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HomeMy WebLinkAbout20080989 Ver 1_Stormwater Info_20080709 Stonemont Stormwater Calculations B&F Consulting 2805 Tobermory Lane Raleigh NC 27606 919 618 0180 UIR@f qow7g f?) JUL 9 2008 DENR - WATER QUAUTy WLTIANDS AND STORMWATER BRANrH • • Stonemont Stormwater Calculations B&F Consulting 2805 Tobermory Lane Raleigh NC 27606 9196180180 • Wet Detention Basin Calculations, Worksheets and O&M Agreements 0 C7 0 Stonemont Anti-flotation calculations Outlet structures for ponds Provide Concrete "waffle box" Exterior dimensions 4'X 4' length width A 4 B 4 C 4 Bouyant force Concrete factor of height (Ibs) (Ibs) saftey 4 1.3 1298 2803 2.2 4 1.9 1897 2803 1.5 4 1.3 1298 2803 2.2 Use concrete weight as 150 Ibs/c.f. Thus, resistant force for concrete is (150-62.4) X 2 X 4 X 4 = 2800 Ibs. • 0 0- POND A C7 Permit Number: (to be provided by DWQ) Drainage Area Number: • rI • BMP element: Potential problem: How I will rernediate the problem: The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the swale sediment off-site. The pipe is cracked or Replace the pipe. otherwise damaged. Erosion is occurring in the Regrade the swale if necessary to swale. smooth it over and provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. The forebay Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design depth for possible. Remove the sediment and sediment storage. dispose of it in a location where it will not cause impacts to streams or the BMP. Erosion has occurred. Provide additional erosion protection such as reinforced turf matting or riprap if needed to prevent future erosion problems. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it on the plants rather than spraying. The vegetated shelf Best professional practices Prune according to best professional show that pruning is needed practices to maintain optimal plant health. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application to establish the ground cover if a soil test indicates it is necessary. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it orl the plants rather than spraying. The main treatment area Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design sediment possible. Remove the sediment and storage depth. dispose of it in a location where it will not cause impacts to streams or the BMP. Algal growth covers over Consult a professional to remove 50% of the area. and control the algal growth. Cattails, phragmites or other Remove the plants by wiping them invasive plants cover 50% of with pesticide (do not spray). the basin surface. Form SW401-Wet Detention Basin O&M-Rev.3 Page 2 of 4 Permit Number: (to be provided by DWQ) Drainage Area Number: • BMP element: Potential problem: How I will remediate the problem: The embankment Shrubs have started to grow Remove shrubs immediately. on the embankment. Evidence of muskrat or Use traps to remove muskrats and beaver activity is present. consult a professional to remove beavers. A tree has started to grow on Consult a dam safety specialist to the embankment. remove the tree. An annual inspection by an Make all needed repairs. appropriate professional shows that the embankment needs repair. The outlet device Clogging has occurred. Clean out the outlet device. Dispose of the sediment off-site. The outlet device is damaged Repair or replace the outlet device. The receiving water Erosion or other signs of Contact the local NC Division of damage have occurred at the Water Quality Regional Office, or outlet. the 401 Oversight Unit at 919-733- 1786. The measuring device used to determine the sediment elevation shall be such • that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the permanent pool depth reads 319.0 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 324.0 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM ill in the blanks) n 0 Permanent Pool Elevation 326.0 Sediment Removal E. 324.0 ol ----------------- Sediment Removal Elevation 319.0 Volume Bottom E evatio 322.0 ------------------------------- ----------- ---Bottom Elevation 316.0 1-ft n Storage Sedimei Storage FOREBAY MAIN POND Form SW401-Wet Detention Basin O&M-Rev.3 Page 3 of 4 • Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: "A" Print name: :::W1 ?.T6 Mdg:S <V- Title:_ McDU Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, S • rt , 6 7isuC S, .T? , a Notary Public for the State of A9 County of Gc ?? •2 , do hereby certify that Cc w o??`S L rv n,e S J ""'p personally appeared before me this day of ?.?.? 2" S! and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, _5"'. = (-7 ?`?? ZZr U G = `may 'OU g?-` ,?-?'••'` SEAL • My commission expires ? • L/ ?D Form SW401-Wet Detention Basin O&M-Rev.3 Page 4 of 4 Address: 140 TOyyftsle'Lc,tt C.OUQT Permit Number: 0- (to be provided by DWQ) Drainage Area Number: Wet Detention Basin Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the vegetated filter if one is provided. This system (check one): ? does ® does not incorporate a vegetated filter at the outlet. This system (check one): ? does ® does not incorporate pretreatment other than a forebay. Important maintenance procedures: - Immediately after the wet detention basin is established, the plants on the vegetated shelf and perimeter of the basin should be watered twice weekly if needed, until the plants become established (commonly six weeks). - No portion of the wet detention pond should be fertilized after the first initial fertilization that is required to establish the plants on the vegetated shelf. - Stable groundcover should be maintained in the drainage area to reduce the sediment load to the wet detention basin. - If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through the emergency drain should be minimized to the maximum extent practical. • - Once a year, a dam safety expert should inspect the embankment. After the wet detention pond is established, it should be inspected once a month and within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County). Records of operation and maintenance should be kept in a known set location and must be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire BMP Trash/debris is resent. Remove the trash/debris. The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to detention basin erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Vegetation is too short or too Maintain vegetation at a height of long. a roximatel six inches. Form SW401-Wet Detention Basin O&M-Rev.3 Page 1 of 4 Permit Number: (to be provided by DWQ) • I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: Print name: Curtis Jones, Jr. Title: member Address: 140 Towerview Court, Cary, NC Phone: 919-669-1246 Signature: Date: Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, M 152k( 4• PC-?,kL GIl , a Notary Public for the State of M4 rf?h of n I/ns, , County of 1 Akin , do hereby certify that C,Jrfis Tones Yr, personally appeared before me this 92?? day of ZC06, and acknowledge the due execution of the forgoing filter st ip, riparian buffer, and/or level spreader maintenance requirements. Witness my hand and official seal, SEAL 0 My commission expires old. 2 ! 700 Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3 DWQ Project 0 DIVISION OF WATER QUALITY - LEVEL SPREADER WORKSHEET (112007) 1. PROJECT INFORMATION (please complete the following information): Project Name : S -DNNSVOAJZ' Contact Person: I:SS ELL grIg4 rnF Phone Number: (fl l) 69;-D1A0 Level Spreader ID: Level Spreader Length ft. (perpendicular to flow) Drainage Area ac. (on-site and off-site drainage to the level spreader) Impervious Area ac. (on-site and off-site drainage to the level spreader) Forebay Area cu ft. (0.2% of the contributing impervious surface area) Maximum Filter Strip/Buffer Slope % (6% for forested, leaf littler cover, 8% for thick ground cover grass Max. Discharge from 1"/Hr Storm cfs Max. Discharge to Level Spreader cfs Filter Strip/ Zone 2 Buffer Vegetation 4^ (thick ground cover or grass; canopied forest with leaf litter groundcover) Pre-treatment or Bypass Method Used II. REQUIRED ITEMS CHECKLIST Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details, a detailed drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for additional information and will substantially delay final review and approval of the project. Applicants Initials VAA Project Site was visited prior to designing level spreader. 1921 Bypass conveyance method is specified and plan details and calculations are provided. ?,?_Alternative design option is specified and plan details and calculations are provided. Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING BUFFER CONDITIONS. Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer. /G_Pre-Formed Scour Holes are on flat slopes only. No structures are located in protected buffers (must meet no practical alternatives criteria). Design Alternative (if any) and Bypass method used: Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass discharge. No structures are located in protected buffers. d1o Plan details for the bypass and outlets are provided. QAhL_The operation and maintenance agreement includes annual erosion and vegetation repair. The operation and maintenance agreement signed and notarized by the responsible party is provided. Permit No. (to be provided by DWQ) 7 a$oC W A tfigpG A ,?1i11111111111111?R 0 y hICDENR ` STORMWATER MANAGEMENT PERMIT APPLICATION FORM 401 CERTIFICATION APPLICATION FORM WET DETENTION BASIN SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information. I. PROJECT INFORMATION Project name Stonemont Contact person Russell Briggs, P.E. Phone number 919-618-0180 Date 7-Jul-08 Drainage area number "A" II. DESIGN INFORMATION Site Characteristics Drainage area 244,371.60 ft2 Impervious area 96,703.20 ft2 % impervious 39.57 % Design rainfall depth 1.00 in Storage Volume: Non-SR Waters Minimum volume required 8,349.00 ft3 Volume provided 9,800.00 ft3 Storage Volume: SR Waters 1-yr, 24-hr runoff depth in Pre-development 1-yr, 24-hr runoff ft3 . Post-development 1-yr, 24-hr runoff ft3 Minimum volume required ft3 Volume provided ft3 Peak Flow Calculations 1-yr, 24-hr rainfall depth 2.89 in Rational C, pre-development 0.25 (unitless) Rational C, post-development 0.55 (unitless) Rainfall intensity: 1-yr, 24-hr storm 4.90 in/hr Pre-development 1-yr, 24-hr peak flow 6.87 ft3/sec Post-development 1-yr, 24-hr peak flow 15.12 ft3/sec Pre/Post 1-yr, 24-hr peak flow control 8.25 ft3/sec Basin Elevations Basin bottom elevation 316.30 ft Sediment cleanout elevation 320.00 ft Bottom of shelf elevation 325.50 ft Permanent pool elevation 326.00 ft SHWT elevation 320.00 ft Top of shelf elevation 326.50 ft Temporary pool elevation 325.40 ft • Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 1 of 2 Permit No. (to be provided by DWQ) II. DESIGN INFORMATION Volume and Surface Area Calculations SA/DA ratio 1.73 (unitless) Surface area at the bottom of shelf 4,531.00 ftz Volume at the bottom of shelf 15,454.00 ft3 Permanent pool, surface area required 4,227.00 ftz Permanent pool, surface area provided 6,038.00 ftz OK Permanent pool volume 18,128.00 ft3 Average depth for SA/DA tables 3.00 ft OK Surface area at the top of shelf 7,637.00 ft2 Volume at the top of shelf 21,547.00 ft3 Forebay volume 3,986.00 ft3 Forebay % of permanent pool volume 21.99 % OK Temporary pool, surface area provided 8,249.00 ftz Drawdown Calculations Treatment volume drawdown time 4.00 days OK Treatment volume discharge rate 0.50 ft3/s Pre-development 1-yr, 24-hr discharge 6.87 ft3/s OK Post-development 1-yr, 24-hr discharge 6.78 ft3/s OK Additional Information Diameter of orifice 1 in Design TSS removal 85 % Basin side slopes 3.00 :1 OK Vegetated shelf slope 10.00 :1 OK Vegetated shelf width 10.00 ft OK Length of flowpath to width ratio 3.00 :1 OK Length to width ratio 1.50 :1 OK Trash rack for overflow & orifice? Y (Y or N) OK Freeboard provided 1.00 ft OK Vegetated filter provided? y (Y or N) OK Recorded drainage easement provided? y (Y or N) OK Capures all runoff at ultimate build-out? y (Y or N) OK Drain mechanism for maintenance or emergencies drain via pump • Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2 Permit No (to be provided by DWQ) III. REQUIRED ITEMS CHECKLIST Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Pagel Plan Initials Sheet No. J0 J21 4n 12 1. Plans (1" 50' or larger) of the entire site showing: Design at ultimate build-out, Off-site drainage (if applicable), Delineated drainage basins (include Rational C coefficient per basin), Basin dimensions, Pretreatment system, High flow bypass system, Maintenance access, Proposed drainage easement and public right of way (ROW), Overflow device, and Boundaries of drainage easement. P213 C 1?3 3 2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing: - Outlet structuretwith trash rack or similar, - Maintenance access, - Permanent pool dimensions, - Forebay and main pond with hardened emergency spillway, - Basin cross-section, - Vegetation specification for planting shelf, and - Filter strip. C17 3 3. Section view of the dry detention basin (1" = 20' or larger) showing: Side slopes, 3:1 or lower, Pretreatment and treatment areas, and Inlet and outlet structures. !1/?7 CV-3 38 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified ?( on the plans prior to use as a wet detention basin. ?C?(Uk)5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay, to verify volume provided. 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the entire drainage area is stabilized. 7. The supporting calculations. 8. A copy of the signed and notarized operation and maintenance (0&M) agreement. >? /} 9. A copy of the deed restrictions (if required). 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County soil maps are not an acceptable source of soils information. • Form SW401-Wet Detention Basin-Rev.4 Part III. Required Items Checklist, Page 1 of 1 0 Basin "A" Area of Right of way 1.83 acres Impervious area in street right of way 1.24 acres Number of lots 11.5 Typical impervious area per lot (%) Drive, sidewalk 600 sf Footprint 3000 sf Deck 120 sf 3720 Impervious area of lots: 0.98 acres Total drainage area 5.61 acres Total impervious area, lots + r/w 2.22 % impervious 40% Use 40 % criteria 40% SA/DA ratio for S depth 1.73% SA 0.10 acres Treatment volume V =3630xRox(0.05+0.9xIQ)xA where V = Volume of runoff to be controlled (ft3) Ro = Design storm rainfall depth (1") A = watershed area (ac.) V = 8349 cf • Pond A Average Pond Depth = 3.0 NOTE: Excludes sediment storage Elevation SF Area CF Volume Shelf from e.325.5 to e.326.5 329.5 11177 49405 328 9419 33958 327.5 8317 29524 326.5 7637 21547 <-shelf 326 6038 18128 <-n.pool 325.5 4531 15486 <-shelf 324 3408 9532 322 2100 4024 320 1057 867 319 676 0 <-sediment storage elevation (start avg. depth calc here) 318 305 0 316 0 0 Sed. Storage depth = 3.0 ft Forebay Volume Elevation SF Area CF Volume 332 1610 3986 330 950 1426 • 328 476 0 326 140 0 324 0 0 Water Quality Volume: 8349 CF (above normal pool) This volume occurs 1.12 feet above normal pool Set weir at 1.3' above normal pool Volume provided = 9800 0 . Basin A Pond Routing 1-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TIC [min] Intensities, I 1-year [in/hr] • Peak Discharge, Qp 1-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 1-year [inches] Volume of Runoff, V, from 6-hour storm 1-year [inches] 1-year [acre-feet] Time-to-Peak, Tp (for use in routing) 1-year [minutes] Time Interval for Routing • 1-year [minutes] 3.39 2.22 5.61 0.55 5.0 4.90 15.12 B 98.0 61.0 75.6 3.2 2.89 v = ((P-.2S)"2)/(P+.8s) 0.92 0.43 Tp = V/(1.39*Qp) 14.9 1 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 • BASIN PARAMETERS Riser Barrel Emergency Spillway 12 = Weir length 24 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 327.3 = Crest elev. Weir 326 = .Invert elev. barrel 329.5 =Crest elev. 326.0 = Initial elev. water level Results Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 1 6.78 327.61 15.12 • ROUTING AND ANALYSIS - 1-year storm Time Inflow Storage Stage [mins] [cfs] [cubic ft] [ft] 0.0 0.0 0 326.00 1.0 0.2 0 326.00 2.0 0.7 10 326.00 3.0 1.5 50 326.01 4.0 2.5 137 326.02 5.0 3.8 289 326.04 6.0 5.3 519 326.08 7.0 6.8 836 326.12 8.0 8.4 1,246 326.18 9.0 10.0 1,752 326.26 10.0 11.4 2,351 326.34 11.0 12.7 3,037 326.44 12.0 13.7 3,799 326.55 13.0 14.5 4,623 326.65 14.0 15.0 5,494 326.76 15.0 15.1 6,393 326.87 16.0 14.9 7,300 326.99 17.0 14.4 8,196 327.10 18.0 13.6 9,059 327.21 • 19.0 12.5 9,873 327.31 20.0 11.5 10,622 327.40 21.0 10.5 11,231 327.48 22.0 9.6 11,681 327.53 23.0 8.8 11,993 327.57 24.0 8.1 12,194 327.59 25.0 7.4 12,308 327.60 26.0 6.8 12,357 327.61 27.0 6.2 12,358 327.61 28.0 5.7 12,324 327.60 29.0 5.2 12,267 327.60 30.0 4.8 12,194 327.59 31.0 4.4 12,110 327.58 32.0 4.0 12,021 327.57 33.0 3.7 11,928 327.56 34.0 3.4 11,834 327.55 35.0 3.1 11,741 327.54 36.0 2.8 11,650 327.53 37.0 2.6 11,560 327.52 38.0 2.4 11,474 327.51 327.6 Outflow [cfs] 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 3.0 4.4 5.5 6.2 6.6 6.8 6.8 6.7 6.4 6.2 5.9 5.6 5.3 4.9 4.6 4.3 4.0 3.8 Outlet Hydraulics Q_orifice Q Q_riser em.spil 0.0 0.0 0.0 0.1 0.2 0.3 0.6 0.9 1.4 1.9 2.6 3.4 4.1 4.9 5.7 6.6 7.5 8.3 9.1 9.9 10.6 11.2 11.6 11.8 12.0 12.1 12.1 12.1 12.1 12.1 12.0 11.9 11.9 11.8 11.7 11.6 11.5 11.5 11.4 6.8 < == maximum 1-yr 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 1.3 0 3.0 0 4.4 0 5.5 0 6.2 0 6.6 0 6.8 0 6.8 0 6.7 0 6.4 0 6.2 0 5.9 0 5.6 0 5.3 0 4.9 0 4.6 0 4.3 0 4.0 0 3.8 0 • Basin A Pond Routing 100-yr, 6 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TC [min] Intensities, I 100-year [in/hr] • Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 100-year [inches] Volume of Runoff, V, from 6-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing • 100-year [minutes] 3.39 2.22 5.61 0.55 5.0 9.12 28.14 B 98.0 61.0 75.6 3.2 5.39 v = ((p-.2S)"2)/(p+.8s) 2.83 1.32 Tp = V/(1.39*Qp) 24.5 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 • BASIN PARAMETERS • Riser Barrel Emergency Spillway 12 = Weir length 24 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 327.3 =Crest elev. Weir 326 = Invert elev. barrel 329.5 = Crest elev. 326.0 = Initial elev. water level Results, 100-year 6 hour Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 100 14.70 327.95 28.14 0 ROUTING AND ANALYSIS --100-year 6 hour storm Outlet Hydraulics Time Inflow Storage Stage Outflow Q_orifice Q [mins] [cfs] [cubic ft] [ft] [cfs] em.spi l 0.0 0.0 0 326.00 0.0 0.0 0 2.0 0.5 0 326.00 0.0 0.0 0 4.0 1.8 1 326.00 0.0 0.0 0 6.0 4.0 218 326.03 0.0 0.2 0 8.0 6.8 2 326.00 0.0 0.0 0 10.0 10.0 408 326.06 0.0 0.5 0 12.0 13.6 1,010 326.15 0.0 1.1 0 14.0 17.2 1,825 326.27 0.0 2.0 0 16.0 20.5 2,855 326.42 0.0 3.2 0 18.0 23.5 4,088 326.58 0.0 4.4 0 20.0 25.8 5,497 326.76 0.0 5.7 0 22.0 27.4 7,048 326.95 0.0 7.2 0 24.0 28.1 8,692 327.16 0.0 8.8 0 26.0 27.9 10,378 327.37 0.8 10.4 0 28.0 26.8 12,005 327.57 5.5 11.8 0 30.0 24.8 13,281 327.71 10.5 12.9 0 32.0 22.4 14,141 327.81 13.7 13.7 0 34.0 20.2 14,666 327.87 14.1 14.1 0 36.0 18.1 15,029 327.91 14.4 14.4 0 38.0 16.3 15,251 327.93 14.6 14.6 0 40.0 14.7 15,353 327.95 14.7 14.7 0 42.0 13.2 15,351 327.95 14.7 14.7 0 44.0 11.9 15,261 327.94 14.6 14.6 0 46.0 10.7 15,096 327.92 14.5 14.5 0 48.0 9.6 14,868 327.89 14.3 14.3 0 50.0 8.6 14,587 327.86 14.0 14.0 0 52.0 7.8 14,262 327.82 13.8 13.8 0 54.0 7.0 13,902 327.78 13.3 13.5 0 56.0 6.3 13,524 327.74 11.6 13.1 0 58.0 5.7 13,208 327.70 10.2 12.9 0 60.0 5.1 12,936 327.67 9.0 12.6 0 62.0 4.6 12,698 327.65 8.1 12.4 0 64.0 4.1 12,487 327.62 7.3 12.3 0 66.0 3.7 12,298 327.60 6.6 12.1 0 68.0 3.3 12,126 327.58 5.9 11.9 0 70.0 3.0 11,969 327.56 5.4 11.8 0 72.0 2.7 11,825 327.55 4.9 11.7 0 74.0 2.4 11,692 327.53 4.5 11.6 0 76.0 2.2 11,570 327.52 4.1 11.5 0 327.9 14.7 < ==maximum 100-yr 6 hour Q_riser 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.8 5.5 10.5 14.4 17.0 18.9 20.0 20.6 20.6 20.1 19.2 18.0 16.6 15.0 13.3 11.6 10.2 9.0 8.1 7.3 6.6 5.9 5.4 4.9 4.5 4.1 0 Basin A Pond Routing 100-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TIC [min] Intensities, I 100-year [in/hr] Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 24 hour storm 100-year [inches] Volume of Runoff, V, from 24-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing 100-year [minutes] B 3.39 2.22 5.61 0.55 5.0 9.12 28.14 98.0 61.0 75.6 3.2 7.59 v = ((P-.2S)"2)/(P+.8s) 4.75 2.22 Tp = V/(1.39"Qp) 41.2 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 • BASIN PARAMETERS • Riser Barrel Emergency Spillway 12 = Weir length 24 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 =•Cd barrel 3.00 = Cw 327.3 = Crest elev. Weir 326 = Invert elev. barrel 329.5 = Crest elev. 326.0 = Initial elev. water level Results, 100-yr 24 hour Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 100 17.67 328.37 28.14 0 ROUTING AND ANALYSIS --100-year 24 hour storm Outlet Hydraulics Time Inflow Storage Stage Outflow Q_orifice Q [mins] [cfs] [cubic ft] [ft] [cfs] em.spi l 0.0 0.0 0 326.00 0.0 0.0 0 2.0 0.2 0 326.00 0.0 0.0 0 4.0 0.7 1 326.00 0.0 0.0 0 6.0 1.4 79 326.01 0.0 0.1 0 8.0 2.5 2 326.00 0.0 0.0 0 10.0 3.9 154 326.02 0.0 0.2 0 12.0 5.5 388 326.06 0.0 0.4 0 14.0 7.3 718 326.11 0.0 0.8 0 16.0 9.2 1,156 326.17 0.0 1.3 0 18.0 11.3 1,710 326.25 0.0 1.9 0 20.0 13.4 2,389 326.35 0.0 2.6 0 22.0 15.6 3,195 326.47 0.0 3.5 0 24.0 17.7 4,130 326.59 0.0 4.4 0 26.0 19.7 5,191 326.72 0.0 5.5 0 28.0 21.6 6,374 326.87 0.0 6.6 0 30.0 23.3 7,670 327.03 0.0 7.8 0 32.0 24.8 9,070 327.21 0.0 9.1 0 34.0 26.1 10,559 327.40 1.2 10.5 0 36.0 27.1 12,054 327.57 5.7 11.9 0 38.0 27.7 13,336 327.72 10.7 13.0 0 • 40.0 28.1 14,356 327.83 13.8 13.8 0 42.0 28.1 15,210 327.93 14.6 14.6 0 44.0 27.8 16,022 328.02 15.2 15.2 0 46.0 27.2 16,777 328.09 15.8 15.8 0 48.0 26.3 17,462 328.16 16.3 16.3 0 50.0 25.1 18,063 328.22 16.7 16.7 0 52.0 23.7 18,568 328.27 17.0 17.0 0 54.0 22.2 18,968 328.30 17.3 17.3 0 56.0 20.8 19,265 328.33 17.4 17.4 0 58.0 19.6 19,469 328.35 17.6 17.6 0 60.0 18.4 19,589 328.37 17.6 17.6 0 62.0 17.2 19,633 328.37 17.7 17.7 0 64.0 16.2 19,608 328.37 17.7 17.7 0 66.0 15.2 19,520 328.36 17.6 17.6 0 68.0 14.3 19,376 328.34 17.5 17.5 0 70.0 13.4 19,182 328.33 17.4 17.4 0 72.0 12.6 18,943 328.30 17.2 17.2 0 74.0 11.8 18,663 328.28 17.1 17.1 0 76.0 11.1 18,349 328.24 16.8 16.8 0 328.4 17.7 < ==maximum 100-yr 24 hour Q_riser 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 5.7 10.7 15.4 19.8 24.1 27.9 31.5 34.8 37.6 39.9 41.6 42.8 43.5 43.8 43.6 43.1 42.3 41.1 39.7 38.1 36.4 L_J • Analysis of time to empty Time Inflow Storage Stage 'Outflow [hrs] [cfs] [cubic ft] IN [cfs] 0.0 0.0 9,800 327.30 6.0 0.0 9,066 327.21 12.0 0.0 8,357 327.12 18.0 0.0 7,672 327.03 24.0 0.0 7,010 326.95 30.0 0.0 6,373 326.87 36.0 0.0 5,760 326.79 42.0 0.0 5,171 326.72 48.0 0.0 4,606 326.65 54.0 0.0 4,066 326.58 60.0 0.0 3,549 326.52 66.0 0.0 3,057 326.45 72.0 0.0 2,592 326.38 78.0 0.0 2,156 326.32 84.0 0.0 1,748 326.26 90.0 0.0 1,369 326.20 96.0 0.0 1,019 326.15 102.0 0.0 697 326.10 108.0 0.0 404 326.06 114.0 0.0 140 326.02 120.0 0.0 (94) 63.0 Outlet Hydraulics Q_barrel Q Q_riser em.spil 0.034 9.8 0 0.0 0.033 9.1 0 0.0 0.032 8.5 0 0.0 0.031 7.8 0 0.0 0.030 7.2 0 0.0 0.028 6.6 0 0.0 0.027 6.0 0 0.0 0.026 5.4 0 0.0 0.025 4.9 0 0.0 0.024 4.4 0 0.0 0.023 3.9 0 0.0 0.022 3.4 0 0.0 0.020 2.9 0 0.0 0.019 2.4 0 0.0 0.018 1.9 0 0.0 0.016 1.5 0 0.0 0.015 1.1 0 0.0 0.014 0.8 0 0.0 0.012 0.4 0 0.0 0.011 0.2 0 0.0 0 • Soil Investigation Pond "A" A hand auger was used to advance a test hole approximately 30 inches in depth in two locations of the proposed pond. The soil found appears to be a clay loam. The soil samples were well drained. We recommend a geotechnical engineer, or B&F Consulting be present during construction of this pond in particular to ascertain whether a lining material (clay) will be required as the pond is excavated to its proposed depths. The presence of the nearby stream does indicate groundwater availability at a depth of the invert of the stream. 