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Home My WebLink AboutWPO201100071 Presentation 2012-07-03 .W.M+'w✓WVw!'J�.M✓'V^.+Yw1V\ht`./�1 �V '/\V`.fY^Mr./`,a�_N`.rYln/wrV`✓V1r'�r^.�V� ` //\.'�+'wnlv'�Mn/`•fw/`.+,J`.n.'W ln.Mr\Jw ✓`./w/\M.^V`!\r/vim.^V".+V\t1.^Jwftr^v`.nlw/` ` .Mw'V"4'w/'VV`.N"�J`v`w/`.r1/w+'�'Y"wI'v^�i V`J• • • • 4`��.�..�Mnl�:Y�.::..•�.+�Jv`� R ESTO R E ' N STATION nrWv�.r'Y'WW`.�Vw.�\l4`\^Nvv'vVw/ • `:/�h.'V•../�/vY W wnNJ V^.,'V'./w,/'•.rV�,h,.Y`.. \N�.^•�lMM/W lI\/Y>/Y�Jlt`.��lwr^.rye! `• • Erosion Control Narrative • • • J�K. �r N``�y'VVV\1w�W Yam'`n/�/NN N\hlVVv��`M.•Vv^•Jw/`.%v'tN'ti^WYw. ✓�r'1/°J V+N"v'\r"V\Alwl�.'wt�.^t+lr'..+Rr^./V wn/�•r1. 1/v`JYV•✓lN^..MJ\r..L^•.fw.r^.1�J•.rN`./w/` "+1/`.FlMlwnN�lr1_n.^..'VVV`•r'\/\r�..^+!..iV�! w�.nlwvwvw.n.W,.v+n� v�./w/`./w/'vVwIW�WV\.'VtM.rVwI'V�r .JV�r^.N^./wi•`.M/`JwAJV'ti/+/`.r^V`./\/w1�r' `./��Y./\r'W\IwNW`✓w/INWW��\/wr y W+.M ./�lw.W\M.rV\iWV W V�iW\/�lVwi�/V�N\ ;,"..n..+w�vY.s.nivwr+"v JY`,IVVIN�M 'WYYY�nM.rW+it,fv^MN r�lwlt vW V�.+VY�I�r�/'ln_rwA.�1.1JY�N'./wr' wIJ wV�/�J �v�I�W'Y •wniw `:MMNWWVvw.^J�NvYV`.!'VVVV� wv�Mti�.� tin. .,•�irni.n \/\rYw.rV�/w,^�lvVw^J.rr'\MNwI^.i NP Engineering Dated: August 28, 2011 w ..,..., ti.... .., ,, ,..� ..YWY Ww•.iwti�vwvw.nnn•"w'v�"� ^..vvv.nnnrv�nn✓wv�.�.nl..w1 Revised:July 3, 2012 Restore'n Station • Erosion Control Narrative Table of Contents I. Narrative II. Drainage Areas III. Erosion Control worksheets NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone: 434.531.7387 • Email: nat.perkins@gmail.com Restore'n Station Erosion Control Narrative I. NARRATIVE PROJECT DESCRIPTION: This project consists of the construction of a two story convenience store building (2,775 sf footprint) and associated site amenities and parking areas. The project scope includes grading and installation of asphalt travel ways and parking spaces, and utilities (well and septic). The project site is 4.06 acres and lies within the Stockton Creek water supply watershed. The disturbed area for the project is approximately 4.0 acres. Erosion control for the site will be managed using perimeter controls and the installation of a temporary sediment basin and silt trap. EXISTING SITE CONDITIONS: The site is located on Rockfish Gap Turnpike (SR 250) approximately 0.78 miles west of the intersection with Miller School Road (SR 240). The site is currently vacant and grass fields. The site slopes in general from north to south at approximately 5%. ADJACENT AREAS: The site is bounded on the north by SR 250, to the east by Freetown Lane and Highway Commercial zoning (automotive repair shop), to the west by rural area (Crozet Moose Lodge) and to the south by rural area, residential use. Existing surface drainage is directed south to an existing stream. OFF-SITE AREAS: Off-site areas to be disturbed are limited to the southern property line where the storm drainage outfall outlets into the existing stream. This area is delineated with a drainage easement. SOILS: According to the USDA SCS soils mapping, the project site lies in soils: 7B - Braddock loam 36B- Hayesville loam 37C3- Hayesville clay loam NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone: 434.531.7387 • Email: nat.oerkins@gmail.com Restore'n Station Erosion Control Narrative The soils are described as: 7B—Braddock loam, 2 to 7 percent slopes Properties and qualities • Slope: 2 to 7 percent • Depth to restrictive feature: More than 80 inches • Drainage class: Well drained • Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1 .98 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: High (about 9.1 inches) Typical profile • 0 to 8 inches: Loam • 8 to 79 inches: Clay 36B—Havesville loam, 2 to 7 percent slopes Properties and qualities • Slope: 2 to 7 percent • Depth to restrictive feature: More than 80 inches • Drainage class: Well drained • Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1 .98 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: High (about 10.6 inches) Typical profile • 0 to 7 inches: Loam • 7 to 58 inches: Clay • 58 to 67 inches: Sandy clay loam • 67 to 83 inches: Fine sandy loam NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 2 29 01 Phone:434.531.7387 • Email: nat.perkins@gmail.com Restore'n Station Erosion Control Narrative 37C3—Hayesville clay loam, 2 to 7 percent slopes, severely eroded Properties and qualities • Slope: 2 to 7 percent • Depth to restrictive feature: More than 80 inches • Drainage class: Well drained • Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1.98 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: High (about 10.6 inches) Typical profile • 0 to 7 inches: Clay loam • 7 to 58 inches: Clay • 58 to 67 inches: Sandy clay loam • 67 to 83 inches: Fine sandy loam This soil is deep, sloping and well drained. Soil is on narrow convex ridgetops. Slopes are smooth and about 200 to 400 feet long. Permeability and available water capacity of this soil is high. Depth to bedrock is approximately 80 inches. Potential frost action and shrink-swell potential is high, limiting the use of this soil as a building site or roadfill. CRITICAL EROSION AREAS: There are no areas defined as critically erosive. However, care should be taken on a daily basis to maintain the erosion control structures to prevent silt from leaving the construction site. Specifically, silt fence is to be constructed along the sides of the work zone to intercept and detain sediment. A construction entrance is to be provided to prevent tracking of mud into the public right-of- way by construction vehicles. Wash water is to be trucked in or obtained from a metered well. Wash water is to be directed to silt fence. Inlet protection is to be provided to prevent sediment from entering the storm drain system upon construction of the on-site storm drain inlets. NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 2 29 01 Phone:434.531.7387 • Email: nat.perkins@gmail.com Restore'n Station ' Erosion Control Narrative CONSTRUCTION SEQUENCE/PHASING: Construction shall follow the follow sequencing and phasing plan to minimize erosion. The erosion control measures shall be in three phases: Phase 1 1) Install silt fence (SF) along all property lines. 2) Install Construction Entrance (CE) as indicated on the plans and any tree protection. 3) Install temporary diversion dikes, silt trap and sediment basin. 4) Demolish existing improvements as necessary. 5) Clear and grub, strip top soil and stockpile for re-spread. Haul unsuitable material off-site to an approved disposal location. 6) Rough grade site, install new utilities (storm drain, septic, haul excess material off-site as necessary to an approved disposal location. Phase 2 7) Install inlet protection (IP) around the proposed drop inlets. 8) Proof roll subgrade in areas to receive asphalt pavement. Upon proof roll approval by geotechnical engineer, install aggregate base, prime coat and asphalt paving per phasing sequence. 9) Install building structures and stripe paving. 10) Provide temporary seeding and other erosion control devices to minimize transport of sediment. 11) Prepare landscaping areas. 12) Apply permanent seeding (PS), landscaping and mulch (MU) to all denuded areas as indicated on the plans as soon as possible. Phase 3 13)Temporary sediment control structures are to remain in place and will be removed only when a satisfactory stand of permanent grass is present. Upon approval, remove temporary erosion control measures, remove unsuitable material to an approved location, and stabilize affected areas. 14) Remove temporary EC measures (silt traps, diversion dikes); 15) Install Rain Tank #1 and #2 for the permanent storm water management facility; 16) Project closeout and bond release. NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone:434.531.7387 • Email: nat.perkins@gmail.com Restore'n Station ' Erosion Control Narrative EROSION AND SEDIMENT CONTROL MEASURES: The measures noted below and on the accompanying drawings are to be constructed and maintained by the contractor in accordance with the latest edition of the Albemarle County Code and the Virginia Erosion and Sedimentation Control Handbook, Third Edition, 1992. Symbols, details, and dimensions used are taken from the handbook, as well as the Virginia Department of Transportation Road and Bridge Standards, Volume 1, 2001. A. STRUCTURAL PRACTICES: 1. Temporary construction entrance (CE), 3.02: Temporary construction entrance shall be provided and maintained as shown on the plan sheet. 