DATE: OF ^ CCOHP LIS, ffED AS ,)HowrJ !leaVE: rl:;;~:~-~:;~-~'-.r-;~- __.'~__.<c____ lit"')) lb) ,I"" linl i U Lt I i I NORTHWEsrERN"T~E'R'R'ITORI ES;+NC: a JLS Group Company Engineers. Land Surveyors. Geologists. Materials Testing 717 SOUTH PEABODY. PORT ANGELES, WASHINGTON 98362. (360) 452-8491 @ NT' I f'\ \ ..,"', , " I' I I! ; II f j:, !i ,,-,-. :1 I ! '~..~! . , ..~-~~~} www.nli4u.cominfo@nli4u.com ro-,o ',,+, I --- -E- l% ( l'1 '10 ~------ // ~ b'1, o \ t\~O It ~ "2.:-S0 ~ Il~ , I ) , // , / I // I 0" I C\/ P'\ 0\0 ~ [--~ -TR F\ ,u~ F L R p...l:::Jj PRQ 1-1 C U u /JT"( U D^k' CONTOu.(<__ HA PP//0G ]35 : Y 1/ ~ ;i I) .~ l! Y : - /WJ t _~-L__ f') .f-, r --/\:-v ~ +-[~.')'--'.lf-[~"'-'t~[--"[r"'Yl]-"'IE~~'f~::;:\ '1. 1 I DJ r-.-------.-..---~.-..~--.....ll Ii: 1 d-'~ I II [,111 Ll LI L..'! I L,.. j I ll_.u~.,.t-......,,~~.~,._. ._,.._..._",r..__.Ji.,~_-::,~.:-'JI...,:.~(.,,:_,,[.,.~.~_,.;~_"'~;l,(,",':.;.I..r.,,..,;_.,.,.~..,-' . r: :\<T.~( Ir-' . _ "r ! _. __ __.__" _ _ ~ ~_ _ -. _ ! j :'_-:_'!_t:-~~_:_).~!_::<~~i,~__.J / ;' vi ~ / i / j' / I I I I i I i I i ! I I I ,--Lzoo 0\0 ~ ~ ,,~ ~ i;;;" /~ i ! I I / i o I C1J I 1 t ! oy i I QJI f'..j; ~ I j / I ~._- / /' .., .~ S T R '_oj' ;: DESIGNED BY: PROJECT: FOR: SHT: OF DATE: ) I / i .I j (1 . I f ; I i I'l= 100 ( I f ! / i J / / i J i ~ NT' NORTHWESTERN TERRITORIES, INC. a JLS Group Company Engineers' Land Surveyors' Geologists' Materials Testing 717 SOUTH PEABODY. PORT ANGELES, WASHINGTON 98362. (360) 452.8491 www.nli4u.cominfo@nti4u.com --.L~~ 700 S{:3 (0 EC\< =- 5 bS HouSE'- - ..q I 0 ~ CAd~.p.ro c:; = t S 5' "3- Sl+-o p =- /0 r::; 0 CeJ-JC(s) 4LO-- .w-,.} CLG) ~17 I Fr 0 S'~ ( ? Cj S~1 FtrI2___ ecJD F_~~~_e~~_~~_Q! u - !~:!.~ c-_~!_ r;;bS! 70-0 ::-- 0 ,g I -=t g./ LF 4/CJ0(70 U :' r;S17 ==7 5~,7 u= /hS/700 ;'2,30= /& :;cJ/700 - 2,30 .. I.fZlJ!7UU ~ D.sA --- 777/700 - J,[/ ~ ~ 51.. 7 l' ~'f flIJ I I I Ge;" F= ~_jo!~1 ~~] [fC 3571 ~ L~I 1 r/ ~H ) M73 ()(Y73' /' \? '::) z} \ / rJ ') /' ). ~,(, L/;; .~ j ~ S T R I DATE: ~ DESIGNED BY: w g PROJECT: "- " 8 FOR: w ~ SH~ OF -- ---- 2-"5.0 u= 9 () < 4 L-F 4-1 itA f L0JGTl-i ~ SO (-C;lj')ur FLOw <i- f ScJ APA;-(:,T 20% UJ--{I T G WLO&{ST 2~ . (;; L'-=- . S,~L(~ ll,f L(=- 70Q S: +0 f (r .SF (-) i'y. l 't-Cl n..t9-GL "I . 72 ~JS4/ .3 S 4') .;- ? 00::: S. 0 7 S,071<.IO:::' C:;O,7 ~\/! Q) ::::-- SO . "'i. } c: ( -) 0 cJ~} j -.:=-..:.._~ '---- (31\(.(0\ ~ S I; 0 U-~ C 70--;)) ') --===::===-. 5 (6 S de ere. a-S'S""u--t-,)'\.___J.' { ,.. " I! ( ~ ct :': " c:-~9-~,..J 'v:? ~~-~:;.";-::> l~r~D:'~~' -~ . (~~!~ "-r-\T.jJ- r~ -~-:';~\~1 I r ~,_.._,-~- u...:, U' ~ - '-~.~.~~-.--=~ i I in) n, . ' IJI II b 1: /J =.'7 ')OOI1J ~ Wi ! ! l.oJ.,. i 1,,_,. [I L.---j[:i:~T(:~C;'7iJ-~'7>,"7" DE')~ '.. -,,;~ ".(;" COli,.; fY _..:_...:.-':..9~~.~~~~/il:!!~i II' Di:VELOPM[=NT ---------.._h...........,.___ _~_ ._ ~ NT' NORTHWESTERN TERRITORIES, INC. a JLS Group Company Engineers. Land Surveyors. Geologists. Materials Testing 717 SOUTH PEABODY. PORT ANGELES, WASHINGTON 96362. (360) 452.6491 www.nti4u.cominfo@nti4u.com f\f2-tA C!\:LC<;' hJk STRUCTU~E Roor,; 6 UPf(jCWAY. M87\SlAI2.CfctCAlTS !?-y tAt PROM !lPCt{ITCCTS sere PLA/J () HOU_.S.E (,'Jor Ij)CL GA(:;:J'\6~ g COvEI2~u C),/, [Y'j ':::" 4/00 Sf=" --,- ~ lU()c)(;. D:..cvs oAl b,S;, Of-- 110116 ('/.Jar 1;.)C.LUfj;/v6 E;1c/E oV~/(-1\AJ6) I ) r;; =- (S 7 ~F) Sf:-.:::- 40~ 5(-:=; TOT/!' L- -= 5 G::; S P , GA;kA0f: (CNCL ccJV E'rc.eo WJI;'L.-Lc)::::, /0 S3 :) F o GJdJJv?J!;; COr) G P 1\7) ( :3 7 y: VI- - ?~g SF) LES: S J ! 6:7nJ G- L\ (I '5,-'J -=- 7 77 ~/= · SHoP CoNe P/rr) (:?-4X.20 :=: LtW5F) LEsS 3 ( E::r\UE:- ( bU Sr-:-j ::::: 4cOSF o D R--I V (w 1'/ ([ r { ()J (bEe ;/J /tY-) & P 1\-{~.t<II'J G A(2c-fC<, = \ 2.) ~ 00 Sr=- t> G TIIt.tI1Tet) LPnv{J<:;,. CAr.J;,rJ G ::= JOb s: SF o 1'\ Ll ()uJ (^I, l) CC -Put2_ u r t L{ T t G--s - b Ou S (: C Tv 8f: f2c:rnJI26i'.)) "'SrfDP (>JU[ /AJCL GkAvGL D~/~euJA'I) = IGS'O Sf' TcrrA L G 12-d vtJ(J DlS[tA ~B I:A.JG : 4{OGJ + S(;S; + /0~3 +-777+ 420 -t ('2, qUo -f lOb b -tSOO-f [<050:= 23) GJ&:>SF r ~ TOTAL IH,oEl2tJluvcs: · Rou~ =- 1-1 (J fa + 10S~ + 1&,50 =- 740'1 S!=- i--~--'~--'--~ 1 L___."".""..... ~.~ i .. .,1 UTi: fi S or~ COiTr~1Y ! (if!'! or CGr,,1MUNIT'{ DEVELOPMr-NT .- >.. .._'-~--..~~-.._"------~...-.-.~~-------..:~~~ ~ b"LCk/_ -=- j?b5: S~ () CurJG PM)~ - 777 + 42.0 - t !97 s c Cl D C2./ VE'w J\'! - 12..\ cr uu ~ p q IUT^- L t IA P~vL Ovts' -::: 74-0Q +- ~ bS +-1 [q 7,( f2{ Croo ::::: 1..2; Or { 'J S T R I DATE: L ~ DESIGNED BY: :i w g PROJECT: Q, " 8 FOR: w ~ SHT OF ~ NT' NORTHWESTERN TERRITORIES, INC. a JLS Group Company Engineers. Land Surveyors. Geologists. Materials Testing 717 SOUTH PEABODY. PORT ANGElES, WASHINGTON 98362. (360) 452.8491 www.nli4u.cominfo@nti4u.com 8/24/04 6:59:25 am Shareware Release Colebrook Drainage Incremental Flow Approximation For Dispersion Unit Sizing page 1 ==============~=========================================~===~======== BASIN ID: 100a SBUH METHODOLOGY TOTAL AREA. . . . . . . : RAINFALL TyPE....: PRECIPITATION.... : TIME INTERVAL....: BASIN SUMMARY NAME: 100yr post - runoff (200'dwy) 0.09 Acres TYPE1A 3.50 inches 10.00 min BASEFLOWS: AREA.. : CN.... : TC.... : 0.00 cfs PERV 0.02 Acres 86.00 17.27 min IMP 0.07 Acres 89.00 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 200.00 ns:0.1500 p2yr: 1.50 s:0.0500 impTcReach - Sheet L: 200.00 ns:0.0110 p2yr: 1.50 s:0.0500 PEAK RATE: 0.04 cfs VOL: 0.02 Ac-ft TIME: 480 min BASIN ID: 100b SBUH METHODOLOGY TOTAL AREA... ....: RAINFALL TyPE....: PRECIPITATION. . . . : TIME INTERVAL....: NAME: 100yr post - runoff (lOO'dwy) 0.04 Acres TYPE1A 3.50 inches 10.00 min BASEFLOWS: AREA. . : CN.... : TC.... : 0.00 cfs PERV 0.01 Acres 86.00 9.92 min IMP 0.04 Acres 89.00 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 100.00 ns:0.1500 p2yr: 1.50 s:0.0500 impTcReach - Sheet L: 100.00 ns:0.0110 p2yr: 1.50 s:0.0500 PEAK RATE: 0.02 cfs VOL: 0.01 Ac-ft TIME: 480 min BASIN ID: 100c SBUH METHODOLOGY TOTAL AREA.......: RAINFALL TYPE. . . . : PRECIPITATION. . . . : TIME INTERVAL....: NAME: 100yr - roof/cone (1500sf) 0.03 Acres TYPE1A 3.50 inches 10.00 min BASEFLOWS: AREA. . : CN. . . . : TC.... : 0.00 cfs PERV 0.00 Acres 86.00 5.00 min IMP 0.03 Acres 98.00 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 200.00 ns:0.1500 p2yr: 1.50 s:0.0500 impTcReach - Sheet L: 200.00 ns:0.0110 p2yr: 1.50 s:0.0500 PEAK RATE: 0.03 cfs VOL: 0.01 Ac-ft TIME: 480 min 5' U M1 vyta I-'VJ Dnve~ =? C).OLC{'S 1/0-0 !f/1ea./ ~+ f2uor; leo-nc. =t 0.0"3 c.fs I / SO 0 sf !!~.:~Y"~ ~. [[~fW~'n~"Ji:~:~'.'..' 1,1) J l---~'~'-~~'~'" I' I ;,,<, I : II \ Ii' ,ll U, SEP = 7 2004 11 ) I I . '"c.,_" I J i ! L._-~._~__~.~-l r , JfYFEf1S0N COUN"IY LDEPT OF COMMUNITY D[VELOfJMEN~ Sizes of 24-hour design storms for selected locations in the Puget Sound Basin Rainfall in inches LOCATION 6 Month 2 Year 10 Year 25 Year 100 Year Event Event Event Event Event Port Angeles 1.34 2.10 3.25 3.75 4.60 Sequim 0.99 1.55 2.45 2.95 3.25 Forks 3.19 5.00 7.00 10.00 11.00 Port Townsend 0.70 1.10 1.75 2.00 2.40 Port Hadlock 0.89 1.40 2.20 2.60 3.00 Port Ludlow 1.00 1.50 2.20 3.00 3.50 Source: NOAA Precipitation Atlas (Received @ NTI on 4/13/93) F:\Document Prep\24 hour rainfall in inches.wpd .__.....-..........,.,..-~"'---~-".....=-.==.--~-=~~."~=='~~"'--...1 r~1 r...7~-- =l~' .(F':.. r.~ 1.1 \V7 rr~ r~r~.\\ 1 .~ !_~-!; L~.l __j l.J tL . ~ \ i l)" r-~'--~~~.~~.~-~llll I ['II I \' J J \, i.\ll SEP.. .'.~'...7. 2.-".0.0.4 I L!j lJ Ll ~.~- L-J'EFfEf1-sorTco'uN"lY I DEPT or COMMur~.l"rj'Y~2~~~~!.~_~~~ DATA rot<. FLQAJ G CAJeidA 7/0AJ s 1).1 U Ut T ION S I] D ~/()-Cwt\ y eN -= 'i?~ GRAvEL~) ()t\u {S r Wf DC:; (N~ 8& Gl?.~S;: S'-I\OU LOI":: 1'2 S" C))(oG /0 0 Y R r<..P'J t fi.) ~ s, <:; / A.J I :L yl~ RAt Ai::::. /, ~ / N S I M \A lA,T/U".J LE:-AJeoff 1000. - 200' ~ too b - (GO'-==t 0.. 00Cf fie D~/;)EC/J/I')' O,OIl -Ac. Sl-+OuLOEI~ o 0"3 SAC Dr2/UEcvf\ Y ) o. OOCZ 1\ C :; H OctL-D [;r2 SH~b-T FLcJw E2 S % OD GRA-~s; OR S H(} 0 Tt-{ Nt IJ T7 f1G Of- 0!JIVC2"A./TI2A-TrOAJ -= S; H oj pE:A. sorrw/'cRG sSUH )/.hULATIO~ ' 7YPE lA SrOi<-H ) 2) RODF / CO'A) G eN = 9f? ROUP"& C0NC 'PA v E \' CJ () YR f2A OJ - 3,S; /.x...J) 2- '-fT<. l2Ar -'J - LI C;;; / k) S';fptU/Jt--t;u;..J Me::A::: ISQOsF- O,O?SAC MIU rrMG: Of- (O,vctMTN.j,-t/o/J -- J;;' H/J-..J Pc'(( SOr-:-rcJA~6 rr.'~-'[E~'~-'~~]-\\lrr[~:s II, rr?~ l~---. --~~-"-'~"""'--~---ll.ll.i ! Ii 'I - ", I J; III t\ S t: p", I 2004 ! l<~,:') I I \ : ii, "(_~iTT;,t~~:~i;~(~?l~}~~UOi~;"':.. ~ S T R I DATE: _J DESIGNED BY: PROJECT: FOR: ~ SH~ OF ~ NT' NORTHWESTERN TERRITORIES, INC. a JLS Group Company Engineers' Land Surveyors' Geologists' Materials Testing 717 SOUTH PEABODY. PORT ANGELES, WASHINGTON 98362. (360) 452.8491 www.nti4u.cominfo@nti4u.com STORHWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN " Table III-1.3 SCS Western Washington Runoff Curve Numbers (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour storm duration. LAND USE DESCRIPTION Cultivated land(l): Mountain open areas: Meadow or pasture: Wood or forest land: Wood or forest land: Orchard: .winter condition CURVE NUMBERS BY HYDROLOGIC SOIL GROUP A B C D 86 91 94 95 74 82 89 92 65 78 85 89 42 64 76 81 55 72 81 86 81 88 92 94 low growing brush & grasslands undisturbed young second growth or brush with cover crop Open spaces, lawns, parks, golf courses, landscaping. Good condition: Fair condition: Gravel roads & parking lots: Dirt roads & parkinq lots: cemeteries, grass cover on c75% of the area grass cover on 50-75% of the area 68 80 86 90 77 85 90 92 76 85 89 91 72 98 82 98 87 89 98 Impervious surfaces, pavement, roofs etc. 100 100 , Open water bodies: Single family residential(2): Dwelling UnitjGross Acre 1.0 DUjGA 1. 5 DUjGA 2.0 DUjGA 2.5 DUjGA 3.0 DUjGA 3.5 DUjGA 4.0 DUjGA 4.5 DUjGA 5.0 DUjGA 5.5 DUjGA 6.0 DUjGA 6.5 DUjGA 7.0 DUjGA PUD's, condos, apartments, commercial bus'inesses & industrial areas 98 . lakes, wetlands, ponds etc. 100 100 %Impervious(3) 15 20 25 30 34 38 42 46 48 50 52 54 56 Separate curve number shall be selected for pervious & impervious portions of the site or basin t~~'---~~ ~.'~'-~.=-"-~~'~-.~--~--<"-~.~., ,., ..-=,----~"....-~ ~._r."C_-.<_' i fF:\ [E ~ t~~ [I \V/ l IllJ ) r--'~~'-'----------~-~' ',I r~'> 1 I ,'! 11.1 tJI SEP ~ 7 2004 ! c'c~~;')~',;!Il~~'~SS'FTY r~~E!iT I ...........-... ...-n..-_.......___....Ch. .....__~___~ ~:"'~.>l Wil L I: L:J; % impervious must be computed (1 ) (2 ) (3 ) For a more detailed description of agricultural land use curve numbers refer to Na~ional Engineering Handbook, Sec. 4, Hydrology, Chapter 9, August 1972. Assumes roof and driveway runoff is directed into streetjstorm system. The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. ...... Irr-1-12 FEBRUARY, 1992 Agnew Ahl Aits Alderwood Arents, Alderwood Arents, Everett Ashoe BaldhiJ/ BameslOn Baumgarc; Beausite Belfast Bellingham Bellingham variant Boistfon Bow Briscot Buckley Bunker Cagey Carlsborg Casey Cassolary Cathcart Centralia Chehalis Chesaw Cinebar Clallalll Clayton Coastal beaches Colter Custer Custer, Drained Dabob Delphi Dick Dimal Dupont Earlmont Edgewick Eld Elwell Esquatzel E verelt Everson Galvin Getchell Giles Godfrey Greenwater Grove Harstine Hannit Hoh August 2001 Hoko Hoodsport Hoogdal Hoypus Huel lndianola Jonas Jumpe Kalaloch Kapowsin Katula Kilchis Kitsap Klaus Klone Lates Lebam Lummi Lynnwood Lystair Mal Manley Mashel Maytown McKenna McMurray Melbourne Menzel Mixed Alluvial Molson Mukilteo Naff Nargar National Neilton Newberg Nisqually Nooksack Nonna Ogarty Olete Olomount Olympic Orcas Oridia Orting Oso Ovall Pastik Pheeney Phelan Pilchuck Potchub Poulsbo Prather i-:;=:~~'~:-~fO"~:;:';'-""-" ""~""-' I r' I~ fr~: WI U:: ,,' ~ 1-' -~ :::..~. '; .,~ . 'I t fl [I Gr:J:J(l(lI! -l _., i , L., [ _'._ _ __j~~',',_r<:.~.:'i _" ,~, Volume 1/1 - Hydrologic Analysis and Flow Control BMPsLl!~!:~~).i,:'.CJ.'."2~19 ~_;.~. s no iTld\('~. 'I'll(' soilltold:'l 10 or Illore iudll'S of \mtl~r available for plant.e;. 1(lInoff is slow, :llId t1\(~ hnzard of watl'r ('I'osioll ,light.. A s('aSlJlI:d \\,a(N fable is :d. a d(~pth of I to 2 feet.. ,bout fiO to 70 r)(~ITc'.nt. of (.Ill: a<T('a~(~ is us(:d for crops. .-,(sture, Itay, and sil:tl!:c~ frolll lllixcd grasses alld Iegum"/i are t.he principal ('I"ol's. A varil'!.y (,f gard('1I vq!,"elahl(~s, berri('s, alld tl'(~(' frui!., filay 1)(' grown. Capahility unit. JIl\\'-l; \\"()od- lalld group :1d2. Ag;.cw !:-lilt loalll, :W 10 ~O perecnt slop.~!:< (AgE),.u This soil iR mailllv along oce:Ul bluffs or canyon sidemdls. Tile subsoil in lll'allY plae(~s eOlltains strata of silt.y day loam, filiI' sandy loam, silty day, and sandy day loam. H.