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HomeMy WebLinkAboutstormwater reportSTORMWATER IMPACT STATEMENT AND NARRATIVE JANUARY, 2013 SPRING LAKE KINGDOM HALL SPRING LAKE, HARNETT COUNTY, NORTH CAROLINA OWNER: SPRING LAKE CONGREGATION OF JEHOVAH'S WITNESSES, INC. 2415 ROSEHILL ROAD FAYETTEVILLE, NORTH CAROLINA 28301 ENGINEERS: RIVERS AND ASSOCIATES, INC. 107 EAST SECOND STREET GREENVILLE, NORTH CAROLINA 27835 252- 752 -3974 NC LIC NO. F -0334 Jg l STORMWATER MANAGEMEN PLAN: SPRING LAKE KINGDOM HALL SPRING LAKE, HARNETT COUNTY, NORTH CAROLINA JAN, 2013 LOCATION: This site is located on a secondary state road (Raynor Road - SR 2052) approximately 600 feet east of the intersection of NC 210 and SR 2052 on the north side of SR 20525 in an unincorporated area of southern Harnett County, North Carolina. SITE DESCRIPTION: The site is a gently sloping (2 % + -), cleared site previously possibly used for agricultural purposes in the past. No improvements are present on the site. Soil types on this site consist of predominantly Norfolk loamy sand (No). The Seasonal High Water Table was estimated at 36" below the ground surface in the area to be utilized for treatment. A soil report with Ksat infiltration results is attached. There are no wetlands or streams located on the property. PROPOSED PROJECT: The proposed project consists of the construction of a 5,000 SF single story building and associated paved parking. The total disturbed area is approximately 1.6 acres. The project includes site building sewer to on -site septic disposal and water tap for water. The front half (south and bulk of development area) of the site drains into the existing state road ditch and the property to the south east where it eventually discharges into the Upper Little River in the Cape Fear basin. The back half of the site (north and predominantly the septic disposal area) of the site drains overland across adjacent property (same ownership) to a natural swale and eventually to the Upper Little River. An offsite area drains to the site from the west (approximately 1.2 ac.) and is currently or intermittently cultivated farm land. Runoff from this area will be collected, treated, and discharged from the site. Stormwater Management - In accordance with NCDNR's interactive map, this site is subject to state Phase II water quality treatment regulations. 2 STORMWATER MANAGEMENT MEASURES: The soil analysis of the site in the area to be utilized for treatment indicated low Ksat infiltration rates (0.29 in/hr). This infiltration rate is below the threshold for an infiltration BMP. The SHWT was estimated at 36" below the ground surface. This depth combine with the relative low elevation differential across the site rendered a Bioretention BMP to be impractical. A stormwater wetland is proposed which will meet the Phase II treatment and discharge control requirements. The proposed wetland has been sized to accommodate the on and off site drainage areas and routing is attached showing no increase in the discharge for the 1 year - 24 hour storm in accordance with the Phase II requirements. The basins are capable of containing the expected runoff volume from the 1, 2, 10, 25 -yr storms without increased discharge to surface waters. An analysis point was chosen at the south west corner of the site where discharge occurs from a combination of the existing DOT roadway ditch and the proposed wetland outlet. Results are tabulated below: RETURN PERIOD PRE DEVELOPMENT PEAK (CFS) POST DEVELOPMENT PEAK (CFS) WETLAND STAGE (FEET) WETLAND STORAGE (CF) 1 3.46 1.96 215.15 4,937 2 5.31 3.30 215.37 6,127 10 11.10 10.89 216.00 9,561 25 14.94 14.68 1 216.31 11,642 100 21.37 22.07 1 216.71 14,414 No detrimental stormwater impacts are anticipated as a result of this development. Calculations, drainage area maps, and backup attached. 