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HomeMy WebLinkAboutSW4240602_Stormwater Narrative_20240625 STORMWATER NARRATIVE For: Fiddlers Ridge Subdivision Bingham and Parks Road Davie County, North Carolina ADI Project No. 23-009 `,%S_• CAR /", /, AL 9r: , ;,J'> GINE1 �"1,vC N.CP\`� Developer: Baltimore RE,LLC 323 Riverbend Drive Advance,North Carolina 27006 Prepared by: Allied Design,Inc. A4720 Kester Mill Road Winston-Salem,NC 27103 (336)765-2377 scausey@allied-engsurv.com STORM WATER NARRATIVE FIDDLERS RIDGE TABLE OF CONTENTS A. Introduction B. Methodology C. Site Design and Assessment D. Conclusion Appendix A. Outlet Stabilization Calculations B. Ditch Calculations Allied Design Inc. Project No.: 23-009 Page 1 STORM WATER NARRATIVE FIDDLERS RIDGE A. Introduction Fiddlers Ridge is a proposed 9.92-acre, 20 lot, single-family, residential development located off Bingham and Parks Road in Davie County. Based on anticipated development on the lots, the calculated BUA Percentage for the property will be less than 24%. Consequently, the project can be permitted under the "Low Density" (LD) provisions of the program. This will exempt the project from design and construction of permanent, stormwater quality control measures. Development under the LD option will require that the project meet the minimum design criteria outlined in 15A NCAC 02H .1003. More specifically the project: 1) must meet the Density Thresholds; 2) must utilize Dispersed Flow; 3) must provide Vegetated Conveyances; 4) may be allowed to use Curb Outlet Systems; 5) must provide Vegetated Setbacks; 6) requires that Storm water Outlets be designed to not cause erosion; and (7) requires that deed restrictions and protective covenants are applied as necessary to protect the designed low density practices. Guidance for development under The Low Density option is taken from the NCDEQ Stormwater BMP Manual, Chapter E-1, "Low Density". B. Low Density Design Considerations 1. Development Threshold The total project area for the subdivision is 9.92 acres. The number of proposed lots is 20. Deed restrictions will limit the maximum built upon area per lot to 3,800 sf which will result in an overall BUA of less than 24%. 2. Dispersed Flow As outlined in the Dispersed Flow requirements of the NCDEQ Stormwater Manual this project must be designed to maximize dispersed flow through vegetated areas and minimize channelization. Downspouts from the proposed homes will spill onto grade and not be piped. This will allow infiltration and Allied Design Inc. Project No.: 23-009 Page 2 STORM WATER NARRATIVE FIDDLERS RIDGE reduced erosion as runoff drains toward the roadway side ditches and swales between homes. 3. Vegetative Conveyances Stormwater runoff that cannot be maintained as shallow flow will be transported by Vegetated Conveyances. These conveyances will be lined with vegetation and designed to carry runoff from the 10-year storm at a non- erosive velocity. Side slopes will be 3:1 maximum, the longitudinal slopes will be held as flat as possible and a 2' minimum bottom width will be provided. 4. Curb Outlet Systems The project does not include curb and gutter streets. The roadways will be constructed with "ribbon" pavement and side ditches. Several inlets will be placed along the side ditches to capture accumulated runoff. Outlets from the pipe will discharge into vegetated swales designed in accordance with the above guidelines. It should be noted that the storm drainage system as illustrated on the plans has been previously installed. 