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HomeMy WebLinkAboutBLD2006-00498 Stormwater Management • FINAL STORMWATER MANAGEMENT PLAN AKERS RESIDENCE 223 Rainshadow Drive Port Townsend, WA. St©rmwat , J. kV Required � of w AS'siyA� P • , z '• ;eAtjISTE �� / i/'/ /U . APPROVED EXP. DATE: 05 / 05 / OS STORM WATER PLAN NOV 1 4 2006 JEFFER • O N U U 4 9 8 SIGPT T REq ' I E rj JEFFERON COUNTY OCR REcETEJI ) Prepared by Michael J. Anderson PE&PLS No. 27665 330 Cleveland Street jff "'''' ,001)H!1,11 Port Townsend, WA 908368 2 SBUH/SCS METHOD FOR COMPUTING RUNOFF HYDROGRAPH STORM OPTIONS: �V/(• RYW"Y 1 - S .C.S . TYPE-lA !✓' 2 - 7-DAY DESIGN STORM 3 - STORM DATA FILE SPECIFY STORM OPTION: 1 S.C.S. TYPE-lA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 2 , 24 , 1 . 12 ******************** S.C.S. TYPE-lA DISTRIBUTION ******************** ********* 2-YEAR 24-HOUR STORM **** 1 . 12" TOTAL PRECIP. ********* ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1 3 . 71 , 86 , 0 . 12 , 98 , 5 . 0 DATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN 3.8 3 . 7 86 . 0 . 1 98 . 0 5 . 0 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) . 17 7 . 83 3904 ENTER [d: ] [path] filename[ .ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c : 2yr .pre FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP n STORM OPTIONS: R tt. �\,� y" irk 1 - S .C.S. TYPE-lA 2 - 7-DAY DESIGN STORM 3 - STORM DATA FILE SPECIFY STORM OPTION: i S .C.S . TYPE-lA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 100 , 24 , 2 . 50 :,:r:x:t:*************** S .C.S . TYPE :** ****** * ***** -lA DISTRIBUTION *' ***** ° 100-YEAR 24-HOUR STORM **** 2 . 50" TOTAL PRECIP , ********* ENTER: A(PER`I , iN(PE-V) ; A( IlitE zV) , ON( IMPERV) , TO FOR BASIN NO . J 3 71 , 86 , 0 , 12 , 98 , 7_ 0 DATA PRINT-OJT. AREA(ACRES) PERVIOUS ("IMPERVIOUS TC(MINUTES) • 471 A CN -A CN 3 . 8 3 . 7 86 . 0 . 1 98 . 0 5 . 0 . PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) 1 . 24 7 . 67 17735 ENTER [d: ] [path] filename[ . ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c :100yr . pre FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP n STORM OPTIONS: 1 - S.C.S. TYPE-1A 2 - 7-DAY DESIGN STORM 3 - STORM DATA FILE SPECIFY STORM OPTION: 1 S.C. S . TYPE-lA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 2 , 24 , 1 . 12 ******************** S.C.S. TYPE-lA DISTRIBUTION ******************** ********* 2-YEAR 24-HOUR STORM **** 1 . 12" TOTAL PRECIP. ********* ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1 3 . 21 , 86 , 0 . 62 , 98 , 10 . 0 DATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN 3 . 8 3 . 2 86 . 0 . 6 98 . 0 10 . 0 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) . 25 7 . 83 5074 ENTER [d : ] [path] filename[ . ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c : 2yr. pst FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP STORM OPTIONS : RECE1A 1 I_ 1 - S .C.S . TYPE-lA 2 - 7-DAY DESIGN STORM k, 3 - STORM DATA FILE SPECIFY STORM OPTION: S . C .S . TYPE-1A RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 100 , 24 , 2 . 50111 ******************** S .C . S . TYPE-lA DISTRIBUTION ******************** ********* 100-YEAR 24-HOUR STORM **** 2 . 50" TOTAL PRECIP. ********* ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1 3 . 21 , 86 , 0 . 62 , 98 , 10 . 