2. Silt Fence (SF), 3.05: Silt fence barriers shall be installed down slope of areas with minimal grades to filter runoff from sheet flow as indicated on the plan sheet. 3. Storm Drain Inlet Protection (IP), 3.07: Storm drain inlet protection shall be provided for inlets as shown on the plans. 4. Temporary Diversion Dike (DD), 3.09: Temporary diversion dikes shall be provided as shown on the plans or as needed to divert water to the silt traps. 5. Rock Check Dams (CD), 3.20: Rock check dams are to be installed in the diversion ditches as needed to reduce velocity of concentrated flow and the potential of erosion. 6. Dust Control (DC), 3.39: Provide dust control in areas subject to surface and air movement of duct where on-site and off-site damage is likely to occur if preventive measures are not taken. 7. Temporary silt trap shall be installed and maintained per VESC 3.13. 8. Temporary sediment basin shall be installed and maintained per VESC 3.14. B. VEGETATIVE MEASURES: 1. Topsoiling & Stockpiling (TO), 3.30: Topsoil will be stripped from areas to be graded and stockpiled for later use. Stockpiles are to be stabilized with temporary vegetation and have silt fence installed along the lower perimeter. Stockpile locations to be approved by owner. 2. Temporary Seeding (TS), 3.31: All denuded areas which will be left dormant for extended periods of time shall be seeded with fast germinating temporary vegetation immediately following grading. Seed selection will be dependent on the time of year in accordance with the VESC. 3. Permanent Seeding (PS), 3.32: Permanent seeding shall be provided on site to provide stabilization for all disturbed areas. Seeding rates are in pounds per acre. For high maintenance lawn areas apply 200-250 pounds of Kentucky 31 fescue, 2 pounds of red top grass, and 20 pounds of NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 2 29 01 Phone: 434.531.7387 • Email: nat.oerkins@amail.com Restore'n Station • Erosion Control Narrative seasonal nurse crop. The seasonal nurse crop used is based on the following seeding dates: a. From February 16 through April, use annual rye; b. From May 1 through August 15, use foxtail millet; c. From August 16 through October, use annual rye; d. From November through February 15, use winter rye; All permanent seeding shall be fertilized, limed and mulched at the following rates: Fertilizer 10-20-10 at a rate of 1000 pounds per acre: lime of agricultural grade limestone at a rate of 2 tons per acre: and straw mulch at a rate of 1 1/2 tons per acre. Before seeding, 4 inches of topsoil shall be spread in areas to be seeded. Apply fertilizer and lime uniformly and mix well into top 4 inches of seed bed. Prepare soil for permanent seeding by tillage of topsoil in place to loosen thoroughly and breakup all clods to a depth of 6 inches. Remove all stumps and roots, coarse vegetation, stones larger than 1 1/2 inches and all construction debris. Soil shall be worked by suitable agricultural equipment to a depth of not less than 4 inches. Surface shall be uniform, smooth and drainable. A firm and compact seed bed is required. 4. Mulching (MU), 3.35: All temporary and permanent seeding shall be straw mulched. C. MINIMUM STANDARDS: MS-1 Stablilization of denuded areas: Permanent or temporary soil stabilization shall be applied to denuded areas with 7 days after final grade is reached on any portion of the site. Temporary soil stabilization shall be applied within 7 days to denuded areas that may not be at final grade, but will remain dormant or undisturbed for longer than 30 days. Permanent stabilization shall be applied to areas that are to be left dormant for more than one year. MS-2 Stablilization of soil stockpiles: During construction of the project, soil stockpiles and borrow areas shall be stabilized or protected with sediment trapping measures. The contractor is responsible for temporary