5. Vegetated Setbacks There are no streams located on the property. Vegetated setbacks will not be required. 6. Stormwater Outlets Stormwater outlets shall be designed such that discharge from the 10-year storm will be released at non-erosive velocities. Outlet stabilization will be provided at the stormwater outlets and will be designed in accordance with the erosion control design manual and will. 7. Deed Restrictions and Protective Covenants Allied Design Inc. Project No.: 23-009 Page 3 STORM WATER NARRATIVE FIDDLERS RIDGE The permittee will record deed restrictions and protective covenants in the Davidson County Register of Deeds. These documents will limit the allowable built upon area for each lot to 3,800 sf. The restriction and covenants will "ensure the project is maintained in perpetuity consistent with the plans and specifications approved by the permitting authority". C. Conclusion As noted, construction of this project has been completed. This post-construction stormwater permit is being submitted for approval retroactively. This Stormwater Narrative concludes that the original design of the project was completed in accordance with the Low-Density provisions of the MDC. The design of the stormwater drainage system intentionally releases stormwater water at the same two pre-developed locations. The proposed grading plan and stormdrainage system was designed to maintain pre-developed patterns as closely as possible. This plan intends to provide dispersed flow and avoid concentrated discharge. This report and the site construction documents demonstrate that: 1. The project meets the density threshold requirement of less than 24% impervious (BUA) coverage. 2. The project utilizes dispersed flow to allow shallow release of stormwater runoff, minimizes channelization and releases channelized flow through a vegetated area. 3. Where vegetated conveyances are utilized, they are designed to be non- erosive for the 25-year storm (exceeds the 10-year storm requirement), are constructed with 3:1 (or flatter) side slopes, have a 2' minimum bottom width. 4. Where curb outlets [inlets] are utilized, runoff is released such that a vegetated areas are utilized, and outlet stabilization is used at the end of the pipes. Allied Design Inc. Project No.: 23-009 Page 4 STORM WATER NARRATIVE FIDDLERS RIDGE 5. Vegetated setbacks are not required. 6. Stormwater outlets will include appropriately sized outlet stabilization. 7. Deed restrictions and protective covenants will be recorded in the Davidson County register of deeds limiting the built upon area on each individual lot to 3,800 sq. ft. of impervious coverage. Allied Design Inc. Project No.: 23-009 Page 5 STORM WATER NARRATIVE FIDDLERS RIDGE Appendix Allied Design Inc. Project No.: 23-009 Page 6 i1\. Allied Design Inc. PROJECT NAME Fiddler's Ridge Outlet Stabilization CIVIL ENGINEERING • LAND SURVEYING PROJECT NO. 23 009 SHEET 1 OF 1 4720 Kester Mill Road BY WAB DATE 18-Mar-24 Winston-Salem,North Carolina 27103 CHECKED BY SMC REV 18-Mar-24 Ph.336.765.2377 e•Fax 336.760.8886 Outlet Stabilization II 3 .�111�� 1�11`III II:: Outlettl W = Do + La 1 �`m'I!ry!nni ii-- P P . - Iwun1•n•u 11!i IP •1 diameter(Do) t Iwlllllll�l I ; 1'l La —.1 80 mil a. 