00 DATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN 3 . 8 3 . 2 86 . 0 . 6 98 . 0 10 . 0 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) 1 . 29 7 . 83 19586 ENTER Ed : ] [path] filename[ .ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c : 100yr.pst FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP s KING COUNTY DEPARTMENT OF PUBLIC WORKS Surface Water Management Division HYDROGRAPH PROGRAMS Version 4 . 21B 1 - INFO ON THIS PROGRAM 2 - SBUHYD 3 - MODIFIED SBUHYD 4 - ROUTE 5 - ROUTE2 6 - ADDHYD 7 - BASEFLOW 8 - PLOTHYD 9 - DATA 10 - RDFAC 11 - RETURN TO DOS ENTER OPTION: 10-'1,tom I� `�� p� 10 R/D FACILITY DESIGN ROUTINE SPECIFY TYPE OF R/D FACILITY: 1 - POND 4 - INFILTRATION POND T DP JEH, .r ` k '_y s 2 - TANK 5 - INFILTRATION TANK 3 - VAULT 6 - GRAVEL TRENCH/BED 4 ENTER: POND SIDE SLOPE (HORIZ . COMPONENT) 3 1Q S S T71 R/D FACILITY DESIGN ROUTINE SPECIFY TYPE OF R/D FACILITY: 'to,J 1 1 - POND 4 - INFILTRATION POND iC a (. 1\I t 11005 2 - TANK 5 - INFILTRATION TANK 3 - VAULT 6 - GRAVEL TRENCH/BED 4 ENTER: POND SIDE SLOPE (HORIZ. COMPONENT) 3 ENTER: EFFECTIVE STORAGE DEPTH( ft ) BEFORE OVERFLOW 2 . 0 ENTER: VERT-PERM(min/in) , PERM-SURFACE (0 = SIDES ONLY, 1 = SIDES AND BOTTOM) 6 , 1 ENTER Ed: ] [path] filename[ .ext ] OF PRIMARY DESIGN INFLOW HYDROGRAPH: c : 2yr.pst PRIMARY DESIGN INFLOW PEAK = . 25 CFS ENTER PRIMARY DESIGN RELEASE RATE(cfs) : 0 ENTER NUMBER OF INFLOW HYDROGRAPHS TO BE TESTED FOR PERFORMANCE (5 MAXIMUM) : 0 ENTER: NUMBER OF ORIFICES , RISER-HEAD( ft) , RISER-DIAMETER( in) 1 , 2 . 0 , 6 ERROR: NUMBER OF ORIFICES MUST BE ZERO IF RELEASE RATE IS ZERO CORRECTION: INPUTTED NUMBER HAS BEEN SET TO ZERO - EXECUTION CONTINUES RISER OVERFLOW DEPTH FOR PRIMARY PEAK INFLOW = . 14 FT SPECIFY ITERATION DISPLAY: Y - YES, N - NO �) n SPECIFY: R - REVIEW/REVISE INPUT, C - CONTINUE c JEfrT ;'r1I INITIAL STORAGE VALUE FOR ITERATION PURPOSES: 5046 CU-FT PERFORMANCE: INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE DESIGN HYD: . 25 . 00 . 00 1 . 99 461 SPECIFY: D - DOCUMENT, R - REVISE, A - ADJUST ORIF, E - ENLARGE, S - STOP d PERFORMANCE: INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE DESIGN HYD: . 25 . 00 . 00 2 . 00 461 STRUCTURE DATA: R/D-POND ( 3 . 0 : 1 SIDE SLOPES) RISER-HEAD POND-BOTTOM-AREA TOP-AREA(@1 ' F.B. ) STOR-DEPTH STORAGE-VOLUME 2 . 00 FT 73 . 7 SQ-FT 725 . 5 SQ-FT 2 . 00 FT 461 CU-FT PERMEABLE SURFACE : POND SIDES AND BOTTOM ROUTING DATA: STAGE(FT) DISCHARGE(CFS S STORAGE(CU-FT) PERM-ARAW SQ-FT) gel . 06 . 00 . 0 . 0 . 20 . 00 17 . 0 97 . 0 . 40 . 00 39 . 0 123 . 2 . 60 . 00 66 . 5 152 . 2 . 80 . 00 100 . 1 184 . 2 1 . 00 . 00 140 . 3 219 . 0 1 . 20 . 00 187 . 9 256 . 7 1 . 40 . 00 243 . 2 297 . 2 1 . 60 . 00 306 . 9 340 . 7 1 . 80 . 00 379 . 7 387. 0 2 . 00 . 00 462 . 0 436 . 2 2 . 10 . 15 506 . 9 461 . 9 2 . 20 . 42 554 . 4 488 . 3 2 . 30 . 52 604 . 5 515 . 4 2 . 40 . 60 657 . 4 543 . 3 2 . 50 . 67 713. 2 571 . 9 AVERAGE VERTICAL PERMEABILITY: 6. 0 MINUTES/INCH SPECIFY: F - FILE, N - NEWJOB, P - PRINT IF/OF, R - REVISE, S - STOP s KING COUNTY DEPARTMENT OF PUBLIC WORKS Surface Water Management Division HYDROGRAPH PROGRAMS Version 4 . 21B 1 - INFO ON THIS PROGRAM 2 - SBUHYD 3 - MODIFIED SBUHYD 4 - ROUTE 5 - ROUTE2 6 - ADDHYD 7 - BASEFLOW 8 - PLOTHYD 9 - DATA 10 - RDFAC 11 - RETURN TO DOS RECERii) 2 411 SBUH/SCS METHOD FOR COMPUTING RUNOFF HYDROGRAPH Ili — rWa y STORM OPTIONS : 60►14M' [F. 1 - S.C.S. TYPE-1A k� 6y 2 - 7-DAY DESIGN STORM �1 (i7 `,� 3 - STORM DATA FILE / t35 SPECIFY STORM OPTION: (.