protection, permanent stabilization of all stockpiles on site, as well as borrow areas and soil intentionally transported from the project site. MS-3 Permanent Vegetative Cover: A permanent vegetative cover shall be established on denuded areas not otherwise permanently stabilized. Permanent vegetation shall not be considered established until a ground cover is achieved that, in the opinion of the E&S inspector, is uniform and mature enough to survive and inhibit erosion. NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone: 434.531.7387 • Email: nat.oerkins@gmail.com Restore'n Station • Erosion Control Narrative MS-4 Timing and stabilization of silt trapping measures: Storm inlet protection, silt fencing, and other measures intended to trap sediment shall be constructed as a first step in any land disturbing activities and shall be made functional before upslope land disturbance takes place. MS-5 Stabilization of earthen structures: Stabilization measures shall be applied to earthen structures such as dikes and diversions immediately after installation. MS-6 Sediment basin and traps: The sediment trap and sediment basin shall be installed as soon as the erosion control fencing is installed. Excavation under, and in the embankments shall be free of organics (roots and vegetation). Sediment shall be removed and the facility restored to its original dimensions when the sediment has accumulated to one half the wet storage volume for the silt trap, and once the sediment reaches the sediment cleanout elevation for the sediment basin. MS-7 Cut to Fill slopes: Cut to fill slopes shall be constructed in a manner that will minimize erosion. Slopes that are found to be eroding excessively within one year of permanent stabilization shall be provided with additional slope stabilizing measures until the problem is corrected. MS-8 Concentrated run-off down cut or fill slopes: Concentrated runoff shall not flow down cut or fill slopes unless contained within an adequate temporary or permanent channel, flume or slope drain structure. MS-9 Water seepage from a slope face: Whenever water seeps from a slope face, adequate drainage or other protection shall be provided. MS-10 Storm Inlet Protection: All storm inlets that are operable during construction shall be protected so that sediment laden water cannot enter the conveyance system without first being filtered or otherwise treated to remove sediment. MS-1 1 Stabilization of outlets: Not used. MS-12 Work in live watercourses: Not used. MS-13 Crossing a live watercourse: Not used. MS-14 Applicable Regulation: NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone:434.531.7387 • Email: nat.perkins@gmail.com 4 Restore'n Station • Erosion Control Narrative All applicable federal, state and local regulations pertaining to working in or crossing live watercourses shall be met. MS-15 Stabilization of bed and banks: Not used. MS-16 Underground utilities: Underground utility lines shall be installed in accordance with the following standards, in addition to other applicable criteria: a. No more than 500 lineal feet of trench may be opened at one time; b. Where consistent with safety and space considerations, excavated material is to be placed on the uphill side of trenches, except for any diversion ditches; c. Effluent from dewatering operations shall be filtered or passed through an approved sediment trapping device, or both, and discharged in a manner that does not adversely affect flowing streams or offsite property; d. Trench backfill material shall be properly compacted in order to minimize erosion and promote stabilization; e. Restabilization shall be accomplished in accordance with these regulations; f. All applicable safety regulations shall be complied with at all times. MS-17 Construction access routes: Where construction vehicle access routes intersect paved or public roads, provisions shall be made to minimize the transport of sediment by vehicular tracking onto the paved surface. Where sediment is transported onto a paved or public road, the road surface shall be cleaned thoroughly at the end of each day. Sediment shall be removed by