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HomeMy WebLinkAboutSDP200500005 Plan - E&S 2005-01-31 'wore Pet Supplies Plus ■ '; ° f 1-�� " . Erosion and Sediment Control Narrative 28 March 2005 Project Description COMMtiNl i` �- � i The project site is located on the northwest side of Seminole Trail, U.S. Route 29, at its intersection with Greenbrier Drive. This site is currently an existing developed site. A restaurant structure was formerly located on the site that has been previously demolished. All paving, the concrete building pad, sidewalks, and curb remain in place. The site is approximately 1.03 acres, all of which is proposed for disturbance. This project will provide a new commercial building, primarily for Pet Supplies Plus, but a small of the building will be rented to a yet- to -be- determined tenant. This project will include asphalt parking, concrete sidewalks, and a concrete dumpster pad. Surface runoff from the site will discharge through curb and drop inlets, and a pipe system. An existing 48 -inch concrete pipe conveys storm water from upstream sources through the site. To provide an adequate foundation for the new building the 48 -inch pipe must be relocated as it passes through the site. Runoff from the site will be directed toward this relocated 48 -inch pipe. Adjacent Areas The site is bounded on the northwest by the Super 8 Motel and on the northeast by WM Management LTD including a gas pipeline owned by Charlottesville Department of Public Works. U.S. 29 is located on the southeast side and across Greenbrier Drive on the southwest side is Whiting Oil Company. Existing Site Conditions The site was previously developed for commercial use. Presently the site is 85 percent impervious. After the site has been redeveloped by Pet Supplies Plus the site will be 81 percent impervious. Offsite Areas No offsite areas are proposed to be disturbed. Soils The Albemarle County Soil Survey identifies the soils on this site as urban land where the land use is over 80 percent impervious. Critical Erosion Areas There are no existing critical slopes that will be disturbed. Erosion and Sediment Control Measures Unless otherwise indicated, all erosion and sediment control practices will be constructed and maintained according to minimum standards and specifications of the Virginia Erosion and Sediment Control Handbook (1992). Pet Supplies Plus Page 2 Erosion and Sediment Control Plan 28 March 2005 Minimum Standards Installation of all erosion and sediment control measures shall conform to the 1992 Virginia Erosion and Sediment Control Handbook. Critical measures required on this project are summarized below: 1. 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 for longer than 30 days. Permanent stabilization shall be applied to areas that are to be left dormant for more than one year. 2. During construction of the project, soil stockpiles and borrow areas 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 borrow areas and soil intentionally transported from the project site. 3. 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 is uniform, mature enough to survive and will inhibit erosion. 4. Sediment control measures intended to trap sediment shall be installed as a first step in any land - disturbing activity and shall be made functional before upslope land disturbance takes place. 5. Stabilization measures shall be applied to earthen structures such as dams, dikes and diversions immediately after installation. 6. Cut and fill slopes shall be designed and 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. 7. Concentrated runoff shall not flow down cut or fill slopes unless contained within an adequate temporary or permanent channel, flume or slope drain structure. 8. Whenever water seeps from a slope face, adequate drainage or other protection shall be provided. 9. All storm sewer inlets that are made 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. 10. Before newly constructed stormwater conveyance channels or pipes are made operational, adequate outlet protection and any required temporary or permanent channel lining shall be installed in both the conveyance channel and receiving channel. 11. When installing the drop inlets and the new piping system that will replace the existing on -site 48 -inch pipe, a pumping system will be installed to pump any off -site storm water around the construction site. The upstream end of the 48 -inch pipe will be temporarily blocked (a supported plywood barrier or other suitable method could be used) and the accumulated water will be pumped back into the 48 -inch pipe at a downstream location. At no time will accumulated Pet Supplies Plus Page 3 Erosion and Sediment Control Plan 28 March 2005 runoff be allowed to drain to the existing downstream 48 -inch pipe. Accumulated runoff within the construction trench will be allowed to dry before continuing with installation of the drop inlets and pipe. 12. Underground utility lines shall be installed in accordance with the following standards in addition to other applicable criteria: a. No more than 500 linear feet of trench may be opened at one time. b. Excavated material shall be placed on the uphill side of trenches. 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 off -site property. d. Material used for backfilling trenches shall be properly compacted in order to minimize erosion and promote stabilization. e. Restabilization shall be accomplished in accordance with these regulations. f. Applicable safety regulations shall be complied with. 13. 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 surface, the road surface 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. Street washing shall be allowed only after sediment is removed in this manner. This provision shall apply to individual development lots as well as to larger land - disturbing activities. 14. All temporary erosion and sediment control measures shall be removed within 30 days after final site stabilization or after the temporary measures are no longer needed, unless otherwise authorized by the local program 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. 