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HomeMy WebLinkAboutBLD2013-00144 Drainage/Stormwater • • DRAINAGE & EROSION CONTROL REPORT FOR THE PROPERTY LOCATED AT SECTION 2, TOWNSHIP 29 NORTH, RANGE 1 WEST, W.M. JEFFERSON COUNTY, WASHINGTON PARCEL NO. 601 1 0201 2 j Ti` 'f E VA, 1f�A� Prepared for MAY 1 4 2013 CHRIS CLEGG JiffEJISON COUNTY BCD w� r NTI Engineering & Land Surveying 717 South Peabody Port Angeles, WA 98362 360-452-8491 www.nti4u.com January 4, 2013 • INTRODUCTION NTI Engineering and Land Surveying was requested by Balance Associates, Architects to develop a Stormwater Management Plan and report for Mr. Chris Clegg's proposed residential home site at parcel 601-102-012, Section 2, Township 29 North, Range 1 West, W.M., Jefferson County, Washington. As part of this analysis, an on-site stormwater infiltration/dispersion system has been designed and a temporary erosion and sediment control plan has been prepared for the construction of a private single- family residence and driveway. II. DESCRIPTION OF SITE The lot is located on the shoreline of Dabob Bay and is bordered on the North, East and South by residential lots. Access to the site is from Kens Way, which runs along the east line of the site. The development area of the site slopes towards the shore at approx. 25%. The western portion of the site slopes steeply to the shoreline and is designated as a landslide and erosion hazard area. The lot is undeveloped and is covered with grass, sparse trees and brush in the proposed development area. The underlying soils are mapped as Cassolary sandy loam (CfD), which is classified in hydrologic soils group "C". The soils were examined and found to consist of 12 inches of gravelly sandy loam over top of gravelly sand with silt. III. METHODOLOGY Jefferson County requires the use of the Department of Ecology (DOE) February 2005 Stormwater Management Manual for Western Washington. The proposed new impervious surface area is more than 2,000 sf. but less than 5,000 sf. Referring to Figure 2.2, minimum requirements 1-5 are required. Minimum requirements #1 thru #5 will be addressed as follows: Minimum Requirement #1 Preparation of Stormwater Site Plan • A complete site plan has been included in the appendix of this report. Minimum Requirement #2 Construction Stormwater Pollution Prevention (SWPP) • The SWPPP includes twelve elements. Each element will be addressed separately as follows: Element #1 Mark Clearing Limits o A note has been provided on the SWPPP requiring setback lines and buffer to be marked prior to clearing activities. Element #2 Establish Construction Access o The construction access to the site will be the same as the final driveway access. A note has been provided on the SWPPP requiring gravel surfacing on the driveway prior to clearing/grading activities. 2 • • Element #3 Control Flow Rates o All runoff from new impervious surfaces will be partially infiltrated onsite. Evidence from a site visit indicated a seasonally high GWT. Dispersion will also occur. Element #4 Install Sediment Controls o To minimize erosion during construction, straw wattles will be installed, see plan for location and details. Element#5 Stabilize Soils o 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. o All exposed soils caused by construction activities shall be stabilized and hydroseeded or sodded upon completion of the project. Element #6 Protect Slopes o The steep western slope will be protected by the buffer setback. Element #7 Protect Drain Inlets o There are no inlets existing that will require protection. Element#8 Stabilize Channels and Outlets o No channels or outlets existing within or down-slope of the building site. Stormwater during construction will sheet flow across the site through the temporary BMPs. Element #9 Control Pollutants o 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 stormwater. o To minimize pollutants generated by heavy equipment and vehicles, all maintenance and repairs shall be conducted using spill prevention measures such as drip pans. Element#10 Control De-watering o The underlying soils are permeable, the need for dewatering should be minimal. It is recommended however, that construction take place during the dry season. If de-watering is necessary it shall be done in compliance with the 2005 DOE manual. Element #11 Maintain BMPs (best management practices) o 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. 