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HomeMy WebLinkAboutWPO200500044 Study Stormwater Management Plan 2005-10-03 SOIL EROSION ANI) SF'DIMENT CONTROL REPORT .1., ran -., ,i, -- - ‘• . . s. r ‘ . e . . .7., o, , ,,,,... ,1 , . ,. ,. , e rt ..lt• ili . ': , ..",' +r tt. `� 1 L. i Reviewed and Approved b the. Wo• 1420.8 Community Development Department 2005 5 - zo-o5 Date: JO - '3 - o5- ,e -Atelrz'i/ Signature r PREPARED BY B . AUBREY HUFFMAN AND ASSOCIATES , LTD. CIVIL ENGINEERING-LAND SURVEYING-LAND PLANNING CHARLOTTESVILLE,VIRGINIA SOIL EROSION AND SEDIMENT CONTROL REPORT Prepared By B.Aubrey Huffman and Associates,Ltd. Civil Engineering-Land Surveying-Land Planing P.O.Box 6124 Charlottesville,Virginia 22906 PROJECT BENDING BRANCH 1 Date: May 20,2005 Location: The property is situated on the North side of Still Meadow Avenue approximately 200' to the Northeast with it's intersections of Northfield Road ( State Route 1427 ) and Northfield Circle ( State Route 1436 ). The properties are Parcel 2 and Parcel P-1A on Tax Map Sheet 62A(3) of Albemarle County Tax Maps. Project Description: The purpose of this plan is to grade for a 10 lot subdivision,detention/storm water bmp basin and road as shown on the attached plan. Disturbed areas for this construction will be approximately 4.8 acres. Existing Site Conditions: The existing site is presently covered with dense grasses,weeds,underbrush of various kinds and trees of various species.The average slope of the land ranges from 5 to 50 percent. Sedimentation controls will be constructed at points as shown on the attached plan and/or described in this report. Adjacent Property: The area to the North of the site is currently occupied by Still Meadow Subdivison. The area to the East of the site is currently occupied by South Fork Rivanna River. The area to the South of the site is currently occupied by Southern Railroad. The area to the West of the site is currently occupied by Still Meadow Avenue. Soil Type: The soils in this area consist of Elioak loam, Glenelg loam and Hazel loam. 2 Handbook: Any references to the handbook will mean The Vuginia Erosion and Sediment Control Handbook,Third Edition, 1992. All persons implementing a Soil Erosion plan should have access to the above book should they need clarification or other information in order to comply with the Soil Erosion Ordinance. Critical Erosion Areas: There will be little storm water runoff crossing this site from other sites. This project anticipates no difficult erosion problems caused by the new construction. An attempt will be made both during and after construction to avoid the construction of storm water runoff and to minimize the velocity of discharge form ditches and pipes. During the time of construction, surface storm water will be diverted away from the newly created faces of cut and fill slopes. Erosion and Sediment Control Measures: Unless otherwise indicated, all vegetative and structural erosion and sedimentation control practices will be constructed and maintained according to the minimum standards and specifications of the current edition of the handbook. Particular measures shall be constructed as indicated on the attached plan. As soon as these measures and all other temporary sediment control measures are no longer needed, they will be removed and the areas of their former existence will be cleaned up and stabilized in a workman like manner in conformance with the specifications outlined in minimum standards 1.5 (18) of the handbook. The contractor shall apply additional erosion and sediment control measures, as determined necessary by the program authority,to maintain consistency with the purpose and intent of the Virginia Erosion and Sediment Control Regulations. 