•� 1 S.C.S. TYPE-lA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 2 , 24 , 1 . 12 ******************** S.C.S. TYPE-IA DISTRIBUTION ******************** ********* 2-YEAR 24-HOUR STORM **** 1 . 12" TOTAL PRECIP. ********* ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. ] 3 . 60 , 86 , 0 . 23 , 98 , 10 . 0 DATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN 3. 8 3. 6 86 . 0 . 2 98 . 0 10 . 0 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) . 17 7. 83 4158 ENTER [d: ] [path] filename[ .ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c : 2yr.pst FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP g STORM OPTIONS: RECEVET ' 1 - S.C.S. TYPE-lA 2 - 7-DAY DESIGN STORM 3 - STORM DATA FILE SPECIFY STORM OPTION: F; ,.�� i� 1 ; S .C.S . TYPE-lA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) 100 , 24 , 2 . 50 ******************** S .C.S . TYPE-lA DISTRIBUTION ******************** ********* 100-YEAR 24-HOUR STORM **** 2 . 50" TOTAL PRECIP. ********* ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1 3 . 60 , 86 , 0 . 23 ,98 , 10 . 00 )ATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) ,M, ® 9 A CN A CN • t 3 . 8 3 . 6 86 . 0 . 2 98 . 0 10 . 0 12t9OP PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) t • /' �", f/ fi 1 . 18 7 . 83 18132 O ► ( I- 'JClC� ENTER Ed: ] [path] filenameI .ext ] FOR STORAGE OF COMPUTED HYDROGRAPH: c : 100yr. pst FILE ALREADY EXIST; OVERWRITE (Y or N) ? y SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP s KING COUNTY DEPARTMENT OF PUBLIC WORKS Surface Water Management Division HYDROGRAPH PROGRAMS Version 4 . 21B 1 - INFO ON THIS PROGRAM 2 - SBUHYD 3 - MODIFIED SBUHYD 4 - ROUTE 5 - ROUTE2 6 - ADDHYD 7 - BASEFLOW 8 - PLOTHYD 9 - DATA 10 - RDFAC 11 - RETURN TO DOS ENTER OPTION: 10 R/D FACILITY DESIGN ROUTINE SPECIFY TYPE OF R/D FACILITY: 01,41, '� $ I' ' 1 - POND 4 - INFILTRATION POND r 2 - TANK 5 - INFILTRATION TANK 3 - VAULT 6 - GRAVEL TRENCH/BED 4 E 5 ENTER: POND SIDE SLOPE (HORIZ. COMPONENT) ' 3 ENTER: EFFECTIVE STORAGE DEPTH( ft ) BEFORE OVERFLOW 2 . 0 ENTER: VERT-PERM(min/in) , PERM-SURFACE ( 0 = SIDES ONLY, 1 = SIDES AND BOTTOM) 6 , 1 ENTER Ed : ] [path] filename[ . ext ] OF PRIMARY DESIGN INFLOW HYDROGRAPH: c : 100yr . pst PRIMARY DESIGN INFLOW PEAK = 1 . 18 CFS ENTER PRIMARY DESIGN RELEA RATE(cfs) : • `��� 0 ENTER NUMBER OF INFLOW HYDROGRAPHS TO BE TESTED FOR PERFORMANCE ( 5 MAXIMUM) : 0 ENTER: NUMBER OF ORIFICES, RISER-HEAD( ft) , RISER-DIAMETER( in) 0 , 2 . 0 , 6 RISER OVERFLOW DEPTH FOR PRIMARY PEAK INFLOW = 1 . 56 FT SPECIFY ITERATION DISPLAY: Y - YES, N - NO n SPECIFY: R - REVIEW/REVISE INPUT, C - CONTINUE c INITIAL STORAGE VALUE FOR ITERATION PURPOSES: 18114 CU-FT PERFORMANCE: INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE DESIGN HYD: 1 . 18 . 00 . 00 2 . 00 2351 SPECIFY: D - DOCUMENT, R - REVISE, A - ADJUST ORIF, E - ENLARGE, S - STOP d PERFORMANCE: INFLOW TARGET-OUTFLOW ACTUAL-OUTFLOW PK-STAGE STORAGE DESIGN HYD: 1 . 18 . 00 . 00 2 . 00 2351 STRUCTURE DATA: R/D-POND ( 3 . 0 : 1 SIDE SLOPES) RISER-HEAD POND-BOTTOM-AREA TOP-AREA(@1 ' F.B. ) STOR-DEPTH STORAGE-VOLUME 2 . 00 FT 774 . 2 SQ-FT 2160 .6 SQ-FT 2 . 