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Home My WebLink AboutSW6220203_Plansheet C6.7 - SCM Detail_20220225STORMWATER MANAGEMENT NOTES: 1. THE DEVELOPER OR HIS AGENT SHALL CONTACT THE DESIGN ENGINEER WHEN THE BEST MANAGEMENT PRACTICE(S) ARE CONSTRUCTED AND ABOUT TO BECOME OPERATIONAL SO A FINAL INSPECTION CAN BE PERFORMED TO DETERMINE COMPLIANCE WITH THE APPROVED PLAN CAN BE PERFORMED. 2. ANNUAL MAINTENANCE INSPECTION AND REPORT REQUIRED - THE OWNER OF A PERMITTED STRUCTURAL STORMWATER BMP/CONTROL SHALL ANNUALLY SUBMIT A MAINTENANCE AND INSPECTION REPORT FOR EACH BMP TO THE STORMWATER ADMINISTRATOR. ANNUAL INSPECTIONS SHALL BEGIN WITHIN ONE YEAR OF THE RECORDATION OF ANY DEED(S) SHOWING STORMWATER BMPs/CONTROL STRUCTURES. 3. UPON COMPLETION OF THE PROJECT, AND BEFORE A CERTIFICATE OF OCCUPANCY SHALL BE GRANTED, THE ENGINEER OF RECORD SHALL CERTIFY THAT THE COMPLETED PROJECT IS IN ACCORDANCE WITH THE APPROVED STORMWATER MANAGEMENT PLANS AND DESIGNS. 4. A FINAL INSPECTION OF THE SITE AND STORMWATER MANAGEMENT BMP/CONTROLS TO BE SCHEDULED WITH AND COMPLETED BY THE PROJECT ENGINEER. 5. NCDEQ AND THEIR ASSIGNS HAVE RIGHT TO ACCESS THE STORMWATER CONTROL(s) FOR INSPECTIONS OR MAINTENANCE AS NECESSARY. 6. THE ENGINEER'S CERTIFICATION OF COMPLETION WILL BE REQUIRED PRIOR TO THE FINAL PLAT OR CERTIFICATE OF OCCUPANCY. THE STORMWATER CONTROL IS TO BE INSPECTED TO ENSURE IT IS FUNCTIONING AS DESIGNED AND HAS FULL DESIGN VOLUME PRIOR TO ISSUANCE OF THE FINAL CERTIFICATE OF OCCUPANCY. 7. THE PROPERTY OWNER IS RESPONSIBLE FOR MAINTAINING THE STORMWATER CONTROLS(s) ACCORDING TO THE APPROVED MAINTENANCE PLAN AND DIRECTION OF NCDEQ. EXISTING GRADE = 380.2 76 OPERATION & MAINTENANCE PROVISIONS (INFILTRATION) BMP element: Potentialproblem: How to remediate the problem The entire infiltration basin Trash/debris is present Remove the trash/debris The grass filter strip or other pretreatment Areas of bare soil and/or erosive gullies Regrade the soil if necessary to remove area have formed the gully, plant ground cover and water until established. Provide lime and a one-time fertilizer application Sediment has accumulated to a depth Search for the source of the sediment and greater than three inches remedy the problem if possible. Remove the sediment and dispose of it in a location where it will not cause impacts to streams or the SCM The flow diversion structure (if applicable) The structure is clogged Unclog the conveyance and dispose of any sediment in a location where it will not cause impacts to streams or the SCM The structure is damaged Make any necessary repairs or replace if damage is too much for repair The inlet device The inlet pipe is clogged (if applicable) Unclog the pipe and dispose of any sediment in a location where it will not cause impacts to streams or the SCM The inlet pipe is cracked or otherwise Repair or replace the pipe damaged (if applicable) Erosion is occurring in the swale Regrade the swale if necessary and (if applicable) provide