3 Structural Practices: Safety Fence: Locations of these barriers are shown on the plans. These barricades shall not be removed until the site is adequately stabilized in the opinion of the County Inspector. Silt Fence Barrier: A silt fence bather will be used for sediment control during all phases of construction. Locations and details for the constructions of these bathers are shown on the plan. These barricades shall not be removed until the site is adequately stabilized in the opinion of the Erosion Sediment Control inspector. Temporary Diversion Dike: A temporary ridge of compacted soil located at the top or base of a sloping disturbed area to divert sediment laden runoff from a disturbed area to a sediment trapping facility. Locations and details for the construction of these barriers are shown on the plan.Damages caused by construction traffic or other activity must be replaced before the end of each working day Temporary Sediment Basin: A temporary basin with a controlled storm water release structure, formed by constructing an embankment of compacted soil across a drainage way. These basins are generally used for areas of three acres or greater. Stormwater Conveyance Channel: A permanent manmade channel designed to safely convey concentrated runoff water away from a developing area without damage from erosion. Storm Drain Inlet Protection: All pipe inlets will be protected during the time of construction. This protection will consist of the standard use of temporary stone sediment bathers placed around the intake of the structure. These measures will be checked periodically and cleaned or reinforced as necec.cary to insure their continuous and efficient operation. 4 Dust Control: If during construction a problem with dust arises,the contractor will take measures as outlined in the handbook under dust control to reduce the presence of air born substances. Outlet Protection: All runoff from this site will enter existing swales as shown on the plan. Temporary Construction Entrance: A 12 foot by 70 foot paved wash rack will be installed at the entrance to the hard surface access of the site.This item will be maintained as necessary to clean mud and debris from the tires of departing vehicles. Construction entrance shall utilize flow berms and grading to assure wash water runs to a settling basin adjoining the paved area and not onto existing street. Construction Road Stabilization: All roads and parking areas on the site shall be stabilized with gravel immediately after grading. Construction traffic shall be limited to access roads and areas to be graded. Traffic is prohibited from entering drainage swales or streams. Roadbeds shall be at least 14 feet wide for one-way traffic and a minimum 20 feet wide for two way traffic. Vegetative Practices: Topsoil Stockpile: Topsoil shall be stripped from areas to be graded and stockpiled for later use. Areas where topsoil does not exist or where topsoil exists in a very thin layer shall be exempt from this practice. Stockpile locations shall be selected by the project engineer. 5 Tree Preservation and Protection: All tree protection is to be in accordance with the latest edition of the Virginia Erosion and Sediment Control Handbook. Minimum Standards: Soil stabilization refers to measures,which protect soil from the erosive forces of raindrop impact and flowing water. Applicable practices include vegetative establishment, mulching, and the early application of gravel base on areas to be paved. Soil stabilization measures should be selected to be appropriate for the time of year,site conditions,and estimated period of use. Permanent or temporary soil stabilization shall be applied to denuded areas within seven days after final grade is reached on any portion of the site. Temporary soil stabilization shall be applied within seven days to denuded areas that may not be at final grade but will remain dormant (undisturbed) for longer than thirty days. Permanent stabilization shall be applied to areas that are to be left dormant for more than one year. During construction of the project, soil stockpiles shall be stabilized or protected with sediment trapping measures. The applicant is responsible for the temporary protection and permanent stabilization of all soil stockpiles on site as well as soil intentionally transported from the project site. 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 local program administrator or his designated agent, is uniform, mature enough to survive,and will inhibit erosion. L 6 Where construction vehicle access mutes intersect paved 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 public road surface, the road shall be cleaned thoroughly at the end of each day. Sediment shall be removed from the roads by shoveling or sweeping and transported to a sediment control disposal area. "Stint washing shall be allowed only after sediment is removed in this manner. This provision shall apply to individual subdivision lots as well as to larger land disturbing