\lllofT is ra pid. :lnd t.lll) hazard {,f watcrl'rosioTl is severe. Most an~ls of this soil are wooded. When used for building sites, t.he soil oft.cn slides \\'h(,1I sa.turated. Capability unit VIe-1; woodland group :kJ2. Ahl Sel"ies The Ahl s"ries eonsiRts of wdl-draineu, very gravelly loam soils underlain bv basalt Iwdroek at. a depth of 24 to 40 inches. Tlwse soil:s are on mountainous terrain. Slopes range from fiO to 00 IlC'reenL Elevat.ion ranges from 800 to about :~,OOO f(~et. These /ioils formed ill \\'eut.hercd basalt under a. dominantly conifcrow-; forest of Douglas-fir, wcstern hemlock, and wcstem redeednr. Allnual precipitation is 60 to 80 inches. The llV('r:ll(e annual air temrwraturc is about 4H"P. The above :~2"J'; groll'illg; Si~asnn ranges from 150 to HIO days. and t.lw above ~soF ~rowing season ranges from ISO to 2:m days. These soils aTe associated mainly with Grove. Lystair, Ol~~tc, and Tritun soils. In a r(~presclltativ(: profile a thin layer of organic litter 1~(WCl'f; the smfnee. The upper :3 inches of the soil is dark fish-browll vcry gravelly loam. Below this, to a depth of IJdles is V(~ry grave II V loam that is dark red in tile upper i)m.t and 'I'lxldisll Grown III t.he lower purt. Beneath this, and extending to a depth of :i8 inehc~s, is mostly angular basalt pebble.s and fracture'd, \w~ather('d basalt. Bas-'llt bedrock is at a depth of 38 inches. A.hl soils are used mainly for tree pl'Oduct.ion and for wild- life habitat. and rccrentioll areas. Ahl \'(~ry gnl\'elly loam, 50 lo 70 percent slopes (AhF).-This very steep soil is in the mOllntains. . Repres('lItative profile in SE3-'4NW;;,{SE~i sec. 34, T. 27 N., It. 2 \V.. 1.2 mill~S south of U.s. Highway 101 along i\Jt. Walker ]load, 15 feet cast of road. 01-3 inches to I inch, needles, leaves, t.wigs, bark, moss, and fmg- ments of wood. 02-[ inl"h to 0, df'c"Jmpnsing organic lil.t{>r. B2Iir-.0 to ;: inchf'S, dark reddish-hrown (iiYR ;3/-1.1 very gravelly loam reddish brown (2.ii Y It 5/-1) dry; weak, fine and very fUlIJ, 'graulll:ir strudllre; soft;, ,'cry friable, slightly sticky, pln.stie, stne,uT; many line, medium, and large roots; 55 per- cent a1\glllar I n':'a I t pebbl<'>l; medium acid; c1w.Lr, wavy bound- nry. (2 to Ii ilH:hc., thicki B22iru -:1 10 20 inches, dark-red (:2.iiYR :ljl;.l VCI'y gravelly loam, reddish hrown (2.fiY[t 51-I) dry; weak, tine, I!;ranular anet suh- nngular hlocky sl rtlelme; soft, very f riahle, slightly sticky. plastic, slIwar}'; nUlIlY tille, nH.'diUI11, IInd lurge roots; !i!i per- ,'en!. lIngular b'L~alt, pebblf'S 1\nd 5 percent rounded pebbles; medium aeid; gradual, wavy houndary. (10 to IS illehcs !.hick) B3..-20 t.o:lO indH~~, rc.'ddi~h-hl'Owll (5Ylt 4/4) very gravellj' [oalll, light reddish hrowll (5 \'H 6/4) dry; massive; soft., friable, nOllsLi,~ky, 1I(H1pJ,L~t.iC, smeary; common tine rooLs; 70 percent angular hn0al[, pebbles; slightly acid; gradual, wavy boulldary. (8 to 12 illche.~ thick) . C---30 to ;Jf; inehe.~, ~lO percent. fmeLun.,,1 bnsalt. hedroek. j\falcnal in voids is reddish-hrown (5YE -1/4) very graveUy loam, light .'lOlL flllHVIGY reddiHh bro\\'1I (!i \' H till) dl')'; 1l\II><.s;ve; Hli/l;hlly IIcid; /l;l'IIdllnl, .wa.vy. 1)(1l1l1:j,~.'"y. (I to .I.~ inehe,:; I.hie") l1-n.1K IlldH~, b"".1I I, I ll'd 1Il<. "- Dept.h t.o ImolalL bedrock ran!,;,,,, fr'lIIl 2.1 [0 .(() inc.he,". The Bir horizollol are very grllvelly loalll "I' vcrI' ).(l'ILvcll~' Hilt. 1ll/L1n, The C horiwll iH more illllll SO ,;,'rcenL fl'll<:l.'l\:,'d hasalt: hcdl'llck. Tncluded with t.hi::; soil in mapping al'(, small awns of Roek outerop and of Triton soils. This soil is well dmincd. Pel'llwabilit.v is modcmte. Roots p(met.mte to the lwdnwk. This soil !r(;lds 2 to 4 illdlelJ of water a.vailable for planLe;. H Ilnolf is vI:ry rapid, mid t.he hazard of erosion is vel'Y sl'ven~. This soil is IIscd m:tin'ly for trc'c prodlldion and for wildlife habita.t and recreatiull an:as. Capabilit.y unit VIIe-1; wood- land group :~d2. Ahl-Rock ollterop cOlnplex, 50 to <)0 percent slopes (AkF).-This mapping: unit is made tip of about. 50 to 70 percent Ahl very gravelly loam. It. is :30 to 50 pereent Rock outcrop and stony areas. The AIlI soil is 2.1 t.o 30 inches deep in most places. Almost all the acreage of the mmplex is used for tree production and for wildlife habitat and recrc.at.ion areJ\s. Capability unit VIIs-I; wocxllRnd group 4x2. Alderwo(){l Series The AJdenHlod Reri{~s consistR of modera.tely w,,11 drained soils that. have a very sl()\\']y pernH'<lhl(~ cemented layer at a depth of 20 to 40 inches. Slopes r:wge from 0 to 50 percent. Elevation ranges from 100 to 800 fed. These soils formed in glacial till under a forest of mixed eoniferouE and broad- leaNed vegetation. Annual pre('ipiblt.ion ranges from 25 to 50 indH~'3. Tho average annual air temperature is abont 49"F. The above 32010' growing season ranges from 160 to 260 days, and t.h(' above 2S"F growing season ranges from 220 to 320 davs. These soils are assodatcd mainly with Beausitc, Case);, Clallam, Dick, Everett, Hoypus, In{iianoh, Sinclair, and Whidb(~y soils. In a repr{'.scnt~tt.i \'0 profile a thin layer of organic litter covers the surface. The top 1 iuth of the soil is very dark grayish-brown gravdly fino sandy loam. Below this, to a dept.h of 12 inell(~S. is dark Yl'llowish-brown gravelly sandy loam. Benc.ath this layer, and continuing to a. depth of 30 inches, is gravelly :Jandy loam th:tt is brown in the upper part and dark grayish hrO\HI and prominently mottled in the lower part. The next layer is a dark gmyish-brown cemented la.yer t.hat formed in very compact glacial till. Rounded pebbles, cobblestones, ancl stones arc on the surface and throughout the profile. Alderwood soils are used mainly for tree production and for wildlife habita I. and reereatio!l :lrC.fJ.S. u'ss than 30 percent of the acreage is used for growing pasture plnnts, hay plants, and diversified farm crops. :'\Jdcrwood gravelly salHI)' loam, 0 to L5 pel"cenl slopes (AIC)..--This nearly level t.o rolling soil is on glacial terraces. In most places t.he stope is 5 to 10 percent.. Reprcscubttivc profile 100 yards \\"(:st of house, southwest side of Beausite Lake; SE!iNE};{SEy.{ sec. 28, '1'. 29 N., R.I W.: 01-1~~ inches to .1.;1 inch, needles, leaves, bark, and frugment.~ of wood. 02-!..~ inch to 0, hlack (!iYlt 2,11) part.ly deell.ycd leave;;, uecdle.~, bark. and fr'lgmenL~ of w"r,d; !l1c."lium acid; abrupt, wavy boundary. CY:i I") I !.-:! inch('_~ thick) r A2--0 t.o I inch, very dark Rrayi"!..bro,,,u (10' II 3/2) grav:-lIy line >landy 10al1l, pale brown nU:l{tur}Jd,t~..;",:cl+k;'yefrJlO~;:;' Ii) ,Ji~,. lI,,; u~: U Wi E:: I' ./ I fr'I"I! I, t} i u \.\1 )M'__~_..'_.'''''' "1 I i I ! ! i i i l -_._~---.A .1rFF,~n~:(]k (~{':i jU"J-Y "i ! 'DOli ,mIW1W~ON COHN'I'Y J\lmA, WM;fllNn'I'ON gr:llIlIl:tr sl.rlldllre; ~(Ifl., very friable, lIollsticky !Lnd IIlIn- pla.'li(~; 11I:l11.\' fino alld IlIedilllll rnol.~; :!:, pcrc~('.1\1. pohhlt,.~; lI\t'dilllll ,,,,id; dear, XIIIIIOth IHllllHlarr. (!'; 10 II.~ illche:J Ihide) 112Ii""1I I 10 Ii ill(.it<,., dad, ydlowixit.llI:own-(IOYlt -trt) ~I'll\'ol\y xlllldy 10/lnl, (lal,' hrowlI (ItlYll.li/:ll drr; weak, fillo, p;ranullll' ~tl'l"'(.IIf1'; slightly hard, friahle, ..lifdlf.ly Htieky /lnd slighlly plllxtic; lIlallY tine '''HI nll"lilllll rool.~; COllllllon hard iron- Illllng;:llll"''' r'OI"~r,,1 i'\II~; .10 per<.'olll. gravel; medillm Hcid; gr:ldll:d, \I'IlVY (Jollndar.\'. U lo (i inehCH thick) 1122irollu'-ll t., 12 illdles. dllrk yellowi.'ih-hrown (IOY It 4i4) I!;mvelly ~andy Inam, Pille brown (11IYlt li;:l) dry; weak, fine, slIbangll- IIlr blo"ky slntdllre; t<lighlly IHtr.-l, friable, Hlightly stieky alld sli~hll.\' pl,c'ili...; ""'n)' line IllHl nwdillm reinl:;: commOn hard irlln-lllHlIg:lII(~~e (~lIn"ret.ionH; .W percent pehbles; slightly aeid; dellI', wavy l.lfHIIHbry. (5 to 7 in"hos (.hick) In ..12 III 21 ill(~h<,:<, brown (IOYlt 'l/:!) ~mvcll.\' sandy luam, Pltle 1"'OWll (IOYH. Ii!:!) dry; lVeak, linc, slIbanJ!;lIlar blocky st.rllc- I.lll'('; slighlly hard, friable, Hlip;htl.\, sticky, slig;hlly plnstie; Illany fille :llHIIIH'd illm I'on!.~; 45 pereent grnvel; ;;lightly acid; ('Ielll'. slTloolh hOllll(hry. (li (.0 12 indies thick) CI.~J 1.0 :\0 incl,,~., dark grayi"h-brown (LIIYH. ,1/2) gmvelly ::and)' loam, li/{ht gm.v (IOYll. 7/2) dry; many medium, p,,,..ni- 111m I., yellowish-red (.'; Y H 4/U) TlIol.lle;;; massive; hard, firm, ~Iighfly sl i"ky, slightly plast.ic; few line find medium 1'00t.~; .\.~ perr'.en(. gmvel; medilllll aeid; gradual, wuvy bouudrrry. (-I 10 III indIP_~ Ihil:k) C:!Si[Il--~;1O (.0 48 illches, d,u'k grayish-brown (IOYR .i/2) weakly ('l~lllellf.ed ~l'avclly sandy Inrrm, lip;ht. gruy (lOYlt 7/2) dl')'; 'llall.\' ('oars", prolllilH'nt" yellowish-red (5YR 4fG) mol.He;;; 1I1:L"...ive; extn~rncly hard, extremely finn; no 1'001:;; slighl.!y 'lO'id. (HIt" IX iuehc,.; thick) C:l.-..IX in!:h".':, very compact gravelly sandy loam glacial t.iIl. (;'.Inn)' feet tbiel() The depth In (.he cemented layer ranj!;e.~ from 20 to .W inches. Tlw A:! :md B:liren horizons nllll!;e from velT dark gnwish brown I" dark yellowish browll. Their c<ml.ent of '~(;arse fragments ranges frolll 20 t.) :j\) percent. and avel'll.gc,; marc than ;Ii) percent,. In p1ne(,1~ ihe lippeI' parI of t.he CI horiuHl is eompaet gra\'eHy loamy fmud. Few tn fn:lny hard iron-mangane.>e L'Ollcretions arc in the A2, B2il'en, '\llll B22irc:n horizolls. Small :u'cas of sandy, vcry gravelly, or eobbly soils are induded \\'it.1l lhis ::;oil ill mapping. . This soil i,; mod(~ratelv well drained. I\~l'meability above the c:enwlltcd layer is moderately rapid. Roots pctll~trate to th(.~ l'(,lllcntcd layer and flatten out 011 top of it. A pcrched water table is above the cemented layer during the winter months. This soil holds 2 to 4 inches of water available for plant.<;. Runoff is slow to medium, and the hazard of water erosion is sli~ht tD moderate. This soil is used for permanent past.ure of mixed grasses and legul\ws. Both hay and silage are commonly produced. Small grains, vegdablcs, berrie.s, and fruit trees are also grown. Capability unit IVe-l; woodland group 3d2. Aldcrwood gravelly sandy IOllJu, 15 to 30 percent slopes (AID).--.This moderately steep soil is in places where the rolling glacial upland terraces converge toward raviup.s and ..,tccp dminageways. RUllOff is medium to rapid, and thc hazard of water ('rosion is ll1olkrat.c to R(:vcre. This soil is used mainl\' for t.l'<_'C produd.il.ln and for wildlife habitat and recreat.ion :;reI13. rt is also :mited to permanent hay and pasture erops. Capa- bility unit V [e-l; woodland group 3d2. Alderwood gravclly sandy loan1, 30 to 50 percent slopes (AIE)..--This :;tC(:p soil is on glaciated upland.." generally in slllall an'IiS along Rteop morainal margins or mllyon sidewalls. On t.he upper third of the KlopeR, the surface bver and subsoil are often 20 to 2,-1 inches thick over the c~nwnkd layer. Alon?; the bottom slopes, dept.h to the eenwnled I:wer is :W t.o 4.0 inches. Jncluckd wit.it t.his soil in mapping :tre small areas of Aldcr\\'ood gravelly sandy loam ilnd Alderwood gravelly D loalll, LS (n :\0 p(~rccllt slop(\,;, as wdl fi:-; slllall ILrC:lS of Jt:vcn~t(., Illdiallola, lIoypus, Nillelll.i1', and Whidbcy soils, 15 f.o :\0 percl'lll. slop(,,;. Itulloff is rapid, !llld Ul(~ har,iLl'd of \\'al,el' (~roKi()n iK scvc('(~. Thii:' soil is us(~d for tn'l) pl'Odudioll alld for wildlife' habif.at and ('('l'['catiol\ :tr('~I.<;. Capability unit VJc-l; \\.ooelland gl'lHlp :-ld2. Alden~o()(l gravelly IOUlll, 0 lo 15 percenl slopes (AmC)...-This ncarly Icvd to rolling; soil is 011 glacial (.('rrace'..,. The surfacc bYl~r alld subsoil are gra.velly loam. Ineluckd with t.his soil in mapping are small traets having shain or sandstonn at a d(~pl.h of 20 Lo 3G inelle'S. P,,-rmcabilit.y is IlIod(~ra.t.e. ThiR soil holds :{ t.o G inches of waLcr available for plants. This soil is use'c! mainly for tree production and for wildlife habi t.at a.nd rccreation awas. Capability unit I Ve-l; \\'ood- land group ~~d:2. Alrlel'wo(ul gravell..,. IOatll, 15 to 30 percellt slopes (AmD)..-This lIloderatdy steep soil is in area..,; where the rolling upla.nd glacia.l terraces converge with the steep drainagmvay ravines. TIH) surf:tce layer and subsoil are gravelly loam, This soil holds :3 to G inches of wat.C'r available for plant.':;. Pcrmeability is moderate. llulloff is medium to rapid, and the hazard of (~rosjoll is moderate t.o s(~v('.re. This soil is used mainly for tree produd.ion and for wildlife habitat and reercation areas. Capabilit.y unit VIe-I; woodland group 3d2. Alderwood-Quilecnc ('omplcx, () t.o 15 percell l slopes (AuC).