3 Southeastern Soil & Environmental Associates,, Inc. P.O. Box 9321 Fayetteville, NC 28311 Phone /Fax (910) 822 -4640 Email mike @southeasternsoll.com February 24. 2012 Mr. David Smith, PE 6131 Falls of Neuse Road Suite 300 Raleigh, NC 27609 Re: Hydraulic conductivity (permeability) analysis & seasonal water table determination (SHWT) for stormwater retention area, Kingdom Hall (Spring Lake) site, PID 010524 0018 18, Raynor Road, Harnett County, North Carolina Dear Mr. Smith, An evaluation of soil properties and hydraulic conductivity (Ksat) has been conducted at your request on the aforementioned property. The purpose of the investigation was to detennine soil water table depths (SHWT) based on soil profiles. In addition, Ksat was to be provided at a depth 2.0 feet above the SHWT elevation for use with stormwater retention basin design. Saturated hydraulic conductivity of the unsaturated zone was measured in a similar method as described in the Soil Science Society of America Journal, Vol. 53, no 5, Sept. - Oct. 1989, "A Constant Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone" and Comparison of the Glover Solution with the Simultaneous Equations Approach for Measuring Hydraulic Conductivity." This consists of advancing a small diameter bore hole to a predetermined depth (typically 2 feet above SHWT). At this depth. a constant head (pressure) was established and maintained. Flow measurements were made at timed intervals after flow stabilized. Soils at the proposed basin site are most similar to the Norfolk soil series (see attached boring log). Two borings were advanced to 8.0 feet, Seasonal High Water Table (SHWT) as determined by evidence of colors of chrorna 2 or less (and /or concentrations of high redox mottles) was encountered at a depth of 36 inches below the ground surface. SOIUSITE EVALUATION + SOIL PHYSICAL ANALYSIS + LAND USE/SUBDIVISION PLANNING GROUNDWATER DRAINAGE/MOUNDING + SURFACE/SUBSURFACE WASTE TREATMENT SYSTEMS, EVALUATION & DESIGN TWO compact constant head permeameter (CC HP) tests were conducted at a depth of 1.00 feet below the ground surface. The measured Ksat rate in boring 1 was 8.05 cm/1 -ir (equivalent to 3.17 inches,'hour). The measured Ksat rate in boring 2 was 0.73 cmlhr (equivalent to 0.29 inches /hour). The attached map shows locations of the sample points as well as Ksat location. It should be noted that the reported SI IWT does not necessarily- reflect the elevation of static groundwater (due to variations in groundwater recharge rates_ annual rainfall. drought conditions, etc.). The data presented in this report are limited by a number of considerations. The primary consideration is that soil formations can be highly variable. The soils found on this site can be subject to inclusions of other soil types, perched water, artesian conditions and /or layers of undulating low permeability clay seams. These and other soil conditions can have an affect on the steady state of groundwater flow. To the extent possible;, we have identified the soil types that will impact the ilow of groundwater, and have provided a professional opinion as to the depth of SIIWT. I trust this is the information you require at this tune. Sincerely, Mike Eaker NC Licensed Soil Scientist #1030 