activities. All temporary erosion and sediment control measures shall be removed within thirty days after final site stabilization or after the temporary measures are no longer needed, unless otherwise authorized by the local program administrator. Trapped sediment and the disturbed soil areas resulting from the disposition of temporary measures chaff be permanently stabilized to prevent further erosion and sedimentation. Management Strategies: Construction should be sequenced so that grading operations can begin and end as quickly as possible. Sediment basins and traps, perimeter dikes, sediment bathers and other measures intended to trap sediment on site must be constructed as a first step in grading and be made functional before upslope land disturbance takes place. Earthen structures such as dams, dikes, and diversions must be seeded and mulched immediately after installation. Areas which are not to be disturbed shall be clearly marked by flags, signs, or other means to indicate to construction personnel the limits of construction and disturbed areas. The job superintendent shall be responsible for the installation and maintenance of all erosion and sediment control practices. • { Maintenance: In general, all erosion and sediment control measures will be checked weekly and after each significance rainfall. The following items will be checked in particular: 1. Sediment traps will be checked regularly for sediment clean out. • 2. Gravel outlets will be checked regularly for sediment buildup which will prevent drainage. If the gravel is clogged with silt,it will be removed and cleaned or replaced. 3. Bathers will be checked regularly for undermining or deterioration of the bales. 4. Material removed from the sediment control devices will be placed in fill areas,covered over,and eventually stabili7M in accordance with the project specifications. 5. All seeded areas will be checked regularly to see that a good stand is maintained. Areas should be fertilized and reseeded as needed. Permanent Stabilization: All areas disturbed by construction will be stabilized with permanent seeding immediately following final grading. See attached specifications taken from Virginia Erosion Control Handbook 3 RD edition 1992. 8 PERMANENT SEEDING Definition: The establishment of perennial vegetative cover on distributed areas by planting seed. Site Specific Seeding Mixtures For Piedmont Area Total Lbs. Per Acre Minimum Care Lawn Commercial or Residential 175-200 lbs. -Kentucky 31 or Turf-Type Tall Fescue 95-100% -Improved Perennila Ryegrass 0-5% -Kentucky Bluegrass 0-5% High maintenance Lawn 200 250 lbs. -Kentucky 31 or Turf-Type Tall Fescue 100% General ,Slope,3:1 or,less -Kentucky 31 Fescue 128 lbs. -Red Top Grass 2 lbs. -Seasonal Nurse Crop* 20 lbs,. 150 lbs. Low Maintenance Slope Steeper than 3:1 -Kentucky 31 Fescue 108 lbs. -Red Top Grass 2 lbs. -Seasonal Nurse Crop* 20 lbs. -Crownvetch** 20 lbs. 150 lbs. 9 *Use seasonal nurse crop in accordance with seeding dates as listed below: February 16th through April Annual Rye May 1st through August 15 Fox-tail Millet August 16th through October Annual Rye November through February 15th Winter Rye **Substitute Sericea lespedeza for Crownvetch east of Farmville, Va. (May through Sept. use hulled Sericea,all other periods use unhulled Sericea). If Flatpea is used in lieu of Crownvetch, increase rate to 30 lbs./acre. All legume seed must be properly inoculated. Weeping Lovegrass may be added to any slope or low-maintenance mix during warmer seeding periods;add 10-20 lbs./acre in mixes. Seedbed Requirements: Vegetation should not be established on slopes that are unsuitable due to inappropriate soil texture,poor internal structure or internal drainage,volume of overland flow,or excessive steepness,until measures have been taken to correct these problems. To maintain a good stand of vegetation, the soil must meet certain minimum requirements as a growth medium. The existing soil must have these characteristics: 1. Enough fine grained material to maintain adequate moisture and nutrient supply. 2. Sufficient pore space to permit root penetration. A bulk density of 1.2 to 1.5 indicates that sufficient pore space is present A fine granular or crumb-like structure is also favorable. 3. Sufficient depth of soil to provide an adequate root zone. The depth to rock or impermeable layers such as hardpans shall be 12 inches or more,except on slopes steeper that 2:1 where the addition of soil is not feasible. 