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HomeMy WebLinkAboutSW7060118_HISTORICAL FILE_20060217STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW-7/ilQDllY DOC TYPE ❑CURRENT PERMIT ❑ APPROVED PLANS HISTORICAL FILE DOC DATE YYYYMMDD Nite associates ARCHITECTURE / ENGINEERING / TECHNOLOGY Response to Review Comments February 9, 2006 Ms. Amy L. Franklin NCDENR — Land Quality Section 943 Washington Square Mall Washington, NC 27889 RE: BCSIBath Elementary Additions and Renovations REC%i; v D FEB 1 1 20.' DWQ-WARD Amy, SGI.� Thank you for your recent comments regarding the referenced Project in•Gay In response to your letter received February 61 ., 2006, please find the following information. I a6ew comment 1 ,Please note that the roof drains must be directed to the stormwafer treatment system. Response 1 Note has been added to C201 grading plan indicating that all roof vertical roof drains will be tied into the stormwater system. I a6iew comment 2 Please note that the length to width ratio must be 3:1. The current ratio is 2.5:1. Response 2 Pond has been adjusted to the correct ratio of 3:1 maintaining the engineered surface area. Review comment 3 Please clearly label the temporary pool elevation on the cross sections. Also please label the permanent pool and Temporary pool on the scaled pond detail. Response 3 Labels have been provided accordingly. 2600 Meridian Drive /Greenville, NC 27834 / tel252.757,0333 / fax 252,757,1330 / e-mail: dtsmith®hiteassoc.com , R view comment 4 'tiytease show/label the pond slopes (3:1, 6:1, etc) on the cross section detail. Response 4 Labels have been provided accordingly. Review comment 5 Please show the 10 foot vegetative shelf. Response 5 Label and shading has been provided to delineate shelf. Review comment 6 Please explain impervious area calculations. Example: Building area should include the total new building area and not only 2,684 ft2. Also all of the new pavement area should be treated. Response 6 Please see attached revised Stormwater Permit Application. The 2,684 should read 82,684 due to a typo error. I hope the information provided by this letter will prove sufficient of the continued review of this project. If you should have any questions or should need additional information, please do not hesitate to call. spectfully, To nth Hite Associates fc: Steve Janowski Dr. Jeffrey Moss, Superintendent, BCS file: JGH / regulatory attachemnts Nite associates �r;� l�f���il�i�It►�`'��I��i]I;�`1�l�I�il�[I]�II!�'I Response to Review Comments February 27, 2006 Ms. Amy L. Franklin NCDENR — Land Quality Section 943 Washington Square Mall Washington, NC 27889 RE: BCSIBath Elementary Additions and Renovations Amy, FEH L' a ?1!06 Attached drawing package was revised per recent comments regarding the referenced Project in Bath. In response to your letter received February 61h, 2006, please find the following information. 