00 FT 2351 CU-FT PERMEABLE SURFACE: POND SIDES AND BOTTOM ROUTING DATA: STAGE(FT) DISCHARGE(CFS) STORAGE(CU-FT) PERM-AREA(SQ-FT) . 00 . 00 . 0 . 0 . 20 . 00 162 . 0 846 . 4 .40 . 00 338 . 8 921 . 6 . 60 . 00 530 . 8 999 . 6 . 80 . 00 738 .8 1080 . 5 1 . 00 . 00 963 . 2 1164 . 3 1 . 20 . 00 1204 . 7 1251 . 0 1 . 40 . 00 1463 . 8 1340 . 5 1 . 60 . 00 1741 . 1 1433 . 0 1 . 80 . 00 2037 . 2 1528 . 3 2 . 00 . 00 2352 . 6 1626 . 5 2 . 10 15 2517 . 8 1676 . 6 � ,�� •j � Ak \ rill 2 . 20 . . 42 2688 . 0 1727. 5 � V1--4 2 . 30 . 52 2863 . 1 1779 . 1 2 . 40 . 60 3043 . 6 1831 . 4 2 . 50 . 67 3229 . 4 1884 . 5 2 . 60 . 73 3420 .6 1938 . 2 2 . 70 . 79 3617 . 1 1992 . 7 2 . 80 . 85 3819 . 1 2048 . 0 � 2 . 90 . 90 4026. 7 2103 . 9 3 . 00 . 95 4239 . 9 2160 . 5 3. 10 . 99 4458 . 9 2217 . 9 3 . 20 1 . 04 4683 . 5 2276 . 0 3 . 30 1 . 08 4914 . 1 2334 . 8 3 . 40 1 . 12 40 5150 . 5 239 ��� • 3 . 50 1 . 16 5393 . 0 245 / AVERAGE VERTICAL PERMEABILITY: 6 . 0 MINUTES/INCH SPECIFY: F - FILE, N - NEWJOB, P - PRINT IF/OF, R - REVISE, S - STOP s KING COUNTY DEPARTMENT OF PUBLIC WORKS Surface Water Management Division HYDROGRAPH PROGRAMS Version 4 . 21B 1 - INFO ON THIS PROGRAM 2 - SBUHYD 3 - MODIFIED SBUHYD 4 - ROUTE 5 - ROUTE2 6 - ADDHYD 7 - BASEFLOW 8 - PLOTHYD 9 - DATA 10 - RDFAC 11 - RETURN TO DOS RECEJ1 "1r j y3: I • ATTACHMENT "A" OPERATIONS & MAINTENANCE MANUAL AKERS RESIDENCE PORT TOWNSEND, JEFFERSON COUNTY, WA. IRECE VPII") • 4 C D S • No. 1 —Detention Ponds Maintenance Defect Conditions When Maintenance Is Results Expected When Component Needed Maintenance Is Performed Beaver Dams Dam results in change or function of Facility is returned to design function. the facility. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) Insects When insects such as wasps and Insects destroyed or removed from site. hornets interfere with maintenance activities. Apply insecticides in compliance with adopted IPM policies Tree Growth Tree growth does not allow Trees do not hinder maintenance and Hazard maintenance access or interferes activities. Harvested trees should be Trees with maintenance activity(i.e.,slope recycled into mulch or other beneficial mowing,silt removal,vectoring,or uses(e.g.,alders for firewood). equipment movements). If trees are not interfering with access or Remove hazard Trees maintenance,do not remove If dead,diseased,or dying trees are identified (Use a certified Arborist to determine health of tree or removal requirements) Side Slopes Erosion Eroded damage over 2 inches deep Slopes should be stabilized using of Pond where cause of damage is still appropriate erosion control measure(s); present or where there is potential for e.g.,rock reinforcement, planting of continued erosion. grass,compaction. Any erosion observed on a If erosion is occurring on compacted compacted berm embankment berms a licensed civil engineer should be consulted to resolve source of erosion. Storage Area Sediment Accumulated sediment that exceeds Sediment cleaned out to designed pond 10%of the designed pond depth shape and depth;pond reseeded if unless otherwise specified or affects necessary to control erosion. inletting or outletting condition of the facility. Liner(If Liner is visible and has more than Liner repaired or replaced. Liner is fully Applicable) three 1/4-inch holes in it. covered. RiE( 4ii1 � r:: February 2005 Volume V—Runoff