4. A favorable pH range for plant growth. If the soil is so acidic that a pH range of 6.0-7.0 cannot be attained by addition of pH-modifying materials, then the soil is considered an unsuitable environment for plant roots and further soil modification would be required. 10 5. Freedom from toxic amounts of materials harmful to plant growth. 6. Freedom from excessive quantities of roots, branches,large stones,large clods of earth,or trash of any kind. Clods and stones may be left on slopes steeper than 3:1 if they do not significantly impede good cepd soil contact. If any of the above criteria cannot be met, i.e., if the existing soil is too coarse, dense, shallow, acidic, or contaminated to foster vegetation, then topsoil shall be applied in accordance with TOPSOILING, Std. &Spec. 3.30 as described in the handbook. Necessary structural erosion and sediment control practices will be installed prior to seeding. Grading will be carried out according to the approved plan. Surfaces will be roughened in accordance with SURFACE ROUGHENING, Std. &Spec. 3.29 as described in the handbook. Soil Conditioners: In order to modify the texture, structure, or drainage characteristics of a soil, the following materials may be added to the soil: 1. Peat is a very costly conditioner,but works well. If added,it shall be sphagnum moss peat,hypnum moss peat,reed-sedge peat or peat humus,from fresh-water sources. Peat shall be shredded and conditioned in storage piles for at least six months after excavation. 2. Sand shall be clean and free of toxic materials. Sand modification is ineffective unless you are adding 80 to 90%sand on a volume basis. THis is extremely difficult to do on site. ff this practice is considered,consult a professional authority to ensure that it is properly done. • 11 3. Vermiculite shall be horticultural grade and free of toxic substances. It is an impractical modifier for larger acreage due to expense. 4. Raw Manure is more commonly used in agricultural applications. However,when stored properly and allowed to compost,it will stabilize nitrogen and other nutrients. Manure,in its composted form,is a viable soil conditioner,however,its use should be based on site-specific recommendations offered by a professional in this field. 5. Thoroughly rotted sawdust shall have 6 pounds of nitrogen added to each cubic yard and shall be free of stones,sticks,and toxic substances. 6. The use of treated sewage sludge has benefitted from continuing advancements in its applications in the agricultural community. When composted,it offers an alternative soil amendment Limitations include a Potentially undesirable pH(because of lime added during the treatment process)and the possible presence of heavy metals. This practice should be thoroughly evaluated by a professional and be used in accordance with any local,state, and federal regulations. Lime and Fertilizer: Lime and fertilizer needs should be determined by soil tests. Soil tests may be performed by the Cooperative Extension Service Soil Testing Laboratory at WI & SU, or by a reputable commercial laboratory. Information concerning the State Soil Testing Laboratory is available from county extension agents. 12 Under unusual conditions where it is not possible to obtain a soil test, the following soil amendments will be applied: Lime Coastal Plain: 2 tons/acre pulverized agricultural grade limestone(90 lbs./1,000 sq. ft.. Piedmont and Appalacian Region: 2 tons/acre agricultural grade limestone(90 lbs./1,000 sq.ft.). Note: An agricultural grade of limestone should always be used Fertilizer Mixed grasses and legumes: 1,000 lbs./acre 10-20-10 or equivalent nutrients (23 lbs./1,000 sq.ft.). Legume stands only: 1,000 lbs./acre 5-20-10 (23 lbs./1,000 sq.ft.)is preferred however, 1,000 lbs./acre of 10-20-10 or equivalent may be used. Grass stands only: 1,000 lbs./acre 10-20-10 or equivalent nutrients, (23 lbs./1,000 sq.ft.). Other fertilizer formulations,including slow-release sources of nitrogen(preferred from a water quality standpoint),may be used provided they can supply the same amounts and proportions of plant nutrients. 