--.This nmppill~ unit is made tip of about GO percent Alderwood gravdly sandy loam, 0 to 15 percent slopes, and about ~30 pe)'(~cnt, Qnileellesilt, loam, 0 to 15 perccnt slopes. The mostly rolling Alderwood soil is on glacia.l moraines. The nearly level to strongly sloping Quilcene soil is mostly in arC:1S adjacent. to the moraines. About 10 percent of t.he acreage is Everett, Hoypus, a11<l Indianola soils. lIto:-;t of this acreage is wooded. A small acreage has beell cleared and planted to pasture. Capability unit IVe~l; woodland group :3d2. Beausite Series The Hl'ausite series l:onsists of well-drained soils underlain by strongly cemented s:mdstone conglomerate at. a depth of 20 to 3G inches. They arc on the sich" of valleys, mostly south :lIld southeast of Discovery Bay in the northeastern part of Jefferson Count.y. Slopes range from 0 to 50 percent. Elevat.ion mngeH from 50 to 1,500 feet. These soils formed under a dominantly coniferous forest. in weat.hered con- glomerat.e consisting of mixed acid n,nd baslc roekH. Annual precipit.ation ranges from :m to '10 inches. The l1vemge annual air temperature is about 500F. The above :no1" growing season range's from about 220 to 250 da.ys. and the a.bove lSDI<' growing sea.'''HlIl ranges from about, 270 (0 300 d:tys. The.se soils arc as:-;oeiakd mainly wit.h Alderwood, Everett., lndia.nola, Quilc('[w, and Sinclair soils. III a representative profile a thin layer of organie litter eov(~rs the surface. The upper 22 inches of t.he soil is gravelly sandy loam that is dark brown in t.he upper part and dark ydlowish brown in the lowC'r part. Below this, t.o a depth of ;n in(~hesJ is brown and grayish-browll very gravelly sandy loam. lkneath.this layer i::; stroll!!;ly ('('men led, very gravelly mUldst.011C (,ollgl()l11(~rate. ..~...--"". .............,..,... ...-........".... .... ....-. .__._~.._...,..~.".l BculIsite soils arc lIsud nht.iXly filL tif~.c nt.(ld~lct..l9(1 :IT.J;d I'0t.\ 'Idl" I b' 1 .." 'I J' I", '. ,I \'" " 1'i; \ WI lie la rlat. llIH recreation ~~re,r& ','., ,," ",',' ;.,::, I' \ II ! i ~:::;-:! "'''-1111 i : I. !! \ ~ !.; I,,!, "I ,1 t. ! -~! -, : I j .j I I j ;.,j'; t 1 L.! 1 L.~~,1 I i \ i ", ."..~~ i, JE~:f.En~Ul,: C:nUNTY I [\C-T~T OF cn~/:[,,~~__n\LrY UFVELOFf,~~ttr!- ; (i.[ HOIL SUHVEY TAIl['I'; S.---!j'stiJllaletl soi! /Im/i-' i.l" Ilslt~r'isk ill the first eoll1l11n indicat."s t.hat. lIt b~<;t OIl(' mllpping nnit in that serics is made lip of two or II10re killds of soil. Th(, soils ill slIl.I, other s"nes that ILppclLrin the first colllll1n of this ta"I". ,\"SI:IICe of dala illdical('" II,aL Dcpth t.o- 13cdl'Ock I Scasonal high water tablc I Dcpth from surfacc of t.ypical prolile 1 Chl.<;sificalion Ullified AM.;r 10 Coarsc f rnet.i(Jl1 greaicr Ihall :l illehes Soil serics alld map symbols USDA tcxturc Inches Feet Inches Percent ..\gncw: AgB, AgE,uuhu,u"u >60 1-2 0-9 Silt loam n n. n.. __ U l'vfL 01' CL 1\-'1 9-52 Silty clay loamn__uu CL A-7 52-60 Gravclly silty clay CL A-7 - - - - - - - - -- loam. '..\hl: AhF, AkFn'h.n_uuuu. 24-40 >5 0-30 Very gravclly loam_h' GI\f, SI\f A-I or 1\-2 0-20 Rock outcrop part of AkF too 30 Basalt. variablc for valid estimatcs. . .-\ldcrll'ood: AIC, AID, AlE, AuCuuuuuu >60 22-3 0-30 Gravelly sandy loam___ S:\1 A.1 01' .-\.2 10-25 For Quilrcnc part of AuC, 30-48 'Vcakly cemcntcd and GI\for S\f A-lor A-2 0-25 sec Quilccnc scrics. vcry compact gravel- ly sandy loam, AmC, AmD.n__uu'hun.u glacial till. >60 22-3 0--33 Gravclly loamnn___.. GM A-4 0-20 33-45 Weakly cemented and G:\1 or 8:\1 A-2 or A.l 0-25 very compact gravel- ly loam, glacial till. *Beausite: BaD, 8aE, BdD, BdE, BeE__.._ 20-36 >5 0-33 Gravelly sandy loam 8M A-lor A-2 25-35 For Alderll'ood part of BdD, and very gravelly sec Alderwood series, unit sandy loam. AIC. For Alderwood part of 33 Sandstone con- BdE, see Alderwood scries, glomerate. unit AlE. Rock outcrop part of BeE too variable for valid estimates. Bclfast: Bf_.._.._.._.....___._..___.. >60 3 >5 0-60 Stratified sandy loam, SM or j\1L A.4 0-20 sandy loam, and loam with sand, pebbles, and cobbles. ML Bg..._......__.._._._._.._... >60 3 >5 0-60 Stratificd silt loam, A-4 100 fine sandy loam, and loam. Bh..........___.___._.._._... >60 32-4 (}-GO Stratified silt loam and Iv1L or CL A-4 or A-6 100 silty clay loam. i'I'1L or CL Bk_..........._....._._...._. >60 3 Yz-l 0-60 Stratified silt loam, A.4 or A-6 100 fine sandy loam, loam and clay loam. Bm.. __u.. 'U__'n_'_hn'h >60 3 Yz-l 0-20 Silty clay loam and CL A-6 0 sandy clay loam. SM or ML 20-60 Stratified silt loam, A.4 0 finc sandy loam, and clay loam. *Calawah: CGB, CND, CVBuuu. >60 2-3 0-40 Silt loam and silty clay [\1L or CL .-\.4 or 1\.6 0 For Snahopish part of eND, loam. scc Snahopish scries, unit Heavy silty clay loam CL A-7 0 SPD. For Tcalwhit part of 40--60 CVB, sec Tcalwhit scrics, and silty clay. unit TEB. Carlsborg: CaC, CaD"__hu,,,,, >60 >5 0-60 Gravclly loamy sandn_ 8Ivf A.l or :\.2 0-10 Casey: SiI[ I " CdB................_._._._... >60 1-2 0-17 Fine sandy loam. _.... 17-60 Clay (with thin layer CH -" ~;-T--~.\-l.~/ -~ -:E .=-~-;-.~~;,:_.L_ of loamy line sand). !i '<i I., I'"' \ I H ~~} iL.l \ f . -." II i j I ~. ;J lUll L,~.J I I ~-~'FF' ) ,<\P I ut- I .-.-- ._-_._---~.._~._-_._.-. --~.-. .._-~~.--"=~- I JIWFlmSON COUN'l'Y AHI~A, WASIllNGl'ON (i;') crties si!/mjicant in en!lincr:rin!l nlnppini; units may Illlv(, different properties nnd limitntiolls, and for this reHson it is Il(~ecssnry to folio\\' clln.fldly the instrlldions to!' rderrini; [0 ;he soil is too variablc 01' thnt no estimate was lllade. > means more than; <, less tlmn] -_._--------~--~------------------ Pcrccn(Ui;e plLHsinJ,: sieve~' No.4 No. 10 No. 40 No. 200 (4.7 mm) (2.0 mm) (0.42 mm) (0.074 mill) PCl'IllCa- bility Availuble wuter capueity Reuetion Shrillk. swell paten tinl Corrosivity tn- Uncoated st.eel Concret.e Fro,;t- aelion potential 11lches per Inches per inch huur of 80il pll 100 100 90-100 70-80 0.li-2.0 0.16-0.18 5.6-6.5 Low or Iligh__..... I\Ioderate. .. Slight. moderate. 100 lOa 90-100 80-90 0.2-0.6 O. 18-0.20 6.1-6.5 Modemte.... . High.__.... Low. 80-90 75-85 70.-80 liO-70 0.2-0.6 0.15-0.17 6.6-7.3 Modemte.... . High....... Low. 40-60 30-40 20-35 15-25 0.6-2.0 0.08-0.10 5.6-6.5 Low _ _ .. __ .. . I\-Ioderate.. _ Moderate .. None. 60-70 55-65 25-35 20-30 2.0-6.0 0.07-0.09 5.6-6.5 Low. . ... . . . . :\[odcmte.. . Moderate.. . Slight. 40-70 35-65 20-45 10-30 <0.06 ------------ ---------- Low. . . . . .. . . Moderate.. . ;\Ioderate. 60-70 55-65 45-55 35-45 0.6-2.0 0.12-0.14 - 6.1-6.5 Low... u ----I ]\[oderate.. . Low. . . . u . Slight. 40-70 35-65 30-55 20-35 <0.06 ------------ ---------- Low. . __ .. u . I\Iodemte___ Low. I 60-70 50-65 25-35 15-2;j 2.0-6.0 0.06-0.08 5.6-6.5 Low.. __.. u. l\Iodemte... I\Iodemtc. __ ::\ one. 80-100 70-100 65-80 35-65 0.6-2.0 0.12-0.14 5.6-6. 5 Low.. __ u... Moderate... Moderate.. . None. 100 100 70-8:j 50-80 0.6-2.0 0.15-0.17 5.6-6.5 Low _ _ _. .. . . . Moderate._. Low or ' None. , g5-100 gO-lOO 80-90 70-85 0.2-0.6 0,19-0.21 6.1-7.3 Low or Moderate... LO:~~~r~.t~~ I Slight. moderate. r~LI 100 90-100 60-75 50-70 0,2-0,6 0.18-0.20 6.1-7.3 Low or High....... Slight. moderat.e. 100 9.'HOO 8,j-90 55-85 0.2-0.6 0.17-0.19 6.1-7.3 Moderate. __.. High...... . Low. . . . . . . Sligh t. 100 95-100 70-85 45-65 0.6-2.0 0.14-0.16 6.1-7.3 Low _ _ _ . . '. _ . High.._____ Low. 100 100 95-100 80-95 0,2-0.6 0.17-0.20 4,5-5.0 Low or High.__..__ High..... --I Slight. moderate. I 100 100 95-100 85-95 0.06-0.2 o . 18-0 . 20 4.5-5.0 Moderate.... . High...____ High. 70-80 45-55 :~0-'1O 10-20 6,0-20.0 0.05-0.07 5,6-6.5 Low...______ Moderate__. i\Ioclerate__. None. 100 100 100 100 li5-80 !l0-100 :1:j-.'iO 80-85 o fl-2.0 <O,(JG O. ] 3-0. l;i 0.14-0.16 6 . 1-6 . 5 G.6-7,3 Low. . . _ . . . . ./ High".....u I P r ~---- :'f.r '-v' ~- -- - " Sl i' In-' ---: _" -! / Jg 1-._\. ~ r' ,16\.: i-' ,r i'\ i!: ['> r " h1l!:;lt".,.. J<-, ):lo\\'. ,;_. " I'!! 1,0"1 ! r \ \ I I;: i; ,- ~ . '~----=::._..,::~':' --~-""1 i I i I ,I _~;f_/ I 'I : I ! ' r"' , Ii I' ! !! ' 11 ! 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G 00 N l~ ~ 'is o o u 8. 10 ..s .~-;';'rEr-J'; ~ .---' Parcel Prinl Page I of 1 Parcel Number: 821085002 06/11/2004 Owner Mailing Address: TODD N COLEBROOK CYNTHIA F COLEBROOK 21 BARQUE LN PORT LUDLOW WA 983659729 Site Address: Section: Qtr Section: Township: Range: Planning area: Sub Division: Land Use Code: 8 SW1j4 28N lE Port Ludlow (7) PORT LUDLOW NO 6 9100 - VACANT LAND School District: Rre Dist: Tax Status: Tax Code: Chimacum (49) Port Ludlow (3) Taxable 231 Property Description: PORT LUDLOW NO 6 I LOT 2(REV)V9jPG40-41 8j17-28N-R1E I REVISION V13jP107 I I ... -- ----------------------.------ ; 0 No Photo Available ___I 1'7;:~'\< r~~f'.!T,j.~~ .qr~.!i\;7...I-E..~.:.;::~.-1 11 )! L~ l..~D II \~! ,to' 1 ['J\ \ I ;~~ ---..--.-.-....-~--.-...~" i I I' 11 ! I 'I ,.--., ......:~. /u U{ iitl'~. 7 ;>004 -L~I Ii . 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Q · .J . ;/ -. cf.o:ct ~ -0( -~ .~ o ~ otfUlH' XVd H:n f1RL vOOZl6ZILO APPENDIX 3 - Storm Water Manual BMPs for Erosion, Sediment Control & Drainage Dispersion ...-......_--"""' i (,""<'"'\ W." I! I'" \ \ : i r~ ", j I' ) I '" ~ : ',', I L. <' I I'! !" i' I" ' '[' , I \ \ . i ' 'I iI, ~ n ; I h . l I ,_ _ , I [l] Li.l .) '- ! !"~::;,",, i ! I i ~ . ~ ""^ "" ,,, . _ .1 ' I'. I,,' -(" "v I "'- L LI ".,,-,j~' '';<!. I ,r- ) r ( _ '\..... l . ~ T, r. ".," f ., r < I ~:.:~~r (.u~~~~:....: U\ ' 1.'.1) )MFr~ I , ~ 'r.~" _-~-_4__~~.~.~>~.._.u. aMP C103: High Visibility Plastic or Metal Fence Purpose Conditions of Use Design and Installation Specifications jl1aintemmce Standards .. 1.~~ ,- -- Fencing is intended to: (1) restrict clearing to approved limits; (2) prevent diShlrbance of sensitive areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and, (4) protect arcas where marking with survey tape may not provide adequate protection. To establish clearing limits, plastic or metal fence may be used: . At the boundary of sensitive areas. their buffers, and other areas required to be left uncleared. . As necessary to control vehicle access to and on the site. . High visibility plastic fence shall be composed ofa high-density polyethylene material and shall be at least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center (maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope soan be used as a top stringer to prevent sagging between posts. The fence color shall be high visibility orange. The fence tensile strength shall be 360 lbs.lft. using the ASTM 04595 testing method. . Metal fences shall be designed and installed according to the manufacturer's specifications. . Metal fences shall be at least 3 feet high and must be highly visible. . Fences shall not be wired or st<:lpled to trees. . If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. lK~~I~,(~,-ll-. ---lij IL Ll! '" !(1) i : ~~rj[~i,~2t?!;~y)'!'~ i{:}f'~~'" 4-6 Volume /I - Construction Storm water Pollution Prevention August 2001 BMP C105: Stabilized Construction Entrance Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by vel1icles or equipment by constructing a stabilized pad of quarry spalls at entrances to construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to detemline exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and installation Specifications . See Figure 4.2 for details. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: . Grab Tensile Strength (ASTM 04751) 200 psi min. Grab Tensile Elongation (ASTM 04632) 30% max. Mullen Burst Strength (ASTM 03786-80a) 400 psi min. AOS (ASTM 04751) 20-45 (U.S. standard sieve size) . Consider early instaIlation of the first lift of asphalt in area,> that wiU paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose. Hog fuel (wood-based mulch) may be substituted for or combined with quarry spalls in areas that wiIJ not be used for permanent roads. Hog fuel is generally less effective at stabilizing construction entrances and should be used only at sites where the amount of tratlic is very limited. Hog fuel is not recommended for entrance stabilization in urban areas. The effectiveness of hog fuel is highly variable and it generally requires more maintenance than qunny spalls. The inspector may at any time require the use of quarry spaBs if the hog fuel is not preventing sediment from being tracked onto pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in pcmlanenl roadbeds because organics in the subgrade soils cause degradation of the subgrade support over time. 1~~--~fi;-:<"~::-:;"<,::"'::]c'::::'~>~-::;::'1 Fencing (see BMPs Cl 03 and, Cl 04) shall be installed fr1\e9f1;s<<ty t~ 11 ~\'l tE fr'\'\ I restrict traffic to the constructIon entrance. I LJ~ r-~'-----"'''_P'''''~''lll i: i I Fj II ,I: i i i III III EFP. I il)! I "'L.~...n.u.. ',.. . . ( .. 