1. Added Permanent and Temporary pool elevations to plan and details. Labeled contours within Pond I hope the revised information provided on these plans will prove sufficient of the continued review of this project. If you should have any questions or should need additional information, please do not hesitate to call. Respectfully, Tod Sfnith Hite Associates fc: Steve Janowski Dr. Jeffrey Moss, Superintendent, BCS file: JGH / regulatory attachemnts 2600 Meridian Drive /Greenville, NC 27834 / 1e1252.757.0333 / fax 252.757.1330 / e-marl; dtsmith®hiteassoc.com W A TER Michael F. Easley, Governor William G. Ross Jr., Secretary North Carolina Department of Environment and Natural Resources -� Alan W. Klimek, P.E. Director Division of Water Quality February 22, 2006 Dr. Jeffrey Moss Superintendent, Beaufort County Schools 321 Smaw Road Washington, NC 27889 Subject: Stormwater Review SW7060118 Bath Elementary School Addition Beaufort County Dear Dr. Moss: This office received a Coastal Stormwater permit application and plans for the subject project on January 17, 2006. A preliminary review of your project indicates that before a State Stormwater permit can be issued the following additional information is needed. ➢ Please clearly label the temporary pool elevation on cross sections. Also please label the permanent pool and temporary pool elevations on the scaled pond detail. ➢ Please provide the surface area in square feet for the temporary pool elevation. The above requested information must be received in this office prior to March 24, 2006 or your application will be returned as incomplete. The return of this project will necessitate resubmittal of all required items including the application fee. If you need additional time to submit the required information, please mail or fax your request for time extension to this office at the Letterhead address. You should also be aware that the Stormwater Rules require that the permit be issued prior to any development activity. Construction without a permit is a violation of 15A NCAC 21-1.1000 and North Carolina General Statute 143-215.1 and may result in civil penalties of up to $10,000 per day. Please reference the Stormwater Project Number above on all correspondence. if you have questions, please feel free to contact me at (252) 948-3934, Sincerely, Amy L. Franklin Environmental Engineer Washington Regional Office cc: Washington Regional Office J. Stephen Janoswski, PE ^o�f` NhCaro AW11rru North Carolina Division of Water Quality Washington Regional Office Phone (252) 946-6481 FAX (252) 946.9215 Internet ncwaterquality.or9 943 Washington Square Mall, Washington, NC 27889 An Equal OpportunitylAffirmative Action Employer — 50% Recycled110% Posi Consumer Paper Customer Service 1-877-623-6748 O�O� W AT �9QG y Michael F. Easley, Governor ►^' K c Wdliam G. Ross Jr., secretary North Carolina Department of Environment and Natural Resources Wit Dr. Jeffrey Moss Superintendent, Beaufort County Schools 321 Smaw Road Washington, NC 27889 Dear Dr. Moss: Alan W. Klimek, P.E. Director Division of Water Quality February 2, 2006 Subject: Stormwater Review SW7060118 Bath Elementary School Addition Beaufort County This office received a Coastal Stormwater permit application and plans for the subject project on January 17, 2006. A preliminary review of your project indicates that before a State Stormwater permit can be issued the following additional information is needed. ➢ Please note that the roof drains must be directed to the stormwater treatment system. ➢ Please note that the length to width ratio must be 3:1. The current ratio is approximately 2.5:1 ➢ Please clearly label the temporary pool elevation on cross sections. Also please label the permanent pool and temporary pool on the scaled pond detail. ➢ Please show/label the pond slopes (3:1, 6:1, etc.) on the cross section detail. ➢ Please show the 10 