3 • S o After construction is complete, maintenance of permanent erosion and sediment control measures are the owner's responsibility. o All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization is achieved or as needed if longer. Element #12 Manage The Project o 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. Minimum Requirement #3 Source Control of Pollution • As stated in Element #9, to minimize pollutants generated by heavy equipment and vehicles, all maintenance and repairs shall be conducted using spill prevention measures such as drip pans. • Source control of pollutants during construction can be maintained on this job by implementing the temporary erosion and sediment control measures set forth. • Long-term source control of pollution is the responsibility of the property owner and includes all categories of household and yard chemicals and pollutants. Minimum Requirement #4 Preservation of Natural Drainage Systems and Outfalls • The natural drainage route on the site is infiltration and sheet flow of excess to the west. • The vegetated portion of the site will continue to sheet flow as it did prior to development. Minimum Requirement #5 On-site Stormwater Management • The roof downspouts will be directed to an infiltration/dispersion system designed to provide dispersion of excess flow on the surface. This facility will be located a minimum at least 10 feet from property lines. • The runoff from the driveway will be directed to rock dispersion pads on the south side of the driveway. • Routine observation and maintenance by the owner is highly recommended and necessary to maintain a functioning drainage system on site. A functioning drainage system should infiltrate and if necessary disperse the runoff without causing erosion on site or downstream. IV. CONCLUSIONS Prior to breaking ground the temporary erosion control measures set forth in this report and plan shall be installed on site to minimize erosion and control sediment discharge during construction activities. These measures include a straw wattle and standard soil stabilization BMP's. During construction temporary erosion control measures should be inspected regularly and repaired as necessary. Once the site is developed and stabilized, these BMPs can be removed. 4 • • V. LIMITATIONS This report has been prepared for the exclusive use of Chris Clegg 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 condi- tions 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 construction sites, especially when the topography has been altered years ago. Such unexpected 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. NTI ENGINEERING & SURVEYING ws/<s 4 1 tii O o -fie *1 �? Iti 9 45910 � �c9FG/STE - S/ONALE Zach Iota Justin C. Wilson, PE En veering Technician Principal Engineer • • APPENDIX A.) STORMWATER SITE SUBMITTAL TEMPLATE B.) STORM WATER CALCULATION WORKSHEET C.) FIGURE 1 : NEW DEVELOPMENT FLOWCHART D.) CRITICAL AREA MAPS(JEFFERSON CO.) • • APPENDIX A • • �gON c 49 7:4 JEFFERSON COUNTY 4404 ►� •4 DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street • Port Townsend • Washington 98368 qs, O 360/379-4450 . 360/379-4451 Fax 41N01. http://www.co.jefferson.wa.us/commdevelopment/ STORMWATER SITE PLAN SUBMITTAL TEMPLATE MLA# PROJECT/APPLICANT NAME: Chris Clegg 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 stormwater 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. Private single family residence and driveway. The residence will be built in the center of the lot near the north setback line. Existing Conditions Summary 2. Describe the existing topography. Indicate contours on the site map. The development area slopes downward to the west at approximately 25% . 3. Describe the existing vegetation. Indicate native vegetation areas on the site map. There is grass, sparse trees and brush in the development area. 4. Describe the existing soils. Indicate soil type on the site map. The underlying soils are mapped as Cassolary sandy loam (CfD) , which is classified in hydrologic soils group "C" . 5. Describe the existing site hydrology(i.e., drainage; behavior of water on the site—above, below, and on the ground). Indicate existing stormwater 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. The natural drainage route on the site is infiltration and sheet flow of excess to the west. 6. Describe any excess levels of noise generated by the proposed use or activity: -None- stormwater site plan template.doc-rev.10/12/2003 5 • • 7. Describe significant geographic features and critical areas (i.e., environmentally sensitive areas such as wetlands, streams, steep slopes,etc.)on the site. Indicate location on the site map. The western portion of the site slopes steeply to the shoreline and is designated as a landslide and erosion hazard area. 8. Describe the general vicinity of the site, including adjacent land uses and structures, utilities, roads, and sensitive/critical areas (streams,wetlands, lakes,steep slopes,etc.). To the west of the parcel is Dabob Bay. To the north and south is residential lots . To the east the driveway connects to Kens Way. An existing water line connects to a main on Kens Way. Landslide hazard/steep slope at the west