13 I Incorporation Lime and fertilizer shall be incorporated into the top 4-6 inches of the soil by discing or other means whenever possible. For erosion control,when applying lime and fertilizer with a hydroseeder,apply to a rough,loose surface. Seeding: Certified seed will be used for all permanent seeding whenever possible. Certified seed is inspected by the Virginia Crop Improvement Association or the certifying agency in other states. The seed must meet published state standards and bear an official"Certified Seed" label. ORGANIC MULCH MATERIALS AND APPLICATION RATES Mulches Rates Notes Straw or Hay 1 1/2-2 70-90 lbs Free from weeds and tons(min. per 1000 coarse matter.Must 2 tons for sq.ft. be anchored. Spread winter with mulch blower cover) or dry by hand. per acre Fiber Mulch Minimum 35 lbs. Do not use as much 1500 lbs. per 1,000 for winter cover or per acre sq.ft. during hot,dry periods.*Apply as slurry. Corn Stalks 4-6 tons 185-275 Cut or shredded in per acre lbs.per 4-6"lengths. Air- 1,000 sq. dried. Do not use ft. in fine turf areas. Apply with mulch blower or by hand. 14 Wood Chips 4-6 tons 185-275 Free of coarse per acre lbs.per matter. Air-dried. 1,000 sq. Treat with 12 lbs. ft. nitrogen per ton. Do not use in fine turf areas. Apply with mulch blower, chip handler,or by hand. Bark Chips 50-70 cu 1-2 cu. Free of coarse or yds.per yds.per matter. Air-dried. Shredded acre 1,000 sq. Do not use in fine Bark ft. turf areas. Apply with mulch blower, chip handler,or by hand. * When fiber mulch is the only available mulch during periods when straw should be used, apply at a minimum rate of 2,000 lbs./acre or 45 lbs./1,000 sq.ft. TEMPORARY SEEDING Definition: The establishment of a temporary vegetative cover on disturbed areas by seeding with appropriate growing annual plants. Purposes: 1. To reduce erosion and sediment by stabilizing disturbed areas that will not be brought to final grade for a period of more that 30 days. 2. To reduce damage from sediment and runoff to downstream or off-site areas,and to provide protection to bare soils exposed during construction until permanent vegetation or other erosion control measures can be established. Conditions Where Practice Applies: Where exposed soil surfaces are not to be fine-graded for periods longer than 30 days. Such areas include denuded areas, soil stockpiles ,dikes,dams, sides of sediment,basins, temporary roadbanks, etc. (see MS #1 and MS #2). A permanent vegetative cover shall be applied to areas that will be left dormant for a period of more than one year. 15 Planning Considerations: Sheet erosion, caused by the impact of rain on bare soil, is the source of most fine particles in sediment. To reduce this sediment load in runoff,the soil surface itself should be protected. The most efficient and economical means of controlling sheet and rill erosion is to establish vegetative cover. Annual plants which sprout rapidly and survive for only one growing season are suitable for establishing temporary vegetative cover. Temporary seeding is encouraged whenever possible to aid in "controlling" construction sites. Temporary seeding also prevents costly maintenance operations on other erosion control systems. For example, sediment basin clean outs will be reduced if the drainage area of the basin is seeded where grading and construction are not taking place. Perimeter dikes will be more effective if not choked with sediment. Temporary seeding is essential to preserve the integrity of earthen structures used to control sediment,such as dikes,diversions,and the banks and dams of sediment basins. Proper seedbed preparation and the use of quality seed are important in this practice just as in permanent seeding. Failure to carefully follow sound agronomic recommendations will often result in an inadequate stand of vegetation that provides little or no erosion control. Specifications: Prior to seeding,install necessary erosion control practices such as dikes,waterways,and basins. Plant Selection: Select plants appropriate to the season and site conditions from Tables 3.31-B and 3.31-C. Note that Table 3.31-B presents plants which can be used without extensive evaluation of site conditions;Table 3.31-c presents more in-depth information on the plant materials. 16 Seedbed Preparation: To control erosion on bare soil surfaces, plants must be able to germinate and grow. Seedbed preparation is essential. 