Treatment BMPs 4-31 • No. 1 —Detention Ponds Maintenance Defect Conditions When Maintenance Is Results Expected When Component Needed Maintenance Is Performed Pond Berms Settlements Any part of berm which has settled 4 Dike is built back to the design (Dikes) inches lower than the design elevation. elevation. If settlement is apparent, measure berm to determine amount of settlement. Settling can be an indication of more severe problems with the berm or outlet works. A licensed civil engineer should be consulted to determine the source of the settlement. Piping Discernable water flow through pond Piping eliminated. Erosion potential berm. Ongoing erosion with potential resolved. for erosion to continue. (Recommend a Goethechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Emergency Tree Growth Tree growth on emergency spillways Trees should be removed. If root Overflow/ creates blockage problems and may system is small(base less than 4 Spillway and cause failure of the berm due to inches)the root system may be left in Berms over 4 uncontrolled overtopping. place. Otherwise the roots should be feet in height. removed and the berm restored. A Tree growth on berms over 4 feet in licensed civil engineer should be height may lead to piping through the consulted for proper berm/spillway berm which could lead to failure of restoration. the berm. Piping Discernable water flow through pond Piping eliminated. Erosion potential berm. Ongoing erosion with potential resolved. for erosion to continue. (Recommend a Goethechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Emergency Emergency Only one layer of rock exists above Rocks and pad depth are restored to Overflow/ Overflow/ native soil in area five square feet or design standards. Spillway Spillway larger, or any exposure of native soil at the top of out flow path of spillway. (Rip-rap on inside slopes need not be replaced.) Erosion See"Side Slopes of Pond" 4-32 Volume V—Runoff Treatment BMPs February 2005 S . No. 2—Infiltration Maintenance Defect Conditions When Maintenance Is Results Expected When Component Needed Maintenance Is Performed General Trash &Debris See"Detention Ponds"(No. 1). See"Detention Ponds" (No. 1). Poisonous/Noxious See"Detention Ponds"(No. 1). See"Detention Ponds" Vegetation (No. 1). Contaminants and See"Detention Ponds"(No. 1). See"Detention Ponds" Pollution (No. 1). Rodent Holes See"Detention Ponds"(No. 1). See"Detention Ponds" (No. 1) Storage Area Sediment Water ponding in infiltration pond after Sediment is removed rainfall ceases and appropriate time and/or facility is cleaned allowed for infiltration. so that infiltration system works according to (A percolation test pit or test of facility design. indicates facility is only working at 90%of its designed capabilities. If two inches or more sediment is present,remove). Filter Bags(if Filled with Sediment and debris fill bag more than 1/2 Filter bag is replaced or applicable) Sediment and full. system is redesigned. Debris Rock Filters Sediment and By visual inspection, little or no water flows Gravel in rock filter is Debris through filter during heavy rain storms. replaced. Side Slopes of Erosion See"Detention Ponds"(No. 1). See"Detention Ponds" Pond (No. 1). Emergency Tree Growth See"Detention Ponds"(No. 1). See"Detention Ponds" Overflow Spillway (No. 1). and