end. Permanent Stormwater Control Plan This portion of the Stormwater Site Plan consists of the selection and installation of the appropriate stormwater control BMPs and facilities to remain in place after construction of the project is completed. "Medium" size projects are required to have the totals calculated of all impervious surfaces, pollution-generating impervious surfaces, and pollution-generating pervious surfaces to verify that the thresholds for treatment facilities and flow control facilities are not exceeded. g. Describe the developed site hydrology, as proposed. Indicate whether stormwater will be fully dispersed (i.e., per BMP T5.30 in the Manual)or, if not, what types of stormwater flow control will be utilized for the site or specific threshold discharge areas within the site. Locate these facilities on the site plan and differentiate proposed facilities from existing facilities. The stormwater runoff from the roof downspouts will be routed to an infiltration/dispersion trench with excess flow in the form of sheet flow. The runoff from the driveway will be routed to quarry spall dispersion pads spaced evenly throughout the length of the driveway. The undisturbed areas will continue as sheet flow. 10. If the project requires the use of stormwater treatment facilities, describe the types of stormwater treatment facilities proposed for use on the site. Locate these facilities on the site plan and differentiate proposed facilities from existing facilities. [This is normally for"large"projects or projects that involve the potential for dispersion of contaminants.] -None- 11. Describe the performance goals and standards applicable to the project. Minimum Requirements #1-#5 of the DOE Stormwater Management Manual are required and the Drainage & Erosion Control Report has been prepared in accordance with these requirements . 12. Describe the flow control system. An infiltration trench will control the flow of stormwater. Excess flow will be diverted through the trench and away from the site via sheet flow. stormwater site plan template.doc—rev.10/12/2003 6 • • 13. Describe the water quality system. —None- 14. Describe the conveyance system analysis and design. For new the home runoff will be collected by roof drains and conveyed by downspouts to an infiltration/dispersion trench. For the driveway, runoff will be conveyed by a series of gravel berms to rock pads where it will be dispersed across native vegetation. 15. Describe the source of fill material, physical characteristics of fill material,and deposition of excess material. 1) Drain Rock - Clean, rounded aggregate for trenches . 2) Gravel Pad - Compacted crushed rock for pads . 16. Proposed methods of placement and compaction consistent with the applicable standards on Appendix Chapter 33 of the Uniform Building Code. No compaction of drain rock necessary. Light compaction of gravel pads may be needed. 17. Describe the proposed surfacing material. The driveway will be surfaced with clean crushed rock. 18. Describe methods for restoration of the site. All disturbed areas will be hydroseeded or sodded upon completion of construction activities . 19. An Operation and Maintenance Manual is required for each flow control and treatment facility. [This is normally required for "large"projects only and only those for which facilities are required to control flow or treat runoff.] If included, list the Manuals here. —None- 20. List here and include any special reports or studies conducted to prepare the Stormwater Site Plan. —None- 21. List other necessary permits and approvals as required by other regulatory agencies. If those permits or approvals include conditions that affect the drainage plan or contain more restrictive drainage-related requirements,describe those conditions or restrictions here. -None- stormwater site plan template.doc—rev.10/12/2003 7 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN(SWPPP) The Construction SWPPP addresses sediment and erosion control during construction. The BMPs indicated by the applicant in the template that follows must be installed on the ground during all construction phases of the project. The proponent is responsible for preventing sediment and erosion impacts to environmentally sensitive areas and off-site areas. Consult the Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet for guidance, particularly with rural residential development. SECTION I—CONSTRUCTION SWPPP NARRATIVE 1. Construction Stormwater Pollution Plan Elements. Describe how each of the Construction SWPPP elements has been or will be addressed. Identify the type and location of BMPs used to satisfy the required element. If an element is not applicable to the proposal,justify in writing. Descriptions of the 12 Elements are found at section 2.5.2 of the Manual(beginning on page 2-15). 