N542300. I j i N542200: N542100 I N542000„ N541900i SOIL/SITE EVALUATION • SOIL PHYSICAL ANALYSIS • LAND USEISUBDIVISION PLANNING GROUNDWATER DRAINAGE,'MOUNDING • SURFACE/SUBSURFACE WASTE TREATMENT SYSTEMS, EVALUATION & DESIGN ��»������������ �����0 � ����������������0 Associates, ������mm���������mnw ����00 �� ��mm�0m��mmmmm��mm���� Inc. �mm�� p.O. Box Vnr1 Fayetteville, NC28m1, Phone/Fax (g1u)uue4o4z smai/m|ke@ouumoaooemaoiinnm Typical Profile Description for Kingdom Hall Lake), Road, Harnett County, North Carolina This mnp unit consists of well drained soils onuplands. These soils formed in loamy marine sediments. Slopes range from 0to2percent. /\p -0to4 inubcm� very dark brown (lOy83/2) loamy sand; weak fine granular structure: very friable, many fine roots; abrupt smooth boundary. E - 5 to 8 inches, dark grayish brown (I OYR 4/2) loamy sand, weak fine granular structure; ven 6iob|o� few small roots, abrupt smooth boundary. B1\ 8 to 26 inches, olive brown (2.5y 4/3) sandy clay loam; weak fine subuugu|uzb|ooky structure; friable. slightly sticky, slightly plastic; clay coating and bridging of sand grains; many Fine roots; abrupt smooth boundary. B12-26to3bioohca-,light yellowish brown i2.5Y 6/4\ sandy loam; few medium prominent yellowish red (5l/05/6)mottles, weak fine granular structure; very ffiah|e;gradual wavy boundary. Cl '36to68 inches; very pale brown (}OYB8/2) loamy sand; common coarse prominent yellowish red (5YFi5/6) and common fiumdistinct light yellowish brown (l.5l'6/4)mottles, pockets of sandy loam, weak fine granular structure; very friable; abrupt smooth boundary. C2 - 68 to 86 inches; very pale brown (I OYR 8/2) loamy sand; common coarse prominent ye|)onviyb nad(5YK 5/6) mottles; massive; Finn, abrupt smooth boundary. C3g-O6too6 inches, white (l0YR8/l) gravelly loamy sand; massive structure; finn SHWT(0, 36 inches below ground surface (I OYR 8/2) SOIUSITE EVALUATION ~ SOIL PHYSICAL ANALYSIS ° LAND USE/SUBDIVISION PLANNING GROUNDWATER DRAINAGE/MOUNDING - SURFACEISUBSURFACE WASTE TREATMENT SYSTEMS, EVALUATION & DESIGN RIVERS & ASSOCIATES, INC. Engineers /Planners /Surveyors JOB KH SHEET NO. OF PRODUCT 204-1 (Single Sheets) 205-1 (Padded) Fo,,a, 14A, L T 411 A- (T. p ( -ro t-' p P) "'� t (p G 9 li-I RIVERS & ASSOCIATES, INC. ngi nee rs/Pla n n ers/Su rveyo rs One Springfield Center 6131 Falls Of Neuse Road, Suite 300 RALEIGH, NORTH CAROLINA (919) 848 -3347 Fax (919) 848 -0319 JOB 45 °, JL t 1-'Awf _ V SHEET NO. _ CALCULATED BY CHECKED BY_ SCALE OF DATE DATE PRODUCT 204 -1 j;;ingle Sheets) 205 -1 (Padded) Precipitation Frequency Data Server Page 1 , NOAA Atlas 14, Volume 2, Version 3 Location name: Spring Lake, North Carolina, US* - ,,. Coordinates: 35.2390, - 78.9296 (& * Elevation: 216ft* source: Google Maps wd POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular ! PF graphical I Maps & aerials PF tabular PDS -based point precipitation frequency estimates with 90% confidence intervals (in inches)' Duration Average recurrence interval(years) 1 2 5 10 25 25 50 100 100 200 500 1000 5 -mm 0.433 0.511 0.595 0.657 7 -6031 T-6-38-3­10.833 --o.-878 .878 T-6--932 - 0.932 F- -6- -975 (0.391 - 0.483) 0.692 (0.462 - 0.570) 0.817 (0.537 - 0.663) 0.952 (0.593 - 0.731) 1.05 (0.656 - 0.812) (0.702 - 0.868) F 1.25 (0.742 - 0.922) 1.32 (0.779 - 0.971) 1.39 (0.819 -1.03) 1.47 (0.851 -1.08) 10 -min 1(0.625-0.772)1(0.739-0.912)1(0.861-1.06) (0.948 -1.17) 1 (1.05 -1.29) 1 (1.12 -1.38) 1 (1.18 -1.47) 1 (1.23 -1.54) (1.30 -1.63) 1.54 (1.34 -1.70) 0.865 -T-03-7--,.