Berms over 4 feet in height. Piping See"Detention Ponds"(No. 1). See"Detention Ponds" (No. 1). Emergency Rock Missing See"Detention Ponds"(No. 1). See"Detention Ponds" Overflow Spillway (No. 1). Erosion See"Detention Ponds"(No. 1). See"Detention Ponds" (No. 1). Pre-settling Facility or sump 6"or designed sediment trap depth of Sediment is removed. Ponds and Vaults filled with Sediment sediment. and/or debris 1 JfiE I r r ,1 February 2005 Volume V—Runoff Treatment BMPs 4-33 S • No. 8—Typical Biofiltration Swale Maintenance Defect or Condition When Recommended Maintenance to Correct Component Problem Maintenance is Needed Problem General Sediment Sediment depth exceeds 2 Remove sediment deposits on grass Accumulation on inches. treatment area of the bio-swale. When • Grass finished,swale should be level from side to side and drain freely toward outlet. There should be no areas of standing water once inflow has ceased. Standing Water When water stands in the Any of the following may apply: remove swale between storms and sediment or trash blockages,improve does not drain freely. grade from head to foot of swale,remove clogged check dams, add underdrains or convert to a wet biofiltration swale. Flow spreader Flow spreader uneven or Level the spreader and clean so that flows clogged so that flows are not are spread evenly over entire swale width. uniformly distributed through entire swale width. Constant When small quantities of Add a low-flow pea-gravel drain the length Baseflow water continually flow through of the swale or by-pass the baseflow the swale,even when it has around the swale. been dry for weeks,and an eroded,muddy channel has formed in the swale bottom. Poor Vegetation When grass is sparse or bare Determine why grass growth is poor and Coverage or eroded patches occur in correct that condition. Re-plant with plugs more than 10%of the swale of grass from the upper slope: plant in the bottom. swale bottom at 8-inch intervals. Or re- seed into loosened,fertile soil. Vegetation When the grass becomes Mow vegetation or remove nuisance excessively tall(greater than vegetation so that flow not impeded. 10-inches);when nuisance Grass should be mowed to a height of 3 to weeds and other vegetation 4 inches. Remove grass clippings. starts to take over. Excessive Grass growth is poor because If possible,trim back over-hanging limbs Shading sunlight does not reach and remove brushy vegetation on swale. adjacent slopes. Inlet/Outlet Inlet/outlet areas clogged with Remove material so that there is no sediment and/or debris. clogging or blockage in the inlet and outlet area. Trash and Trash and debris Remove trash and debris from bioswale. Debris accumulated in the bio-swale. Accumulation Erosion/Scouring Eroded or scoured swale For ruts or bare areas less than 12 inches bottom due to flow wide, repair the damaged area by filling channelization, or higher with crushed gravel. If bare areas are flows. large,generally greater than 12 inches wide,the swale should be re-graded and re-seeded. For smaller bare areas, overseed when bare spots are evident,or take plugs of grass from the upper slope and plant in the swale bottom at 8-inch intervals. February 2005 Volume V—Runoff Treatment BMPs 4-39 I • No. 9—Wet Biofiltration Swale Maintenance Defect or Condition When Maintenance is Recommended