foot vegetated shelf. ➢ Please explain impervious area calculations. Example: Building area should include the total new building area and not only 2,684 fe. Also all of the new pavement area should be treated. The above requested information must be received in this office prior to March 4, 2006 or your application will be returned as incomplete. The return of this project will necessitate resubmittal of all required items including the application fee. If you need additional time to submit the required information, please mail or fax your request for time extension to this office at the Letterhead address. You should also be aware that the Stormwater Rules require that the permit be issued prior to any development activity. Construction without a permit is a violation of 15A NCAC 211.1000 and North Carolina General Statute 143-215.1 and may result in civil penalties of up to $10,000 per day. Please reference the Stormwater Project Number above on all correspondence. If you have questions, please feel free to contact me at (252) 948-3934. Sincerely, J� d4o�'� 4 n r V L-.- Amy L. Franklin Environmental Engineer Washington Regional Office cc: ✓Washington Regional Office J. Stephen Janoswski, PE TOCU th or hCaro NNatural North Carolina Division of Water Quality Washington Regional Office Phone (252) 946-6481 FAX (252) 946-9215 Customer Service Internet h2o.enr.state.nc.us 943 Washington Square Mall, Washington, NC 27889 1-877-623-6748 An Equal Opportunity/Affirmative Action Employer— 5U% Recycledl14%Post Consumer Paper STORM WATER MANAGEMENT NARRATIVE JAN 1 1 2606 BATH ELEMENTARY SCHOOL ADDITIONS I3EAUFORT COUNTY, NORTH CAROLINA DWQ-WARD Narrative This project site consists of a single 16.34 acre drainage basin of which 4.66 acres is off - site all of'which will be collected in an existing and proposed storm drainage system that will drain directly through a wet detention facility. All the storm water runoff generated by the proposed construction of these facilities will be conveyed to the wet detention facility for treatment. Runoff from this site eventually drains to Back Creek east of the site in the Tar Pamlico River Basin. The property is bounded by existing residential to the east, Hwy 92 to the north and NC 1741 to the west.. The. purpose of the wet detention facility is to reduce TSS by 90% in a project located in the 20 coastal counties for the new impervious development on this site. The SA/DA was selected from the chart for coastal counties with a TSS removal of 90% with no vegetative filter required. The completed project will consist of one 16.34 acre drainage area draining into the ,proposed stormwater wet detention pond via the proposed storm drainage system, proposed drainage swales and sheet flow fi•om the surrounding area. The watershed breakdown is as follows: Existing Pavement/Walks Existing pavement removed Existing Buildings New Pavement/walks New New Buildings On -site (1 1.68 ac) IMPERVIOUS AREA CALCULATIONS 51.401 sf (29,97 I )sf 56,012 sf 84,178 sf 26,672 sf ✓ Off -Site (4.66 ac) IMPERV. AREA CALCS. l-Exist. Imperv. 