0 • E POND B • Permit Number: (to be provided by DWQ) Drainage Area Number: is • Wet Detention Basin Operation and Maintenance Agreement of structures, safety of the public, and the removal efficiency of the BMP. I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the vegetated filter if one is provided. This system (check one): ? does ® does not incorporate a vegetated filter at the outlet. This system (check one): ? does ® does not incorporate pretreatment other than a forebay. Important maintenance procedures: - Immediately after the wet detention basin is established, the plants on the vegetated shelf and perimeter of the basin should be watered twice weekly if needed, until the plants become established (commonly six weeks). - No portion of the wet detention pond should be fertilized after the first initial fertilization that is required to establish the plants on the vegetated shelf. - Stable groundcover should be maintained in the drainage area to reduce the sediment load to the wet detention basin. - If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through the emergency drain should be minimized to the maximum extent practical. • - Once a year, a dam safety expert should inspect the embankment. After the wet detention pond is established, it should be inspected once a month and within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County). Records of operation and maintenance should be kept in a known set location and must be available upon request. Inspection activities shall be petformed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire BMP Trash/debris is resent. Remove the trash/debris. The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to detention basin erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Vegetation is too short or too Maintain vegetation at a height of long. approximately six inches. Form SW401-Wet Detention Basin O&M-Rev.3 Page 1 of 4 Permit Number: (to be provided by DWQ) Drainage Area Number: • C] E BMP element: Potential problem: How I will remediate the problem: The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the swale sediment off-site. The pipe is cracked or Replace the pipe. otherwise damaged. Erosion is occurring in the Regrade the swale if necessary to swale. smooth it over and provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. The forebay Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design depth for possible. Remove the sediment and sediment storage. dispose of it in a location where it will not cause impacts to streams or the BMP. Erosion has occurred. Provide additional erosion protection such as reinforced turf matting or riprap if needed to prevent future erosion problems. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it on the plants rather than spraying. The vegetated shelf Best professional practices Prune according to best professional show that pruning is needed practices to maintain optimal plant health. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application to establish the ground cover if a soil test indicates it is necessary. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it on the plants rather than spraying. The main treatment area Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design sediment possible. Remove the sediment and storage depth. dispose of it in a location where it will not cause impacts to streams or the BMP. Algal growth covers over Consult a professional to remove 50% of the area. and control the algal growth. Cattails, phragmites or other Remove the plants by wiping them invasive plants cover 50% of with pesticide (do not spray). the basin surface. Form SW401-Wet Detention Basin O&M-Rev.3 Page 2 of 4 Permit Number: • (to be provided by DWQ) Drainage Area Number: BMP element: Potential problem: How I will remediate the problem: The embankment Shrubs have started to grow Remove shrubs immediately. on the embankment. Evidence of muskrat or Use traps to remove muskrats and beaver activity is present. consult a professional to remove beavers. A tree has started to grow on Consult a dam safety specialist to the embankment. remove the tree. An annual inspection by an Make all needed repairs. appropriate professional shows that the embankment needs repair. The outlet device Clogging has occurred. Clean out the outlet device. Dispose of the sediment off-site. The outlet device is damaged Repair or replace the outlet device. The receiving water Erosion or other signs of Contact the local NC Division of damage have occurred at the Water Quality Regional Office, or outlet. the 401 Oversight Unit at 919-733- 1786. The measuring device used to determine the sediment elevation shall be such . that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the permanent pool depth reads 323.0 feet in the main pond, the sediment shall be removed. • When the permanent pool depth reads 326.0 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM ill in the blanks) 0 Permanent Pool Elevation 330.0 Sediment Removal E. 326.0 Pe anen Pool - - - - - - - - - - - - - - - - - Volume Sediment Removal Elevation 323.0 Volume - Bottom E evatio 324.0 -ft Min. -------------------------------------------- -----Sediment Bottom Elevation 320.0 1-ft r Storage Sedimei Storage FOREBAY MAIN POND Form SW401-Wet Detention Basin O&M-Rev.3 Page 3 of 4 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: "B" Print name: 1-11U23:5 I_f,S' JV_ Title: T Address: . GAJ2 -e d C_ Phone Signat Date: 3/o S Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, S, xl L 444?s .Q , a Notary Public for the State of VLl L , County of l)u le e , do hereby certify that & Js personally appeared before me this 13 day of T,,LL?e_ 200k, and acknowledge the due execution of the forgoing wet detention basin aintenance requirements. Witness my hand and official seal, r ?? OTAR} S 03 ?C) SEAL My commission expires i • I-/ Zm[/ • Form SW401-Wet Detention Basin O&M-Rev.3 Page 4 of 4 ' Permit No. (to be provided by DWQ) oC W nT?q EWA AYNIbIIk .A111111111111I111111F ?' y WaENR ` The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information. 11. PROJECT INFORMATION Project name Stonemont Contact person Russell Briggs, P.E. Phone number 919-618-0180 Date 7-Jul-08 Drainage area number "B" II. DESIGN INFORMATION Site Characteristics Drainage area 300,564.00 ft Impervious area 143,748.00 f' % impervious 47.83 % Design rainfall depth 1.00 in Storage Volume: Non-SR Waters Minimum volume required 12,044.00 ft3 Volume provided 15,068.00 ft3 Storage Volume: SR Waters 1-yr, 24-hr runoff depth in Pre-development 1-yr, 24-hr runoff • Post-development 1-yr, 24-hr runoff ft3 ft3 Minimum volume required ft3 Volume provided ft3 Peak Flow Calculations 1-yr, 24-hr rainfall depth 2.89 in Rational C, pre-development 0.25 (unitless) Rational C, post-development 0.62 (unitless) Rainfall intensity: 1-yr, 24-hr storm 4.90 in/hr Pre-development 1-yr, 24-hr peak flow 8.45 ft3/sec Post-development 1-yr, 24-hr peak flow 20.96 ft3/sec Pre/Post 1-yr, 24-hr peak flow control 12.51 ft3/sec Basin Elevations Basin bottom elevation 320.00 ft Sediment cleanout elevation 323.00 ft Bottom of shelf elevation 329.50 ft Permanent pool elevation 330.00 ft SHWT elevation 323.00 ft Top of shelf elevation 330.50 ft Temporary pool elevation 331.55 ft • 401 CERTIFICATION APPLICATION FORM STORMWATER This form must be filled MANAGEMENT out, printed PERMIT and submitted. APPLICATION FORM WET DETENTION BASIN SUPPLEMENT Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 1 of 2 Permit No. (to be provided by DWQ) ll. DESIGN INFORMATION Volume and Surface Area Calculations SA/DA ratio 2.03 (unitless) • Surface area at the bottom of shelf 4,531.00 ftz Volume at the bottom of shelf 15,454.00 ft3 Permanent pool, surface area required 4,227.00 ftz Permanent pool, surface area provided 6,007.00 ftz OK Permanent pool volume 18,094.00 ft3 Average depth for SA/DA tables 3.01 ft OK Surface area at the top of shelf 7,592.00 ftz Volume at the top of shelf 21,494.00 ft3 Forebay volume 3,800.00 ft3 Forebay % of permanent pool volume 21.00 % OK Temporary pool, surface area provided 8,249.00 ftz Drawdown Calculations Treatment volume drawdown time 4.00 days OK Treatment volume discharge rate 0.04 ft3/s Pre-development 1-yr, 24-hr discharge 8.45 ft3/s OK Post-development 1-yr, 24-hr discharge 8.03 ft3/s OK Additional Information Diameter of orifice 1 in Design TSS removal 85 % Basin side slopes 3.00 :1 OK Vegetated shelf slope 10.00 :1 OK Vegetated shelf width 10.00 ft OK Length of flowpath to width ratio 3.00 :1 OK Length to width ratio 1.50 :1 OK Trash rack for overflow & orifice? Y (Y or N) OK Freeboard provided 1.00 ft OK . Vegetated filter provided? Y (Y or N) OK Recorded drainage easement provided? y (Y or N) OK Capures all runoff at ultimate build-out? y (Y or N) OK Drain mechanism for maintenance or emergencies drain via pump • Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2 Permit N (to be provided by DWQ) • III. REQUIRED ITEMS CHECKLIST Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Pagel Plan Initials Sheet No. pip ?F 1. Plans (1" 50' or larger) of the entire site showing: - Design at ultimate build-out, - Off-site drainage (if applicable), - Delineated drainage basins (include Rational C coefficient per basin), - Basin dimensions, - Pretreatment system, - High flow bypass system, - Maintenance access, - Proposed drainage easement and public right of way (ROW), - Overflow device, and - Boundaries of drainage easement. • detention basin. M G A CS 5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay, to verify volume provided. 3 ?1 r" 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the entire drainage area is stabilized. _?_ ?F 2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing: 1 _ - -Maintenance access, - Permanent pool dimensions, Forebay and main pond with hardened emergency spillway, - Basin cross-section, -Vegetation specification for planting shelf, and Outlet on the plans structure prior to with use as trash a rack wet or similar, - Filter strip. G17 3 (? 3. Section view of the dry detention basin (1" = 20'or larger) showing: -Side slopes, 3:1 or lower, - Pretreatment and treatment areas, and -Inlet and outlet structures. C 3.3;F 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified 7. The supporting calculations. n U 8. A copy of the signed and notarized operation and maintenance (0&M) agreement. _ F 9. A copy of the deed restrictions (if required). bt lf*-t 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County soil maps are not an acceptable source of soils information. Form SW401-Wet Detention Basin-Rev.4 Part III. Required Items Checklist, Page 1 of 1 0 Basin "B" Area of Right of way 3.5 acres Impervious area in street right of way 2.12 acres Number of lots 8 Typical impervious area per lot (%) Drive, sidewalk 600 sf Footprint 3000 sf Deck 120 sf 3720 Impervious area of lots: 0.68 acres Area of Rec Center 1.004 acres Impervious area of Rec Cen ter 0.4 acres Total drainage area 6.90 acres Total impervious area, lots + r/w + rec center 3.20 % impervious 46% Use 50 % criteria 50% SA/DA ratio for 3' depth 2.06% SA 0.14 acres 6191.62 • Treatment volume V =3630xROx(O.05+0.9x1a)xA where V = Volume of runoff to be controlled (ft3) Ro = Design storm rainfall depth (P) A = watershed area (ac.) V = 11717 cf 0 • C Pond B Average Pond Depth = 3.01 (excludes sediment storage) Elevation SF Area CF Volume Shelf from e.329.5 to e.330.5 334 11239 54420 332 9153 34052 331.5 8618 29599 330.5 7592 21494 330 6007 18094 <-n.pool 20% of NP volume = 3619 cf 329.5 4536 15458 <-shelf 328 3412 9497 326 2095 3990 324 1053 842 323 631 0 <-sediment storage elevation (start avg. depth calc here) 322 309 0 320 0 0 Sed. Storage depth = 3.0 ft Forebay Volume Elevation SF Area CF Volume 332 1630 4565 330 967 1968 328 476 525 326 49 0 Water Quality Volume: 12044 CF (above normal pool) This volume occurs 1.55 feet above normal pool Set weir at 1.9' above normal pool Volume provided = 15068 0 Pond Routing 1-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TC [min] Intensities, I 1-year [in/hr] • Peak Discharge, Qp 1-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 1-year [inches] Volume of Runoff, V, from 6-hour storm 1-year [inches] 1-year [acre-feet] Time-to-Peak, Tp (for use in routing) 1-year [minutes] Time Interval for Routing 1-year [minutes] • Basin B B 3.70 3.20 6.90 0.60 5.0 4.90 20.29 98.0 61.0 78.2 2.8 2.89 v = ((p-.2S)"2)/(p+.8s) 1.06 0.61 Tp = V/(1.39"Qp) 