12 Required Elements—Construction SWPPP 1. Mark Clearing Limits. A note has been provided on the SWPPP requiring setback lines and buffer to be marked prior to clearing activities. 2. Establish Construction Access. The construction access to the site will be the same as the final driveway access . A note has been provided on the SWPPP requiring gravel surfacing on the driveway prior to clearing/grading activities 3. Control Flow Rates. All runoff from new impervious surfaces will be infiltrated onsite and dispersed as necessary. 4. Install Sediment Controls. To minimize erosion during construction, straw wattles will be installed, see plan for location and details . 5. Stabilize Soils. All exposed soils caused by construction activities shall be stabilized and hydroseeded or sodded upon completion of the project. 6. Protect Slopes. The steep western slope will be protected by the buffer setback. 7. Protect Drain Inlets. There are no inlets existing that will require protection. stormwater site plan template.doc—rev.10/12/2003 8 • • 12 Required Elements—Construction SWPPP(continued) 8. Stabilize Channels and Outlets. No channels or outlets existing within or down-slope of the building site . Stormwater during construction will sheet flow across the site through the temporary BMPs . 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 stnrrnI.Latr 10. Control De-Watering(the act of pumping groundwater or stormwater away from an active construction site). The underlying soils are permeable, the need for dewatering should be minimal. It is recommended however, that construction take place during the dry season. If de-watering is necessary it shall be done in compliance with the 2005 DOE manual . 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. 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. Description of the adjacent areas that may be affected by site disturbance (e.g., streams, lakes, wetlands, residential areas, roads). Adjacent areas will be unaffected. b. Description of the downstream drainage path leading from the site to the receiving body of water(minimum distance of 400 yards). _ Drainage leaving the site will be in the form of sheet flow. The sheet flow will follow the natural topography of the site to the west where it will flow into Dabob Bay. 3. Environmentally Sensitive Areas. a. Description of environmentally sensitive areas that are on or adjacent to the site. Landslide hazard stormwater site plan template.doc—rev.10/12/2003 9 • • b. Description of special requirements for working in or near environmentally sensitive areas. Setbacks must be met. See geotechnical report. 4. Erosion Problem Areas. Description of potential erosion problems on site in the context of the characteristics of the on-site soils(e.g., erodibility,settleability, permeability, depth,texture,soil structure). The Jefferson County Critical Areas Map does not list any portion of this parcel as having erosion hazard. 5. Construction Phasing. a. Construction sequence b. Construction phasing(if proposed) 6. Construction Schedule. Wet season is October 1 through April 30(page 2-21 of the Manual). Provide a proposed construction schedule. II. Wet Season Construction Activities. a. Proposed wet season construction activities. b. Proposed wet season construction activities for environmentally sensitive areas. 7. Financial/Ownership Responsibilities. a. Identify the property owner responsible for the initiation of bonds and/or other financial securities. b. Describe bonds and/or other evidence of financial responsibility for liability associated with erosion and sedimentation impacts. 8. Engineering Calculations. Provide Design Calculations on a separate sheet for the following, if applicable. a. Sediment Ponds/Traps. b. Diversions. c. Waterways. d. Runoff/Stormwater Detention Calculations stormwater site plan template.doc—rev.10/12/2003 10 • • SECTION II—EROSION AND SEDIMENT CONTROL PLAN Sediment and erosion control measures may be depicted on the master land use application plot plan,a stormwater site plan,and/or a separate Construction SWPPP site plan. This is a checklist to ensure that the following are depicted on a site plan: 1. General. a. Vicinity Map b. Jefferson County Approval Block c. Erosion and Sediment Control Notes 2. Site Plan. a. Legal description of subject property. b. North arrow. c. Indicate boundaries of existing vegetation(e.g.,tree lines, pasture areas, etc.). d. Identify and label areas of potential erosion problems. e. Identify FEMA base flood boundaries and Shoreline Management boundaries(if applicable). f. Show existing and proposed contours. g. Indicate drainage basins and direction of flow for individual drainage areas. h. Label final grade contours and identify developed condition drainage basins. i. Delineate areas that are to be cleared and graded. j. Show all cut and fill slopes indicating top and bottom of slope catch lines. 