85,255 sf The existing drainage basin has 192,668 sf or 4.42 acres of impervious area. Upon completion of the proposed site improvements, the site will have 273,547 sf or 6.28 acres of impervious area and will be 38.43% built upon area. The wet detention pond will treat all of the stormwater ru1iofl'generated by this increase in impervious. area. The watershed that drains into the vet detention pond is collected by a curb system with curb inlets and drop inlets connected by storm drain pipes that will discharge stormwater runoff into the fore -bay area of the wet detention pond. The average depth of the pond is four feet. The required surface area to drainage area ratio for a project with 38.43 % impervious area is 3.37% based on a 90% TSS removal and a 4 foot depth. The surface area to drainage area of the temporary pool provided is 3.37%. The wet detention pond has a surface area of 24,102 sf with the normal pool elevation at 6.5. The bottom elevation is to be 2.5 with an additional foot of depth excavated for sediment storage during construction. The permanent pool volume is 68569 cf and the forebay volume is 21,875 cf. The outlet structure consists of an 8 ft by 8 ft box. The basin is designed to capture the first I" of runoff to a depth of two feet. The outlet for this temporary storage volume is 2.0 inches in diarneter and will release the F of runoff in approximately 3 days. The principal spillway is designed for the 10 year storm and is established at elevation 7.41 which is the top of the temporary storage. The 10 year design storm was routed through the detention facility to provide an emergency spillway adequate to handle this storm. The emergency spillway and outlet are protected with grass. 1L and ASSOCIATES ENGINEERING, SURVEYING & PLANNING Michael W. Baldwin, PLS J.S. Janowski, PE WET DETENTION FOR BATH ELEMENTARY SCHOOL BEAUFORT COUNTY, NORTH CAROLINA 1015 Conference Drive ❑ capture 1st inch of runoff 10 YEAR 11 /28/05 2/3 2 4_ �y�,,�rr rt.rutr Ht'N, Greenville, North Carohna. 7858 ❑ 252-756-1390 ❑ Fax: 252-321-1412 Email: admin@boldwinandassociatesnc.com - Site Conditions Predevelopment Total watershed area 16.34 acres on site - Impervious Area C= 0.95 CN= 98 2.47 acres On site -Open Space - Good Con C= 0.3 CN= 74 5.73 acres off site - Impervious Area C= 0.95 CN= 98 1.96 acres off site -Open Space - Good Con, C= 0.3 CN= 74 2.70 acres Hydraulic Length 2240 feet Vertical Relief 6.5 feet 24-hr, 10 yr rainfall 4.4 inches Time of Concentration channel flow L 0395 channel — 28.1 X 1 28.1 minutes II 1 128 Composite C based on published values (exhibit 1-Malcom) 0.41 R g h Rainfall Intensity = I = 2 132 18 4.05 inches per hr (h + T ` ! 10 203 22 25 246 23 100 302 25 Peak Discharge Q = CIA 27.28 cfs E Site Conditions Post Development Total watershed area on site - Impervious Area On site -Open Space - Good Con off site - Impervious Area off site -Open Space - Good Con Hydraulic Length Vertical Relief 24-hr, 10 yr rainfall Design Hydrogfaph Formulation Composite CN 1000 S= -10 CN Runoff Q* _ �P — 0.2S)2 P + 0.85 Time of Concentration channel flow (not overland) 13 i1.385 1 f = -I 128 Composite C = Rainfall Intensity = 1 = 9 (h+T) C= C= C= C= Peak Discharge Q CIA Time to peak T Vol — 1.39Q,, Storage Required 0.95 0.3 0.95 0.3 28.1 X CN= CN= CN= CN= R 9 h 2 132 18 10 203 22 25 246 23 100 302 25 Required to store the 1 st inch of runoff (from Rv Calculations below) 3 16.34 acres 98 4.32 acres 74 3.88 acres 98 1.96 acres 74 2.70 2240 feet 6.5 feet 4A inches 67.5 4.82 1.43 inches 1 28.1 minutes 0.49 4.05 inches per hr 32.15 cfs 31.6 minutes 23,482 cf Pond Runoff Storage Volume Requirements Rv = 0.05+,009(1) 1 = 38.4% % Rv = 0.40 inches/inches Volume