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Illl 111 ww�lwww w■■_11C w ■■ . ��' Ir/L' .:"A:11?IL? 11111111/ Ol In w1 wawol■ra■ w w w ' �S- iwlwwri �Irl;liril!ntntomnnul Es' , w 1 w�w� w r ii.••'/r ur4uII 0i IIIIIIIIIIIIII p- w ill I —"err* �-%i! I•A:d muuumu wl I sari I/wr' r�iwll.11IIIIIll11111111111111111 OC I -r •IM. �r/r 1■11111111111111111111111111 • =�.7 Iwlll 111111111111111 ■w■ �f11."iri��—,�i li iiw�1ww =1unuuunul LO , � �• ������r �M� !wi i=�11ii■ii!lii°iiiii 1 billilllig ����� •• iHII 'o 3 5 - 10 ' 20 50 100 200 500 1000 Discharge(ft3/sec) Curves may not be extrapolated. Figure 8.06a Design of outlet protection protection from a round pipe flowing full,minimum tailwater condition(Tw<0.5 diameter). Pipe apron NCDOT Outlet Diameter Discharge d50 La W dmax thickness riprap (in) (cfs) (ft) (ft) (ft) (ft) (ft) Class 100 18 9.38 0.35 10.0 11.5 0.5 0.8 B 200 18 2.03 0.35 10.0 11.5 0.5 0.8 B I TAKEN FROM THE NORTH CAROLINA EROSION AND SEDIMENT CONTROL DITCH SCHEDULE -25 YEAR STORM DESIGN FIDDLER'S RIDGE BERMUDA RUN, NORTH CAROLINA March 26, 2024 z -J z Z w _O 2 O W I 1- w Q O z Q W W CO O w H U W Z W_ H H O O § W W } Q d w 0 U_ Z C J O 0 I- 2 w I Z W O w z = = w 0 co I U C� H W w U WO z d H J 0 0 z co H 0 w w w z Q 0 o z O i= U o o co U) o > U (AC) (IN/HR) (CFS) (FT/FT) (FT) ("X" : 1) (FT) (FPS) 1 0.27 0.60 5 7.55 1.22 2.55% 2 3 0.26 1.65 S75 D 2 0.49 0.60 5 7.55 2.22 2.55% 2 3 0.35 2.10 S75 D 3 1.22 0.60 5 7.55 5.53 2.00% 2 3 0.57 2.60 S75 D 4 0.65 0.60 5 7.55 2.94 2.00% 2 3 0.43 2.05 S75 D 5 0.54 0.60 5 7.55 2.45 1.00% 2 3 0.53 1.30 S75 D 6 0.53 0.60 5 7.55 2.40 1.00% 2 3 0.52 1.29 S75 D 7 0.44 0.60 5 7.55 1.99 4.55% 2 3 0.26 2.74 S75 D 8 0.40 0.60 5 7.55 1.81 4.55% 2 3 0.25 2.63 S75 D 9 1.55 0.60 5 7.55 7.02 1.15% 12 3 0.38 1.42 S75 D 10 0.90 0.60 5 7.55 4.08 1.15% 12 3 0.29 1.10 S75 D 11 0.24 0.60 5 7.55 9.38 2.50% 4 3 0.51 3.30 S75 D 12 0.23 0.60 5 7.55 2.03 2.50% 8 3 0.18 1.33 S75 D ElNORTH North American Green AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#1 Name Ditch#1 Discharge 1.22 Channel Slope 0 .0255 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 1 .22 cfs 1 .65 ft/s 0 .26 ft 0 .049 3 .81 lbs/ft2 0 .32 lbs/ft2 1 1.9 S TABLE Substrate Unreinforced Straight 1 .22 cfs 1 .65 ft/s 0 .26 ft 0 .049 4 Ibs/ft2 0 .42 Ibs/ft2 9 .5 S TABLE Vegetation ElNORTH North American Green AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#2 Name Ditch#2 Discharge 2.22 Channel Slope 0 .0255 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 2 .22 cfs 2 .1 ft/s 0 .35 ft 0 .045 3 .18 lbs/ft2 0 .4 lbs/ft2 7 .94 S TABLE -- Substrate Unreinforced Straight 2 .22 cfs 2 .1 ft/s 0 .35 ft 0 .045 4 lbs/ft2 0 .55 lbs/ft2 7 .23 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#3 Name Ditch#3 Discharge 5.53 Channel Slope 0 .02 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 5 .53 cfs 2 .6 ft/s 0 .57 ft 0 .042 2 .79 lbs/ft2 0 .47 lbs/ft2 5 .91 S TABLE Substrate Unreinforced Straight 5 .53 cfs 2 .6 ft/s 0 .57 ft 0 .042 4 Ibs/ft2 0 .71 Ibs/ft2 5 .6 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#4 Name Ditch#4 Discharge 2.94 Channel Slope 0 .02 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 2 .94 cfs 2 .05 ft/s 0 .43 ft 0 .046 3 .34 lbs/ft2 0 .38 lbs/ft2 8 .85 S TABLE Substrate Unreinforced Straight 2 .94 cfs 2 .05 ft/s 0 .43 ft 0 .046 4 Ibs/ft2 0 .54 Ibs/ft2 7 .37 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#5 Name