shoveling or sweeping and transported to a sediment disposal area. Street washing shall be allowed only after sediment is removed in this manner. This provision shall apply to individual development lots as well as larger land-disturbing activities. MS-18 Temporary E&S Control measure removal: All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization or after temporary measures are no longer needed, unless otherwise authorized by the local E&S authority. Trapped sediment and the disturbed soil areas resulting from the disposition of temporary measures shall be permanently stabilized to prevent further erosion and sedimentation. MS-19 Adequacy of receiving channels: Properties and waterways downstream from the development site shall be protected from sediment deposition, erosion and damage due to increases in volume, velocity and peak flow rates of storm water runoff for NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone:434.531.7387 • Email: nat.oerkins@gmail.com Restore'n Station Erosion Control Narrative the stated frequency storm of 24-hour duration. This will be accomplished by limiting the post development volume and velocity to pre- development levels. D. MAINTENANCE: All erosion and sediment control structures and systems shall be maintained, inspected, and repaired as needed to insure continued performance of their intended function. All erosion and sediment control measures shall be checked at the end of each day and after every rainfall event. 1. Damage to erosion control measures caused by construction traffic or other activity shall be repaired before the end of each working day. 2. Maintain all seeded areas until a uniform stand is accepted. 3. Provide for equipment washing as needed to prevent the transport of soil onto existing asphalt roadways. 4. Both temporary and permanent roads and parking areas may require periodic top dressing with new gravel. 5. Silt fence barriers will be checked daily for undermining or deterioration of the fabric. Sediment shall be removed when the level reaches half way to the top of the barrier. 6. Sediment shall be removed from around the inlet protection trap structure and restored to its original dimensions when the sediment has accumulated to one-half the design depth of the trap. The trap structure shall be removed and the area stabilized when the remaining drainage area has been properly stabilized. 7. Temporary diversion dikes shall be inspected regularly and repairs made if needed. 8. Sediment accumulated within diversions shall be removed from the channel and repairs made as necessary. 9. Sediment should be removed from rock check dams when it reaches one-half of the original height of the measure. Regular inspections should be made to insure that the center of the dam is lower than the edges. Erosion caused by high flows around the edges of the dam should be corrected immediately. 10. All soil stabilization blankets and matting shall be inspected after rainstorms to check for erosion and undermining. If washout or breakage occurs, reinstall the material after repairing damage to the slope or ditch. 11. Sediment shall be removed from the sediment trap and restored to its original dimensions when the sediment has accumulated to one half the wet storage volume. NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone:434.531.7387 • Email: nat.perkins@gmail.com t Restore'n Station Erosion Control Narrative II. Drainage Areas -r .t, 1t , ,..1 v Vk t ' t: "f :Mts* I s .YI 7C3 t' l it - - • ,: � 7rt' s 1y ,= v i i Ii i5 , �1 `\ C I .j Via. i 200 ft L._-----� Pre-development Drainage Area Drainage Area #1 - area draining to the location of the sediment basin. NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 22901 Phone:434.531.7387 • Email: nat.nerkins@gmail.com • Restore'n Station Erosion Control Narrative il, _ cD f Sr �� • � (� ,[` �y��'} r r? �'t'A F' ... Vie+' ��yq(([''' t _-:..