-21 1.33 1.48 1.58 1.67 15 -min 1(0.782-0.965)1(0.929-1.15) 1 (1.09 -1.34) 1 (1.20 -1.48) 1 (1.33 -1.64) 1 (1.42 -1.75) 1 (1.49 -1.85) 1.76 1 (1.56 -1.94) 1.86 (1.63 -2.05) 1.93 (1.68 -2.13) 1-1 9--jj 1.42 171 1.93 2.19 2.38 2.56 30 -min (1.07 -1.32) (1.28 -1.58) (1.55 -1.91) (1.74 -2.14) (1.96 -2.43) (2.13 -2.64) (2.28 -2.84) 2.73 (2.42 -3.03 2.95 2.60 -3.27 ( ) 3.12 ) (2.72 -3.45 1.48 1.78 2.19 2.51 2.91 -3.2-2-77-1-53--T-3-.-83-- 3.53 60 -min (1.34 -1.65) 1.7-3-7F--2-.10--1F--2.-62-7 1 (1.61 -1.99) 1 (1.98 -2.45) (2.26 -2.79) 3.03 1 (2.61 -3.23) 3.57 .22 1 (2.89 -3.57) 4.00 1 (3.14 -3.91) 4.43 3.83 1 (3.40 -4.24) 4.24 (3.72 -4.69) 4.55 (3.98 -5.04) 2 -hr (1.55 -1.96) 1.84 (1.88 -2.37) 2.23 1 (2.35 -2.96) 2.80 1 (2.70 -3.42) 326 1 (3.17 -4.03) 3.88 1 (3.53 -4.51) 4.39 1 (3.89 -4.99) F--49-1-]F--547 4.86 1 (4.24 -5.47) 5.44 (4.70 -6.12) 5.90 (5.06 -6.64) 3 -hr (1.65 -2.09) F--2.-2o--T--266 (2.00 -2.52) - (2.51 -3.16) 3.34 (2.91 -3.68) 3.90 (3.44 -4.37) 4.66 (3.87 -4.95) 5.29 (4.30 -5.53) 5.94 . (4.74 -6.14) 6.63 6.22 (5.34 -6.99 ) 7.59 6.84 ) 1(5.81-7.68) 6 -hr (1.99 -2.45) (2.41 -2.96) (3.02 -3.71) (3.51 -4.33) (4.17 -5.16) (4.70 -5.85) (5.24 -6.57) (5.79 -7.30) (6.54 -8.36) 8.37 ) (7.13 -9.23 12 -hr 2.59 F---3.-14---]F--3-.9-7 4.65 5.60 6.39 7.22 8.11 9.38 10.4 (2.35 -2.88) (2.84 -3.48) (3.59 -4.41) (4.18 -5.15) (4.99 -6.19) (5.66 -7.04) (6.34 -7.95) (7.04 -8.91) (8.02 -10.3) (8.80 -11.4 ) 24 -hr 3.06 3.70 4.69 5.46 6.54 7.40 8.29 9.22 10.5 1 5- 2.84 -3.30) (3.43 -4.00) (4.34 -5.06) 5.39 1 (5.01 -5.80) 5.67 (5.05 -5.90) 6.26 1 (5.80 -6.72) 6.57 (6.02 -7.06) 7.46 1 (6.88 -8.01) 7.80 (6.79 -7.98) 8.41 (7.74 -9.04) 8.79 (7.59 -8.94) (8.42 -9.94) (9.53 -11.3) (10.4 -12.4) 2 -day 3.56 (3.31 -3.83) 3.77 4.29 (3.99 -4.62) 4.54 9.40 1 (8.63 -10.1) 9.81 10.4 1 (9.53 -11.2) 10.9 11.8 (10.8 -12.8) --1-2.3--]F--13.-5 13.0 (11.7 -14.0) 3 -day (3.52 -4.05) 1 (4.24 -4.87) 1 (5.28 -6.08) 1 (6.10 -7.03) 1 (7.22 -8.35) 1 (8.11 -9.41) 1 (9.01 -10.5) 1 (9.95 -11.6) (11.2 -13.2) (12.2 -14.5 ) 3.99 4580 ] F--5.-9-6-7F-6-.88---1 F8.15 9.17 10.2 11.3 12.8 4 -day (3.73 -4.27) 4.62 1 (4.49 -5.13) 5.52 1 (5.56 -6.37) 6.77 1 (6.41 -7.34) 7.77 1 (7.56 -8.69) --g-.1-3--]F--10-2-7 1 (8.47 -9.78) 1 (9.40 -10.9) 11.3 1 (10.4 -12.1) 12.5 (11.7 -13.7 ) 14.1 14.0 1(12.7-15.0) 7 -day (4.30 -4.95) 5.27 1 (5.14 -5.92) 6.29 1 (6.30 -7.27) 7.59 1 (7.22 -8.33) 8.62 1 (8.46 -9.79) 10.0 1 (9.44 -11.0) 11.1 1 (10.5 -12.2) 12.2 1 (11.5 -13.4) 13.3 (12.9 -15.1) -1-4-.9-7-1650-7 15.3 (14.0 -16.5) 10 -day (4.95 -5.62) 1 (5.90 -6.70) 11 (7.12 -8.08) 11 (8.07 -9.17) 1 (9.33 -10.6) 1 (10.3 -11.8) 1 (11.3 -13.0) 1 (12.3 -14.2) (13.7 -15.8) (14.7 -17.1) 7.10 840 999 11.2--]F--i2 9 14.2 1 15.5 F 16.9 18.7 20 -day (6.66 -7.57) 11 (7.88 -8.97) 1 (9.35 -10.6) 1 (10.5 -12.0) 1 (12.0 -13.8) 1 (13.2 -15.1) 1 (14.4 -16.6) 1 (15.6 -18.0) (17.2 -20.0) 20.1 (18.5 -21.6) 8.84 10.4 12.2 13.5 15.3 16.7 18.1 19.4 30 -day (8.32 -9.41) 11.2 (9.80 -11.1) 112 1 (11.4 -13.0) 15.1 1 (12.7 -14.4) 16.6 1 (14.3 -16.3) 18.6 1 (15.6 -17.8) 20.1 1 (16.8 -19.3) 21.5 1 (18.1 -20.7) 22.9 ] 21.2 (19.7 -22.7) F-2-4.8-T--2-6.-2 22.7 (20.9 -24.2 ) 45 -day (10.6 -11.9) 1 (12.4 -13.9) 1 (14.3 -16.0) 1 (15.7 -17.6) 1 (17.5 -19.7) 1 (18.8 -21.3) 1 (20.2 -22.8) 1 (21.4 -24.4) (23.1 -26.4) (24.4 -27.9) 13.4 15.7 17.9 19.5 21.7 23.3 24.8 26.4 60 -day (12.7 -14.2) (14.9 -16.6) (16.9 -18.9) (18.5 -20.6) (20.5 -22.9) (22.0 -24.6) (23.4 -26.2) (24.8 -27.8) 28.3 (26.6 -30.0) 29.8 (27.9 -31.6) Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 9V% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 %. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top http: / /hdsc.nws.noaa. gov /hdsc /pfds /pfds _printpage.html ?lat =3 5.23 90 &lon =- 78.9296 &data... 8/17/2012 t4skt xym Xy`9'ARY COX FFEE "i638 LANCA0 ROAiS - MARY \ �OX COFFEE \ P/KEKLLE NO 17653 X ; 16JB LANCASTER ROAD P/KEVI(L N 2786) �9 D.B. P7D: 0/052 0018 19 ZONED: �7A -20M / e X D.B. . PGI ? y�' • / PID: 070524 Q018 19 ZONED: RA -20M / / `JN107 /719,(1/7(1!1 35 Z61 0350dONd X ae 1 Iw xc' X / \ 1 ti� Q'O.. 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Hydrograph Inflow Peak Outflow (cfs) Hydrograph No. type Hyd(s) description (origin) 1 -Yr 2 -Yr 3 -Yr 5 -Yr I 10 -Yr I 25 -Yr I 50 -Yr 100 -Yr 1 2 3 4 5 6 7 8 9 SCS Runoff - - - - - -- SCS Runoff - - - - - -- Combine 1,2 Reservoir 3 SCS Runoff - - - - - -- SCS Runoff - - - - - -- Combine 5,6 Combine 4,7 SCS Runoff - - - - - -- 1.320 2.081 - - - - - -- - - - - - -- 4.474 6.081 3.443 4.552 - - - - - -- - - - - - -- 7.692 9.625 4.651 6.501 - - - - - -- - - - - - -- 11.96 15.45 0.445 1.553 - - - - - -- - - - - - -- 6.557 8.593 1.190 1.721 - - - - - -- - - - - - -- 3.319 4.353 0.786 1.120 - - - - - -- - - - - - -- 2.104 2.731 1.934 2.783 - - - - - -- - - - - - -- 5.329 6.973 1.956 3.302 - - - - - -- - - - - - -- 10.89 14.68 3.463 5.310 - - - - - -- - - - - - -- 1 11.10 1 14.94 g - - - - - -- 8.806 OFFSITE -1 - - - - - -- 12.74 ONSITE WL - - - - - -- 21.20 TO WL - - - - - -- 14.11 WL ROUTE ..T°.-J - - - - - -- 6.057 OFFSITE -2 - - - - - -- 3.772 SITE - BYPASS - - - - - -- 9.682 BYPASS - -- - 22.07 POI oSr DVI TID-CA » - - - - - -- 21.37 PREDEVELOPMENT Proj. file: WETLAND- SCS.gpw Wednesday, Jan 9 2013, 10:37 AM Hydraflow Hydrographs by Intelisolve w t Hyd. No. Hydrograph type (origin) Peak flow (cfs) Time interval (min) Time to peak (min) Volume (cuft) Inflow hyd(s) Maximum elevation (ft) Maximum storage (cuft) Hydrograph description 1 SCS Runoff 1.320 1 720 3,176 - - -- - - - - -- - - - - -- OFFSITE -1 2 SCS Runoff 3.443 1 718 6,993 - - -- - - - - -- - - - - -- ONSITE WL 3 Combine 4.651 1 718 10,170 1,2 - - - - -- - - - - -- TO WL 4 Reservoir 0.445 1 751 7,931 3 215.15 4,937 WL ROUTE 5 SCS Runoff 1.190 1 720 2,721 - - -- - - - - -- - - - - -- OFFSITE -2 6 SCS Runoff 0.786 1 718 1,583 - - -- - - - - -- - - - - -- SITE - BYPASS 7 Combine 1.934 1 719 4,304 5,6 - - - - -- - - - - -- BYPASS 8 Combine 1.956 1 719 12,235 4, 7 - - - - -- - - - - -- POI 9 SCS Runoff 3.463 1 722 9,259 - - -- - - - - -- - - - - -- PREDEVELOPMENT WETLAND- SCS.gpw Return Perio : 1 Year Wednesday, Jan 9 2013, 10:37 AM Hydraflow Hydrographs by Intelisolve Hyd. No. Hydrograph type (origin) Peak flow (cfs) Time interval (min) Time to peak (min) Volume (cuft) Inflow hyd(s) Maximum elevation (ft) Maximum storage (cuft) Hydrograph description 1 SCS Runoff 2.081 1 720 4,815 - - -- - - - - -- - - - - -- OFFSITE -1 2 SCS Runoff 4.552 1 718 9,353 - - -- - - - - -- - - - - -- ONSITE WL 3 Combine 6.501 1 718 14,168 1,2 - - - - -- - - - - -- TO WL 4 Reservoir 1.553 1 728 11,916 3 215.37 6,127 WL ROUTE 5 SCS Runoff 1.721 1 720 3,897 - - -- - - - - -- - - - - -- OFFSITE -2 6 SCS Runoff 1.120 1 718 2,249 - - -- - - - - -- - - - - -- SITE - BYPASS 7 Combine 2.783 1 719 6,146 5,6 - - - - -- - - - - -- BYPASS 8 Combine 3.302 1 721 18,062 4,7 - - - - -- - - - - -- POI 9 SCS Runoff 5.310 1 722 13,754 - - -- - - - - -- - - - - -- PREDEVELOPMENT WETLAND- SCS.gpw Return Perio . 