15.7 1 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 0.30 0.98 0 BASIN PARAMETERS L J Riser Barrel Emergency Spillway 12 = Weir length 24 = Dia. barrel (inches) 40 = Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 331.90 = Crest elev. Weir 330 ='Invert elev. barrel 334.0 = Crest elev. 330.0 = Initial elev. water level Results Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 1 8.03 332.25 20.29 0 • ROUTING AND ANALYSIS - 1-year storm Time Inflow Storage Stage [mins] [cfs] [cubic ft] IN 0.0 0.0 0 330.00 1.0 0.2 0 330.00 2.0 0.8 12 330.00 3.0 1.8 60 330.01 4.0 3.1 167 330.02 5.0 4.7 352 330.05 6.0 6.5 632 330.09 7.0 8.4 1,020 330.15 8.0 10.5 1,526 330.22 9.0 12.5 2,153 330.32 10.0 14.4 2,901 330.43 11.0 16.1 3,763 330.54 12.0 17.6 4,731 330.66 13.0 18.8 5,789 330.79 14.0 19.7 6,920 330.93 15.0 20.2 8,102 331.08 16.0 20.3 9,314 331.23 17.0 19.9 10,530 331.38 18.0 19.2 11,726 331.52 • 19.0 18.1 12,880 331.65 20.0 16.8 13,969 331.78 21.0 15.5 14,977 331.89 22.0 14.2 15,904 332.00 23.0 13.1 16,689 332.07 24.0 12.1 17,304 332.13 25.0 11.1 17,761 332.18 26.0 10.2 18,079 332.21 27.0 9.4 18,284 332.23 28.0 8.7 18,400 332.24 29.0 8.0 18,447 332.25 30.0 7.3 18,444 332.24 31.0 6.8 18,403 332.24 32.0 6.2 18,335 332.23 33.0 5.7 18,249 332.23 34.0 5.3 18,151 332.22 35.0 4.9 18,045 332.21 36.0 4.5 17,934 332.19 37.0 4.1 17,822 332.18 38.0 3.8 17,709 332.17 332.2 Outflow [cfs] 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 2.8 4.5 5.8 6.8 7.5 7.9 8.0 8.0 7.9 7.7 7.4 7.0 6.7 6.3 6.0 5.6 Outlet Hydraulics Q_orifice Q em.spil 0.0 0 0.0 0 0.0 0 0.1 0 0.2 0 0.4 0 0.7 0 1.1 0 1.7 0 2.4 0 3.2 0 4.1 0 5.0 0 6.0 0 7.1 0 8.2 0 9.3 0 10.4 0 11.5 0 12.5 0 13.4 0 14.3 0 15.1 0 15.6 0 16.1 0 16.4 0 16.6 0 16.7 0 16.8 0 16.9 0 16.9 0 16.8 0 16.8 0 16.7 0 16.7 0 16.6 0 16.5 0 16.4 0 16.4 0 8.0 < _= maximum 2-yr Q_riser 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 2.8 4.5 5.8 6.8 7.5 7.9 8.0 8.0 7.9 7.7 7.4 7.0 6.7 6.3 6.0 5.6 0 • Analysis of time to empty Time Inflow Storage Stage Outflow [hrs] [cfs] [cubic ft] [ft] [cfs] • 0.0 0.0 12,044 331.56 0.037 6.0 0.0 11,246 331.47 0.036 12.0 0.0 10,471 331.37 0.035 18.0 0.0 9,719 331.28 0.034 24.0 0.0 8,990 331.19 0.033 30.0 0.0 8,286 331.10 0.032 36.0 0.0 7,605 331.02 0.030 42.0 0.0 6,947 330.94 0.029 48.0 0.0 6,314 330.86 0.028 54.0 0.0 5,704 330.78 0.027 60.0 0.0 5,118 330.71 0.026 66.0 0.0 4,556 330.64 0.025 72.0 0.0 4,018 330.58 0.024 78.0 0.0 3,503 330.51 0.023 84.0 0.0 3,012 330.44 0.021 90.0 0.0 2,549 330.37 0.020 96.0 0.0 2,115 330.31 0.019 102.0 0.0 1,709 330.25 0.017 108.0 0.0 1,332 330.20 0.016 114.0 0.0 984 330.14 0.015 120.0 0.0 665 63.0 66.0 69.0 0 Basin B t Pond Routing 100-yr, 6 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TIC [min] Intensities, I 100-year [in/hr] • Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 100-year [inches] Volume of Runoff, V, from 6-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing . 100-year [minutes] 3.60 3.30 6.90 0.65 5.0 9.12 40.90 B 98.0 61.0 78.7 2.7 5.39 V = ((P-.2S)"2)/(P+.8s) 3.06 1.76 Tp = V/(1.39*Qp) 22.5 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 Basin B Pond Routing 100-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc Tc [min] Intensities, I 100-year [in/hr] Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 24 hour storm 100-year [inches] Volume of Runoff, V, from 24-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing • 100-year [minutes] 3.60 3.30 6.90 0.65 5.0 9.12 40.90 B 98.0 61.0 78.7 2.7 7.59 v = ((p-.2S)"2)/(p+.8s) 5.03 2.89 Tp = V/(1.39"Qp) 36.9 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 0 BASIN PARAMETERS • Riser Barrel Emergency Spillway 12 = Weir length 24 = Dia. barrel (inches) 40 = Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 331.90 =Crest elev. Weir 330 = Invert elev. barrel 340.0 = Crest elev. z width of basin 330.0 = Initial elev. water level Results 100 year 24 hour storm Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 100 22.73 333.26 40.90 • • ROUTING AND ANALYSIS --100-year 24 hour storm Outlet Hydraulics Time Inflow Storage Stage .Outflow Q_orifice Q [mins] [cfs] [cubic ft] [ft] [cfs] em.spil 0.0 0.0 0 330.00 0.0 0.0 0 2.0 0.3 0 330.00 0.0 0.0 0 4.0 1.2 1 330.00 0.0 0.0 0 6.0 2.6 142 330.02 0.0 0.2 0 8.0 4.6 2 330.00 0.0 0.0 0 10.0 7.0 275 330.04 0.0 0.3 0 12.0 9.8 693 330.10 0.0 0.8 0 14.0 12.9 1,278 330.19 0.0 1.4 0 16.0 16.2 2,050 330.30 0.0 2.3 0 18.0 19.6 3,021 330.44 0.0 3.4 0 20.0 23.1 4,199 330.60 0.0 4.5 0 22.0 26.5 5,585 330.77 0.0 5.8 0 24.0 29.7 7,175 330.97 0.0 7.3 0 26.0 32.7 8,958 331.19 0.0 9.0 0 28.0 35.3 10,918 331.43 0.0 10.8 0 30.0 37.4 13,034 331.67 0.0 12.6 0 32.0 39.1 15,281 331.92 0.2 14.5 0 34.0 40.3 17,619 332.16 5.4 16.3 0 36.0 40.8 19,712 332.37 12.7 17.7 0 38.0 40.8 21,399 332.53 183 18.7 0 • 40.0 40.2 22,726 332.66 19.5 19.5 0 42.0 39.0 23,969 332.79 20.2 20.2 0 44.0 37.3 25,101 332.90 20.8 20.8 0 46.0 35.1 26,092 332.99 21.3 21.3 0 48.0 32.8 26,920 333.08 21.8 21.8 0 50.0 30.6 27,581 333.14 22.1 22.1 0 52.0 28.5 28,089 333.19 22.4 22.4 0 54.0 26.5 28,456 333.23 22.5 22.5 0 56.0 24.7 28,697 333.25 22.7 22.7 0 58.0 23.1 28,822 333.26 22.7 22.7 0 60.0 21.5 28,843 333.26 22.7 22.7 0 62.0 20.0 28,768 333.26 22.7 22.7 0 64.0 18.7 28,609 333.24 22.6 22.6 0 66.0 17.4 28,372 333.22 22.5 22.5 0 68.0 16.2 28,067 333.19 22.3 22.3 0 70.0 15.1 27,699 333.15 22.2 22.2 0 72.0 14.1 27,277 333.11 21.9 21.9 0 74.0 13.1 26,805 333.06 21.7 21.7 0 76.0 12.2 26,291 333.01 21.4 21.4 0 333.3 22.7 < _= maximum 100-yr 24 hour storm Q_riser 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 5.4 12.7 20.0 26.5 33.1 39.5 45.4 50.5 54.7 58.1 60.5 62.1 63.0 63.1 62.6 61.5 60.0 57.9 55.5 52.8 49.8 46.6 0 Soil Investigation Pond "B" A hand auger was used to advance a test hole approximately 30 inches in depth in two locations of the proposed pond. The soil found appears to be a sandy loam, with a predominance of quartz material throughout the sample. The soil samples were well drained. We recommend a geotechnical engineer, or B&F Consulting be present during construction of this pond in particular to ascertain whether a lining material (clay) will be required as the pond is excavated to its proposed depths. The presence of the nearby stream does indicate groundwater availability at a depth of the invert of the stream. • POND C 0 0 Permit Number: CJ (to be provided by DWQ) Drainage Area Number: Wet Detention Basin Operation and Maintenance Agreement of structures, safety of the public, and the removal efficiency of the BMP. I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the vegetated filter if one is provided. This system (check one): ? does ®does not incorporate a vegetated filter at the outlet. This system (check one): ? does ® does not incorporate pretreatment other than a forebay. Important maintenance procedures: - Immediately after the wet detention basin is established, the plants on the vegetated shelf and perimeter of the basin should be watered twice weekly if needed, until the plants become established (commonly six weeks). - No portion of the wet detention pond should be fertilized after the first initial fertilization that is required to establish the plants on the vegetated shelf. - Stable groundcover should be maintained in the drainage area to reduce the sediment load to the wet detention basin. - If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through the emergency drain should be minimized to the maximum extent practical. • - Once a year, a dam safety expert should inspect the embankment. After the wet detention pond is established, it should be inspected once a month and within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County). Records of operation and maintenance should be kept in a known set location and must be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire BMP Trash/ debris is resent. Remove the trash/ debris. The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to detention basin erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Vegetation is too short or too Maintain vegetation at a height of long. a roximatel six inches. Form SW401-Wet Detention Basin O&M-Rev.3 Page 1 of 4 Permit Number: • • E (to be provided by DWQ) Drainage Area Number: BMP element: Potential problem: How I will remediate the problem: The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the Swale sediment off-site. The pipe is cracked or Replace the pipe. otherwise damaged. Erosion is occurring in the Regrade the swale if necessary to swale. smooth it over and provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. The forebay Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design depth for possible. Remove the sediment and sediment storage. dispose of it in a location where it will not cause impacts to streams or the BMP. Erosion has occurred. Provide additional erosion protection such as reinforced turf matting or riprap if needed to prevent future erosion problems. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it on the plants rather than spraying. The vegetated shelf Best professional practices Prune according to best professional shoal that pruning is needed practices to maintain optimal plant health. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application to establish the. ground cover if a soil test indicates it is necessary. Weeds are present. Remove the weeds, preferably by hand. If pesticide is used, wipe it on the plants rather than spraying. The main treatment area Sediment has accumulated to Search for the source of the a depth greater than the sediment and remedy the problem if original design sediment possible. Remove the sediment and storage depth. dispose of it in a location where it will not cause impacts to streams or the BMP. Algal growth covers over Consult a professional to remove 50% of the area. and control the algal growth. Cattails, phragmites or other Remove the plants by wiping them invasive plants cover 50% of with pesticide (do not spray). the basin surface. Form SW401-Wet Detention Basin O&M-Rev.3 Page 2 of 4 . Permit Number: (to be provided by DWQ) Drainage Area Number: BMP element: Potential problem: How I will remediate the problem: The embankment Shrubs have started to grow Remove shrubs immediately. on the embankment. Evidence of muskrat or Use traps to remove muskrats and beaver activity is present. consult a professional to remove beavers. A tree has started to grow on Consult a dam safety specialist to the embankment. remove the tree. An annual inspection by an Make all needed repairs. appropriate professional shows that the embankment needs repair. The outlet device Clogging has occurred. Clean out the outlet device. Dispose of the sediment off-site. The outlet device is damaged Repair or replace the outlet device. The receiving water Erosion or other signs of Contact the local NC Division of damage have occurred at the Water Quality Regional Office, or outlet. the 401 Oversight Unit at 919-733- 1786. • The measuring device used to determine the sediment elevation shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the permanent pool depth reads 316.0 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 320.0 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM ill in the blanks) • 0 Permanent Pool Elevation 324.0 Sediment Removal . 320.0 ;Pe anen Pool --------------Volume Sediment Removal Elevation 316.0 Volume -------------------------------------------- ------ ottom E evaho 318.0 ft Min. Sediment Bottom Elevation 313.6 1-ft n Storage Sedimet Storage FOREBAY MAIN POND Form SW401-Wet Detention Basin O&M-Rev.3 Page 3 of 4 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: "C" Print name: 6/765 JA. J r. Title: ,Ov? Address: /* 7i¢.. r4olew cl-- 4A-e-c /t/C Phony Signa Date: Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I s =? -_ • . ., cu s _L, , a Notary Public for the State of VO E , County of e , do hereby certify that Cc w ?;s t! SVe,S J r personally appeared before me this _L day of ZCO £f , and acknowledge the due execution of the forgoing wet detention basin ai enance requirements. Witness my hand and official seal, 1?- `l ADg4f '•?N0TAR? ??. C?