4-8 Volume /I - Construction Slormwater Pollution Prevention DEPTAWgu~~'~QQ1~Y IfFf- r~ F-; ,:', (j [.1 '-' ~-1-Y ;~: LOrJ tv'i Er-\~-r / , /J.laintenallce Standards / .;, August 2001 · Whenever possible, the entrance shall be constructed on a fim1, compacted sub grade. This can substantiaHy increase the effectiveness of the pad and reduce the need for maintenance. · Quarry spaBs (or hog fuel) shall be added if the pad is no longer in accordance with the specifications. · If the entrance is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shaH be used. This may include street sweeping, an increase in the dimensions of the entrance, orthe installation ofa wheel wash. · Any sediment tbat is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when sweeping is ineffective and there is a threat to public safety. U'it is necessary to wash the streets, the construction of a small sump shall be considered. The sediment would then be washed into the sump where it can be controlled. · Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. · If vehicles are entering or exiting the site at points other tban the construction entrance(s), fencing (see BMPs CI03 and el04) shall be installed to control traffic. · Upon project completion and site stabilization, all construction accesses intended as pennanent access tor maintenance shaH be pennanently stabilized. Driveway shaN meellhe requirements of the pennitting agency It is recommended that the entrance be crowned so that runoff draIns off the pad )m- ~~~~-----~-~---._- ! [N' F r;",)C", n ,\., " "_ ..~ II [::,)) ~L~~.:~ !1 'IV} fE i r\ \ I J I r -~---'''''- I,. ~\ '---'11 i ;! , \ '~. I' " r "\ ' i Ii i i I .. ~ '1 - 'j I ..!"~~ U' l/l bi-q Ii.,;); '-\~'J UI <~. ".. ' 12" m1n.lhlckness ~ '<; "\ I L__._.__~ i !.~._.' Provldalull WkllhEiOl J[ "<'C ;-;'\, ;-.~, - -"" .__J 'ngroBsJogross ar :1 'Ll \...' d)lJ!J~ Y ~)FPT OF CO~,1i1 IN;';, f)fl,!ELOP;,F'-f' FI ure 4.2 - Stabilized Construction Entrance -'-.-.. , , GeotexUlo Volume 1/ - Construction Stormw8ter Pollution Proventlon 4-9 BMP C233: Silt Fence Purpose Conditions of Use Design and Installation Specifications '" Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. See Figure 4.20 for details on silt fence construction. · Silt fence may be used downslope of all disturbed areas. · Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow, Any concentrated flows must be conveyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be tre<lted solely by a silt fence, rather than by a sediment pond, is when the area draining to the fence is one acre or less and flow rates are less than 0.5 cfs. · Silt fences should not be constructed in streams or used in V-shaped ditches. They are not an adequate method of silt control for anything deeper than sheet or overland flow. Joints in filter fabric shall be splicEKi at posts. Use staples, wire rings or equivale~tlo attach fabric to posts 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used ~ If I I I I I I I I c 'E '" Riter fabric-- c 'E '" - .~,llfiiI " ,. ,. . I I I J I - "1 r.. - - -6;-;na; - - - .:i r'~---- - Minimum 4"x4" trench ./" , I I ,/ l' / L. /' ~8ackfill.trenSh with native sol / Post spacing may be increased or 3/4 -1.5 washed gravel to 8' if wire backing is used. / 2"x2" wood posts, steel fence posts, or equivalent Figure 4.20 - Silt Fence · Drainage area of I acre or less or in combination with sediment basin in a larger site. · Maximum slope steepness (normal (perpendicular) to fence line) I: l. · Maximum sheet or overland flow path length to the fence of 100 feet. . No flows greater than 0.5 cis. The geotextile used shall meet the 1ollowing standards. All geotextile properties listed below are minimum average roll values (i.c., the test result for any sampled roll in a lot shall meet or excee9:Jhe~y.~lu~s~::~,"'~"'-" . . bl. 4 0) ! i '''\\ Is f'J I,; if \\;7 shown III 1 a e . 1 : II L)~! L~, J.,J] u:~ U I.t ,!r\i I U [1.( i , I , i I. r)[T~_~C~~ 0'" ~~~! !0Cf~' . ~.l :- Jf I;~)tl i j '- j 1<<<<-" i -__.~__l t.,. ; .dY U.OPMENT August 2001 Volume II - Construction Slormwater Pollution Preven/lon !..~.. .~-~.1~1l[) /' 1 ~ .. 4-90 Polymeric Mesh AOS (ASTM 04751) i~~-~--~~~'"'- 11~.rll 7E-~"<-'W~n.~f~-:\\i/"ff,;~'~~:':'-: J i. ,j) r~- q, YJ l.r; I \ 1 ! ! /""':11 . '-'~~:~-~::::J I \ ! Geote:~~~eS~~dards i If u! s ~ ?iJ04')/ 0.60 Olm maximum for slit film wovenS (#30.sicve). o3()' , .- mm maximum for all other geotextilc types (#50 isiivtiJ:;n;:~', :';'".;,L:'..!.~\'~/!7.'.::Y-'-.J 0.15 mm minimum for all fabric types (#IOOsieveJ//;':C!i;Jr: ' . - .......... ":'- \,El OOt1""" 0.02 see-I minilnunl - o.~.~_':_-.:.- r y c!\; Water Permittivity (ASTM D4491) -- Grab Tensile Strength (ASTM D4632) 180 Ibs. Minimum tor cxtm strength fabric. 100 Ibs minimum for standard strength fabric. 30% maximum Grab Tensile Strength (ASTM 04632) --- Ultraviolet Resistance (ASTM 04355) 70% minimum . Standard strength fabrics shall be supported with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the fabric. Silt fence materials are available that have synthetic mesh backing attached. . Fitter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of OOF. to ] 20oF. . ] 00 percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if pelmitted by local regulations. . Standard Notes for construction plans and specifications follow. Refer to Figure 4.20 for standard silt fence details. The contractor shall install and maintain temporary silt fences at the locations shown in the Plans. The silt fences shall be constructed in the areas of clearing, grading, or drainage prior to starting those activities. A silt fence shall not be considered tempor3lY if the silt fence must function beyond the life of the contract. The silt fence shall prevent soil carried by runoff water from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. The minimum height of the top of silt fence shall be 2 feet and the maximum height shall be 2Y2 feet above the original ground surface. The geotextile shall be sewn together at the point of manufacture, or at an approved location as detennined by the Engineer, to form geotextilc lengths as required. All sewn seams shall be located at a support post. Altematively, two sections of silt fence cun be overlapped, provided the Contractor can demonstrate, to the satist~lction of the Engineer, that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. Volume /I - Construction Stormwater Pollution Prevention August 2001 '\ f' ~.. -.... .~ I~I [E ~[E U Wi [E ~I I!FII' ., )004 111! 1'" i \ The geotextile shall be attached on the up-slope side of the posts and support system with staples, wire, or in accordance with the '. i. manufacturer's recommendations. The geotextile shall be attached to the posts in a manner that reduces the potential for geotextile tearing at the staples, wire, or other connection device. Silt fence back-up support for the geotextile in the form of a wire or plastic mesh is dependent on the properties of the geotextile selected for use. Ifwire or plastic back-up mesh is used, the mesh shall be fastened securely to the up-slope of the posts with the gcotextile being up-slope of the mesh back-up support. The geotextile at the bottom of the fence shall be buried in a trench to a minimum depth of 4 inches below the ground surface. The trench shall be baclcfilled and the soil tamped in place over the buried pOltion of the geotextile, such that no flow can pass beneath the fence and scouring can not occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the trench a minimum of 3 inches. The fence posts shall be placed or driven a minimum of 18 inches. A minimum depth of 12 inches is allowed if topsoil or other soft subgrade soil is not present and a minimum depth of 18 inches cannot be reached. Fence post depths shall be increased by 6 inches ifthe fence is located on slopes of 3: I or steeper and the slope is perpendicular to the fence. Ifrequired post deptbs cannot be obtained, the posts shall be adequately secured by bracing or guying to prevent overturning of the fence due to sediment loading. Silt fences shall be located on contour as much as possible, except at the ends of the fence, where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. If the fence must cross contours, with the exception of the ends of the fence, gravel check dams placed perpendicular to the back of the fence shall be used to minimize concentrated flow and erosion along the back of the fence. The gravel check dams shalJ be approximately 1- foot deep at the back of the fence. It shalJ be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. The gravel check dams shall consist of crushed surfacing base course, gravel backfiH for walls, or shoulder ballast. The gravel check dams shall be located every 10 feet along the fence where the fence must cross contours. The slope of the fence line where contours must be crossed shall not be steeper than 3: 1. Wood, steel or equivalent posts shall be used. Wood posts shall havc minimum dimensions of 2 inches by 2 inches by 3 feet minimum length, and shall be free of defects such as knots, splits, or gouges. August 2001 4-91 Volume 1/ - Construction Slormwater Pollution Prevention _ ~_ i " ~r;;~ :1~lrl Steel post,> shall consist of either size No.6 rebar or IJrger)ASTMA ...... .. j' 120 steel pipe with a mini1l1um diameter of I-inch, UJ '[HL, ,Q1'JErsh~pe(;l)i;,';'TY ,_ -._ ... ;. 'Jr \,,-1 .':c..:'_,-" ',,_,;" ''- - steel posts with a minimum weight of 1.35 Ibs.lft. or 6t1fers-recfpost's;'~) .....~. having equivalent strength and bending resistance to the post sizes listed. The spacing of the support posts shall be a maximum of 6 feet. Fence back-up support, if used, shall consist of steel wire with a maximum mesh spacing of 2 inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to ultraviolet radiation as the geotextile it supports. . Silt fence installation using the slicing method specification details follow. Refer to Figure 4.21 for sl1cing method detalls. The base ofbotb end posts must be at least 2 to 4 inches above the top of the silt fence fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before installation. Install posts 3 to 4 feet apart in critical retention areas and 6 to 7 feet apart in standard applications. Install posts 24 inches deep on the downstream side of the silt fence, and as close as possible to the fabric, enabling posts to support the fabric from upstream water pressure. Install posts with the nipples facing away from the silt fence fabric. Attach the fabric to each post with three ties, all spaced within tbe top 8 inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each puncture at least I inch vertically apart. In addition, each tie should be positioned to hang on a post nipple when tightening to prevent sagging. Wrap approximately 6 inches of fabric around the end posts and secure with 3 ties. No more than 24 inches of a 36-inch fabric is allowed above ground level. The rope lock system must be used in all ditch check applications. The installation should be checked and corrected for any deviation before compaction. Use a flat-bladed shovel to tuck fabric deeper into the ground if necessary. Compaction is vitally important for effective results. Compact the soil immediately next to the silt fence fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. ,..-....... '~ 4.92 Volume /I - Construction Stormwater Pollution Prevention August 2001 Maintenance Standard,' '"" August 2001 ~(s~ ~7" 7: i@ ; I'''' ! · Any damage shall be repaired immediateIY'~~::;-:'~\1-crUNTyJ · [[concentrated flows are evident uphill of the fence, they must be " "'!f:L~~,~~'....J intercepted and conveyed to a sediment pond. · H is important to eheck the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. · Sediment deposits shall either be removed when the deposit reaches approximately one-third the height of the silt fence, or a second silt fence shall be installed. · If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced. ......dl... "-19M ........2.... POST SPACING: r taIIX.. .. ..... "'-II FLO_ ~ -.ax. .n ~ ...... ----.-:aFDt.Ic f 1~ ...--.. ~ 1oIfI. b'..... .tct. of p-est 1Ut..,.. *........ ea.c:h ...... ~ am ~ 2... "......~ ~'. with IIfhk..~ $Op..,.J......~ ~ 1oa-,...c-__p.1IIC1t~ POST DUTH. .... - - FO-.I .. ""rfc __ __ .,~ c........... ~.uac_ ~*-gIt\. ~ /): '<< ~ ~ 00~, ~~~ :-;:~~~/~ ~~~~~ ~~~~. /-~~~J ~ ~~~~ '/,/ '/,/ ~ ' ~ {.(? ".1-' '/,/ '-7 /.~~~1e ~ ~%~~ ::v '/,/ -0 'fl <<q- ~ '/,/ ~ ~iN: 1 ~~~~~ o -0 ~~ - ~~ ~ 0: /.~:0~ ~~'\~':.~~ '/,/ '-Y '/,/ /. .~ ~ /~ "~ ~~~ ~~~~ ~ 4/// 0- 0] :4~~4 ~~~ .~~~~ No more than 24- of a 36" fabric Is aftOW&d above ground. ATlACIMEHr DEtMS: . Gaoh.l8bfk:... _.__ . -.. - - pel' poot. aI_ top 8- of labric. *""->n "ad'llledaoonaly. ~_~ It ........... d yo ..~ . tIang - .. an .. pool "'PPI- and ~-=uely. Uoe~ _ (5abol Of _....... RoI 01 sill fence Post inoslaIO<I aIWf compacllon SiIIIF~ c~ ..........lIon Vlbfll!ofy plow II not IllCO!Iptabkl because of hortrontal compaction Figure 4.21 - Slit Fence Installation by Slicing Method Volume 1/ - Construction Stormwater Pollution Prevent/on 4-93 1})I-l~ (~11~rll=\Yr-tEF;~:-7 III:!