2 Year Wednesday, Jan 9 2013,10:37 AM Hydraflow Hydrographs by Intelisolve Hyd. No. Hydrograph type (origin) Peak flow (cfs) Time interval (min) Time to peak (min) Volume (cuft) Inflow hyd(s) Maximum elevation (ft) / Maximum storage (cuft) Hydrograph description 1 SCS Runoff 4.474 1 720 10,123 - - -- - - - - -- - - - - -- OFFSITE -1 2 SCS Runoff 7.692 1 717 16,198 - - -- - - - - -- - - - - -- ONSITE WL 3 Combine 11.96 1 718 26,321 1,2 - - - - -- - - - - -- TO WL 4 Reservoir 6.557 1 724 24,045 3 216.00 9,561 WL ROUTE 5 SCS Runoff 3.319 1 719 7,524 - - -- - - - - -- - - - - -- OFFSITE -2 6 SCS Runoff 2.104 1 718 4,285 - - -- - - - - -- - - - - -- SITE - BYPASS 7 Combine 5.329 1 718 11,809 5,6 - - - - -- - - - - -- BYPASS 8 Combine 10.89 1 721 35,854 4,7 - - - - -- - - - - -- POI 9 SCS Runoff 11.10 1 721 28,059 - - -- - - - - -- - - - - -- PREDEVELOPMENT WETLAND- SCS.gpw Return Perio : 10 Year Wednesday, Jan 9 2013, 10:37 AM Hydraflow Hydrographs by Intelisolve Hyd. No. Hydrograph type (origin) Peak flow (cfs) Time interval (min) Time to peak (min) Volume (cuft) Inflow hyd(s) iirrtu elevation (ft) Maximum storage (cuft) Hydrograph description 1 SCS Runoff 6.081 1 719 13,759 - - -- - - - - -- - - - - -- OFFSITE -1 2 SCS Runoff 9.625 1 717 20,544 - - -- - - - - -- - - - - -- ONSITE WL 3 Combine 15.45 1 718 34,303 1,2 - - - - -- - - - - -- TO WL 4 Reservoir 8.593 1 723 32,017 3 216.31 11,642 WL ROUTE 5 SCS Runoff 4.353 1 719 9,924 - - -- - - - - -- - - - - -- OFFSITE -2 6 SCS Runoff 2.731 1 717 5,626 - - -- - - - - -- - - - - -- SITE - BYPASS 7 Combine 6.973 1 718 15,549 5,6 - - - - -- - - - - -- BYPASS 8 Combine 14.68 1 720 47,566 4,7 - - - - -- - - - - -- POI 9 SCS Runoff 14.94 1 721 37,741 - - -- - - - - -- - - - - -- PREDEVELOPMENT f WETLAND- SCS.gpw Return Perio . 25 Year ` Wednesday, Jan 9 2013, 10:37 AM Hydraflow Hydrographs by Intelisolve Hyd. No. Hydrograph type (origin) Peak flow (cfs) Time interval (min) Time to peak (min) Volume (cuft) Inflow hyd(s) aiimum � elevation (ft)„7) Maximum storage (cult) Hydrograph description 1 SCS Runoff 8.806 1 719 20,023 - - -- - - - - -- - - - - -- OFFSITE -1 2 SCS Runoff 12.74 1 717 27,710 - - -- - - - - -- - - - - -- ONSITE WL 3 Combine 21.20 1 718 47,733 1,2 - - - - -- - - - - -- TO WL 4 Reservoir 14.11 1 722 45,434 3 216.71 14,414 WL ROUTE 5 SCS Runoff 6.057 1 719 13,975 - - -- - - - - -- - - - - -- OFFSITE -2 6 SCS Runoff 3.772 1 717 7,882 - - -- - - - - -- - - - - -- SITE - BYPASS 7 Combine 9.682 1 718 21,858 5,6 - - - - -- - - - - -- BYPASS 8 Combine 22.07 1 721 67,291 4,7 - - - - -- - - - - -- POI 9 SCS Runoff 21.37 1 721 54,299 - - -- - - - - -- - - - - -- PREDEVELOPMENT WETLAND-SCS.gpw Return Period: 100 Year Wednesday, Jan 9 2013,10:37 AM ",, —__ - Hydraflow Hydrographs by Intelisolve Stage / Storage Table Slope ( %) = 1.00 0.00 0.00 0.00 N -Value = .022 .012 .000 .000 Orif. Coeff. = 0.60 0.60 0.00 0.00 Multi -Stage = n/a Yes No No Exfiltration = 0.000 in /hr (Contour) Tailwater Elev. = 0.00 ft Stage (ft) 3.00 2.00 1.00 0.00 0.00 2.00 Total Q Note: Culvert/Orifice outflows have been analyzed under inlet and outlet control. Stage / Discharge 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 Stage (ft) 3.00 2.00 1.00 ___L_ 0.00 22.00 Discharge (cfs) m / \ � ) } k / / � \ / / m \ ) . � f § / / 1F \ + 2 •m m / f { / LU , j / #k § ¢ /L 7 Q � o � 2 0 2 R \ D i CL � 2 2 8 R 8 � � # i....�.,..�....