that must be controlled Volume = (Design rainfall)(Rv)(Drainage Area) Volume = 0.54 ac-ft - 23,482 cf Must store 23,482 cf of water above the permanent pool elevation Permanent Pool Elevation 6.5 STAGE STORAGE DATA surface diff. accum. Elevation area elev storage storage Elevation Stage 6.50 24102 - 6.50 0.00 0.50 12,531 7.00 26022 12,531 7.00 0.5 4.00 112,172 11.00 30064 124,703 11.00 4.5 4 Computed Storage Stage LN(storage) LN(Stage) Stage 0 0 #NUM! #NUMI 0,00 12,531 0.5 9.44 -0.69 0.50 124,703 4.5 11.73 1.50 4,50 1.05 25869.34 Predicted Water Surface Elevation for Temporary Water Quality Pool= Size Outlet Device for Control Structure invert elevation = estimated orifice center elev. _ proposed water surface elev. _ available head (h) _ discharge (d) = coefficient of discharge = Determine the orifice diameter Orifice equation Q = C,/I 2gh Set top of outlet structure at = 7.41 release the remaining flow M SAY ORIFICE WILL DRAIN POND IN 7.41 feet msl 6.50 feet msl 6.58 feet msl 7.41 feet msl 0.83 feet 0.0 cfs 0.6 0.00 feet 2 inches 2.73 DAYS 5 Inflow Hydrograph Additional Flow 0.0 Peak Inflow = Time to Peak = 39.52483998 T (time min) 0 3.16 6.32 949 1265 1581 18.97 22-13 2630 2846 31.62 3478 3)-s4 41,11 4427 47, 43 50.59 53.75 56.92 6008 63.24 8640 69.56 72.73 75.89 79.05 82.21 6537 8854 91.70 94.85 98.02 101.16 10435 107.51 110,67 113,83 116,99 120,16 12332 126.48 T 29 64 13280 32,1 31,6 Inflow Orifice Outflow Weir Outflow Total Outflow O ( cfs) O) cfs) Q { cis) O { cis) 0.00 000 0.00 0.0 0.79 0,00 0.00 0.00 3.07 000 000 0.00 6.62 0. DO 0.00 0.00 11.10 0.00 0,00 0.00 16.06 0. DO 0. DO 0.00 21.02 0.05 0.00 0.05 2551 006 0, DO 0.06 29.06 0.08 0,DO 0.09 31.35 0.09 O. DO 009 32.15 0.10 1,03 1.13 31.37 Oil 3,86 3.98 2909 0.12 7,31 743 25.74 0.13 10,51 10.64 22.60 0,13 12,84 12.98 1985 0.14 14,57 14.70 17.43 0.14 1.533 15.47 15.30 0.14 1584 15.98 13.44 0,14 15.59 15.72 11.60 0.14 15.33 15.47 10.36 0.14 14.57 14.70 9.10 0.14 13,82 13.95 7.99 0,13 13.08 13.22 7.02 0.13 12, 13 12.26 6.is 0.13 11,42 11.55 5.41 0.13 10.51 1064 4.75 0.13 9.84 9.97 4 17 0.13 8.97 909 3 66 0.13 8.33 846 322 0.12 7.51 7-64 2.82 0.12 6.91 7.04 2.48 0.17 6.33 8.46 2-18 0.12 5.96 6.08 1.91 0.12 5.41 5,52 1,68 0.12 4.87 4.99 1-47 0.12 4.53 4.84 1.29 0.12 4-19 4.31 1.14 0.11 3.86 3.98 1.00 Oil 3,54 3.66 0.88 0,11 3.23 3.35 0-77 Oil 2,93 3.05 0.68 0.11 2,79 2.90 0.59 0.11 2,50 2.61 6 13597 0.52 0,11 2,37 2.47 139.13 0.46 0.11 i 2.10 2.20 142,29 0,40 0.11 1.97 2.07 145.45 0.35 0.11 1.84 1.95 148.61 0.31 0.11 1.71 1,82 151.76 0.27 0.11 1,59 1.70 154.94 0.24 0.11 1,47 1.58 158.10 0.21 0.1 1 1.36 1 46 161.26 0.18 0.10 1.24 1.35 164, 42 0.16 0.10 1,14 1.24 167.59 0.14 0.10 1.03 1.13 170,75 0.12 0.10 1.03 1.13 173.91 0.11 0,10 0,93 1.03 177.07 0,10 0.10 083 0.93 18023 0.08 0.10 083 0.93 183,40 0.07 0.10 0.73 084 186.56 0.07 0.10 0,73 0.84 189,72 006 0.10 0.64 0.74 192.86 005 0,10 064 0.74 196.04 0.04 0.10 0.56 066 199.21 0.04 0.10 0.56 066 202.37 0.03 0.10 0.47 057 205.53 0.03 0.10 047 0.57 20869 003 0,10 0.47 0.57 211.85 0.02 0.10 0.40 0.50 215-02 0.02 0.10 0.40 0.50 218.18 0,02 0.10 0.32 042 221.34 0 D2 0.10 0.32 042 224.50 0.01 0.10 0.32 042 227.66 0,01 0.10 0.32 0.42 230.83 0.01 0,10 0,25 0.35 233-99 0.01 0,10 025 0.35 237.15 001 0.10 025 0.35 240.31 001 0,10 0.25 0.35 243.47 0.01 0,10 0.19 0.29 246.04 001 0.10 0.19 0.29 249.80 0,00 0.10 0.19 0.29 252,96 0.00 0,10 0,19 0.29 256.12 0.00 