~ ---',11 ' ill ~J J, " "C'J -, I 5.3<3 other Practices I ur-~- ,2004 It. The BMPs described in this section are other gene I pdGtice;s..:fo~~~ treatment of storm water. [.D"pT 0 JE/"F~RS,~)N ~o.ur{fY .1 ~::. ' r CO~IMlJ!m'r DEVELOPMENT i . ~- ---~j 8MP T5.30 Full Dispersion Purpose and Definition This BMP allows for "fully dispersing" runoff from impervious surfaces and cleared areas of development sites that protect at least 65% of the site (or a threshold discharge area on the site) in a forest or native condition. Applications and Limitations · Rural single family residential developments should use these dispersion BMPs wherever possible to minimize effective impe~ous surface to less than 10% of the development site. · Other types of development that retain 65% of the site (or a threshold discharge area on the site) in a forested or native condition may also use these BMPs to avoid triggering the flow control facility requirement Design Guidelines · Roof Downspouts Roof surfaces that comply with the downspout infiltration requirements in Vol~lme III> Chapter 3> are considered to be "fully dispersed" (i.e., zero percent effective imperviousness). All other roof surfaces are considered to be "fully disp~rsed" (i.e., at or approaching zero percent effective imperviousness) only if they are within a thrCshold discharge area that is or will be more than 65% forested (or native vegetative cover) and lesS than 10% impervious (total), AND if they comply with the downspout dispersion requirements ofBMP T5.10, and have vegetated flow paths through native vegetation exceeding 100 feet · Driveway Dispersion. Driveway surfaces are considered to be "fully dispersed" if they are within a threshold discharge area that is or will be more than 65% forested (or native vegetative cover) and less than 100.10 impervious (total), AND if they comply with the driveway dispersion BMPs- BMP 5.11 and BMP T5.12 - and have flow paths through native vegetation exceeding 100 feel This also holds true for any driveway surfaces that comply with the roadway dispersion BMPs described below. 5-20 Volume V -" RunoffTrestment BMPs '. '. -" August 2001 . I!D)~j~]L~!~ [ -,-:-1 i i 1''\ I I ~ l! j t ! I Roadway Dispersion BMPs I: i ! i I Sfi]". 7 2004 i i" i 'Jlm~~,"~~.___._~.~__l .i i R?a~way surfaces a:e considered to b7 Itfull~ disp~rs~fd" An~~*,i~~~)~Y)1:~rr OPiv!H " I WIthin a threshold dIscharge area that IS or wIll be moredthan'65%-.-~:_'"'.. "'"--' forested (or native vegetative cover) and, less than 10% impervious (total), AND if they comply with the following dispersion requirements: 1. Roadway runoff dispersion is allowed only on rural neighborhood collectors and local access streets. To the extent feasible, driveways should be dispersed to the same standards as roadways to ensure adequate water quaiity protection of downstream resources. 2. The road section shall be designed to minimize collection and concentration of roadway runoff. Sheet flow over roadway fill slopes (i.~., where roadway subgrade is above adjacent right-of- way) should be used wherever possible to avoid concentration. 3. When it is necessary to collect and concentrate runofffrom the roadway and adjacent upstream areas (e.g., in a ditch on a cut slope), concentrated flows shall be incrementally discharged from the ditch via cross culverts or at the ends of cut sections. These incremental discharges of newly concentrated flows shall not exceed 0.5 cfs at anyone discharge point from a ditch for the 100- year runoff event Where flows at a 'particular ditch discharge point were already concentrated under existing site conditions (e.g., in a natural channel that crosses the roadway alignment), the O.5-cfs limit would be ill addition to the existing concentrated peak flows. 4. Ditch discharge points with up to 0.2 cfs discharge for the peak. 1 DO-year flow~sliaIl use'rOck pads or disPersion trenches to disperse flows. Ditch discharge points with between 0.2 and 0.5 cfs discharge for the lOO-year peak flow shall use only dispersion trenches to disperse flows. 5. Dispersion trenches shall be designed to accept surface flows (free discharge) from a pipe, culvert, or ditch end, shall be aligned perpendicular to the flowpath, and shall be minimum 2 feet by 2 feet in section, 50 feet in length, filled with %-inch to 1 %..inch washed rock, and provided with a level notched grade board (see Figure 5.2). Manifolds may be used to split flows up to 2 cfs discharge for the IOO-year peak flow between up to 4 trenches. Dispersion trenches shall have a minimum spacing of 50 feet. 6. After being dispersed with rock pads or trenches, flows from ditch discharge points must traverse a minimum of 100 feet of undisturbed native vegetation before leaving the project site, or ._.';_'~_..:....:..:..-;...'-=-__.::;:c=::::=--. . ___._____.____~._ August 2001 Volume V - Runoff Iroatment.BMP.$.:____...... ..~~..'...,~.. ....... ...6::?L""H' ~I~ 8~o~~:4~1~1 .. Ii i ~~~~~~r::~:~~;~:~e~el carrying eXiS~g..coIiceiJtraied\~\(.____~J Note: In order to provide the laO-foot jlowpath length to an existing channel, some roadway runoff may unavoidably enter the channel undispersed Also note that water quality treatment may be waived for roadway runoff dispersed through 100 feet of undisturbed native vegetation. 7. Flowpaths from adjacent discharge points must not intersect within the 100- foot flowpath lengths, and dispersed flow from a discharge point must not be mtercepted by another discharge point. To enhance the flow control and water quality effects of dispersion, the flowpath shall not exceed 15% slope, and shall be located within designated open space. Note: Runoff may be conveyed to an area meeting these jlowpath criteria. ./ 8. Ditch discharge points shall be located a minimum of 100 feet upgradient of steep slopes (i.e., slopes steeper than 40%), wetlands, and streams. 9. Where the Local Plan Approval Authority determines there is a potential for significant adverse impacts downstream (e.g., erosive steep slopes or existing downstream drainage problems), dispersion of roadway runoff may not be allowed, or other measures may be required. Cleared Area Dispersion BMPs . The runoff from cleared areas that are comprised of bare soil, non- native landscaping, lawn, and/or pasture is considered to be "fully dispersed" ifit is dispersed through at least 25 feet of native vegetation in accordance with the following criteria: 1. The contributing flowpath of cleared area being dispersed must be no more than 150 feet, AND 2. Slopes within the 25-foot minimum flowpath through native vegetation should be no steeper than 8%. If this criterion can not be met due to site constraints, the 25-foot flowpath length must be increased 1.5 feet for each percent increase in slope above 8%. 5-22 Volume V - Runoff Treatment BMPs August 2001 15) ~ tC IE n Wi IE ln1l ..nl S FP - 7 ?004. llJ) BMP T5.1 0 Downspout Dispersion Purpose and Definition I I .!UHRS()N r.O! INTY ; firTT nr r.ryc.l/I}! !~!iT'{ flE\lt!.OP~.,~ENT i I .-..-___.___~_,......_,~-I Downspout dispersion BMPs are splashblocks or gravel-filled trenches that serve to spread roof runoff over vegetated pervious areas. Dispersion attenuates peak flows by slowing entry of the runoff into the conveyance system, allows for some infiltration, and provides some water quality benefits. Applications and Limitations · Downspout dispersion is required on all subdivision single family lots which meet one of the following criteria: 1. Lots greater than or equal to 22,000 square feet where downspout infiltration is not being provided according to the requirements in Volume III, Chapter 3. 2. Lots smaller than 22,000 square feet where soils are not suitable for downspout infiltration as determined in Volume III, Chapter 3 and where the..design criteria below can be met. · All other projects required to apply Roof Downspout BMPs must provide downspout dispersion if downspout infiltration is not feasible or applicable as determined in Volume III, Chapter 3, and if the design criteria below can be met. General Design Guidelines · Dispersion trenches designed as shown in the Figures 5.1 and 5.2 shall be used for all downspout dispersion applications except where splashblocks are allowed below. See Figure 5.3 for a typical splashblock. · Splashblocks may be used for downspouts discharging to a vegetated flowpath at least 50 feet in length as measured from the downspout to the downstream property line, structure, sensitive steep slope, stream, wetland, or other impervious surface. Sensitive area buffers may count toward flowpath lengths. The vegetated flowpath must be covered with well-established lawn or pasture, landscaping with well- established groundcover, or native vegetation with natural groundcover. The groundcover shall be dense enough to help disperse and infiltrate flows and to prevent erosion. · If the vegetated flowpath (measured as defined above) is less than 25 feet on a subdivision single-family lot, a perforated stub-out connection may be used in lieu of downspout dispersion (See Volume III, Chapter 3). A perforated stub-out may also be used where implementation of downspout dispersion might cause erosion or flooding problems, either on site or on adjacent lots. This provision might bc appropriatc, for example, for lots constructcd 011 steep hills August 2001 5-3 Volume V - Runoff Treatment BMPs 1- -. . ..- . ,~r~ s~p~: :4~ I~ i , I i where downspout discharge could be cumulative and mightposeraIRSON COUNTY potential hazard for lower lying lots, or where dispersed flows couiCi""'^" nF\'~i~'!"" create problems for adjacent offsite lots. This provision does not apply to situations where lots are flat and onsite downspout dispersal would result in saturated yards. ----' Note: For all other types ofprojects, the use of a peiforated stub-out in lieu of downspout dispersion shall be as determined by the Local Plan Approval Authority. 4>> pat pir:e 1 iii' . 8/..," washed rock TRENCH X-SECTION NTS slcpe- :~ modi catch basin or yard drai n I :::; 700 sq. ft. 2' ;~ 1CI levEl trencl"Bs :> 700 sq. ft. Tyr:e I CB st an d3.rd disj::ersion trench wi mtcl"Bd grace board lergh 1 a per 700 sq ft of roof area, PLAN VIEW OF ROOF NTS Figure 5.1 Typical Dispersion Trench 5.4 Volume V - Runoff Treatment BMPs August 2001 Q IL) l' ~ ~ ~ l(; IE U Wi ~. fnl ull SfP ~ 7 2004 11~1 , . ...._',7.'~..._J i \..'\ UJ',.~'_IY _ I 'Vii i)f.Jfv'iriH j ,.,.:::~_.~ erd caporph.g llCMI to second d ispersaJ ~/l2 r-.:; h if necessary . c lean ou~ w)Ii! from pipe . 4" 0 r 6" perbraed pipe lad flatJlevel t notched 9 ra:Je board 2'':>:: 2' notches 18'0.C. t ..... ~ inflU2 n~ pipe (max cBs!;) n fbw ~ 0.5 C FS per ~renc h) o type I CB 'hvsold COV2r ......... t PLAN NTS fl::w to o~t-e r brar-.:;hing C8's as necessary 1'.0 min (pipe 0 D. ,I11'D min. I 18'0.C I -r--~//,..__- ~ ~2" T~---'~~~v=t \/--- 2"gracE . T board rDtct",s 2" SECTION A-A NTS rWTES: i. Th is ~/l2 r~ h st811 t", con5truc~d so as b pre\o'en~ poi nt di9:: t.=<rge 3nd,Q r elDsDn. 2. Trenct",s moo! be placed no cbser ~han 50 fee~ b one 3rot~'" r (100 feet abrg fbwline) 3. TrenchardgracE toad mlJ5tbe 1eV21. A I!;) n to foll:.w con~olJrsofsie. 4. Su P p:> rt post spac ing 3S r-=qlJire::J by so il co rd nons t.o ensu Ie 9 racE board remains level. "15"10 rrox fer 11 0)/ cmtrov\'later qJ8J ity treat rreti in rural areas. Figure 5.2 Standard Dispersion Trench with Notched Grade Board August 2001 Volume V - Runoff Treatment BMPs 5-5 roc( dO\vl1spoiJ serves up to 700 s1. d ro c( rr;~:~~~~~~~~e;~<~"--\~'-.:; :;7l I ~J (;~(~:l~' .:j[lJ) I ,/ [i+ [f1 SON 'COliN'fV nEPT OF COMMlH~!TY otVELOPMl:NT -,~._--~-_. --~ - ~---- -- ~---------.:~._" 50'min. veg elate d noVl path \ spas h _\ ti ock do\vl1s poli: ex! emi on NTS splash block Figure 5.3 Typical Downspout Splashblock Dispersion Additional Design Criteria For Dispersion Trenches · A vegetated flowpath of at least 25 feet in length must be maintained between the outlet of the trench and any property line, structure, stream, wetland, or impervious surface. A vegetated flowpath of at least 50 feet in length must be maintained between the outlet of the trench and any steep slope. Sensitive area buffers may count towards flowpath lengths. · Trenches serving up to 700 square feet of roof area may be simple I a- foot-long by 2-foot wide gravel filled trenches as shown on Figure 5- 1. For roof areas larger than 700 square feet, a dispersion trench with notched grade board as shown in Figure 5-2 may be used as approved by the Local Plan Approval Authority. The total length of this design must provide at least 10 feet of trench per 700 square feet of roof area and not exceed 50 feet. · A setback of at least 5 feet must be maintained between any edge of the trench and any structure or property line. · No erosion or flooding of downstream properties may result. · Runoff discharged towards landslide hazard areas must be evaluated by a geotechnical engineer or qualified geologist. The discharge point 5-6 Volume V - Runoff Treatment BMPs August 2001 ImnO)/ fE ~ InlnEl~.1 L ~I SE/' ~ 7 2004 hi i I L_ I may not be placed on or above slopes greater than 2P0i or a~ils.