� f w" •• �6,03l7i,Y_.. • + e fi a ,-- E Jnr 1 t. .C..S _55 If= 4x.:4! �, 5_; egg£ a tt 1 ' ' - - 4 '+ o07.7 gr...:.. \ r4JC '1 j fl ri ++ it% if'"j.rs, 200 ft ' y Pre-development Drainage Area Drainage Area #2-area draining to the location of the silt trap. Ill. Erosion Control Worksheets NP ENGINEERING 680 IVY FARM DRIVE • CHARLOTTESVILLE, VA 2 29 01 Phone: 434.531.7387 • Email: nat.oerkins@gmail.com • Sediment Basin Design(SB#1) MIN,I'WI SPILLWAY CREST OF EMERGENCY 2'WIiNOUT SPILLWAY drainage area(acres) 4.68 DESIGN HIGH WATER basin volumes:(using 2'contour intervals) fn-R.STORY ELEV) Elev(ft) Contour area(sf) Volume(cy) Cum vol(cy) I I I I I I I I I Eanta 1 671 0 0.0 0.0 �� RISER CREST 672 1302.35 24.12 24.12 oar- STORAGE ,,,, OE NC DEVICE 674 2118.72 126.71 150.82 *[ 676 3132.03 194.47 345.30 STORAGE 678 4301.67 275.32 620.62SME '/" ELEA/EWE POINT 680 5776.91 373.28 993.90 (�WET M STORAGE REDVCEO TO 3II Cl,,. ACRE) wet storage: wet storage required(cy)(67'DA) 313.6 design high water 680.0 dewatering orifice elevation(ft) 675.7 top of darn(ft) 681.0 wet storage provided at this elevation(cy) 327.6 top width of dam(ft) 6.0 available volume before cleanout(cy)(33'DA) 154.4 bottom of basin(ft) 671.0 cleanout elevation(ft) 674.1 approx.bottom dimensions: 47'x51' distance from cleanout to orifice(ft)(>1') 1.6 upstream face slope: 2:1 downstream face slope: 3:1 dry storage: dry storage required(cy)(67'DA) 313.6 baffles: yes principle spillway crest(ft) 678.03 length of flow,L(ft) 59.8 dry storage provided at this elevation(cy( 313.6 effective width,We(ft) 2.1 diameter of dewatering orifice(in) 3.0 L/We (baffles required if>2) 28.2 diameter of flexible tubing(in)(orifice+2") 6.0 collars: yes runoff: depth of water at spillway crest(ft) 7.0 C(use 0.45 for bare earth) 0.45 slope of upstream face(Z:1) 2 tc(min) 14 slope of barrel(Sb) 0.015 I 2yr 3.6 Q 2yr 7.5 length of barrel in saturated zone(Ls) 50 I 25yr 5.7 Q 25yr 12.0 number collars required 2 dimension of collars 5x5 principle spillway: available head(ft) 1.4 emergency spillway: yes diameter riser(in) 33 required capacity(Q25-Qp)(cfs) 4.5 spillway capacity,Qp(cfs) 7.5 bottom width(ft) 8 diameter trash rack(In) 54 slope of exist channel(ft/ft) 0.039 barrel length(ft) 63.17 minimun length of exit channel(ft) 32 head on barrel through embankment(ft) 8.4 crest of spillway(ft) 679.4 diameter of barrel(in) 15 Sediment Trap Design (ST #1 - A) drainage area (acres) (<3) 0.85 ( rI VARIABLE CREST OF STONE WEIR trap volumes: OR/GINAL I , VARIABLES GROUND elevation (ft) area (sf) volume(cy) cum.vol.(cy) ELEV. <._.'gilt :vi.,,.�� 678 310.48 0 0.0 11eliIr.�' DRY STORAGE r `�� VARIABLE* N��"�� r 680 546.01 31.7 31.7 _ �;�"t-,ta t 682 1216.86 65.3 97.0 WET STORAGE 4, MAX. 684 2124.22 123.7 220.8 (EXCAVATED) `FILTER CLOTH ORIGINAL GROUNDNA ELEV. *SEE PLATE 3.73-I COARSE AGGREGATE�* CLASS I RIPRAP wet storage: wet storage required(cy) (67*DA) 57.0 bottom of stone weir(ft) 680.8 wet storage provided at this elevation (cy) 57.0 slope of wet storage sides 1:1 weir length(ft) (6xDA) 5.1 dry storage: bottom of trap elevation (ft) 678 dry storage required (cy) (67*DA) 57.0 bottom trap dimensions: 13.5x37.5 crest of stone weir 682.3 top of dam elevation (ft) 684 dry storage provided at this elevation (cy) 57.0 top width of dam (ft) 5 slope of dry storage sides 2:1 top trap dimensions 30'xl 15' t Sediment Trap Design (ST #1 - B) drainage area(acres) (<3) 0.35 I 1•I�ARIABIE*1 trap volumes: ORIGINAL CREST OF STONE WEIR VARIABLE* GROUND elevation (ft) area (sf) volume(cy) cum.vol.(cy) ELEV. y`:� 4�� ,D 676 0 0 0.0 ��2 VPwJa 678 99.13 0.0 0.0 DRY STORAGE N==er `��i�` q VARIABLE* 680 232.92 12.3 12.3 �,l►kert`rk 1 682 672.03 33.5 45.8 WET STORAGE 684 232.92 33.5 79.3 (EXCAVATED) r, MAX. FILTER CLOTH ORIGINAL GROUND ELEV. •SEE PLATE 3.13-1 COARSE AGGREGATE... CLASS I RIPRAP wet storage: wet storage required(cy) (67*DA) 23.5 bottom of stone weir(ft) 681.2 wet storage provided at this elevation (cy) 23.5 slope of wet storage sides 1:1 weir length(ft) (6xDA) (to be 5.1'as per Ph 1) 2.1 dry storage: bottom of trap elevation (ft) 678 dry storage required (cy) (67*DA) 23.5 bottom trap dimensions: 8.9x20 crest of stone weir 683.2 top of dam elevation (ft) 684 dry storage provided at this elevation (cy) 23.5 top width of dam (ft) 5 slope of dry storage sides 2:1 top trap dimensions 32.5x76.5