erosion control devices such as reinforced turf matting or rip -rap to avoid future erosion problems Stone verge is clogged or covered in Remove sediment and clogged stone and sediment (if applicable) replace with clean stone The basin More than four inches of sediment has Search for the source of the sediment and accumulated remedy the problem if possible. Remove the sediment and dispose of it in a location where it will not cause impacts to streams or the SCM Erosion of the basin surface has occurred Provide additional erosion protection such or riprap is displaced as reinforced turf matting or riprop if needed to prevent future erosion problems Water is standing more than three days Replace the top few inches of soil to see after a storm event if this corrects the standing water problem. If not, consult an appropriate professional for a more extensive repair The embankment Shrubs or trees are growing on the Remove trees and shrubs immediately embankment An annual inspection by an appropriate Make needed repairs immediately professional shows that the embankment needs repair The outlet device Clogging has occurred Clean out the outlet device and dispose of sediment in a location where it will not cause impacts to streams or the SCM The outlet device is damaged Repair or replace the outlet device The receiving water Erosion or other signs of damage have Repair the damage and improve the flow occurred at the outlet dissipation structure Discharges from the infiltration trench are Contact the local NCDEQ Regional Office causing erosion or sedimentation in the receiving water OPERATION AND MAINTENANCE: North Carolina storm water rules require quarterly inspections by the regulating agency of infiltration areas as a minimum. More frequent inspections by the land owner or system operator are strongly encouraged to ensure the proper operation of infiltration areas. A. Rainfall Event 1. Inspect the basin after every rainfall event greater than 1.5 inches. B. Monthly Inspection 1. Inspect the basin monthly 2. Check the infiltration area side slopes; remove trash and repair eroded areas before the next rainfall event. 3. Check the vegetative and rock filters for sediment accumulation, erosion and proper operation of the flow spreader mechanism and repair as necessary. C. Quarterly Inspection 1. Inspect the collection system (i.e. catch basin, pipes and grass swales) for proper functioning. Clear accumulated trash from basin grates and basin bottoms. Check piping for obstructions. 2. Check pond inlet pipes for undercutting, replace rip -rap and repair broken pipes. 3. Reseed grassed swales, including the vegetated filter if applicable, twice a year as necessary. Repair eroded areas immediately. D. Six Month Inspection 1. Remove accumulated sediment from the bottom of the outlet structure or other areas where accumulated sediment is noted. 