15. Properties and waterways downstream from development sites shall be protected from sediment deposition, erosion and damage due to increases in volume, velocity and peak flow rate of stormwater runoff for the stated frequency storm of 24 -hour duration in accordance with the following standards and criteria: a. Concentrated stormwater runoff leaving a development site shall be discharged directly into an adequate natural or man -made receiving channel, pipe or storm sewer system. For those sites where runoff is discharged into a pipe or pipe system, downstream stability analyses at the outfall of the pipe or pipe system shall be performed. b. Adequacy of all channels and pipes shall be verified in the following manner: Pet Supplies Plus Page 4 Erosion and Sediment Control Plan 28 March 2005 (1) The applicant shall demonstrate that the total drainage area to the point of analysis within the channel is one hundred times grater than the contributing drainage area of the project in question; or (2) (a) Natural channels shall be analyzed by the use of a two -year storm to verify that stormwater will not overtop channel banks nor cause erosion of channel bed or banks; and (b) All previously constructed man -made channels shall be analyzed by the use of a ten -year storm to verify that stormwater will not overtop its banks and by the use of a two -year storm to demonstrate that stormwater will not cause erosion of channel bed or banks; and (c) Pipes and storm sewer systems shall be analyzed by the use of a ten -year storm to verify that stormwater will be contained within the pipe or system. c. If existing natural receiving channels or previously constructed man -made channels or pipes are not adequate, the applicant shall: (1) Improve the channel to a condition where a ten -year storm will not overtop the banks and a two -year storm will not cause erosion to the channel bed or banks; or (2) Improve the pipe or pipe system to a condition where the ten -year storm is contained within the appurtenances; or (3) Develop a site design that will not cause the pre- development peak runoff rate from a two -year storm to increase when runoff outfalls into a natural channel or will not cause the pre - development peak runoff rate from a ten -year storm to increase when runoff outfalls into a man -made channel; or (4) Provide a combination of channel improvement, stormwater detention or other measures which is satisfactory to the plan- approving authority to prevent downstream erosion. d. The applicant shall provide evidence of permission to make the improvements. e. All hydrologic analyses shall be based on the existing watershed characteristics and the ultimate development of the subject project. f. If the applicant chooses an option that includes stormwater detention he shall obtain approval from the locality of a plan for maintenance of the detention facilities. The plan shall set forth the maintenance requirements of the facility and the person responsible for performing the maintenance. g. Outfall from a detention facility shall be discharged to a receiving channel, and energy dissipators shall be placed at the outfall of all detention facilities as necessary to provide a stabilized transition from the facility to the receiving channel. h. All on -site channels must be verified to be adequate. Pet Supplies Plus Page 5 Erosion and Sediment Control Plan 28 March 2005 i. Increased volumes of sheet flows that may cause erosion or sedimentation on adjacent property shall be diverted to a stable outlet, adequate channel, pipe or pipe system, or to a detention facility. j. In applying these stormwater runoff criteria, individual lots or parcels in a residential, commercial or industrial development shall not be considered to be separate development projects. Instead, the development, as a whole, shall be considered to be a single development project. Hydrologic parameters that reflect the ultimate development condition shall be used in all engineering calculations. k. All measures used to protect properties and waterways shall be employed in a manner which minimizes impacts on the physical, chemical and biological integrity of rivers, streams and other waters of the state. Since the Pet Supply Plus site is 85 percent impervious prior to development and 81 percent impervious after development is completed, there will be a decrease in the overall quantity of storm water runoff, both discharge rate and volume. Therefore, additional storm water detention is not warranted. Furthermore, this development will result in an improvement to the overall water quality discharging from the site. Management Strategies 1. Construction should be sequenced so that grading operations can begin and end as quickly as possible. 2. The job contractor shall be responsible for the installation and maintenance of all erosion and sediment control practices. 3. Sediment trapping measures shall be installed as a first step in grading and shall be seeded and mulched immediately following installation. 4. Areas which are not to be disturbed shall be clearly marked by flags, signs, etc. Temporary Stabilization Measures 1. Temporary Construction Entrance - E &S Std. & Spec. 3.02 A paved Temporary Construction Entrance and temporary diversion dike shall be constructed where shown on the plans. See detail per County Design Standards Manual, Chapter 5, Appendix WR -1. 2. Silt Fence - E &S Std. & Spec. 3.05 Silt Fence shall be installed as shown on the plans. 3. Storm Drain Inlet Protection - E &S Std. & Spec. 3.07 Storm Drain Inlet Protection shall be installed as shown on the plans. s i Pet Supplies Plus Page 6 Erosion and Sediment Control Plan 28 March 2005 4. Temporary Seeding - E & S Std. & Spec. 3.31 Temporary vegetative cover is to be established on rough graded areas that will not be brought to final grade for a year or less. Such areas include denuded areas, soil stockpiles, dikes, sides of sediment basins, temporary road banks, cut slopes, etc. All areas which are to be temporarily seeded shall be seeded in accordance with Minimum Standards No. 1, and shall be seeded with annual rye grass at 1 -1/2 lbs /1,000 sq. ft. (including liming, mulching, fertilizing as required). 5. Dust Control - E &S Std. & Spec. 3.39 Dust Control practices shall be employed to prevent surface and air movement of dust from exposed soil surfaces and reduce the presence of airborne substances which may be harmful or injurious to human health, welfare, or safety, or to animal or plant life. Permanent Stabilization Measures 1. Permanent Seeding: E &S Std. & Spec. 3.32 All areas disturbed by construction, except areas designated for temporary seeding, will be stabilized with permanent seeding immediately following finish grading. Unless otherwise specified, permanent seeding will be done with Kentucky 31 Fescue and a nurse crop of annual rye (including liming, mulching and fertilizing as required) according to E &S Std. and Spec. 3.32 of the 1992 Virginia Erosion and Sediment Control Handbook. 2. Mulching - E &S Std. & Spec. 3.35 Mulch shall be applied to all seeded areas in accordance with E &S Std. & Spec. 3.35. Organic mulches such as straw, wood chips (from trees cleared on site), bark chips and shredded bark may be used. Fiber mulch may be used at times other than dry summer months or late fall, and it may be used to anchor straw mulch. The use of chemical mulches and soil binders will be allowed. Rates of application shall conform to Table 3.35 -A of the Virginia Erosion and Sediment Control Handbook. Mulch shall be firmly anchored and checked often for erosion. Any erosion noted shall be quickly rectified and additional mulch applied. Maintenance All erosion and sediment control measures will be checked weekly, after each runoff - producing rainfall event and repaired as necessary. Seeded areas will be checked regularly to ensure that a good stand is maintained. Reseeding and straw mulch will be applied as necessary.