0,00 0.00 0.00 259.28 0.00 0.00 0,00 0.00 Stormwater routing 6 2 Spillway inch 7.41 T (time min) Q cfs Storage Stave Outflow Elevation orifice Weir 0 0.00 0 0.00 0.0 6.50 0.00 3.16 0.79 0 0.00 0.0 6.50 0.00 0.0 6.32 3.07 149 0.01 0.0 6,51 0.00 0.0 9.49 6.62 731 0.03 0.0 6.53 0.00 0.0 12.65 11.10 1987 0.09 0.0 6.59 0.00 0.0 15.81 16.06 4092 0.17 0.0 6.67 0.00 0.0 18.97 21.02 7139 0.29 0.0 6.79 0.05 0.0 22.13 25.51 11118 0.45 0.1 6.95 0.06 0.0 25.30 29.06 15945 0.63 0.1 7.13 0.08 0.0 28.46 31.35 21444 0.84 0.1 7.34 0.09 0.0 31.62 32.15 27375 1.06 1.1 7.56 0.10 1.0 34.78 31.37 33258 1.27 4.0 7.77 0.11 3.9, 37.94 29.09 38455 1.46 7.4 7.96 0.12 7.3 41.11 25.74 42564 1.61 10.6 8.11 0,13 10.5 44.27 22.60 45430 1.71 13.0 8.21 0.13 12.8 47.43 19.85 47256 1.78 14.7 8.28 0.14 14.6 50.59 17.43 48232 1.81 15.5 8.31 0.14 15.3 53.75 15.30 48605 1.83 16.0 8.33 0,14 15.8 56.92 13.44 48476 1.82 15.7 8.32 0.14 15.6 60.08 11.80 48042 1,81 15.5 8.31 0.14 15.3 63.24 10.36 47347 1.78 14,7 8.28 0.14 14.6 66.40 9.10 46523 1.75 14.0 8.25 0.14 13.8 69.56 7.99 45602 1,72 13.2 8.22 0.13 13.1 72.73 7,02 44610 1.68 12.3 8.18 0.13 12.1 75.89 6.16 43615 1.65 11,6 8.15 0.13 11.4 79.05 5.41 42592 1.61 10.6 8.11 0.13 10.5 82.21 4.75 41600 1,58 10.0 8.08 0.13 9.8 85.37 4.17 40611 1.54 9.1 8.04 0.13 9.0 88.54 3.66 39677 1.51 8.5 8.01 0.13 8.3 91.70 322 38767 1.47 7.6 7.97 0.12 7,5 94.86 2.82 37928 1.44 7.0 7.94 0.12 6.9 98.02 2.48 37129 1.41 6.5 7.91 0.12 6.3 101.18 2.18 36375 1.39 6.1 7.89 0.12 6.0 104,35 1.91 35635 1.36 5.5 7.86 0.12 5.4 107.51 1.68 34949 1.33 5.0 7.83 0.12 4.9 110.67 1.47 34321 1.31 4.6 7.81 0.12 4.5 113,83 1.29 33720 1.29 4.3 7.79 0.12 4.2 116.99 1,14 33149 1,27 4.0 7.77' 0.11 3.9 120.16 1.00 32610 1.25 3.7 7.75 0.11 3.5 123,32 0.88 32105 1,23 3.3 7.73 0.11 3.2 126.48 0.77 31637 1.21 3.0 7.71 0.11 2.9 .129.64 0.68 31205 1.20 2.9 7.70 0.11 2.8 8 32 Spillway 10.25 Weir 132.80 0.59 30783 1.18 2.6 7.68 0.11 2.5 135.97 0.52 30399 1.17 2.5 7.67 0.11 2.4 139.13 0.46 30029 1.15 2.2 7.65 0.11 2.1 142.29 0.40 29697 1.14 2.1 7.64 0,11 2.0 145.45 0.35 29380 1,13 1.9 7.63 0.11 1.8 148.61 0.31 29078 1.12 1.8 7.62 0.11 1,7 151.78 0.27 28792 1.11 1.7 7.61 0.11 1.6 154.94 0.24 28521 1.10 1.6 7.60 0.11 1.5 158.10 0.21 28267 1.09 1.5 7.59 0.11 1.4 161.26 0.18 28029 1.08 1.3 7.58 0.10 1.2 164.42 0.16 27808 1.07 1.2 7.57 0.10 1.1 167.59 0.14 27604 1.06 1.1 7.56 0.10 1.0 170.75 0.12 27416 1.06 1.1 7.56 0.10 1.0 173.91 0.11 27225 1.05 1.0 7.55 0.10 0.9 177.07 0.10 27050 1.04 0.9 7.54 0.10 0.8 180.23 0.08 26891 1.04 0.9 7.54 0.10 0.8 183.40 0.07 26731 1.03 0.8 7.53 0.10 0.7 186.56 0.07 26586 1.03 0.8 7.53 0.10 0.7 189.72 0.06 26440 1.02 0.7 7.52 0.10 0.6 192.88 0.05 26309 1.02 0.7 7.52 0.10 0.6 196.04 0.04 26178 1.01 0.7 7.51 0.10 0.6 199.21 0.04 26061 1.01 0.7 7.51 0.10 0.6' 202.37 0.03 25944 1.00 0.6 7.50 0.10 0.5 205.53 0.03 25842 1.00 0.6 7.50 0.10 0.5 208.69 0.03 25738 1.00 0.6 7.50 0.10 0.5 211.85 0.02 25635 0.99 0.5 7.49 0.10 0.4 215.02 0.02 25545 0.99 0.5 7.49 0.10 0.4 218.18 0.02 25455 0.98 0.4 7.48 0.10 0.3 221.34 0.02 25378 0.98 0.4 7.48 0.10 0.3 224.50 0.01 25301 0.98 0.4 7.48 0.10 0.3 227.66 0.01 25224 0.98 0.4 7.48 0.10 0.3 230.83 0.01 25146 0.97 0.4 7.47 0.10 0.3 233.99 0.01 25081 0.97 0.4 7.47 0.10 0.3 237.15 0.01 25016 0.97 0.4 7.47 0.10 0.3 240.31 0.01 24950 0.97 0.4 7.47 0.10 0.3 243.47 0.01 24884 0.96 0.3 7.46 0.10 0,2 246.64 0.01 24831 0.96 0.3 7.46 0.10 0.2 249.80 