~ erosion hazard areas without evaluation by a geotechA;:cfal ~[lgnte'ftr'9l); O~~lJOPMP' qualified geologist and jurisdiction approval. --------:. · For sites with septic systems, the discharge point must be downgradient of the drainfield primary and reserve areas. This requirement can be waived by the jurisdiction's pennit review staff if site topography will clearly prohibit flows from intersecting the drainfield. Additional Design Criteria For Splash blocks In general, if the ground is sloped away from the foundation, and there is adequate vegetation and area for effective dispersion, splashblocks will adequately disperse storm runoff If the ground is fairly level, if the structure includes a basement, or if foundation drains are proposed, splashblocks with downspout extensions may be a better choice because the discharge point is moved away from the foundation. Downspout extensions can include piping to a splashblock/discharge point a considerable distance from the downspout, as long as the runoff can travel through a well-vegetated area as described below. The following conditions must be met to lIse splashblocks: · A vegetated flowpath of at least 50 feet must be maintained between the discharge point and any property line, structure, steep slope, stream, wetland, lake, or other impervious surface. Sensitive area buffers may cOllnt toward flowpath lengths. · A maximum of 700 square feet of roof area may drain to each splashblock. · A splashblock or a pad of crushed rock (2 feet wide by 3 feet long by 6 inches deep) shall be placed at each downspout discharge point. · No erosion or flooding of downstream properties may result. · Runoff discharged towards landslide hazard areas must be evaluated by a geotechnical engineer or qualified geologist. Splashblocks may not be placed on or above slopes greater than 20% or above erosion hazard areas without evaluation by a geotechnical engineer or qualified geologist and approval by the Local Plan Approval Authority. · For sites with septic systems, the discharge point must be downslope of the primary and reserve drain field areas. This requirement can be waived by the Local Plan Approval Authority if site topography clearly prohibits flows from intersecting the drainfield. August 2001 5-7 Volume V - Runoff Treetment BMPs Ii 0-)'] '-'- !, I L.: ~ 1,'----....--.-.--. ,r,.1 BMP T5.11 Concentrated Flow Dispersion I U Ui::; 7 Purpose and Definition I I.... ."C,'C""" Jr-,. ",,",(, Dispersion of concentrated flows from driveways or othef"p'C:ly~~~~t;';-ii~;~Y through a vegetated pervious area attenuates peak flows by slowing'entry of the runoff into the conveyance system, allows for some infiltration, and provides some water quality benefits. See Figure 5.4. Applications and Limitations r->=--- I ~~,\ n --'''---111 I! ?n(J~.l II U J ",., i[~_j I J · Any situation where concentrated flow can be dispersed through vegetation. · Dispersion for driveways will generally only be effective for single- family residences on large lots and in rural short plats. Lots proposed by short plats in urban areas will generally be too small to provide effective dispersion of driveway runoff. · Figure 5.4 shows two possible ways of spreading flows from steep driveways. Design Guidelines · A vegetated flowpath of at least 50 feet should be maintained between the discharge point and any property line, structure, steep slope, stream, lake, wetland, lake, or other impervious surface. · A maximum of 700 square feet of impervious area may drain to each dispersion BMP. · A pad of crushed rock (2 feet wide by 3 feet long by 6 inches deep) shall be placed at each discharge point. · No erosion or flooding of downstream properties may result. · Runoff discharged towards landslide hazard areas must be evaluated by a geotechnical engineer or qualified geologist. The discharge point shall not be placed on or above slopes greater than 20% or above erosion hazard areas without evaluation by a geotechnical engineer or qualified geologist and approval by the Local Plan Approval Authority. · For sites with septic systems, the discharge point should be downgradient of the drainfield primary and reserve areas. This requirement may be waived by the Local Plan Approval Authority if site topography clearly prohibits flows from intersecting the drain field. 5-8 Volume V - Runoff Treatment BMPs August 2001 <;:/ ..... '} ( I , ( I 24' {BJ fE T{frIWIfJnJr)~ Inl SEP ~ 7 2004 LV) <{?" "), I ( ) J J -::.-- JFERSorv COUNTY 'U!vlMUNITY DEVELOPMENT 6" m in BERM DETAIL J ) I U\: J Dia naJ bffm-'" ~,' I WitWdiPffSim \ ",,'0, 'oJ, \ trerch I ---.... \: -~-....".Q 1...... l ~, ^-' .... )28 ~9'3tat9d J ~09_.(\ 'J \0-. \ ) fk.....';)ah' J / '&", \ I ), , \ ) ) , ~ , I PLAN :steep Driveway \-liltl1 Diagonal Berms ~/ ~/ ~/ , ~~I .nn-n-H! I 'Lo:;aw drain 'Q I ~E': ( I 25' from ROW if'f- J I ) d rhrg....a y sb;:>gSI:r: I I ( bward str'Nt ~ ) f J I Ct: r 700 sq. ft_ max. wtw9il\l d fa ins I : J ) I '..) \. ' .x , , / / 'i"'0\ Ok\" II ~~ \ f - i>i) ',. J '" J ( I DiagJnaJ bff m I with dipffsim r . trerch 1 ,I ) 28 veg<3tat'\ld I I I fkm';)a1h I 1 l \ \ \ PLAN :Steeo Drivewav Vlitl1 Slotted Drains Figure 5.4 Typical Concentrated Flow Dispersion for Steep Driveways August200t 5-9 Volume V - Runoff Treatment BMPs ,0.'''''"''__<,. r""::'..:/ '<<iJ (~~':l P. \1 .,-; i::::J . ';' I.L IW,.,1 LE;..1Lv... L~: U \.'YJ iJ~ ~i' ,.)/ I--'~~'~~'~~'.~-; I 1J1'1 I ;' i= P - 7 100/1 l i "L_<~~__~~~_ ~: ,JEFFEHSON COUNT'! - Purpose and Definition OEPT. OF COMMUNITY DEVELOPMEW -------. ._~~-~~~=-~-_._-_! Sheet flow dispersion is the simplest method of runoff control. This BMP can be used for any impervious or pervious surface that is graded so as to avoid concentrating flows. Because flows are already dispersed as they leave the surface, they need only traverse a narrow band of adjacent vegetation for effective attenuation and treatment. Applications and Limitations Flat or moderately sloping (< 15% slope) impervious surfaces such as driveways, sport courts, patios, and roofs without gutters; sloping cleared areas that are comprised of bare soil, non-native landscaping, lawn, and/or pasture; or any situation where concentration of flows can be avoided. BMP T5.12 Sheet Flow Dispersion Design Guidelines · See Figure 5.5 for details for driveways. · A 2-foot-wide transition zone to discourage channeling should be provided between the edge of the driveway pavement and the downslope vegetation, or under building eaves. This may be an extension of subgrade material (crushed rock), modular pavement, drain rock, or other material acceptable to the Local Plan Approval Authority. · A vegetated buffer width of 10 feet of vegetation must be provided for up to 20 feet of width of paved or impervious surface. An additional 5 feet of width must be added for each addition 20 feet of width or fraction thereof. · A vegetated buffer width of 25 feet of vegetation must be provided for up to 150 feet of contributing cleared area (i.e., bare soil, non-native landscaping, lawn, and/or pasture). Slopes within the 25- foot minimum flowpath through vegetation should be no steeper than 8 percent. If this criterion cannot be met due to site constraints, the 25- foot flowpath length must be increased 1.5 feet for each percent increase in slope above 8%. · No erosion or flooding of downstream properties may result. · Runoff discharge toward landslide hazard areas must be evaluated by a geotechnical engineer or a qualified geologist. The discharge point may not be placed on or above slopes greater than 20% or above erosion hazard areas without evaluation by a geotechnical engineer or qualified geologist and approval by the Local Plan Approval Authority. · For sites with septic systems, the discharge point must be downgradient of the drainfield primary and reserve areas. This requirement may be waived by the Local Plan Approval Authority if site topography clearly prohibits flows from intersecting the draintield. 5-10 Volume V - Runoff Treatment BMPs Augusl 2001 6" m in BERM DETAIL .'\ ... 7 21 kl "', ( r ( 1 I 1 J ( 1 I J 700 sq. ti maX. b..tw""" b..rms -=.~-"...-..,.,., JfHtflS f'; C6l)r~:ryC- ..LE:9.!~11 I7Y DEVELor - -.......~.-...,...------.. , I ( J J J I _______ J ~ ~J I ~ ----,.. 28 w9<3lal..d flo"';)a!h / J / ,- 28 ,- / I ( I f I Diagoral term wfih d~rsjon J lrffich / / / PLAN Driveway Dispersion Trench Driveway Slope Varies and Slopes Toward Street .01 "I I f f J I , I \ 61 "-I ~, J { I J I I J I~ :Q I~ . I ~ I '>o~ / ~~~<z" / "'~ f I I ~I hs-/ .>~ : ~~,~ I , I I I I I Figure 5.5 Sheet Flow Dispersion for Driveways August 2001 Volume V - Runoff Treatment BMPs 5-11 IT:U[l).-r~lfn\f~d\..'1 I j! r' -~~"'~,_._.,' I . ~I I . I r)\jl " r n. I ,1 LJ l! I ,:n:rJ- 7 2004 I.,' I BMP T5.13 Post-Construction Soil Quality and pepth ! i I~_~'__~-~--~._._j Purpose and Definition I n )Ef'fERSON COUNTY : "EP!_ 9~ CO~MUNI!Y DEVEl.OPi', Naturally occurring (undisturbed) soil and vegetation provide import~ni'--- stonnwater functions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment and pollutant biofiltration; water interflow storage and transmission; and pollutant decomposition. These functions are largely lost when development strips away native soil and vegetation and replaces it with minimal topsoil and sod. Not only are these important stonnwater functions lost, but such landscapes themselves become pollution- generating pervious surfaces due to increased use of pesticides, fertilizers and other landscaping and household/industrial chemicals, the concentration of pet wastes, and pollutants that accompany roadside litter. Establishing soil quality and depth regains greater stormwater functions in the post development landscape, provides increased treatment of pollutants and sediments that result from development and habitation, and minimizes the need for some landscaping chemicals, thus reducing pollution through prevention. Applications and Limitations Establishing a minimum soil quality and depth is not the same as preservation of naturally occurring soil and vegetation. It also does not maximize the stonnwater functions that could be attained through greater soil depth and more specialized fonnulations as presented in BMP T5.35, Engineered Soil/Landscape Systems. However, establishing a minimum soil quality and depth will provide improved on-site management of stonnwater flow and water quality. Soil organic matter can be attained through numerous materials such as compost, composted woody material, biosolids, and forest product residuals. It is important that the materials used to meet the soil quality and depth BMP be appropriate and beneficial to the plant cover to be established. Likewise, it is important that imported topsoils improve soil conditions and do not have an excessive percent of clay fines. Design Guidelines · Soil retention. The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. · Soil quality. All areas subject to clearing and grading that have not been covercd by imperviolls surface, incorporated into a drainagc I~lcjlity or engineered as structural filial' slope shall, at project eomplelion, demonstrate the following: 5-12 Volume V ~ Runoff Treatment BMPs August 2001 August 2001 r -~._-~~~-_._---_.__,~~_. I r;, ~)\ IE rr;, fG II ~r ~~ ["~\) L .) r~~=~-=-"-~~ : r , r 1 ) ; '; I ')(J()4 I . t,; [I. IL 1. Retention or enhancement of the moisture infi!ltratic)ll Hll~-9t}iL~QiL_.____1 moisture holding capacity of the original undisturbedsofJn~'ti\'eto ",,~ '. ) ;-; f'/r ~-- !' ~ the site. Areas which have been compacted or have removed some or all of the duff layer or underlying top soil shall be amended to mitigate for lost moisture infiltration and moisrure holding capacity; and 2. A topsoil layer with a minimum organic matter content of ten percent dry weight and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. · These criteria can be met by using on-site native topsoil, incorporating amendments into on-site soil, or importing blended topsoil. Ifblended topsoil is imported, then fines should be limited to twenty-five percent passing through a 200 sieve. · The resulting soil should be conducive to the type of vegetation to be established. jVf aintenance · Soil quality and depth should be established toward the end of construction and once established, should be protected from compaction, such as from large machinery use, and from erosion. · Soil should be planted and mulched after installation. · Plant debris or its equivalent should be left on the soil surface to replenish organic matter. · It should be possible to reduce use of irrigation, fertilizers, herbicides and pesticides. These activities should be adjusted where possible, rather than continuing to implement formerly established practices. Volume V - Runoff Treatment BMPs 5-13 '. ':"'~~~~'~'I r-'~', r,:::; 'f,j if'. P \\ {. i IF' ~'i I r" \ ji" lio Ii" il ,,>/, ,(' \ i II ~\ ("~~~~~o~:~J' ~ II. ,I 'I Jr! ! ~ lM ~ : ~ k , 5.3.2 Site Design BMPs JI I~_~_~..