3. Conveyance Systems. a. Designate locations for swales, interceptor trenches,or ditches. b. Show all temporary and permanent drainage pipes,ditches,or cut-off trenches required for erosion&sediment control. c. Provide minimum slope and cover for all temporary pipes or call out pipe inverts. d. Shows grades,dimensions,and direction of flow in all ditches, swales, culverts and pipes. e. Provide details for bypassing off-site runoff around disturbed areas. f. Indicate locations and outlets of any dewatering systems. 4. Location of Detention Best Management Practices(BMPs). Identify location of detention BMPs. 5. Erosion and Sediment Control Facilities. a. Show the locations of sediment trap(s), pond(s), pipes and structures. b. Dimension pond berm widths and inside and outside pond slopes. c. Indicate the trap/pond storage required and the depth, length,and width dimensions. d. Provide typical section views through pond and outlet structure. e. Provide typical details of gravel cone and standpipe, and/or other filtering devices. f. Detail stabilization techniques for outlet/inlet. g. Detail control/restrictor device location and details. h. Specify mulch and/or recommended cover of berms and slopes. i. Provide rock specifications and detail for rock check dam(s), if applicable. j. Specify spacing for rock check dams as required. k. Provide front and side sections of typical rock check dams. I. Indicate the locations and provide details and specifications for silt fabric. m. Locate the construction entrance and provide a detail. 6. Detailed Drawings. Any structural practices used that are not referenced in the Ecology Manual should be explained and illustrated with detailed drawings. 7. Other Pollutant BMPs. Indicate on the site plan the locations of BMPs to be used for the control of pollutants other than sediment(e.g., concrete wash water). 8. Monitoring Locations. Indicate on the site plan the water quality sampling locations to be used for monitoring water quality on the construction site. Sampling stations should be located upstream and downstream of the project site. stormwater site plan template.doc—rev.10/12/2003 11 • • Stormwater Site Plan Changes If the designer wishes to make changes or revisions to the originally approved Stormwater Site Plan, the proposed revisions shall be submitted to DCD 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-builts")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, I as the applicant/owner attest 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: stormwater site plan template.doc—rev.10/12/2003 12 • Stormwater Site Plan Changes If the designer wishes to make changes or revisions to the originally approved Stormwater Site Plan, the proposed revisions shall be submitted to DCD 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-builts")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, I as the applicant/owner attest 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: stormwater site plan template.doc—rev.10/12/2003 12 • 0 APPENDIX B • • �4��s°N ��� JEFFERSON COUNTY ti DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street• Port Townsend • Washington 98368 •qS, 0�O 360/379-4450 • 360/379-4451 Fax http://www.co.jefferson.wa.us/commdevelopment/ Stormwater Calculation Worksheet MLA# PROJECT/APPLICANT NAME: Chris Clegg DETERMINING STORMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to classify the proposal as"small,""medium,"or"large." The size determines whether a Stormwater Site Plan is required in conjunction with a stand-alone stormwater management permit application, building permit application, or other land use approval application that involves stormwater review. The basic information will also be helpful for completing a Stormwater Site Plan, if required. PARCEL SIZE(I.E.,SITE) Size of parcel 1 . 62 acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet 7 0, 4 51 sq/ft Land-disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover(both vegetative and non-vegetative) and/or the existing soil topography. Land disturbing activities include, but are not limited to clearing, grading, filling, excavation,and compaction associated with stabilization of structures and road construction. Native vegetation is vegetation comprised on 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 species such as Douglas fir,western hemlock,western red cedar,alder,big-leaf maple,and vine maple;shrubs such as willow, elderberry,salmonberry, and salal;herbaceous plants such as sword fern,foam flower, and fireweed. LAND DISTURBING ACTIVITY,CONVERSION OF NATIVE VEGETATION,AND VOLUME OF CUT/FILL Calculate the total area to be cleared, graded,filled, Answer the following two questions