�...., � � RIVERS & ASSOCIATES, INC. Engineers /Planners /Surveyors One Springfield Center 6131 Falls Of Neuse Road, Suite 300 RALEIGH, NORTH CAROLINA (919) 848 -3347 Fax (919) 848 -0319 JOB SHEET NO. OF CALCULATED BY CHECKED BY_ SCALE DATE DATE PRODUCT 204 -1 Single Sheets) 2054(Padtled) Calculate Skimmer Size Basin Volume in Cubic Feet Days to Drain* In NC assume 3 days to drain Estimate Volume of Basin Top of water surface in feet Bottom dimensions in feet Depth in feet 7,290 Cu.Ft 3 Days Width Skimmer Size Orifice Radius Orifice Diameter Feet VOLUME Feet Feet 2.0 Inch 0.8 Inch[es] 1.7 Inch[es] 0 Cu. Ft. • • 0 0 N N 3 m E o 3 0 m a Page 1 Line Line ID Flow Line Line Invert Invert Line HGL HGL Minor HGL Dns No. rate size length EL Dn EL Up slope down up loss Junct line (cfs) (in) (ft) (ft) (ft) N (ft) (ft) (ft) (ft) No. 1 PIPE NO 3 8.61 18 c 64.0 214.00 214.50 0.781 215.12 215.66 n/a 216.47 i End 2 PIPE NO 1 5.32 18 c 168.0 214.50 215.50 0.595 216.47 216.86 0.16 217.01 1 3 PIPE NO 2 1.56 12 c 79.0 214.50 215.00 0.633 216.47 216.62' 0.06 216.68 1 SPRING LAKE KH Number of lines: 3 Run Date: 12 -10 -2012 NOTES: c = cir; e = ellip; b = box; Return period = 10 Yrs. ; *Surcharged (HGL above crown). ; i - Inlet control. Hydraflow Storm Sewers 2005 d a • • �l ® M N d O O O C z z z —� W W W 0 d W N a a o N > O O O O N W C Q $ O O O (0 I- n 04 E N N N N � O D Q C0 ? C0 G U N N N C > ui N N N J 2 O. $ coo CR m Q LO (D (.0 N N N M C 0 O O N d Q $ 'a' �' �' E W N N N p C 0. Lq U O E LO 0 C N N N z CL O e co O Cl) r O c0 G 'a W `-� 6 6 6 N F fA co 00 r N � O O LO M N M O 07 N p O w O C\j in c6 6 C i LO m 0) r-_: r,: ui N � W O O O T I— O d C O O O N C- tfJ I.f) tfJ E 3 U x H e o 0 C� L f� co O N C0 N O < o co v c N C U U O O O + N E f6 u O 04 � N N I— � o C O) � U CO N � — O O U') J O O (0 O Y W n T � 0) N C d U CD C O J W wa w c O N M z 0 0 N N 3 E `0 cn 3 0 c CD R 0. CL o o co O O CD C O ® N O O N O CD Q N O O CL N C6 cam- N U r N O �Y N N M (6 O O O C � O O O O O O LO � N r t O O �t _ O co O O O M M M C O O O O O O M 0 CD 0 O O O CD 3 U C Ur O O O O N _ CD 0 CD O 0 N O O O E Cy O O O O z c CD 0 CD 0 c O O CO Y N N N N N 6 O a (n (c U) C �y O O O a ` _ N N N } � O C O O O II jp Cl) co co -O O O O Q I m O C M M M z N N J CD O O O C v M M M O' 4 O � U O O O O < S _ co co c5 0 N C N � Q + n w CD CD o N E Cf >+ y' O O O N V. O O O c N Cl R O N Co W v M Un L6 _ C� rn O O O II U O O O C N C p Q N O N Co Ci U `? U N LO p O I I N _ m � Y W z M m N C Z W c o J a O Z N CO U) z 0 0 N N 3 m E 3 0 c m 2 d CL CL • • • • • 0 C yS O C O O 0 Y � O o 0 r r r N rnU) ^, C U) ch O O C ON O tl W O O O N V Qin o @ N m C O O 0 LO C U) �% o @ N � C O O J > ON O O W m co 1- (0 N N N Ca 7 d O O v O O O co d N C() O OT d C CL d � co 0) y_ Q) O E 7 C Z CL O M O cl r r J > O CO co N CO 2 a) LO co co N N N > U Lq O > �$ C N N N $ O W O J d' CO 0) CO +- N e t j O) @ N J > r*-: c0 CO W d $ Cfl co 112 N N N i U C0 co O O O E N � O N O O d) R O CO N C y S Il- d) V I— r 3 0 Q r o o CL N LO °o. N N N a) > O U) O C — N N N V O M I _ Y co LO r W Y N C J U) Z7— co O 0 Z_ d � c a J r 04 M CO N O N 3 E 0 0 m rrecipitation rrequency liata server http:// ncisc. nws. noaa. gov' hct se/ ptcts; ptcts _prtntpage.hhnlYiat= 35.239U&... PDS -based point precipitation frequency estimates with 90% confidence intervals (in inches /hour)1 Duration Average recurrence interval (years) 1 �FF������� 2 5 10 25 50 100 200 500 1000 5.20 6.13 7.14 7.88 8.77 9.40 10.0 10 11.2 11.7 5 F -min [(9.35-.151.7) F(9.83- (4.69-5.80) (5.54 6.84) (6.44 -7.96) (7.12 -8.77) (7.87 -9.74) (8.42 -10.4) (8.90 -11.1) 12.4) (10.2 12.9) 4.15 4.90 6.31 6.98 7.48 7.94 8.35 8.84 9.21 10 -min F--5-71--F F (3.75 4.63) (4.43 5.47) 5.17 6.37) (5.69 7.01) (6.27 7.76) 6.71 8.30) (7.07 8.79) (7.40 9.24) (7.78 9.79) (8.04 10.2) 3.46 4.82 5.32 5.90 6.32 6.69 7.02 7.42 7.70 [15 -min F(3.T74.58) F(6.2 F(6. (3.13 -3.86) (4.36 -5.37) (4.80 -5.92) (5.30 -6.56) (5.66 -7.00) (5.96 -7.41) 3 -7.77) 52 -8.21) (6.73 -8.52 ) 2.37 F 2.84 F 3.42 3.85 4.37 4.76 5.12 5.46 5.91 6.24 [-3o-min (2.14 -2.65) (2.57 -3.17) (3.09 -3.82) (3.47 4.29) (3.92 -4.86) 1 (4.26 -5.27) 1 (4.56 -5.67) 1 (4.85 -6.05) 1 (5.19 -6.53) (5.45 -6.90) 1.48 1.78 2.19 2.51 2.91 3.22 3.53 3.83 4.24 4.55 [60-min F(1. (1.34 -1.65) 61 1.99) (1.98 -2.45) (2.26 -2.79) (2.61 -3.23) (2.89 -3.57) (3.14 -3.91) (3.40 -4.24) (3.72 4.69) (3.98 -5.04) 0.866 1.05 1.31 1.52 1.79 2.00 2.21 2.43 2.72 2.95 F 2-hr (0.774 0.980) (0.940 1.19) (1.17 1.48) (1.35 1.71) (1.58 2.02) (1.77 2.25 ) ( 1.94 2.49 ) ( 2.12 2.74 ) ( 2.35 3.06) (2.53 3.32 ) 0.613 0.742 0.932 1.08 1.29 1.46 1.64 1.82 2.07 2.28 F3-hr F(1.2 (0.549 - 0.695) (0.666 - 0.840) (0.835 -1.05) (0.969 -1.22) (1.15 -1.46) 9 -1.65) (1.43 -1.84) (1.58 -2.05) (1.78 -2.33) (1.93 -2.56) -6-hr 0.367 0.444 0.558 0.651 0.778 0.883 0.992 1.11 1.27 1.40 F (0.332 0.409) (0.402 0.494) (0.504 0.620) (0.587 0.722) (0.697 0.862) (0.785 0.977) (0.874 1.10) (0.966 -1.22 ) ( 1.09 1.40) (1.19 1.54 ) 0.215 0.260 0.329 0.386 0.465 0.530 0.599 0.673 0.779 0.865 12 -hr (0.195 - 0.239) (0.236 - 0.289) (0.298 - 0.366) (0.347 - 0.428) (0.415 - 0.513) (0.470 - 0.584) (0.526 - 0.659) (0.584 - 0.740) (0.666 - 0.855) (0.730 - 0.949) 0.127 0.154 0.195 0.228 0.272 0.308 0.345 0.384 0.437 0.480 24 -hr (0.118 - 0.138) (0.143 - 0.167) (0.181 - 0.211) (0.210 - 0.246) (0.251 - 0.294) (0.283 - 0.333) (0.316 - 0.373) (0.351 - 0.414) (0.397 - 0.472) (0.434- 0.518) 0.074 0.089 0.112 0.130 0.155 0.175 0.196 0.217 0.247 0.270 2 -day ( 0 .069 - 0.080) (0.083 - 0.096) (0.104 - 0.121) (0.121 - 0.140) (0.143 - 0.167) (0.161 - 0.188) (0.180 - 0.211) (0.198 - 0.234) (0.224 - 0.266) (0.244 - 0.292) 0.052 0.063 0.079 0.091 mm 0.122 0.136 0.151 0.171 0.187 F3-day (0.049 - 0.056) (0.059 - 0.068) (0.073 - 0.084) (0.085 - 0.098) (0.100 - 0.116) (0.113 - 0.131) (0.125 - 0.146) (0.138 - 0.162) (0.156 - 0.184) (0.170 - 0.201) 0.042 0.050 0.062 0.072 0.085 0.095 0.106 0.118 0.133 0.145 4 -day (0.039 - 0.044) (0.047 - 0.053) (0.058 - 0.066) (0.067 - 0.076) (0.079 - 0.091) (0.088 - 0.102) (0.098 - 0.114) (0.108 - 0.126) (0.122 - 0.142) (0.132 - 0.156) 0.027 0.033 0.040 0.046 0.054 0.061 0.067 0.074 0.084 0.091 7 -day (0.026 -0 029) (0.031 - 0.035) (0.038 - 0.043) (0.043 - 0.050) (0.050 - 0.058) (0.056 - 0.065) (0.062 - 0.072) (0.068 - 0.080) (0.077 - 0.090) (0.083 - 0.098) 0.022 0.026 0.032 0.036 0.042 0.046 0.051 0.056 0.062 0.067 10 -day (0.021 - 0.023) (0.025 - 0.028) (0.030 - 0.034) (0.034 - 0.038) (0.039 - 0.044) (0.043 - 0.049) (0.047 - 0.054) (0.051 - 0.059) (0.057 - 0.066) (0.061 - 0.071) 0.015 0.017 0.021 0.023 0.027 0.030 0.032 0.035 0.039 0.042 20 -day 0 ( .014 - 0.016) (0.016 - 0.019) (0.019-0.022) (0.022 - 0.025) (0.025 - 0.029) (0.028 - 0.032) (0.030 - 0.035) (0.033 - 0.038) (0.036 - 0.042) (0.038 - 0.045) 0.012 F-0. 014 0.017 0.019 0.021 0.023 0.025 0.027 0.029 0.031 30 -day (0.012 - 0.013) (0.014 - 0.015) (0.016 - 0.018) (0.018 - 0.020) (0.020 - 0.023) (0.022 - 0.025) (0.023 - 0.027) (0.025 - 0.029) (0.027 - 0.032) (0.029. 0.034) 0.010 0.012 0.014 0.015 0.017 0.019 0.020 0.021 0.023 0.024 F45-day (0.010 - 0.011) (0.011 - 0.013) (0.013 - 0.015) (0.015 - 0.016) (0.016 - 0.018) (0.017 - 0.020) (0.019 - 0.021) (0.020 - 0.023) (0.021 - 0.024) (0.023 - 0.026) 1 of 5 9/27/2012 9:04 AM Wc-C .Tr& - W C71 LAWP JAF AaA 16-t A L &AL A 4-t (v 5 ouso ast 45. 86-B3 01ROS7 ® zs 13(c.1 Irl-15 1*64-75 o. 'M ST 4- 0. 4o 4 o 4 Ot -790- t S -t &,S5 o, 4�* 7-4.3 A XA Wc-C