~.~.__^_..~~.~ 1 . '. '. JEFFEf1S0N COUNTY ! Th~ two BMPs m th~s sectIOn are general practices P~~s.~(!~'lljt,UNnY DEVEL~PMEN~,_ mamtenance at the SIte. BMP T5.20 Preserving Natural Vegetation Purpose And Definition Preserving natural vegetation on-site to the maximum extent practicable will minimize the impacts of development on stonnwater runoff. Preferably 65 percent or more of the development site should be protected for the purposes of retaining or enhancing existing forest cover and preserving wetlands and stream corridors. Applications and Limitations New development often takes place on tracts of forested land. In fact, building sites are often selected because of the presence of mature trees. However, unless sufficient care is taken and planning done, in the jnterval between buying the property and completing construction much of this resource is likely to be destroyed. The property owner is ultimately responsible for protecting as many trees as possible, with their understory and groundcover. This responsibility is usually exercised by agents, the planners, designers and contractors. It takes 20 to 30 years for newly planted trees to provide the benefits for which trees are so highly valued. Forest and native growth areas allow rainwater to naturally percolate into the soil, recharging ground water for summer stream flows and reducing surface water runoff that creates erosion and flooding. Conifers can hold up to about 50 percent of all rain that falls during a stonn. Twenty to 30 percent of this rain may never reach the ground but evaporates or is taken up by the tree. Forested and native growth areas also may be effective as stonnwater buffers around smaller developments. On lots that are one acre or greater, preservation of 65 percent or more of the site in natural vegetation will allow the use of full dispersion techniques presented in BMP T5.30. Sites that can fully disperse are not required to provide runoff treatment or flow control facilities. Design Guidelines · The preserved area should be situated to minimize the clearing of existing forest cover, to maximize the preservation of wetlands, and to bu frcr stream corridors. · The preservcd area should bc placed in a scparate tract or protected through recorded easemcnts for individual lots. 5-14 Volume V - Runoff Troatment BMPs August 2001 · If feasible, the preserved area should be located downslope from the building sites, since flow control and water quality are enhanced by flow dispersion through duff, undisturbed soils, and native vegetation. · The preserved area should be shown on all property maps and should be clearly marked during clearing and construction on the site. Maintenance · Vegetation and trees should not be removed from the natural growth retention area, except for approved timber harvest activities and the removal of dangerous and diseased trees. I-~.-~~_._.._. -'-_..c. '_.c. "" , 11<\ r-'\ ~l-_.~~~..~7-20~)I<~ _._-,~-~>--_.._._._-_....__._--,-J JEFFEf1S0f'.,! COUNTY DEPT. OF COMMUNiTY DEVELOPMENT lIugust 2001 Volume V - Runoff Troatment BMPs 5-15 r' II ' , I~~"i Ii, BMP T5.21 Better Site Design U U I SEP . ;)004 I W P d D ,r; " L~~_,..~,~,," J urpose an eJlmtlOn JUrEf\SUr~C;(llTfiFy' DEPT. OF COMMUNITY DCVELOPMElfr Fundamental hydrological concepts and stonnwater management concepts"~-'~. can be applied at the site design phase that are: · more integrated with natural topography, · reinforce the hydrologic cycle, · more aesthetically pleasing, and · often less expensive to build. A few site planning principles help to locate development on the least sensitive portions of a site and accommodate residential land use while mitigating its impact on stonnwater quality. Design Guidelines · Define Development Envelope and Protected Areas - The first step in site planning is to define the development envelope. This is done by identifying protected areas, setbacks, easements and other site features, and by consulting applicable local standards and requirements. Site features to be protected may include important existing trees, steep slopes, erosive soils, riparian areas, or wetlands. By keeping the development envelope compact, environmental impacts can be minimized, construction costs can be reduced, and many of the site's most attractive landscape features can be retained. In some cases, economics or other factors may not allow avoidance of all sensitive areas. In these cases, care can be taken to mitigate the impacts of development through site work and other landscape treatments. · Minimize Directly Connected Impervious Areas - Impervious areas directly connected to the stonn drain system are the greatest contributors to urban nonpoint source pollution. Any impervious surface that drains into a catch basin or other conveyance structure is a "directly connected impervious surface." As stormwater runoff flows across parking lots, roadways, and other paved areas, the oil, sediment, metals, and other pollutants are collected and concentrated. If this runoff is collected by a drainage structure and carried directly along impervious gutters or in sealed underground pipes, it has no opportunity for filtering by plant material or infiltration into the soil. It also increases in velocity and amount, causing increased peak-flows in the winter and decreased base-flows in the summer. 5-16 Volume V - Runoff Treatment BMPs August 2001 ~--"'.~=~'~--->-",--.-.~~-_~ u__..~__ ._" ". __'_ "_____'____._~"___ t ('--"'C.......,\. f f~~ f/Z,\ . -; \ l ,OJ ;->.~ i J I 1"') \ Ie Ii, II WI 11;\ I I, /' ..~ ,~;J 'J Cd c~;; ,/L I 1---"--<< '-"- J' I-=~'\ i l" r I liB EID ,= ~l 200fJ, b . . d' '. I ~ J \.1 ! I A aSlc site eSlgn pnnclp e lor stormwater managem nt fSlto minimize these directly connected impervious areas. Ihis d3n-be-dQn.e~.~....... ~'_' b~ limi~ing overall impervio~s land ~overage or by int~tr~\n~-l~~atITj~~~Wi:~~roP dlspersmg runoff from these ImpervIOUS areas. ---.---__~___.. · Maximize Permeability - Within the development envelope, many opportunities are available to maximize the permeability of new construction. These include minimizing impervious areas, paving with permeable materials, clustering buildings, and reducing the land coverage of buildings by smaller footprints. All of these strategies make more land available for infiltration and dispersion through natural vegetation. Clustered driveways, small visitor parking bays and other strategies can also minimize the impact of transportation-related surfaces while still providing adequate access. Once site coverage is minimized through clustering and careful planning, pavement surfaces can be selected for permeability. A patio of brick- on-sand, for example, is more permeable than a large concrete slab. Engineered soil/landscape systems are permeable ground covers suitable for a wide variety of uses. Permeable/porous pavements can be used in place of traditional concrete or asphalt pavements in many low traffic applications. Maximizing permeability at every possible opportunity requires the integration of many small strategies. These strategies will be reflected at all levels of a project, from site planning to materials selection. In addition to the environmental and aesthetic benefits, a high- permeability site plan may allow the reduction or elimination of expensive runoff underground conveyance systems, flow control and treatment facilities, yielding significant savings in development costs. · Build Narrower Streets - More than any other single element, street design has a powerful impact on stormwater quantity and quality. In residential development, streets and other transportation-related structures typically can comprise between 60 and 70 percent of the total impervious area, and, unlike rooftops, streets are almost always directly connected to the storm water conveyance system. The combination of large, directly connected impervious areas, together with the pollutants generated by automobiles, makes the street network a principal contributor to stonnwater pollution in residential areas. Street design is usually mandated by local municipal standards. These standards have been developed to facilitate efficient automobile traffic August 2001 5-17 Volume V - Runoff Treatment BMPs "- ..-/ .~- ./ -.- r. Fe ~ I"E IT W7 frr; ~\ [)~.I~.~"-.- =--~--_::... ..""-'l=- n..i tn\ I 8EP 7 (004 ~ and maximize parking. Most require large impervious Hmd coverage. I In recent years, new street standards have been gaihing kcc~pf~QG~"ftlil~F~:'T'/"" meet the access requirements of local residential stteets\.vhi1'e're'duEihg', F!1f'~,"H impervious land coverage. These standards generally create a new class of street that is narrower than the current local street standard, called an "access" street. An access street is intended only to provide access to a limited number of residences. Because street design is the greatest factor in a residential development's impact on stonnwater quality, it is important that designers, municipalities and developers employ street standards that reduce impervious land coverage. · Maximize Choices for Mobility - Given the costs of automobile use, both in land area consumed and pollutants generated, maximizing choices for mobility is a basic principle for environmentally responsible site design. By designing residential developments to promote alternatives to automobile use, a primary source of stonnwater pollutien can be mitigated. Bicycle lanes and paths, secure bicycle parking at community centers and shops, direct, safe pedestrian connections, and transit facilities are all site-planning elements that maximize choices for mobility. · Use Drainage as a Design Element - Unlike conveyance stonn drain systems that hide water beneath the surface and work independently of surface topography, a drainage system for stormwater infiltration or dispersion can work with natural land forms and land uses to become a major design element of a site plan. By applying storm water management techniques early in the site plan development, the drainage system can suggest pathway alignments, optimum locations for parks and play areas, and potential building sites. In this way, the drainage system helps to generate urban fonn, giving the development an integral, more aesthetically pleasing relationship to the natural features of the site. Not only does the integrated site plan complement the land, it can also save on development costs by minimizing earthwork and expensive drainage features. 5.18 Volume V - Runoff Treatment BMPs August 2001 \ e)') \ r~<\ , ,\ 'I i\ U b, ! l . .0" . ->-~-----;- "- . - -- . . iF~:;-~F;(n;,-_: ceil ~i'-i l/ D"PT or."cO~~'~~'iTi!'P{ Dfvr !UfJIv1ENT ; L . _l-'--l~_~~~_~~_._,~_~~.__:::_~_...o-<._~ ;FP 1 ;'''_'\ \ ; .. \ ; I \ l 1,,1, \) ! \ ) , '-- '"",.C'-.,,.J' APPENDIX 4 - Storm Water Manual References Jefferson County Department Of Community Development STORMWATER MANAGEMENT HANDOUT ~::;:::'"-i ", \ \ Select definitions from the 2001 Department of ~?:olo~. i IJ\ \ I Stormwater Management Manual jOr Western W ashi1ig.\!n\:~:;, . \~ \ L, \..