2. Inspect the embankment taking note of any wet areas where water may be seeping through the soil. E. General Inspection 1. Maximum grass height is to be 6in. 2. No woody vegetation shall be allowed to grow in the infiltration area. 3. Debris shall be removed from blocking the inlet and outlet structures and from areas of potential clogging. 4. Periodic removal of dead vegetation shall be accomplished. 5. All components of the infiltration system must be kept in good working order. ' z cV TOP OF EMBANKMENT = 380.7 100-YEAR STORM ELEVATION = 380.32 SPILLWAY ELEVATION = 380.2 10-YEAR STORM ELEVATION = 378.63 2-YEAR STORM ELEVATION = 377.15 1-YEAR STORM ELEVATION = 376.53 1.0' RAINFALL ELEVATION = 374.85 BOTTOM OF BASIN = 374.8 FILTER MIXTURE (FRm Tar) 1'-O" OF CLEAN ASTM C-33 SAND (MEDIUM AGGREGATE SAND WITH A SIZE RANGE OF 0.02-INCH TO 0.04-INCH DIAMETER) LAYER OF GEOTEXTILE PERMEABLE FILTER FABRIC (MIRAFI N-SERIES OR EQUIVALENT) 1'-0" MIN. UNDISTURBED IN -SITU SOIL SEASONAL HIGH WATER TABLE < 370.2 GRASS SOD NOTE: BRASS SOD SHALL BE EITHER HYBRID BERMUDA GRASS OR CENTIPEDE THAT HAS BEEN GROWN IN A TOIL THAT IS FREE OF AN IMPERMEABLE LAYER (SUCH AS CLAY). 1'- CLEAN SAND INFILTRATION BASIN TYPICAL SECTION NTS NOTES: 1. ALL INFILTRATION BASINS SHALL HAVE AN ACCESS EASEMENT CONNECTING TO A DEDICATED PUBLIC RIGHT OF WAY. 2. ALL DRAINAGE AREAS TO AN INFILTRATION BASIN ARE TO BE STABILIZED PRIOR TO INSTALLATION OF SOILS OR GRASS SOD. 3. THE DRAINAGE AREA OF THE INFILTRATION BASIN WILL BE CAREFULLY MANAGED TO REDUCE THE SEDIMENT LOAD TO THE SAND FILTER SYSTEM. 4. THE WATER LEVEL IN THE MONITORING WELL(S) WILL BE RECORDED ONCE A MONTH AND AFTER EVERY STORM EVENT GREATER THAN 1.5 INCHES. 5. IMMEDIATELY AFTER THE INFILTRATION BASIN IS ESTABLISHED, THE VEGETATION WILL BE WATERED TWICE WEEKLY IF NEEDED UNTIL PLANTS BECOME ESTABLISHED (COMMONLY SIX WEEKS) 6. NO PORTION OF THE INFILTRATION BASIN WILL BE FERTILIZED AFTER THE INITIAL FERTILIZATION THAT IS REQUIRED TO ESTABLISH THE VEGETATION. THE VEGETATION IN AND AROUND THE BASIN WILL BE MAINTAINED AT A HEIGHT OF APPROXIMATELY SIX INCHES. FILTER FABRIC AT BOTTOM AND SIDES OF CLEAN SAND RIP -RAP PRE-TREATMENT FOREBAY AT PIPE INLETS SEE DETAIL THIS SHEET I \\ STORMWATER-\ I� MANAGEMENT EASEMENT < GRASS SPILLWAY LI REFER TO DETAIL ON THIS SHEET---- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - / �18iL7-------------------------- _ I ° L. 379 378 \ \\ \ I ° 377 I 376 \\\ \ -------------------- No OBSERVATION WELL (TYP.) GRAPHIC SCALE 20 0 10 20 40 ( IN FEET ) 1 inch = 20 ft. 80 STORMWATER MANAGEMENT SYSTEM DETAILS 1 NOT TO SCALE TOP OF- I EMBANKMENT ELEV=380.7 STORMWATER- ' I MANAGEMENT EASEMENT I PLAN VIEW GRASS SOD FILTER FABRIC INFIL' SANC REMOVABLE CAP 6" SCHEDULE 40 PVC, SDR35, OR SMOOTH WALL CORRUGATED PLASTIC PIPE WITH 3/8" PERFORATIONS ® 6" ON CENTER (4 HOLES PER ROW) FLUSH WITH PAVEMENT IN PERMEABLE PAVEMENT AREAS 000 00 0 o 0 0 0 z � 0 o o 0 o r cN RATION 0 ° oOIX w MEDIA ° 0 ° 0 0 > 0 000 0 o a w 0 000 0 0 0 0°° O0 0 000 0 0 0 0 SILT FENCE AS NEEDED INSERT 4"-6" INTO IN -SITU SOIL BASE OBSERVATION WELL STORM