• 'z? • -_ AVBLDG =Vr SEAL My commission expires y ZOO Form SW401-Wet Detention Basin O&M-Rev.3 Page 4 of 4 Permit No. (to be provided by DWQ) III. REQUIRED ITEMS CHECKLIST Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. • • Pagel Plan Initials Sheet No. ]Z? 1. Plans (1" 50' or larger) of the entire site showing: Design at ultimate build-out, - Off-site drainage (if applicable), - Delineated drainage basins (include Rational C coefficient per basin), Basin dimensions, Pretreatment system, - High flow bypass system, Maintenance access, Proposed drainage easement and public right of way (ROW), - Overflow device, and Boundaries of drainage easement. C D 3 2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing: Outlet structure with trash rack or similar, - Maintenance access, Permanent pool dimensions, Forebay and main pond with hardened emergency spillway, Basin cross-section, Vegetation specification for planting shelf, and - Filter strip. 3. Section view of the dry detention basin (1" = 20' or larger) showing: - Side slopes, 3:1 or lower, - Pretreatment and treatment areas, and - Inlet and outlet structures. CD 3.3 I 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified on the plans prior to use as a wet detention basin. _ ,,- 1 6 Cx 5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay, CO 36 to verify volume provided. 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the entire drainage area is stabilized. f t `?- *"4 7. The supporting calculations. 8. A copy of the signed and notarized operation and maintenance (0&M) agreement. A 9. A copy of the deed restrictions (if required). FAY) A 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County soil maps are not an acceptable source of soils information. Form SW401-Wet Detention Basin-Rev.4 Part III. Required Items Checklist, Page 1 of 1 Permit No. (to be provided by DWQ) ,?> ??F w Fl rr,9Q O G > • NCaENR STORMWATER MANAGEMENT PERMIT APPLICATION FORM 401 CERTIFICATION APPLICATION FORM WET DETENTION BASIN SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part lll) must be printed, filled out and submitted along with all of the required information. I. PROJECT INFORMATION Project name Stonemont Contact person Russell Briggs, P.E. Phone number 919-618-0180 Date 30-Jun-08 Drainage area number "C II. DESIGN INFORMATION Site Characteristics Drainage area 300,564.00 ft2 Impervious area 118,918.80 ft2 % impervious 39.57 % Design rainfall depth 1.00 in Storage Volume: Non-SR Waters Minimum volume required 10,177.00 ft3 Volume provided 11,488.00 ft3 Storage Volume: SR Waters 1-yr, 24-hr runoff depth in Pre-development 1-yr, 24-hr runoff ft3 `Post-development 1-yr, 24-hr runoff ft3 Minimum volume required ft3 Volume provided ft3 Peak Flow Calculations 1-yr, 24-hr rainfall depth 2,89 in Rational C, pre-development 0.30 (unitless) Rational C, post-development 0.55 (unitless) Rainfall intensity: 1-yr, 24-hr storm 4.90 in/hr Pre-development 1-yr, 24-hr peak flow 10.14 ft3/sec Post-development 1-yr, 24-hr peak flow 18.60 ft3/sec Pre/Post 1-yr, 24-hr peak flow control 8.45 ft3/sec Basin Elevations Basin bottom elevation 313.60 ft Sediment cleanout elevation 316.00 ft Bottom of shelf elevation 323.50 It Permanent pool elevation 324.00 It SHWT elevation 320.00 ft Top of shelf elevation 324.50 ft Temporary pool elevation 325.30 ft • Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 1 of 2 Permit No. (to be provided by DWQ) II. DESIGN INFORMATION Volume and Surface Area Calculations SA/DA ratio 1.73 (unitless) • Surface area at the bottom of shelf 5,155.00 ftz Volume at the bottom of shelf 17,590.00 ft3 Permanent pool, surface area required 5,199.76 ftz Permanent pool, surface area provided 6,800.00 ft OK Permanent pool volume 20,578.00 ft3 Average depth for SA/DA tables 3.03 ft OK Surface area at the top of shelf 8,640.00 ft2 Volume at the top of shelf 24,438.00 ft3 Forebay volume 4,500.00 ft3 Forebay % of permanent pool volume 21.87 % OK Temporary pool, surface area provided 9,595.00 ftz Drawdown Calculations Treatment volume drawdown time 4.00 days OK Treatment volume discharge rate 0.50 ft3/s Pre-development 1-yr, 24-hr discharge 10.14 ft3/s OK Post-development 1-yr, 24-hr discharge 8.70 ft3/s OK Additional Information Diameter of orifice 1 in Design TSS removal 85 % Basin side slopes 3.00 :1 OK Vegetated shelf slope 10.00 :1 OK Vegetated shelf width 10.00 ft OK Length of flowpath to width ratio 3.00 :1 OK Length to width ratio 1.50 :1 OK Trash rack for overflow & orifice? Y (Y or N) OK Freeboard provided 1.00 ft OK • Vegetated filter provided? y (Y or N) OK Recorded drainage easement provided? y (Y or N) OK Capures all runoff at ultimate build-out? y (Y or N) OK Drain mechanism for maintenance or emergencies drain via pump ?J Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2 • Basin "C" • Area of Right of way 1.72 acres Impervious area in street right of way 1.28 acres Number of lots 17 Typical impervious area per lot (%) Drive, sidewalk 600 sf Footprint 3000 sf Deck 120 sf 3720 Impervious area of lots: 1.45 acres Total drainage area 6.90 acres Total impervious area, lots + r/w 2.73 % impervious 40% Use 40% criteria 40% SA/DA ratio for 3' depth 1.73% SA 0.12 acres Treatment volume Treatment volume = V =3630xRox(0.05+0.9xIa)xA where V = Volume of runoff to be controlled (ft3) Ro = Design storm rainfall depth (1") A = watershed area (ac.) 10177 cubic feet • • Pond C Average Pond Depth = 3.03 (excludes sediment storage) Elevation SF Area CF Volume Shelf from e.323.5 to e.324.5 327.5 12349 55827 326 10431 38742 325.3 9595.2 32067 water quality pool 324.5 8640 24438 <-shelf (upper) 324 6800 20578 <-n.pool 20% of NP volume = 4116 cf 323.5 5155 17590 <-shelf (lower) 1543 sf 322 3751 10910 320 2242 4917 318 1143 1532 316 389 0 <-sediment storage elevation (start avg. depth calc here) 315 159 0 314 20 0 313.6 0 0 Sed. Storage depth = 2.4 ft Forebay Volume Elevation SF Area CF Volume 326 1644 4953 324 996 2313 322 475 842 320 176 191 318 15 0 Water Quality Volume: 10177 CF (above normal pool) This volume occurs 1.16 feet above normal pool Set weir at 1.3' above normal pool Volume provided = 11488 cubic feet 0 Pond "C" Pond Routing 1-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TC [min] Intensities, I 1-year [i n/h r] • Peak Discharge, Qp 1-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 1-year [inches] Volume of Runoff, V, from 6-hour storm 1-year [inches] 1-year [acre-feet] Time-to-Peak, Tp (for use in routing) 1-year [minutes] Time Interval for Routing • 1-year [minutes] 4.17 2.73 6.90 0.55 5.0 4.90 18.60 B 98.0 61.0 75.6 3.2 2.89 v = ((p-.2S)"2)/(p+.8s) 0.92 0.53 Tp = V/(1.39*Qp) 14.9 1 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 • BASIN PARAMETERS r-? Riser Barrel Emergency Spillway 12 = Weir length 30 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 325.30 =Crest elev. Weir 324 = Invert elev. barrel 327.5 = Crest elev. 324.0 = Initial elev. water level Results Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 1 8.68 325.66 18.60 0 0 ROUTING AND ANALYSIS - 1-year storm Time Inflow Storage Stage [mins] [cfs] [cubic ft] [ft] 0.0 0.0 0 324.00 1.0 0.2 0 324.00 2.0 0.8 12 324.00 3.0 1.8 61 324.01 4.0 3.1 169 324.02 5.0 4.7 356 324.05 6.0 6.5 638 324.08 7.0 8.4 1,028 324.13 8.0 10.4 1,533 324.20 9.0 12.3 2,155 324.28 10.0 14.1 2,892 324.37 11.0 15.6 3,736 324.48 12.0 16.9 4,673 324.59 13.0 17.9 5,688 324.70 14.0 18.4 6,759 324.82 15.0 18.6 7,865 324.94 16.0 18.3 8,980 325.06 17.0 17.7 10,081 325.18 18.0 16.7 11,143 325.30 • 19.0 15.4 12,144 325.40 20.0 14.1 12,993 325.48 21.0 12.9 13,652 325.55 22.0 11.8 14,131 325.60 23.0 10.9 14,456 325.63 24.0 9.9 14,657 325.65 25.0 9.1 14,762 325.66 26.0 8.4 14,795 325.66 27.0 7.7 14,775 325.66 28.0 7.0 14,718 325.66 29.0 6.4 14,634 325.65 30.0 5.9 14,533 325.64 31.0 5.4 14,421 325.63 32.0 4.9 14,302 325.61 33.0 4.5 14,180 325.60 34.0 4.2 14,058 325.59 35.0 3.8 13,936 325.58 36.0 3.5 13,817 325.57 37.0 3.2 13,700 325.55 38.0 2.9 13,588 325.54 325.7 Outflow [cfs] 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 3.1 4.9 6.4 7.5 8.2 8.6 8.7 8.6 8.4 8.1 7.8 7.4 7.0 6.6 6.2 5.8 5.4 5.1 4.7 Outlet Hydraulics Q_orifice Q Q_riser em.spil 0.0 0.0 0.0 0.1 0.2 0.5 0.9 1.4 2.1 2.9 4.0 5.1 6.2 7.4 8.6 9.9 11.2 12.5 13.7 14.8 15.7 16.4 16.9 17.2 17.4 17.5 17.6 17.5 17.5 17.4 17.3 17.2 17.0 16.9 16.8 16.7 16.5 16.4 16.3 8.7 < ==maximum 2-yr 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 1.2 0 3.1 0 4.9 0 6.4 0 7.5 0 8.2 0 8.6 0 8.7 0 8.6 0 8.4 0 8.1 0 7.8 0 7.4 0 7.0 0 6.6 0 6.2 0 5.8 0 5.4 0 5.1 0 4.7 • Analysis of time to empty r? LJ Time Inflow Storage Stage Outflow [hrs] [cfs] [cubic ft] [ft] [cfs] 0.0 0.0 11,154 325.30 0.034 6.0 0.0 10,420 325.22 0.033 12.0 0.0 9,708 325.14 0.032 18.0 0.0 9,016 325.07 0.031 24.0 0.0 8,346 324.99 0.030 30.0 0.0 7,696 324.92 0.029 36.0 0.0 7,068 324.85 0.028 42.0 0.0 6,461 324.79 0.027 48.0 0.0 5,874 324.72 0.026 54.0 0.0 5,309 324.66 0.025 60.0 0.0 4,765 324.60 0.024 66.0 0.0 4,242 324.54 0.023 72.0 0.0 3,740 324.48 0.022 78.0 0.0 3,260 324.42 0.021 84.0 0.0 2,806 324.36 0.020 90.0 0.0 2,376 324.31 0.019 96.0 0.0 1,972 324.26 0.018 102.0 0.0 1,593 324.21 0.016 108.0 0.0 1,239 324.16 0.015 114.0 0.0 911 324.12 0.014 120.0 0.0 608 63.0 66.0 69.0 0 • Pon "C" Pond Routing 100-yr, 6 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TIC [min] Intensities, I 100-year [in/hr] Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 6 hour storm 100-year [inches] Volume of Runoff, V, from 6-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing 100-year [minutes] B 4.17 2.73 6.90 0.55 5.0 9.12 34.61 98.0 61.0 75.6 3.2 5.39 v = ((P-.2S)"2)/(P+.8s) 2.83 1.63 Tp = V/(1.39*Qp) 24.5 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 0 BASIN PARAMETERS • Riser Barrel Emergency Spillway 12 = Weir length 30 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 325.15 =Crest elev. Weir 324 = Invert elev. barrel 327.5 =Crest elev. 324.0 = Initial elev. water level Results 100-year 6-hour storm Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 100 26.23 326.49 34.61 0 ROUTING AND ANALYSIS --100-year, 6 hour storm Outlet Hydraulics t Time Inflow Storage Stage Outflow Q_orifice Q [mins] [cfs] [cubic ft] IN [cfs] em.spil 0.0 0.0 0 324.00 0.0 0.0 0 2.0 0.6 0 324.00 0.0 0.0 0 4.0 2.2 68 324.01 0.0 0.1 0 6.0 4.9 334 324.04 0.0 0.5 0 8.0 8.3 918 324.12 0.0 1.3 0 10.0 12.4 1,915 324.25 0.0 2.6 0 12.0 16.7 3,398 324.44 0.0 4.6 0 14.0 21.1 5,404 324.67 0.0 7.1 0 16.0 25.3 7,937 324.95 0.0 10.0 0 18.0 28.9 10,970 325.28 0.0 13.5 0 20.0 31.8 14,438 325.63 7.4 17.2 0 22.0 33.7 17,358 325.92 19.3 20.3 0 24.0 34.6 19,086 326.08 22.0 22.0 0 26.0 34.3 20,599 326.21 23.4 23.4 0 28.0 32.9 21,912 326.33 24.6 24.6 0 30.0 30.5 22,914 326.42 25.5 25.5 0 32.0 27.6 23,518 326.47 26.1 26.1 0 34.0 24.8 23,697 326.49 26.2 26.2 0 36.0 22.3 23,523 326.47 26.1 26.1 0 38.0 20.1 23,070 326.43 25.7 25.7 0 40.0 18.0 22,398 326.37 25.0 25.0 0 42.0 16.2 21,559 326.30 24.3 24.3 0 44.0 14.6 20,595 326.21 23.4 23.4 0 46.0 13.1 19,543 326.12 22.4 22.4 0 48.0 11.8 18,431 326.02 21.4 21.4 0 50.0 10.6 17,285 325.91 19.0 20.2 0 52.0 9.5 16,282 325.81 14.5 19.1 0 54.0 8.6 15,687 325.75 12.1 18.5 0 56.0 7.7 15,270 325.71 10.4 18.1 0 58.0 6.9 14,945 325.68 9.2 17.7 0 60.0 6.3 14,672 325.65 8.2 17.4 0 62.0 5.6 14,432 325.63 7.4 17.2 0 64.0 5.1 14,217 325.61 6.7 16.9 0 66.0 4.5 14,020 325.59 6.1 16.7 0 68.0 4.1 13,838 325.57 5.5 16.5 0 70.0 3.7 13,669 325.55 5.0 16.4 0 72.0 3.3 13,512 325.54 4.5 16.2 0 74.0 3.0 13,366 325.52 4.1 16.1 0 76.0 2.7 13,230 325.51 3.7 15.9 0 Q_riser 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.4 19.3 27.3 34.6 41.3 46.8 50.1 51.1 50.2 47.6 43.9 39.5 34.6 29.5 24.4 19.0 14.5 12.1 10.4 9.2 8.2 7.4 6.7 6.1 5.5 5.0 4.5 4.1 3.7 326.5 26.2 < _= maximum 100-yr 6 hr storm • Pon "C" Pond Routing 100-yr, 24 hour storm Stonemont HYDROGRAPH PARAMETERS Item Drainage Area Area Type Lawn, Landscape [acres] Impervious [acres] Drainage Area [acres] Rational C Composite Rational C Time of Concentration, Tc TC [min] Intensities, I 100-year [in/hr] • Peak Discharge, Qp 100-year [cfs] Curve Number, CN Hydrologic Soil Group Impervious CN Lawn, Landscaped CN