> I 2.3 Definitions Related toMinimum Req1~l~~EI~J~:&~Iu~~ A full listing and definition of stonnwater-related words and phrases that are used in this manual is given in the glossary. A few of the key definitions are listed here for ease in understanding the requirements that follow. · Arterial- A road or street primarily for through traffic. A major arterial connects an Interstate Highway to cities and counties. A minor arterial connects major arterials to collectors. A collector connects an arterial to a neighborhood.. A collector is not an arterial. A local access road connects individual homes to a collector. · Effective Impervious surface - Those impervious surfaces that are connected via sheet flow or discrete conveyance to a drainage system. Impervious surfaces on residential development sites are considered ineffective if the runoff is dispersed through at least one hundred feet of native vegetation in accordance with BMP T5.30 ~ "Full Dispersion," as described in Chapter 5 of Volume V. · Highway - A main public road connecting towns and cities · Impervious surface - A hard surface area that either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development. A hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, but are not limited to, roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater. Open, uncovered retention/detention facilities shall not be considered a.s impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling. 2-4 Volume 1- MInimum TechnIcal Requirements August 2001 August 2001 . \\R~,l[~ ju U\~004 JIL~ Replaced impen'ilJlIs surface - For structures, the remov' I and! replacement of any exterior impervious surfaces or found4tion. Lfgril-ij~si}i~-c(ilr7fY. other impervious surfaces, the removal down to bare soil {rTI!:!rS-eDF COMrv\U~~.I1Y_Dt~ELopr...'EN"r course and replacement. . Site - The area defined by the legal boundaries of a parcel or parcels of land that is (are) subject to new development or redevelopment. For road projects, the length of the project site and the right-or-way boundaries define the site. . Source control Bll1P - A structure or operation that is intended to prevent pollutants from coming into contact with stonmvater through physical separation of areas or careful management of activities that are sources ofpolllltants. This manual separates source control BMPs into two types. Structural Source Control Bl\1Ps are physical, stmctural, or mechanical devices, or facilities that are intended to prevent pollutants trom entering stonnwater. Operational Bli-{Ps are non-stmctural practices that prevent or reduce pollutants trom entering stonmvatcr. See Volume IV for details. . Threshold Discharge Area - An onsite area draining to a single natural discharge location or multiple natural discharge locations that combine within one-quarter mile downstream (as detennincd by the shortest tlowpath). The examples in Figure 2.1 below illustrate this definition. The purpose of this definition is to clarify how the thresholds of this manual are applied to project sites with multiple discharge points. Exan\jNe of a Project Site with a Slngkt twuraI Dlsdmrge and a SIngIQ Thn!sllold DIscharge /uU 'NalliraL ...... . _ ____~'~llJe"-</" -. THRESHOLD ' \/~. ,-~ (Shaded)~', _1'-. /. '_, ;,~/" ~ ...~...:: - ....... Example of a ?roJact SIte with Multiple Naturat DilIct\aI'!Jl!" and a Slnglo Thnoshold Dis<:harge Ar&a EnmplaotaProjf>ctSlte with Multiple Natural Oiscl>arges and Multlplo Thl'eshold Discharge Areas ~. 'd~twaJ ~-~~- -t ""\)I' ---}- \A /-l-'( . --..;.--' .. ,r ....... 1laVJral Natural 'i5iS.:h3~_~ _~-- Area 1 Area 2 _ OlD TliflE~ E DISC AREA t, J.,s;AEA 2 ,~~'- / ,--, I -\, 'f ...,- !~ NaIUfal '-. ./ ~ I ~ : '<- Natural J ~ '; DIscharge ! ~ localions j . . \ ' I~ ;II ; Natural -./ ~ : Discharge : I locaOOos f \ \ .' i \ , \ I , ., I . I ~~ I: 14 MikI DownslRlam _.'_ _ _ _ _ _ _ _ __ ~ _ _ _ _ i- -- (shO<tesll\ow path} -i V ~ Figure 2.1 Threshold Discharge Areas -------_._-~---~------ Volume 1- Minimum Technical Requirements 2-7 . F"['~) I rC,' J~ ~---_. nil lJ ul I LalUJ disturbing activi(J' - Any activity that results in movbnen,trok;,; earth, or a change in the existing soil cover (both veg ~mfiveQll;~6!ri:op~!:"i'~" "', vegetative) and/or the existing soil topography. Land disturbIng.... activities include, but are not limited to clearing, grading, filling, and excavation. Compaction that is associated with stabilization of structures and road construction shall also be considered a land disturbing activity. Vegetation maintenance practices are not considered land-disturbing activity. ;f,NT r~<"'-."'~ 1i1~\ I! ) i I L::~ ! ~.i -r '.,i . Jl-{aintenance - Repair and maintenance includes activities conducted on currently serviceable structures, facilitie.s, and equipment that involves no expansion or use beyond that previously existing and results in no significant adverse hydrologic impact. It includes those usual activities taken to prevent a decline, lapse, or cessation in the use of structures and systems. Those usual activities may include and replacement of disfunctioning facilities, including cases \-vhere environmental permits require replacing an existing structure with a different type structure, as long as the functioning characteristics of the original structure are not changed. One example is the replacement of a collapsed, fish blocking, round culvert with a new box culvert under the same span, or width, ofroadway. For further details on the application of this manual to various road management fi.mctions, please see Section 2.2. o Native vegetation - Vegetation comprised of plant species, other than noxious weeds, that are indigenous to the coastal region of the Pacific Northwest and which reasonably could have been expected to naturally occur on the site. Examples include trees such as Douglas Fir, western hemlock, western red cedar, alder, big-leaf maple, and vine maple; shrubs such as willow, elderberry, salmonberry, and salat and herbaceous plants such as sword fern, foam flmver, and fire\vecd. . New development - Land disturbing activities, including Class IV - gencral forest practices that arc conversions from timber land to other uses: structural development, including construction or installation of a building or other stnlcture; creation of impervious surhlces: and subdivision, short subdivision and binding site plans, as defined and applied ill Chapter 58.17 RCW. Projects meeting the definition of redevelopment shall not be considered new development. . Pollution-generating impervious surface (PGlS) - Those impervious suri~lces considered to bc a significant source of pollutants ill storm water runoff. Such surfaces include thosc which (]rc subject to: vehicular use; industrial activities (as fUlther defined in the glossary): or slorage of erodible or leachable materials, wastes, or chemicals, and which receive direct rainfall or the tUn-on or blow-in of rainfall. Erodible or leachable materials, wastes, or chemicals are those August 2001 --------------_._--------_._---------~-------- Volume 1- Minimum Technical Requirements 2-5 \ ,. "- -', (~~'-1"::~--- '";::::u I (", It:~ I fL~ ILJ ,-C_ '.:.-... "-n__ JI,,< i substances which, when exposed to rainfall, leasttrnbly.alterJhe _ ... physical or chemical characteristics of the rai f~l1 n,nkft~;)~x~iririj~s':'U"'!r .. . UFPTIfF'CUl,,,\lUI~I!-f-[]L\CLU, ;-{\LJ~ include erodIble salls that are stockpIled, unc prOC"ess-wastes;""-"~--"- manure, fertilizers, oily substances, ashes, kiln dust, and garbage dumpster leakage. Metal roots are also considered to be POlS unless they are coated with an inert, non-leachable material (e.g., baked-on enamel coating). ('::~~\ .... '1;IUi 'I ,4 II l._j A surface, whether paved or not, shall be considered subject to vehicular use if it is regularly used by motor vehicles. The following are considered regularly-used surfaces: roads, unvegetated road shoulders, bike lanes within the traveled lane of a roadway, driveways, parking lots, unfenced fire lanes, vehicular equipment storage yards, and airport runways, The following are not considered regularly-used surfaces: paved bicycle pathways separated from and not subject to drainage from roads for motor vehicles, fenced firelanes, and infrequently used maintenance access roads. · Pollution-generating perviolls surfaces (PGPS) - Any non- impervious surface subject to use of pesticides and fertilizers or loss of soil. Typical POPS include lawns, landscaped areas, golf courses, parks, cemeteries, and sports fields. · Pre-developed condition - The native vegetation and soils that existed at a site prior to the influence of Euro-American settlement. The pre- developed condition shall be assumed to be a forested land cover unless reasonable, historic iofonnation is prov'ided that indicates the site was prairie prior to settlement. · Project site - That portion of a property, properties, or right of way subject to land disturbing activities, new impervious surfaces, or replaced impervious surfaces. · Receiving waters - Bodies of water or surface water systems to which surface runoff is discharged via a point source of stoffi1water or via sheet flow. ( · Redevelopment- On a site that is already substantially developed (i.e., has 35% or more of existing impervious surface coverage), the creation or addition of impervious surfaces; the expansion of a building footprint or addition or replacement of a structure; structural development including construction, installation or expansion of a building or other structure;; replacement of impervious surface that is not part of 11 routine maintenance activity; and land disturbing activities. 2-6 Volume 1- Minimum Technical Requirements August 2001 Supplemental Guidelines i I":,: '\ li[' i J) -~. ,- I _ I I r''';\ : , ,I! lJ HI i I.., , ' .J ;"';~\-l i f\ \" i I !) '; F ! !...J, !:","~~':-" J LFFL f1 S (1) c: ell! ;.~T Y' Reduction of flows through infiltration decreases stkRffi!cflwili~f~id1iJA\fC: 1f'\>\jl and helps to maintain base tlow throughout the summer months. However, infiltration should only be used where ground water quality is not threatened by such discharges. Volume III includes a description of the Western Washington Hydrology Model. The model provides credits for use of certain downspout designs and other types of Onsite Stonnwater Management BMPs described in Volume V. Using those BMPs reduces the size ofthe required flow control facilities. Application of sufticient types of Onsite Stomlwater Management BMPs can result in reducing the effective impervious area and the converted pervious areas such that a flow control facility is not required. Application of "Full Dispersion", BMP T5.30, also results in eliminating the flow control facility requirement for those areas that are "fully dispersed. " .* Interim Guideline Local governments have a choice to make concerning a flow control standard to use until a now duration standard is adopted and a continuous rainfalllrunoffmodeJ and flow routing program (for sizing orifices and ponds) are available for use. They can continue to use the peak flow standard of the 1992 Puget Sound manual, or use a peak now standard that approximates the results that the proposed flow duration standard would achieve. By adjusting the target peak flow standard, restricting use of variables in the Santa Barbara Urban Hydrograph (SBUH) hydrologic analysis, and applying a volume correction factor, one can estimate the orifice sizes and detention volumes that the proposed flow duration standard would indicate. The following explains how to adjust the SBUH approach to obtain results similar to the output from the King County Runoff Time Series (an application of the Hydrologic Simulation Program _ Fortran) with the proposed flow duration standard as the target. /' " Adjusted target peak now standard. Limit the peak rate of runoff from individual development sites to 50 percent or the pre-developed condition 2-year, 24-hour design storm. Limit the peak rate from the 10-year, 24- hour design stoml to the pre-developed condition peak rate from the 2- year, 24-hour design storm. Limit the peak rate from the I DO-year, 24- hour design stann to the pre-developed condition peak rate from the 10- year, 24-hour design storm. " 2-32 Volume 1- Minimum Technical Requirements August 2001 (' '~_/ - August 2001 ~ f;><-~ -',,- ! [~_; IIU)llG Ii r':\< I II II! I' I,! II I q I Restricted variable assumptions. The flow pa~h lerlgtl~i~~~\ltnyqfo.(. sheet flow runoff in the pre-developed conditiOll (nl:lwlaHonslnust 'notcbe,;;., ." less than 300 feet..---........ .... . !: '. j II \) 11 I j !j! ! i! !, , !k'r"< J , The Manning's effective roughness coefficient for pre-developed forested conditions should be 0.80. For pasture conditions, the coefficient should be 0.15. In the table of curve numbers in Volume Ill, Chapter 2, the curve numbers for pre-developed forest and pasture conditions must be selected from the "fair" category. Volume correction factor: In addition to the above, the pond volume correction factor (applicable to detention and retention facilities) identified in Volume III, Chapter 2 should be used where the pre-developed condition is modeled as pasture. When enlarging the pond to accommodate the volume correction factor, remember to not change the pond depth or the design of the outlet structure. Thus, a.n increase in the surface area is necessary. 2.5.8 Minimum Requirement #8: Wetlands Protection Applicability The requirements below apply only to projects whose stormwater discharges into a wetland, either directly or indirectly through a conveyance system. These requirements must be met in addition to meeting Minimum Requirement #6, RUlloff Treatment. Thresholds The thresholds identified in Minimum Requirement #6 - Runoff Treatment, and Minimum Requirement #7 - Flow Control shall also be applied for discharges to wetlands. Standard Requirement Discharges to wetlands shall maintain the hydrologic conditions, hydrophytic vegetation, and substrate characteristics necessary to support existing and designated uses. A wetland can be considered for hydrologic modification and/or stormwater treatment in accordance with Guide Sheet lB in Appendix [-D. Additional Requirements The standard requirement does not excuse any discharge from the obligation to apply whatever technology Is necessary to comply with stnte water quality standards, Chapter 173-201A WAC, or state Volume 1- Minimum Technical Requirements 2-33