Maintenance to Component Problem Needed Correct Problem General Sediment Sediment depth exceeds 2-inches in Remove sediment deposits in Accumulation 10%of the swale treatment area. treatment area. Water Depth Water not retained to a depth of Build up or repair outlet berm so about 4 inches during':he wet that water is retained in the wet season. swale. Wetland Vegetation becomes sparse and Determine cause of lack of vigor Vegetation does not provide adequate filtration, of vegetation and correct. Replant OR vegetation is crowded out by as needed. For excessive cattail very dense clumps of cattail,which growth,cut cattail shoots back do not allow water to flow through and compost off-site. Note: the clumps. normally wetland vegetation does not need to be harvested unless die-back is causing oxygen depletion in downstream waters. Inlet/Outlet Inlet/outlet area clogged with Remove clogging or blockage in sediment and/or debris. the inlet and outlet areas. Trash and See"Detention Ponds"(No. 1). Remove trash and debris from wet Debris swale. Accumulation Erosion/Scouring Swale has eroded or scoured due to Check design flows to assure flow channelization,or higher flows. swale is large enough to handle flows. By-pass excess flows or enlarge swale. Replant eroded areas with fibrous-rooted plants such as Juncus effusus(soft rush) in wet areas or snowberry (Symphoricarpos albus)in dryer areas. R ; (( 'r' 'lt'\\' ! ; _. 4-40 Volume V—Runoff Treatment BMPs February 2005 O • • Stabilize soil areas upslope of the biofilter to prevent erosion • Fertilizing a biofilter should be avoided if at all possible in any application where nutrient control is an objective. Test the soil for nitrogen,phosphorous,and potassium and consult with a landscape professional about the need for fertilizer in relation to soil nutrition and vegetation requirements. If use of a fertilizer cannot be avoided, use a slow-release fertilizer formulation in the least amount needed. Recommended grasses (see Tables 9.3 and 9.4 below) Table 9.3—Grass Seed Mixes Suitable for Biofiltration Swale Treatment Areas Mix 1 Mix 2 75-80 percent tall or meadow fescue 60-70 percent tall fescue 10-15 percent seaside/colonial 10-15 percent seaside/colonial bentgrass bentgrass . 5-10 percent Redtop 10-15 percent meadow foxtail 6-10 percent alsike clover 1-5 percent marshfield big trefoil 1-6 percent Redtop Note: all percentages are by weight. * based on Briargreen,Inc. Table 9.4—Groundcovers And Grasses Suitable for the Upper Side Slopes of a Biofiltration Swale in Western Washington Groundcovers kinnikinnick* Arctostaphylos uva-ursi St.John's-wort Hypericum perforatum Epimedium Epimedium grandiflorum creeping forget-me-not Omphalodes verna Euonymus lanceolata yellow-root Xanthorhiza simplissima Genista white lawn clover Trifolium repens white sweet clover* Melilotus alba Rubus calycinoides strawberry* Fragaria chiloensis broadleaf lupine* Lupinus latifolius Grasses(drought-tolerant,minimum mowing) dwarf tall fescues Festuca spp.(e.g.,Many Mustang,Silverado) hard fescue Festuca ovina duriuscula(e.g.,Reliant,Aurora) tufted fescue Festuca amethystine buffalo grass Buchloe dactyloides red fescue* Festuca rubra tall fescue grass* Festuca arundinacea blue oatgrass Helictotrichon sempervirens 9-18 Volume V—Runoff Treatment BMPs February 2005 rfiy. •