Ditch#5 Discharge 2.45 Channel Slope 0 .01 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 2 .45 cfs 1 .3 ft/s 0 .53 ft 0 .057 4 lbs/ft2 0 .22 lbs/ft2 1 8.11 S TABLE Substrate Unreinforced Straight 2 .45 cfs 1 .3 ft/s 0 .53 ft 0 .057 4 Ibs/ft2 0 .33 Ibs/ft2 1 2.16 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#6 Name Ditch#6 Discharge 2.4 Channel Slope 0 .01 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 2 .4 cfs 1 .29 ft/s 0 .52 ft 0 .057 4 lbs/ft2 0 .22 lbs/ft2 1 8.28 S TABLE Substrate Unreinforced Straight 2 .4 cfs 1 .29 ft/s 0 .52 ft 0 .057 4 Ibs/ft2 0 .33 Ibs/ft2 1 2.3 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#7 Name Ditch#7 Discharge 1.99 Channel Slope 0 .0455 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Underlying Straight 1 .99 cfs 2 .74 ft/s 0 .26 ft 0 .039 2 .42 lbs/ft2 0 .56 lbs/ft2 4 .29 S TABLE Substrate Unreinforced Straight 1 .99 cfs 2 .74 ft/s 0 .26 ft 0 .039 4 Ibs/ft2 0 .74 Ibs/ft2 5 .4 S TABLE Vegetation NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#8 Name Ditch#8 Discharge 1.81 Channel Slope 0 .0455 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Unreinforced Straight 1 .81 cfs 2 .63 ft/s 0 .25 ft 0 .04 4 lbs/ft2 0 .71 lbs/ft2 5 .66 S TABLE Vegetation Underlying Straight 1 .81 cfs 2 .63 ft/s 0 .25 ft 0 .04 2 .49 lbs/ft2 0 .54 lbs/ft2 4 .59 S TABLE Substrate NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#9 Name Ditch#9 Discharge 7.02 Channel Slope 0 .0115 Channel Bottom Width 1 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Unreinforced Straight 7 .02 cfs 1 .42 ft/s 0 .38 ft 0 .055 4 lbs/ft2 0 .27 lbs/ft2 1 4.84 S TABLE Vegetation Underlying Straight 7 .02 cfs 1 .42 ft/s 0 .38 ft 0 .055 4 lbs/ft2 0 .25 lbs/ft2 1 6.26 S TABLE Substrate NORTH North American G reen AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#10 Name Ditch#10 Discharge 4.08 Channel Slope 0 .0115 Channel Bottom Width 1 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Unreinforced Straight 4 .08 cfs 1 .1 ft/s 0 .29 ft 0 .06 4 lbs/ft2 0 .21 lbs/ft2 1 9.29 S TABLE Vegetation Underlying Straight 4 .08 cfs 1 .1 ft/s 0 .29 ft 0 .06 4 lbs/ft2 0 .19 lbs/ft2 2 0.73 S TABLE Substrate ElNORTH North American Green AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#11 Name Ditch#11 Discharge 9.38 Channel Slope 0 .025 Channel Bottom Width 4 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Unreinforced Straight 9 .38 cfs 3 .3 ft/s 0 .51 ft 0 .038 4 lbs/ft2 0 .8 lbs/ft2 5S TABLE Vegetation Underlying Straight 9 .38 cfs 3 .3 ft/s 0 .51 ft 0 .038 2 .27 lbs/ft2 0 .61 lbs/ft2 3 .71 S TABLE Substrate ElNORTH North American Green AMERICAN 5401 St. Wendel-Cynthiana Rd. Poseyville, Indiana 47633 GREEN Tel. 800.772.2040 > Fax 812.867.0247 w w wnagreen.com ECM D Sv7.0 CHANNEL ANALYSIS >>>Ditch#12 Name Ditch#12 Discharge 2.03 Channel Slope 0 .025 Channel Bottom Width 8 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardence Class D 2-6 in Vegetatibn Type M x(Sod and Bunch) Vegetation Density F air 50-64% Soil Type Clay Loam(CL) Unreinforced Vegetation N ormal Permissible Calculated Safety Staple ePhase R iach D scharge V locity Mannings N Remarks Depth Shear Stress Shear Stress Factor Pattern Unreinforced Straight 2 .03 cfs 1 .33 ft/s 0 .18 ft 0 .054 4 lbs/ft2 0 .28 lbs/ft2 1 4.35 S TABLE Vegetation Underlying Straight 2 .03 cfs 1 .33 ft/s 0 .18 ft 0 .054 4 lbs/ft2 0 .26 lbs/ft2 1 5.35 S TABLE Substrate