0.00 24777 0.96 0.3 7.46 0.10 0.2 252.96 0.00 24722 0.96 0.3 7.46 0.10 0.2 Results of routing the 10 Year Storm Use orifice = 1.7 inches Peak outflow = 15.98 cfs Peak Stage= 1.83 ft Water Elevation= 8.33 msl Peak Storage = 48605 cf Design Spillway 7.41 m s I Length of weir 6.0 ft a] predeveloped flow = 27.28 cfs peak flow was also reduced by = 41.4% Top of Box (emergency spillway) = 10.25 Routing Hydrogriph 35.00 30.00 25.00 20.00 N 15.00 5.00 0.00 O 0 �A ab �R �'9 �l �O %� 4 OHO p 9"5 ;)- 9O �0 �� ti� 1h ,L� ,'1 rye b� �� q �h q �l o, �g �� y1 1 �� ��. gh• O' �o� rL ^moo 1�0 �00 � Time (min) inflow -Orifice Outflow - — Weir Outflow I- - - Total Outflow Hite associates ARCHITECTURE 1 ENGINEERING 1 TECHNOLOGY Letter of Transmittal January 4, 2006 Mr. Roger Thorpe NCDENR — Division of Water Quality 943 Washington Square Mall Washington, NC 27889 RE cE:ivr-.0 JAN 1 /1 2006 DWQ-WARD RE: BCS -- Bath Elementary School — Additions and Renovations BEAUFORT COUNTY SCHOOLS Dear Mr. Thorpe Please find the attached Package for the referenced project for your review and approval for Storm Water management Compliance. 2 sets Site Plans and area drainage maps • Storm Water Management Permit Application • Wet Detention Basin Supplement From • Engineering Narrative and Specifications • Permit Fee for $420.00 (#16569) Should you have any questions, please give me a call. Yours very truly, Todd S ith Hite Associates fc: Dr. Jeff Moss, Superintendent file: JGH/Regulatory Notebook 2600 Meridian Drive / Greenville, NC 27834 / tel 252. 757.0333 / fax 252, 757,1330 / e-mail; mail@hiteassoc. com 4 IRECEIV ED JAN 1 1 2006 DWQ-WARD SOIL EROSION AND SEDIMENTATION CONTROL PLAN NARRATIVE BATH ELEMENTARY SCHOOL BEAUFORT CO , NORTH CAROLINA DECEMBER 12, 2005 I. PROJECT DESCRIPTION This project includes the construction of approximately 24,721 SF of new buildings for the school on a 23 acre site . Approximately 8.7 acres of land wili be disturbed . It. SITE DESCRIPTION The site has slopes averaging Q to 3%. Overall, elevations vary from a high point of 12 msl to a low point of less than 6.5 msl. The site is currently farmed . The soil type is a sandy clay. III ADJACENT PROPERTY The property is bounded on the west by King St and on the north by NC 92. IV. PLANNED STORM WATER MANAGEMENT AND EROSION AND SEDIMENTATION CONTROL MEASURES TEMPORARY GRAVEL CONSTRUCTION ENTRANCE A Temporary Gravel Construction Entrance is to be used at all street connections. TEMPORARY SILT FENCE Temporary Silt Fences are to be placed at the toe of fill sites adjacent to the property line to collect sediment laden runoff, Due to the abundance of fill slopes the silt fence will provide an excellent barrier to protect off -site facilities from sediments. FABRIC DROP INLET PROTECTION Sediment fence will be installed around all catch basins and drop inlets to prevent sediment from entering the storm drainage system. STORM INLET SEDIMENT TRAP Storm inlet sediment traps will be used at concentrated runoff points associated with drop inlets as shown on plans. GRASS LINED CHANNEL Grass lined channels with temporary straw -net liners will be constructed in roadside ditches. TEMPORARY ROCK DAM Temporary Rock Dams shall be installed at locations shown on plans CONSTRUCTION SCHEDULE 1. OBTAIN PLAN APPROVALS AND ALL APPLICABLE PERMITS., 2. FLAG LIMITS OF ROUGH GRADING FOR BUILDING SITE, PARKING LOTS AND ESTABLISH GRADE LIMITS AS NEEDED. 