DRAINAGE PIPE OR CONCRETE FLUME OUTFALL INTO POND SCALE: N.T.S. LENGTH & WIDTH DIMENSIONS TO BE f RIP -RAP APRON DETAIL UNDISTURBED SUBSOIL -- - --j -- TAPER DEPTH - - = -•1 FOREBAY 1 I V 2' RIP -RAP FOREBAY SCALE: N.T.S. .TER MEDIA (SEE NOTE 2) FLOW= NOTES: 1. PRIOR TO INSTALLATION, MANUFACTURER SPECIFICATIONS OF FILTER MEDIA SHALL BE REVIEWED TO ENSURE THAT DISCHARGE FROM FILTER MEDIA SHALL MEET OR EXCEED THE PROVISIONS OF THE CLEAN WATER ACT. 2. ENSURE THAT PUMP PRESSURE DOES NOT EXCEED FILTER MEDIA PRESSURE RATING. 3. FILTER MEDIA MAY BE, BUT NOT LIMITED TO, SAND MEDIA FILTRATION DEVICES, RATED FILTER FABRIC BAGS OR POLYMER BASED DEWATERING PRACTICES. 4. PUMP STRAINER SHALL NOT BE IN CONTACT WITH BOTTOM OF POND. BMP POND DEWATERING FILTER BED ELEVATION 6" CLASS B RIP -RAP OVER FILTER FABRIC BIO-RETENTION POND POINT LEVEL SPILLWAY FLOW Q(100) LONG SLOPE(%) H B W SS CHANNEL LINING TOP OF EMBANKMENT ELEVATION SPILLWAY ELEVATION INFILTRATION 1.086 CFS 3.33% 0.5' 5.0' 8.0' 3:1 STRAW WITH NET NAG 380.7 380.2 SPILLWAY DS75 W EXTEND LINING TO / EXTEND LINING TO TOP OF SPILLWAY TOP OF SPILLWAY \ TOP OF EMBANKMENT=380.7 H CHANNEL LINING ss SPILLWAY ELEVATION=380.2 MATTING SHALL BE AS NOTED OR APPROVED EQUAL. B GRASS SPILLWAY DETAIL GRASS SOD ON SPILLWAY AND SIDE SLOPES STAGE/STORAGE TABCONTOUR E STAGE (FT) ELEVATION (FT) AREA (SF) EN STORAGE (CF) TOTAL STORAGE (CF) 0.0 374.8 1590 0 0 0.2 375.0 1745 334 334 1.2 376.0 2535 2140 2474 2.2 377.0 3385 2960 5434 3.2 378.0 4290 3838 9271 4.2 379.0 5250 4770 14041 5.2 380.0 6270 1 5760 19801 5.9 380.7 7015 1 4650 24451 STORMWATER MANAGEMENT DESIGN INFILTRATION SYSTEM: RIVER BASIN: CAPE FEAR RECEIVING STREAM: MILL CREEK STREAM INDEX: 18-31-11 STREAM CLASS: C HUC: 0304020305 PROJECT COORDINATES: 35.006486N,-79.306113'W POND DESIGN SUMMARY DRAINAGE AREA TO POND: 2.16 ACRES SITE IMPERVIOUS AREA TO POND: 0.98 ACRES OFF -SITE DESIGN IMPERVIOUS AREA TO POND: 0.36 ACRES TOTAL DESIGN IMPERVIOUS AREA TO POND: 1.34 ACRES PRE -DEVELOPED POST -DEVELOPED POST DEVELOPED POST DEVELOPED POST DEVELOPED TO POND TO POND THROUGH POND BYPASS COMBINED DRAINAGE AREA: 2.59 AC 2.16 AC 0.43 AC CURVE NUMBER: 50.4 79.9 53.1 TIME OF CONCENTRATION: 18.9 MIN 5 MIN 10 MIN 1.0" STORM EVENT: 0.062 CFS 0.000 CFS 1-YEAR STORM EVENT. 0.041 CFS 4.698 CFS 0.000 CFS 0.020 CFS 0.020 CFS 2-YEAR STORM EVENT: 0.242 CFS 6.484 CFS 0.000 CFS 0.106 CFS 0.106 CFS 10-YEAR STORM EVENT: 2.032 CFS 11.81 CFS 0.000 CFS 0.580 CFS 0.580 CFS 100-YEAR STORM EVENT: 6.873 CFS 20.52 CFS 1.086 CFS 1.658 CFS 2.744 CFS J CZ c 0 (�LO U CE CC 0 CO z co O co 0 E cn O c0 N Z 2 (j LLI J Q O LO I?O ai C o Ca LL 0 -0 0 co V J Q W M z Q z W G W W 0 a z G �:4 O Uj 1 ►-� Ir 0 0 Q O LU o G O v ) PRELIMINARY DO NOT USE FOR CO � 7�)? *r PLAN STATUS -9-22 11ST SUBMISSION DATE DESCRIPTION RG RG DESIGN DRAWN CHKD SCALE H: 1 " = 30' V: N/A OB No. TSD-058-011 DATE FEBRUARY 9, 2022 -ILE No. SHEET C6' 7 'Cad file name: P:\058-Rhetson Companies\011-DG- Plans\Construction Documents\058-011-SWD.dwq