1. Liming: An evaluation should be conducted to determine if lime is necessary for temporary seeding. In most soils,it takes up to six months for a pH adjustment to occur following the application of lime. Therefore,it may be difficult to justify the cost of liming a temporary site,especially when the soil will later be moved and regraded. The following table may be used to determine the actual need along with suggested application rates. Liming Requirements For Temporary Sites Recommended Application ,pH Test of Agricultural Limestone below 4.2 3 tons per acre 4.2 to 5.2 2 tons per acre 5.2 to 6 1 ton per acre 2. Fertilizer: Shall be applied as 600 lbs./acre of 10-20-10(14 lbs./1,000 sq.ft)or equivalent nutrients. Lime and fertilizer shall be incorporated into the top 2 to 4 inches of the soil if possible. 3. Surface Roughening: If the area has been recently loosened or disturbed, no further roughening is required. When the area is compacted,crusted,or hardened,the soil surface shall be loosened by discing,raking,harrowing,or other acceptable means. 17 4. Tracking: Tracking with bulldozer cleats is most effective on sandy soils. This practice often causes undue compaction of the soil surface, especially in clayey soils,and does not aid plant growth as effectively as other methods of surface roughening. Seeding: Seed shall be evenly applied with a broadcast seeder, drill, multipacker seeder or hydroseeder. Small grains shall be planted no more than one inch deep. Grasses and legumes shall be planted with no less than 1/4"soil cover. Mulching: 1. Seeding made in fall for winter cover and during hot and dry summer months shall be mulched according to MULCHING,Std.&Spec. 3.35 as described in the handbook,except that hydromulches (fiber mulch)will not be considered adequate. Straw mulch should be used during these periods. 2. Temporary seeding made under favorable soil and site conditions during optimum spring and fall seeming dates may not require mulch. Re-seeding: Areas which fail to establish vegetative cover adequate to prevent rill erosion will be reseeded as soon as such areas are identified. 18 i_ TABLE 3.31-B ACCEPTABLE TEMPORARY SEEDING PLANT MATERIALS QUICK REFERENCE FOR ALL REGIONS" Rate Planting Dates Species (lbs./acre) Sept. 1 -Feb. 15 50/50 Mix of 50-100 Annual Ryegrass Lolium multi- forum&Cereal (Winter)Rye Serale cereale Feb. 16-Apr. 30 Annual Ryegrass 60-100 Lolium multi-flomm May 1 -Aug. 31 German Millet 50 Setaria italica 19 Table 3.31-C TEMPORARY SEEDING PLANT MATERIALS, SEEDING RATES,AND DATES Species Seeding Rate OATS 3bu. (up to 100 2 lbs.per (Avena sativis) lbs.,not less 1,000 sq.ft. than 50 lbs.per acre RYE d 2 bu. (up to 110 2.5 lbs.per (Secale cereale) lbs.,not less 1,000 sq.ft. than 50 lbs.per acre GERMAN MILLET 50 lbs.per acre approximately (Setaria italics) 1 lb.per 1,000 sq.ft. ANNUAL RYEGRASS c 60 lbs.per acre 1 1/2 lbs.per (Latium multi- 1,000 sq.ft. flonun) WEEPING LOVEGRASS 15 lbs.per acre 5 1/2 oz.per (Eragrostis 1,000 sq.ft. curvula) KOREAN LESPEDEZA c 25 lbs.per acre approximately (Lespedeza 1 1/2 lbs.per stipulaces) 1,000 sq.ft. c May be used as a cover crop with spring seeding. d Maybe used as a cover crop with fall ceding. 20 Table 3.31-C(Cont.) TEMPORARY SEEDING PLANT MATERIALS. SEEDING RATES,AND DATES NORTH a SOUTH b 3/1 5/1 8/15 2/15 5/1 9/1 to to to to to to Species 4/30 8/15 11/1 4/30 9/1 11/15 OATS X - - X - - (Avena sativa) RYE (Secale cereale) X - X X - X GERMAN MILLET (Setaria italics) - X - - X - ANNUAL RYEGRASS (Lolium multi- florum) X - X X - X WEEPING LOVEGRASS (Eragrostis curvula) - X - - X KOREAN LESPEDEZA (Lespedeza stipulacea) X X - X X - a Northern Piedmont and Mountain region b Southern Piedmont and Coastal Plain X May be planted between these dates -May not be planted between these dates 21 Table 3.31-C(Cont) TEMPORARY SEEDING PLANT MATERIALS, SEEDING RATES,AND DATES Species Plant Characteristics OATS Use spring varieties(e.g.Noble) (Avena sativa) RYE Use for late fall seedings,winter (Secale cereale) cover. Tolerates cold and low moisture. GERMAN MILLET Warm-season annual. Dies at first (Setaria italica) frost. May be added to sununer mixes. ANNUAL RYEGRASS May be added in mixes. Will mow (Lolium multi- out of most stands. fllorum) WEEPING LOVEGRASS Warm-season perennial. May bunch. (Eragrostis Tolerates hot,dry slopes and acid, curvula) infertile soils. May be added to mixes. KOREAN LESPEDEZA Warm season annual legume. Tolerates (Lespedeza acid soils. May be added to mixes. stipulacea) li 22