3. HOLD PRECONSTRUCTION MEETING WITH GRADING CONTRACTOR, EROSION CONROL ADMINISTRATOR, PROJECT ENGINEER AND OWNER. 4. INSTALL PERMANENT WET DETENTION BASIN AND ROCK DAM. DIVERSIONS AND PERIMETER SEDIMENT FENCES AS THE FIRST CONSTRUCTION ACTIVITY PRIOR TO THE INSTALLATION OF ANY FILL. 5, INSTALL PERMANENT PERIMETER SEDIMENT FENCES AS THE FIRST CONSTRUCTION ACTIVITY. PRIOR TO THE INSTALLATION OF ANY FILL. 6. INSTALL TEMPORARY GRAVEL CONSTRUCTION ENTRANCE AND USE EXISTING ACCESS TO SITE. 7. BEGIN TO GRADE THE BUILDING PADS DISTRIBUTING EXCAVATED MATERIAL IN THE FILL SECTIONS. 8. UPON THE COMPLETION OF BUILDING PAD INSTALL NEW ROAD TO ITS TERMINATION POINT AS INDICATED ON PLANS AND INSTALL STONE INLET SEDIMENT TRAPS AT INLET AS INDICATED. 9. GRADE THE BALL FIELDS AND INSTALL DRAINAGE AND SWALES AND INSTALL TEMPORARY EROSION CONTROL MEASURES. 10. PERMANENTLY SEED THE ATHLETIC FIELDS. 11. INSTALL RIP RAP OUTLET PROTECTION OUTLET. 12. BEGIN AND COMPLETE ROUGH GRADING OPERATIONS. 13. BRING BUILDING AND PARKING AREA TO WITHIN 2" OF FINAL SUBGRADE, TEMPORARILY SEED THESE AREAS TO PREVENT EROSION UNTIL SUCH TIME OWNER IS READY TO PROCEED WITH FINAL CONSTRUCTION. 14, TEMPORARILY SEED ALL DISTURBED AREAS WITH THE EXCEPTION OF AREAS WHICH CONSTRUCTION WILL CONTINUE 15, STABILIZATION SHALL OCCUR WITHIN 15 DAYS OF COMPLETION OF GRADING OPERATIONS. 16, ADDITIONAL EROSION AND SEDIMENTATION CONTROL MEASURES MAY BE REQUIRED BY THE STATE OR OWNER IF DEEMED NECESSARY. 17. AFTER SITE IS STABILIZED, REMOVE ALL TEMPORARY MEASURES , FINE GRADE DISTURBED AREAS, AND INSTALL PERMANENT VEGETATION ON THE DISTURBED AREAS. 18. MAINTAIN PERMANENT VEGETATION BY TOP DRESSING WITH 700 LBS PER ACRE OF FERTILIZER EVERY 6 MONTHS UNTIL THE COMPLETION OF THE PROJECT. 19, WITHIN 6" OF FINAL GRADE, RE -DISTRIBUTE G" OF TOP SOIL 20, FINE GRADE, PERMANENTLY SEED AND MULCH ALL LANDSCAPED AREAS 21, REMOVE ALL TEMPORARY EROSION AND SEDIMENTATION CONTROL MEASURES UPON COMPLETION AND STABILIZATION OF PROJECT. VI. MAINTENANCE PLAN All erosion and sediment control practices will be checked for stability and operation following every run-off producing rainfall but in no case less than once every week. Any needed repairs will be made immediately to maintain all practices as designed. Sediment will be removed from behind the silt fence when it becomes 0.5 feet deep. Sediment will be removed from the sediment trap when the storage has been approximately 50% filled. Gravel will be cleaned and replaced when the sediment pool no longer drains properly. All seeded areas will be fertilized, re -seeded as necessary, and mulched according to specifications in the vegetative plan to maintain a vigorous, dense vegetative cover. VII. VICINITY PLAN See Erosion Control Plan Vill. VEGETATION PLAN See Construction Drawings IX. SPECIFICATIONS AND DETAILS A. 6.02............................................ B. 6.06............................................ C. 6.14........................................... D. 6.61............................................ E. 6.60........................................... F. 6.62.................... .......... ...:........ G. 6.81 ............................... ......... ...Land Grading ....Temporary Gravel Construction Entrance ....Mulching .....Fabric Drop Inlet Protection (Temporary) ...Temporary Sediment Trap ....Temporary Sediment Fence .....Rock Check Dam