related to excavated,and/or compacted for proposed development conversion of native vegetation: project. Include in this calculation the area to be cleared for: 2, 043 Does the project convert'/+acres or more of Construction site for structures sq/ft native vegetation to lawn or landscaped areas? Drainfield,septic tank,etc. 1, 300 sq/ft Circle: Yes C No) Well,utilities,etc _ sq/ft Does the project convert 2'/z acres or more of 3, 454 native vegetation to pasture? Driveway, parking, roads,etc. sq/ft Circle: Yes (No) Lawn, landscaping,etc. sq/ft Other compacted surface, etc. sq/ft Indicate Total Volumes of Proposed: Total Land Disturbance 6, 797 sq/ft Cut Fill (cu/yd) [over] stormwater calc worksheet—REV 2/20/2008 1 • • Impervious surface is a hard surface 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. STORMWATER CALULATIONS—IMPERVIOUS SURFACE NEW EXISTING Structures (all roof area) 2, 043 sq/ft Structures(all roof area) sq/ft Sidewalks sq/ft Sidewalks sq/ft Patios 175 sq/ft Patios sq/ft Solid Decks sq/ft Solid Decks sq/ft (without infiltration below) (without infiltration below) Driveway,parking,roads,etc sq/ft Driveway, parking, roads,etc 3, 454 _sq/ft Other sq/ft Other sq/ft Total New sq/ft Total Existing 3, 454 sq/ft TOTAL NEW+TOTAL EXISTING* 5, 6 7 2 sq/ft "This amount will be used to check total lot coverage. The following questions will help determine whether the proposed project is considered development or redevelopment. DEVELOPMENT v. REDEVELOPMENT Divide the total existing impervious surface above by the size of the parcel and convert to a percentage: 5 % Does the site have 35%or more of existing impervious surface? Circle: Yes No FURTHER INSTRUCTIONS: If the answer is yes, the proposal is considered redevelopment and the attached Figure 2 should be used to determine the applicable Minimum Requirements. If the answer is no, the proposal is considered new development and the attached Figure 1 should be used. At this juncture, the applicant should refer to the applicable Flow Chart to determine the Minimum Requirements for stormwater management, DCD staff will help verify the classification of the project and the application requirements. For proponents of "small' projects who must comply only with Minimum Requirement #2—Construction Stormwater Pollution Prevention—an additional submittal is not required. The proponent is responsible for employing the 12 Elements to control erosion and prevent sediment and other pollutants from leaving the site during the construction phase of the project. Pick up the Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet. Proponents of"medium" projects—those that must meet only Minimum Requirements #1 through #5—and for `large" projects—those that must meet all 10 Minimum Requirements—are required to submit a Stormwater Site Plan. DCD has prepared a submittal template of a Stormwater Site Plan, principally for rural residential projects. Complete the template in the Stormwater Site Plan Instructions and Submittal Template or prepare a Stormwater Site Plan using the step-by-step guidance in the Stormwater Management Manual. APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest 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) FOR OFFICE USE ON L t S erer� . s c f r5 :3 MPL 'WO 1Gr r4r-ktfEveLoplight stormwater talc worksheet—REV.2/20/2008 2 • • APPENDIX C • • Start Here Does the site have Yes See Redevelopment 35%or more of — - ---► Minimum existing impervious Requirements and coverage? Flow Chart Does the project convert (Figure 2.3) No '/ acres or more of native ♦ vegetation to lawn or Does the project add No landscaped areas, or 5,000 square feet or convert 2.5 acres or more more of new of native vegetation to impervious surfaces? pasture? Yes Yes No Does the project have ♦ 2,000 square feet or All Minimum more of new, replaced, Requirements apply to or new plus replaced the new impervious impervious surfaces? surfaces and converted pervious surfaces. Yes / No Minimum Does the project have Requirements#1 land-disturbing through#5 apply to 44 activities of 7,000 the new and replaced Yes square feet or more? impervious surfaces -- and the land disturbed. No V See Minimum Requirement #2, Construction Stormwater Pollution Prevention Figure 2.2—Flow Chart for Determining Requirements for New Development February 2005 Volume t—Minimum Technical Requirements 2-9 • • APPENDIX D Map Output41/ • Page 1 of 1 ArcIMS HTML Viewer Map fuyf 40200/ '.. kf14 02025 020' AI Ciif SU20;6 ••"". C0.s,ohsrr r1+i•.r:Zr1f1 WIfva11o2x )11020t'! • td! P1�.,L+lUfO' r tLegend 7 Selected Features i .. • Towns County Sort ^6yl nsr�.2 � 60 t02Jt'+ 6,aSSU20fs o RurelCanl ors 01 JC Roads &)C2oSS Parcels.H rc is•H Shoreline Slope Stability OslabW (�n %n�a0}� lntarn+wti a[c fx. 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