Composite CN S Precipitation Amount, P for 24 hour storm 100-year [inches] Volume of Runoff, V, from 24-hour storm 100-year [inches] 100-year [acre-feet] Time-to-Peak, Tp (for use in routing) 100-year [minutes] Time Interval for Routing • 100-year [minutes] 4.17 2.73 6.90 0.55 5.0 9.12 34.61 B 98.0 61.0 75.6 3.2 7.59 v = ((p-.2S)^2)/(p+.8s) 4.75 2.73 Tp = V/(1.39"Qp) 41.2 2 B&F Consulting, Inc. 2805 Tobermory Lane Raleigh, NC 27606 (919) 618-0180 • BASIN PARAMETERS Riser Barrel Emergency Spillway 12 = Weir length 30 = Dia. barrel (inches) 40 =Length 3.3 = Cw weir 0.6 = Cd barrel 3.00 = Cw 325.15 =Crest elev. Weir 324 = Invert elev. barrel 327.5 =Crest elev. 324.0 = Initial elev. water level Results 100-year, 24-hour storm Event Post Development With Controls No Control Peak Peak Peak Discharge Elevation Discharge [cfs] [cfs] 100 29.28 326.79 34.61 0 0 ROUTING AND ANALYSIS --100-year, 24 hour storm • Time Inflow Storage [mins] [cfs] [cubic ft] 0.0 0.0 0 2.0 0.2 0 4.0 0.8 24 6.0 1.8 120 8.0 3.1 334 10.0 4.8 709 12.0 6.8 1,284 14.0 9.0 2,096 16.0 11.4 3,172 18.0 13.9 4,536 20.0 16.5 6,205 22.0 19.2 8,189 24.0 21.8 10,488 26.0 24.2 13,099 28.0 26.6 15,602 30.0 28.7 17,384 32.0 30.5 18,495 34.0 32.1 19,590 36.0 33.3 20,748 38.0 34.1 21,921 40.0 34.5 23,063 42.0 34.6 24,130 44.0 34.2 25,083 46.0 33.5 25,889 48.0 32.3 26,519 50.0 30.8 26,948 52.0 29.1 27,156 54.0 27.3 27,133 56.0 25.6 26,899 58.0 24.1 26,488 60.0 22.6 25,930 62.0 21.2 25,253 64.0 19.9 24,481 66.0 18.7 23,637 68.0 17.6 22,739 70.0 16.5 21,804 72.0 15.5 20,844 74.0 14.5 19,869 76.0 13.6 18,890 Stage Outflow IN [cfs] Outlet Hydraulics Q_orifice Q Q_riser em.spil 324.00 0.0 0.0 0 324.00 0.0 0.0 0 324.00 0.0 0.0 0 324.02 0.0 0.2 0 324.04 0.0 0.5 0 324.09 0.0 1.0 0 324.17 0.0 1.8 0 324.27 0.0 2.9 0 324.41 0.0 4.3 0 324.57 0.0 6.1 0 324.76 0.0 8.0 0 324.97 0.0 10.3 0 325.23 0.0 12.9 0 325.49 3.4 15.8 0 325.74 11.7 18.4 0 325.92 19.4 20.3 0 326.03 21.4 21.4 0 326.13 22.4 22.4 0 326.23 23.5 23.5 0 326.33 24.6 24.6 0 326.43 25.6 25.6 0 326.52 26.6 26.6 0 326.61 27.5 27.5 0 326.68 28.2 28.2 0 326.73 28.7 28.7 0 326.77 29.1 29.1 0 326.79 29.3 29.3 0 326.79 29.3 29.3 0 326.77 29.1 29.1 0 326.73 28.7 28.7 0 326.68 28.2 28.2 0 326.62 27.6 27.6 0 326.55 27.0 27.0 0 326.48 26.2 26.2 0 326.40 25.3 25.3 0 326.32 24.5 24.5 0 326.24 23.6 23.6 0 326.15 22.7 22.7 0 326.06 21.8 21.8 0 326.8 29.3 < == maximum 100-yr 24-hr storm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.4 11.7 19.4 24.7 29.7 35.3 41.4 47.6 53.6 59.2 64.1 68.0 70.7 72.0 71.8 70.4 67.8 64.3 60.2 55.7 50.8 45.8 40.8 35.8 31.0 26.4 0 Soil Investigation Pond "C" A hand auger was used to advance a test hole approximately 30 inches in depth in two locations of the proposed pond. The soil found appears to be a sandy loam, with a predominance of quartz material throughout the sample. The soil samples were well drained. We recommend a geotechnical engineer, or B&F Consulting be present during construction of this pond in particular to ascertain whether a lining material (clay) will be required as the pond is excavated to its proposed depths. The presence of the nearby stream does indicate groundwater availability at a depth of the invert of the stream. • r1 U Level Spreader Calculations, Worksheets and O&M Agreements 40 Permit Number: (to be provided by DWQ) Drainage Area Number: r- Filter Strip, Restored Riparian Buffer and Level Spreader Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. Important maintenance procedures: - Immediately after the filter strip is established, any newly planted vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - Once a year, the filter strip will be reseeded to maintain a dense growth of vegetation - Stable groundcover will, be maintained in the drainage area to reduce the sediment load to the vegetation. - Two to three times a year, grass filter strips will be mowed and the clippings harvested to promote the growth of thick vegetation with optimum pollutant removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and may be allowed to grow as tall as 12 inches depending on aesthetic requirements . (NIPC,1993). Forested filter strips do not require this type of maintenance. - Once a year, the soil will be aerated if necessary. - Once a year, soil pH will be tested and lime will be added if necessary. After the filter strip is established, it will be inspected quarterly and within 24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County). Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire filter strip Trash/ debris is present. Remove the trash/debris. system The flow splitter device The flow splitter device is Unclog the conveyance and dispose (if applicable) clogged. of an sediment off-site. The flow splitter device is Make any necessary repairs or damaged. replace if damage is too large for repair. • Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3 • • • BMP element: Potential problem: How I will remediate the problem: The swale and the level The swale is clogged with Remove the sediment and dispose lip sediment. of it off-site. The level lip is cracked, Repair or replace lip. settled, undercut, eroded or otherwise damaged. There is erosion around the Regrade the soil to create a berm end of the level spreader that that is higher than the level lip, and shows stormwater has then plant a ground cover and bypassed it. water until it is established. Provide lime and a one-time fertilizer application. Trees or shrubs have begun Remove them. to grow on the swale or just downslo e of the level lip. The bypass channel Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then reestablish proper erosion control. Turf reinforcement is Study the site to see if a larger damaged or ripap is rolling bypass channel is needed (enlarge if downhill. necessary). After this, reestablish the erosion control material. The filter strip Grass is too short or too long Maintain grass at a height of (if applicable). approximately three to six inches. Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Sediment is building up on Remove the sediment and the filter strip. restabilize the soil with vegetation if necessary. Provide lime and a one- time fertilizer application. Plants are desiccated. Provide additional irrigation and fertilizer as needed. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application. Nuisance vegetation is Remove vegetation by hand if choking out desirable species. possible. If pesticide is used, do not allow it to get into the receiving water. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality local Regional Office, or the outlet. 401 Oversight Unit at 919-733-1786. Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance, procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number:- 4 Print name: Curtis Jones, Jr. Title: member Address: 140 Towerview Court, Cary NC ?. Phon Sigm Date: Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. • I, P1.5-Ty W"t nn a Notary Public for the State of ?lvA t'ti Ltd ha , County of do hereby certify that (1--ot 5 ?hncs '_'I?' • personally appeared before me this 9 7d day of Zbo , and acknowledge the due execution of the forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements. My commission expireswr- Z 7 ?,p/ V Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3 Witness my hand and official seal, DWQ Project is DIVISION OF WATER QUALITY - LEVEL SPREADER WORKSHEET (112007) 1. PROJECT INFORMATION (please complete the following information): Project Name : _`?7?bA./CNO,t_/7" Contact Person: TS us SEL _ e_ Phone Number: Level Spreader ID: _F E Level Spreader Length /D ft Drainage Area O.31 ac. Impervious Area ?, L 5 ac. Forebay Area cu ft Maximum Filter Strip/Buffer Slope -5_ % grass (perpendicular to flow) (on-site and off-site drainage to the level spreader) (on-site and off-site drainage to the level spreader) (0.2% of the contributing impervious surface area) (6% for forested, leaf littler cover, 8% for thick ground cover Max. Discharge from 1"7Hr Storm O 3 cfs Max. Discharge to Level Spreader cfs Filter Strip/ Zone 2 Buffer Vegetation cam (thick ground cover or grass; canopied forest with leaf litter groundcover) Pre-treatment or Bypass Method Used II. REQUIRED ITEMS CHECKLIST Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a • requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details, a detailed drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for additional information and will substantially delay final review and approval of the project. Applicants Initials ---1?,_Project Site was visited prior to designing level spreader. -Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING BUFFER CONDITIONS. Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer. S! Pre-Formed Scour Holes are on flat slopes only. -WA No structures are located in protected buffers (must meet no practical alternatives criteria). Design Alternative (if any) and Bypass method used: ----Bypass conveyance method is specified and plan details and calculations are provided. Alternative design option is specified and plan details and calculations are provided. Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass discharge. No structures are located in protected buffers. Plan details for the bypass and outlets are provided. E The operation and maintenance agreement includes annual erosion and vegetation repair. The operation and maintenance agreement signed and notarized by the responsible party is provided.' 0 • ,f • 0 10010 SF FFE=329.0 PAD T01 F RAP MN \\? "E$2 R N SAY so 108 \ AyARRiEE?Af s. c 10010 SF 32'X9 31. TH c. MIN FFE=329.5 - '2lY' SPILL WAY 109 .S. 1 D 11419 SF j 6,112 SF MIN FE=329,5 11302 ?? ' TANDAR CONSTRUCn NTRANCE . . .FUTURE. 5.0. . CL-ROW DON, \ '. WHEN ADJAC -` 12U ?\ 11291 SF Z \ \ ` / .` , 19 ?. `.` B 10894 F \ / o Al- -? Z110Z", , Z- i 14 / 10274 SF Gay r cy? ?MID, lk? 3A 14'704 IN FFE= 6.0 ?fi . SED BASIN 10 fo DRAINA .AREA: 0.28 AC DENUDED 0.28 AC - ON SED. STORA .580 CF 't- 49''18'X3.5'. TN Wt ILLWAY rImMER SF D2 MIN FE=33>5 TEMP. SED BASIN RY NAOE AREA: QA AC-1 26 .1 AC 0 AREA I .. TOR uw szo 4 01 43 SF 10,006 SF MIN FFE =333.5 MH 116 i 112 13148 SF; 10903 F// \ IH A`F\` MIN FFE \ ??••??CC??-- 1 =334.0 51 13 TEMPORARY 10 MIN 000ESF BARRICADE W/ i MFN =335.0 \ `\ TORS SIGNAGE Tea 5 114 \ / WEI PIPE. GeF ??, . AGe \? ::::::. ' •.. OLI SF E 2 G ?j ? .:::++i:%. FFE Y IN 20 E E G' J `\ S 00 Fa F.:. 1536 \ L 7 SED BASIN 2 .JORAINAGE AREA: 2.08 AC I-' NOTE TH' / AA? ippIUDED AREA. 1.42 AC \ / K 11ibbEEEEDDDDD STORACE: 1835 CF FBI (CAPE FE F 1? h 1. 39'X1 18X3.5' DEPTH WILL BE LEFT UNDISTURBED. 10` SPILLWAY SHOWN THIS IS THE 20' ON EITHER SIDE ? NO SKIMMER PROMDED OF THE STREAM BANK EDGE, MHTEXANNA PA U, RECREATI QN B Y WILL S l AREA 1 B AREA = 13.561 AC ' i ALKING TRAILS/PICNIC AREA \ LAND USE. S. F. H04 B 98,639 SF \ l ° I FLOOD Q B P ` `\ EL. 3 ! ?1 N 1 O. TEMP. ;'BASIN 30J DRAINACE AREA: 5.15 AC g34 DENUDED AREA: 251 F S J m I ? SEO. STORAGE: 2451 CF b ? PJ \ ' 46,X139'X3.5' DEPTH J I T20' SPILLWAY SHO 'y0 PRgNDE %gMM5A Qw , F 124 ?j 11976 SF r?,o ; ((,?, ?F O IN FFE='349.0 v?/ ,/CN?p? \\ \ 1' 'A, Q? ^3AQ <IV 125 15861 SF \ \ J IN FFE=352.0 11 f 126 \7465 SF / -7 16789 SF % 3 Permit Number: (to be provided b QWQ) Drainage Area Number: ?_ Filter Strip, Restored Riparian Buffer and Level Spreader Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. Important maintenance procedures: - Immediately after the filter strip is established, any newly planted vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - Once a year, the filter strip will be reseeded to maintain a dense growth of vegetation - Stable groundcover will be maintained in the drainage area to reduce the sediment load to the vegetation. - Two to three times a year, grass filter strips will be mowed and the clippings harvested to promote the growth of thick vegetation with optimum pollutant removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and may be allowed to grow as tall as 12 inches depending on aesthetic requirements (NIPC,1993). Forested filter strips do not require this type of maintenance. - Once a year, the soil will be aerated if necessary. - Once a year, soil pH will be tested and lime will be added if necessary. After the filter strip is established, it will be inspected quarterly and within 24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County). Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be pefformed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire filter strip Trash/ debris is present. Remove the trash/ debris. system The flow splitter device The flow splitter device is Unclog the conveyance and dispose (if applicable) clogged. of an sediment off-site. The flow splitter device is Make any necessary repairs or damaged. replace if damage is too large for repair. • Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3 • • • BMP element: Potential problem: How I will remediate the problem: The swale and the level The swale is clogged with Remove the sediment and dispose lip sediment. of it off-site. The level lip is cracked, Repair or replace lip. settled, undercut, eroded or otherwise damaged. There is erosion around the Regrade the soil to create a berm end of the level spreader that that is higher than the level lip, and shows stormwater has then plant a ground cover and bypassed it. water until it is established. Provide lime and a one-time fertilizer application. Trees or shrubs have begun Remove them. to grow on the swale or just downslo . e of the level lip. The bypass channel Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then reestablish proper erosion control. Turf reinforcement is Study the site to see if a larger damaged or ripap is rolling bypass channel is needed (enlarge if downhill. necessary). After this, reestablish the erosion control material. The filter strip Grass is too short or too long Maintain grass at a height of (if applicable). approximately three to six inches. Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Sediment is building up on Remove the sediment and the filter strip. restabilize the soil with vegetation if necessary. Provide lime and a one- time fertilizer application. Plants are desiccated. Provide additional irrigation and fertilizer as needed. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application. Nuisance vegetation is Remove vegetation by hand if choking out desirable species. possible. If pesticide is used, do not allow it to get into the receiving water. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality local Regional Office, or the outlet. 401 Oversight Unit at 919-733-1786. Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3 Permit Number: (to be provided by DWQ) • I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: _[??-:5 J Print name: Curtis Jones, Jr. Title: member Address:, 140 Tower-view Court, CM, NQ ,:Ph6r Sign, Date Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. 1, PUTY a Notary Public for the State of 1?1 t`? t-APD? Irea , County of ,cam , do hereby certify that U? hnec ? . personally appeared before me this 9 7d day of .. ? ZpD , and acknowledge the due execution of the forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements. Witness my hand and official seal, My commission expires dw,?Ir Z7 ? o,1V Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3 DWQ Project • DIVISION OF WATER QUALITY - LEVEL SPREADER WORKSHEET (1/2007) I. PROJECT INFORMATION (please complete the following information): Project Name 51r4&lt-9641 Contact Person: _ 7?5 %F?_ Phone Number: Level Spreader ID: FCs S Level Spreader Length ,/D ft. Drainage Area 0,44 ac. Impervious Area d . 1 95 ac. Forebay Area 1 cu ft Maximum Filter Strip/Buffer Slope ¢ % grass Max. Discharge from 1°/Hr Storm 02 cfs Max. Discharge to Level Spreader O cfs Filter Strip/ Zone 2 Buffer Vegetation u Lan,- Pre-treatment or Bypass Method Used ?46 II. REQUIRED ITEMS CHECKLIST (perpendicular to flow) (on-site and off-site drainage to the level spreader) (on-site and off-site drainage to the level spreader) (0.2% of the contributing impervious surface area) (6% for forested, leaf littler cover, 8% for thick ground cover (thick ground cover or grass; canopied forest with leaf litter groundcover) Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes • a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details,' a detailed drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for additional information and will substantially delay final review and approval of the project. A_ pplicants Initials Project Site was visited prior to designing level spreader. Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING BUFFER CONDITIONS. Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf C litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer. l 4 ?f+R Pre-Formed Scour Holes are on flat slopes only. No structures are located in protected buffers (must meet no practical alternatives criteria). Design Alternative (if any) and Bypass method used: .?' Bypass conveyance method is specified and plan details and calculations are provided. Alternative design option is specified and plan details and calculations are provided. _ Z?ld Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass discharge. -__LT•B No structures are located in protected buffers. Plan details for the bypass and outlets are provided. The operation and maintenance agreement includes annual erosion and vegetation repair. The operation and maintenance agreement signed and notarized by the responsible party is provided.' • in 'J1 'U • 0 \Iumr- JIAIIVN -<I I'll r. „ W 1566 Sv „a? -'r - 551 AREA DEEDED TO .74 MH 7 25 2J H'Q .LY SPRINGS N 07-262J" ¢7529 SF EES 8. B C11Ap?NEL W/ CONC. WEIR. 10' %tIR \ \ LEVEL SPREAD. AND FES8 FOMASI IN 20' EASEM i ° , \? !• \. i i 230 \ s R. ,?o 2 3 F 15047 SF , D NTp?P. SED 8AS8V 9?? v?zi 1 0 5 NET. 14846 SF / OE AREA: 0.4AAC (? i0 1192 SF ? D UDED AREA: 0,42 WC \ P\ fV? MIN FFE=323. . STORAGE: Tao w IN FFE=328.0 i 8 TM 40SSPILWAY 1, O p ? 231 1 OE 14975 SF 10010 j NET: 14872 SF MIN FFE vl MIN FF'E=323.5 =328.5 36 \ `- B + Na M O ?L 4 TEMPI AREA 0A? A ! \\ W/ EL FF ENUDEO AREA 0.44 AC 232 SEO' STORAGE: 810 CF I '! B CHANNEL 'c fES2 20'%87'X3:5' DEPTH I W( C. ."PIPE & IM 4' SPILLWAY SHOWN I 17690 SF VEL AND 13 CF \ \ C`P PAY NO SKIMMER PROVIDED I FOREBAY I 2q EASEMENT \\ m: \\\ ` FS :5+ !. BAY D MIN FFE=324.5 1 \ \\\ : l \ D D. AREA: 0. .88 p I I \\ 00\ ?? 32'%9 3.3' DEPTH 245 ?0' SPILLWAY 20898 SF 0. s, ' s' 233 MIN FFE=325.0 i 246 S??°??A 6112 SF MIN 8608 SF • \` ??`?e qi4 `.\` ?' ro SF 20804 SF i I 1 i _ NET.- 1623 58 \ \0 I 1 `MIN FFEFE=327.0 .0 MH E2 UT1$SS?? 'BYPASS CHANNEL t 244C. 9 W/ CONR. }$ PIPE AND 10' ER 11 ,? \\ C S LEVEL SPREADER. 14309 SF ; MH 247 ?qM 3 0 3. DRAT AGE A EA:: BASIN 5 224 AC E1 16369 SF DENUDED A:0.54 AC sE0.-_. I NET: 16348 SF ei?u Y ?? _a MIN FFE=328.0 NO SKIMM RPRONDED + \ 40 241 243 'F ?10 SF 12110 SF 10010 SF 248 I? 11179 SF a -yr f 4 P. AMAGE SED BASIN AREA: POND 'a" 00 ?• '/ / 8.90 AC BO • -""-^ ! 1 7 X66. SF ?epDENUDEO AREA 2.74 AC j 53'25' SPILLWAYPTM 14-70, G MIN FFE MH (,'2 DRAINA AREA: 0N .2a AC ' CBS 25 r DENUDED : 0.2e Ac SED. STINtA 580 CF 205 49'X18'X3.5' 1H ILLWAY 207 10010 S 10 06 204 203 I MER 10010 S 202 13138 SF 10010 SF 10010 SF 20 10394 SF 15068 SF )• ---- S 0322'19 "W --??. rS-rMM6-'ER E7ER ------------ 769. 19 ? ? PORARY / RICADE w/j 3363 S / i OH GNAGE ! ! I 1,34 11200 SF SO, 133 mw4%4 11200 Sf? _ Hol FAl1Q A/ /Q n F) r- K I / . , A:h oy ay -7, 1 7 // ???, i VdIN Permit Number: (to be provided by DW ) Drainage Area Number: Filter Strip, Restored Riparian Buffer and Level Spreader Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. Important maintenance procedures: - Immediately after the filter strip is established, any newly planted vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - Once a year, the filter strip will be reseeded to maintain a dense growth of vegetation - Stable groundcover will, be maintained in the drainage area to reduce the sediment load to the vegetation. - Two to three times a year, grass filter strips will be mowed and the clippings harvested to promote the growth of thick vegetation with optimum pollutant removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and may be allowed to grow as tall as 12 inches depending on aesthetic requirements (NIPC,1993). Forested filter strips do not require this type of maintenance. - Once a year, the soil will be aerated if necessary. - Once a year, soil pH will be tested and lime will be added if necessary. After the filter strip is established, it will be inspected quarterly and within 24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County). Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will remediate the problem: The entire filter strip Trash/ debris is present. Remove the trash/ debris. system The flow splitter device The flow splitter device is Unclog the conveyance and dispose (if applicable) clog ed. of an sediment off-site. The flow splitter device is Make any necessary repairs or damaged. replace if damage is too large for re air. • Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3 • • • BMP element: Potential problem: How I will remediate the problem: The swale and the level The swale is clogged with Remove the sediment and dispose lip sediment. of it off-site. The level lip is cracked, Repair or replace lip. settled, undercut, eroded or otherwise damaged. There is erosion around the Regrade the soil to create a berm end of the level spreader that that is higher than the level lip, and shows stormwater has then plant a ground cover and bypassed it. water until it is established. Provide lime and a one-time fertilizer application. Trees or shrubs have begun Remove them. to grow on the swale or just downslo e of the level lip. The bypass channel Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then reestablish proper erosion control. Turf reinforcement is Study the site to see if a larger damaged or ripap is rolling bypass channel is needed (enlarge if downhill. necessary). After this, reestablish the erosion control material. The filter strip Grass is too short or too long Maintain grass at a height of (if applicable). approximately three to six inches. Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Sediment is building up on Remove the sediment and the filter strip. restabilize the soil with vegetation if necessary. Provide lime and a one- time fertilizer application. Plants are desiccated. Provide additional irrigation and fertilizer as needed. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application. Nuisance vegetation is Remove vegetation by hand if choking out desirable species. possible. If pesticide is used, do not allow it to get into the receiving water. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality local Regional Office, or the outlet. 401 Oversight Unit at 919-733-1786. Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3 DWQ Project • DIVISION OF WATER QUALITY - LEVEL SPREADER WORKSHEET (1/2007) I. PROJECT INFORMATION (please Project Name : ! ThA.1.? Contact Person: Ru%SFs the following information): Level Spreader ID: -5;6 6 7 Level Spreader Length 10 ft Drainage Area 0,54 ac. Impervious Area O. i fi3 ac. Forebay Area Maximum Filter Strip/Buffer Slope ? o ft. grass Phone Number: (perpendicular to flow) (on-site and off-site drainage to the level spreader) (on-site and off-site drainage to the level spreader) (0.2% of the contributing impervious surface area) (6% for forested, leaf littler cover, 8% for thick ground cover Max. Discharge from 1 '/Hr Storm 0.3 cfs Max. Discharge to Level Spreader C9. cfs Filter Strip/ Zone 2 Buffer Vegetation 64)W- (thick ground cover or grass; canopied forest with leaf litter groundcover) Pre-treatment or Bypass Method Used II. REQUIRED ITEMS CHECKLIST Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details, '4 detailed drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for additional information and will substantially delay final review and approval of the project. Applicants Initials ? G?" Project Site was visited prior to designing level spreader. i 7 bg Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING BUFFER CONDITIONS. Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer. Pre-Formed Scour Holes are on flat slopes only. No structures are located in protected buffers (must meet no practical alternatives criteria). Design Alternative (if any) and Bypass method used: Bypass conveyance method is specified and plan details and calculations are provided. Alternative design option is specified and plan details and calculations are provided. zzR Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass discharge. -- L? -No structures are located in protected buffers. _1EE -Plan details for the bypass and outlets are provided. The operation and maintenance agreement includes annual erosion and vegetation repair. The operation and maintenance agreement signed and notarized by the responsible party is provided.' 0 Permit Number: (to be provided by DWQ) • I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: F 7 Print name: Curtis Jones, Jr. Title: member Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, 15Ty L • Inn f? , a Notary Public for the State of )]a/ t? t-r4?o? /rte , County of do hereby certify that ?Ur his ..?hr?cs JTr • personally appeared before me this 9 7W day of , _Z008, and acknowledge the due execution of the forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements. • My commission expires - Z ? Q/ D i Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3 Address: 140 Towerview Court, CM, NQ Witness my hand and official seal, L41VG i). m?? 20' ON EITHER SIDE OF THE STREAM BAN t \ \ NOTE THAT THE DOWNSTREAM \\ ?\ PROPERTY LINE FLOOD ELEVATION /? \ \ IS BASED ON FUTURE CONDITIONS AND IS INTERPOLATED FROM (9 / ?'?' \ \ UPSTREAM AND DOWNSTREAM FEMA CROSS SECTIONS ? to ,p F,p \?p?`\\\ \\ e G'( <s;\ THE OLl t / P. SED BASIN.. s\ ?\\ 4 R NAGE AREA: 0.54 c, O -° 1 UDED AREA: 0.34 AC 'n \l "?9\ \\ Q \ LS p 11 M , 88 ST 9 \` \ \ 9?(n??\\ ??? D.U. 1 10 1 EE BYPASS ANNd LAND ? O G W/"" :ANC. WEIR PIPE a f ?\ LEVE7_ S':REAO. AND IB CF \ \ \ 0 \ e"FOREBAY IN 20' EASEMENT \ \?\ \ i 9v/ ?`` \ 16461 SF NET- SF'/ Ciy ?y4+ i t 222 \ MIN FFE=319. 16983 SF 224 /T: 12180 SF 16844 SF E .- //MIN FFE=322.0 - NET: 11609 SF \ 3` ' MIN FFE=321.5 \ ?? \ 12' WIDE ??CB \ `? ?\ M \ 8" ABC DRIVE TO PUMP STAT10 ` MH. \\'QP E N F1 \?` ?\ \ . ? WITHIN .40' ESM" SEE ENLARGEMENT I W21 225 SPACE 2A \\ o ? \ ?p \ 2 2 MINA FFE=323.0 10532 SF \ FHB BG, ???, I 1 MIN FFE=322.0 208,06), SF PUMP STATION G?? r AREA DEEDED TO FP \ ??o? ??? . SLY SPRINGS 220 4,752,r SF 10010 SF 226 \ ` W S CO8. 8 NC.RE . Nr :HEIR \ MIN FFE=324.0 WEIR ' 1 10010 SF vEl SPAO. AND .FESB FOREBAY IN 20' EASO / TEMP.SED BASML 9 . 2 2 7 229 230 21C 15047 SF , o Auk AREA: AREA: o 0. Nc 100101 13330 SF NET: 14646 SF 7 ? . SEO BASIN 7 MIN FIFE ` 10010 SF ' STORAGE: Teo CF 0.30 Ac_ I' MIN FFE=323. ..STORAGE- DEPTH 1 `8'30'110'-Q SPIKIM MLLWAYER $TORAGE: 590.CF I r j 0 S ?1yF?? 17'X3.5' DEPTH 231 4! Ol 4' SPILLWAY NO SKIMMER/ I - ?, 228 14975 SF 1306 SF -- / NET: 14872 SF N FFE a 11306 SF MIN FFE=323.5 ' _9- •7 - I - 31 TEMP. SEO BASIN 4 1' \ AINAGE AREA: 0.44 AC RA r H - - UDED AREA., 0.44 AC B O SM. STORAGE: 810 CF- .I ?I.W •. R. PIPPEE k 1 -- =- S 2 3 2 '20'Xd1 %3.3' DEPTH 1 , - AND 13 C 4' SPILLWAY SHOWN 1 . 1 FORE13AY 2q EASEIM 17690 SF NO SKIMMER PROVIDED <- 9 MIN FfE=324:5 I ' 1 \ 2.1 /T 245 1 IN oo I 20898 SF ' 246 M I ; FFE6 330.0 r 1 T ABLE SF I L 3 6 I 235 234 Z Z3 MIN FFE=325.0 ) 18608 SF. INS =30.0 I! I 11976 SE 12110 SF 12110 SF 23 1 NET: 16258 SF ( 20804 SF , MIN FFE=327.0 1nLANDS10225 SF NET: 10049 SF 1 ! ,/ C L D H A E 2 244 16 --' 24 33o0 ?1 J 4 I BANS 14309 SF MH 1636 11226 SF ?u?NRACE 2.24 Ac NET: 16: NET. 10041 SF D A. ENUOEO 0.54 AC MIN FFE: ., 1 aq I I SED. STIR - 31'X93'X .9' DEPTH . t lYI _ r 8' SPILLAY SHOWN • ,.j) 'U L • 0 Permit Number: (to be provided by DWQ) Drainage Area Number: Filter Strip, Restored Riparian Buffer and Level Spreader Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. Important maintenance procedures: - Immediately after the filter strip is established, any newly planted vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - Once a year, the filter strip will be reseeded to maintain a dense growth of vegetation - Stable groundcover will, be maintained in the drainage area to reduce the sediment load to the vegetation. - Two to three times a year, grass filter strips will be mowed and the clippings harvested to promote the growth of thick vegetation with optimum pollutant removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and may be allowed to grow as tall as 12 inches depending on aesthetic requirements (NIPC,1993). Forested filter strips do not require this type of maintenance. • - Once a year, the soil will be aerated if necessary. - Once a year, soil pH will be tested and lime will be added if necessary. After the filter strip is established, it will be inspected quarterly and within 24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County). Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problem: How I will rernediate the problem: The entire filter strip Trash/debris is present. Remove the trash/ debris. system The flow splitter device The flow splitter device is Unclog the conveyance and dispose (if applicable) clogged. of an sediment off-site. The flow splitter device is Make any necessary repairs or damaged. replace if damage is too large for repair. C7 Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3 C] • • BMP element: Potential problem: How I will remediate the problem: The Swale and the level The swale is clogged with Remove the sediment and dispose lip sediment. of it off-site. The level lip is cracked, Repair or replace lip. settled, undercut, eroded or otherwise damaged. There is erosion around the Regrade the soil to create a berm end of the level spreader that that is higher than the level lip, and shows stormwater has then plant a ground cover and bypassed it. water until it is established. Provide lime and a one-time fertilizer application. Trees or shrubs have begun Remove them. to grow on the swale or just downslo e of the level lip. The bypass channel Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then reestablish proper erosion control. Turf reinforcement is Study the site to see if a larger damaged or ripap is rolling bypass channel is needed (enlarge if downhill. necessary). After this, reestablish the erosion control material. The filter strip Grass is too short or too long Maintain grass at a height of (if applicable). approximately three to six inches. Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Sediment is building up on Remove the sediment and the filter strip. restabilize the soil with vegetation if necessary. Provide lime and a one- time fertilizer application. Plants are desiccated. Provide additional irrigation and fertilizer as needed. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application. Nuisance vegetation is Remove vegetation by hand if choking out desirable species. possible. If pesticide is used, do not allow it to get into the receiving water. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality local Regional Office, or the outlet. 401 Oversight Unit at 919-733-1786. Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name: Stonemont BMP drainage area number: ?C ! Print name: Curtis Jones. Jr. Title: member Address: 140 Towerview Court, Cary, NC Phone Signat Date:_ W 9 /U6 Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. • I, ?i.5-ry L. P &Canne fl , a Notary Public for the State of ?CJ' 4 at,21 /ha- , County of ke , do hereby certify that (fUt h s 'Tt . personally appeared before me this 9 ?d day of 2!6) , and acknowledge the due execution of the forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements. • My commission expires410)6w,?Ir Z rT 2 D/ a i Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3 Witness my hand and official seal, DWQ Project No. 0 DIVISION OF WATER QUALITY - LEVEL SPREADER WORKSHEET (1/2007) 1. PROJECT INFORMATION (please Project Name : 5 r7d) c- Contact Person: Rus SFt Level Spreader ID: 1=j?6 P. the following information): Level Spreader Length /O ftDrainage Area O . Z ac. Impervious Area , l ac. Forebay Area cu ft Maximum Filter Strip/Buffer Slope % grass Phone Number: (perpendicular to flow) (on-site and off-site drainage to the level spreader) (on-site and off-site drainage to the level spreader) (0.2% of the contributing impervious surface area) (6% for forested, leaf littler cover, 8% for thick ground cover Max. Discharge from 1VHr Storm d ),z cfs Max. Discharge to Level Spreader 0.14 cfs Filter Strip/ Zone 2 Buffer Vegetation C AdT (thick ground cover or grass; canopied forest with leaf litter groundcover) Pre-treatment or Bypass Method Used S II. REQUIRED ITEMS CHECKLIST Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details, a detailed drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for additional information and will substantially delay final review and approval of the project. Applicants Initials -.._Project Site was visited prior to designing level spreader. -Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING BUFFER CONDITIONS. Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer. APre-Formed Scour Holes are on flat slopes only. fj, No structures are located in protected buffers (must meet no practical alternatives criteria). Design Alternative (if any) and Bypass method used: ? Bypass conveyance method is specified and plan details and calculations are provided. Alternative design option is specified and plan details and calculations are provided. ,j Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass discharge. ,B No structures are located in protected buffers. Plan details for the bypass and outlets are provided. The operation and maintenance agreement includes annual erosion and vegetation repair. The operation and maintenance agreement signed and notarized by the responsible party is provided.' 0 16 461 SF 11Z 'NET- 13028 SF// IN FFE=319. i \? Y ?0 c?L ?6l ?\ v' i ? 16983 SF \ \ cS? 224 ?pET: 12180 SF 16844 SF 'MIN FFE=322.0 NET: 11609 SF MIN FFE=321.5 \ 12' W M \ ?` 8" ABC MH. TO PUMP WITHIN 4C 2 21 \ /?? -,aP E N F1 SEE ENLARGE[ 10532 SF / 225 SPACE 2A \\ o? ?,, ; MIN FFE=323.0 10532 SF ! ( L MIN FFE=322.0 208,06 ?. ` ?GOy S'S ,?1 T 10010 SF 226 'i Z529 SF MIN FFE=324.0 r 10010 SF w coNa WfiR,N?10 L? ' E 1 SPREAD. AND FE FOREBAY IN 20' EASEME i S - t \ 219 230 229 TEMP.D 9ASML 10010 SF 22 15047 SF / D AINAGE AREA: 0.421AC TEMP. SED BASIN 7 MIN FFE J ( 0010 SF 13. 30 SF NET: 14846 SF o uDEO AREA: 0.42 nc • 0.30 AC_ •Q ' 1 MIN FFE=323. STORAGE: 780 CF \\\ DFD AR 630-AC i 6 'X20 X3.5' DEPTH \ y,R,c1 STORAGE: 590 CF 4' SPILLWAY V" 50'X17'X3.5' DEPTH 4' SPILLWAY/ ?' ' ?^ ? 0 SKIMMERJ•(. NO SKIMMERZ I 8 I 228 23 1 1306 SF 14975 SF BLS n N FFE o 11306 SF NET: 14872 SF 7,- MIN FFE=323.5 31 - o ' -- 4- - -- G1 ? ? i? ?? BASIN AC I S'RF' 0 UDED AREA: 0.44 AC I CHAN p _ SM. STORAGE: 810 OF I W 8 PIPE ? ? 232 2WX61'X3.5' DEPTH.. I 14' SPILLWAY SHOWN I fOREBAY '2 ' CAND I ASE 7690 SF NO SKIMMER PROVIDED 1 I 2 I ?7 ( I 7 MIN FFE=324:5 1 1 ' I 1 SF 245 MIN FFE F 30.0 ? 2 898 SF j g ATMWE ? I 1 l9 3 6F 235 234 233 MIN FFE=325.0 i I 246 ? ? TT j I 12110 SF i t 18608 SS ?acnoNAL 12110 SF 20804 'SF I NET. 162 6258 SF r 10225 SF MIN FFE=327.0 NE.: 100,49 SF + r B I CB\ MIN FFE ?1 H A E 2 244 18 5 2 =330.011226 SF I I 14309 SF t1 MH 1 \ 1631 NET: 10041 SF ( BASIN s E1 DRAINA A GE 2.24 AC ?. , DENUDED A. 0.54 AC NET: 11 SED.. srOR MIN FFI BAY "I1 31'X93 'X 5' DEPTH i 8' SPILL AY SHOWN IN FFE 214 LJ `? 238 No SKIM PROVIDED IN FF 10, 1 SF ? , 1T976 SF 12110 SF 239 240 24 1 2 4 3 24. 12110 SF 10010 SF ( I T 10000 SF + 12110 ,SF 1 2110 SF 11179 S ------------- - ------- MIN FFE _ ! ! j =334.5 213 I i ( Jill. 10010 SF I i `? q o NET: 10008 SF M t SFm L " F 11066 SF 212 11516 SF 1 I ° _ -- - -- NET: 10058 SF MIN FFE=336.0 , ?_-- CMH1 C2 B 25 210 209 2`? r ? --=-?: 211 1081 SF 10010 S 8 207 206 i •12707 SF i 10010 S 10010 S 10010 S 10010 s 204 203 202 -j NET: 10688 SF , TEMPORARY / 10010 SF 10010 SF 10394 SF ;DAM_%XEW SPILL AY' BARRICADE WITHIN UNDtS1. AR A ToFrs SIGN -_------ ------_ - 1 ------ --------- ?a -------- MgIN F6 BUS - 70 >STI7RBE6 PER ETER t$peNANC? FSeR, `\ ` \ S 032 T 2'19 "w 769.19' NOTE THAT EMERGENC S) \\\ ,? \ • .) 0