Shelbyville, KY Stormwater Best Management Practices. Section 2 EROSION PREVENTION AND SEDIMENT CONTROL PLAN

Transcription

1 Section 2 EROSION PREVENTION AND SEDIMENT CONTROL PLAN 2.1 Requirements The City of Shelbyville, KY will require an Erosion Prevention and Sediment Control (EPSC) Plan for most types of development construction. When preparing the EPSC Plan, the design engineer and/or developer should determine the best practices to protect active construction sites by selecting source control and sediment containment practices. In doing so, most erosion problems can be avoided and sediment containment issues can be addressed prior to construction disturbances. Site characteristics such as soil types, topography, slopes, and geography, and construction methods should be thoroughly reviewed when selecting BMPs to implement throughout the life of the project. The design team should be mindful of how the site is changing throughout the project so that BMPs can be repaired, modified or replaced with a more suitable practice. For more information regarding the required elements of an EPSC Plan, refer to Appendix C EPSC Plans. 2.2 Minimize Disturbed Areas Some important decisions must be made prior to BMP selections for a proposed construction site. Construction planning and sequencing are the least expensive methods to reduce and control erosion and sediment. The following points should be considered when to minimize disturbed areas: 1. Do not disturb areas of the construction site that are not scheduled for improvements and keep existing vegetation, even if it is scheduled to be removed, for as long as possible. 2. Carefully schedule and phase construction. Avoid grading during wet months (December through May). Use temporary cover measures (seed or mulch) whenever construction is halted for an extended period. 3. Phase site grading to limit the amount and time of an area s exposure. Exposed areas should be stabilized immediately following the completion of grading. 4. Plan and implement permanent structures throughout the earlier phases of the project. This will maximize the utility practice s usefulness and help with erosion prevention and sediment containment. 2-1

2 5. Avoid delays and work expeditiously on any part of the site. Install landscaping fixture upon the completion of any sequence and prior to moving on to the next phase. Any exposed soil is subject to erosion and sediment transport, even by a single rain drop. Designers and contractors should make every effort to stabilize the following susceptible areas at a construction site prior to and throughout construction: Slopes Highly erosive soils Construction entrances and exits Stream channels Soil stockpiles 2.3 Site Perimeter Controls The contractor must set site perimeter controls to protect areas downstream from erosion, sediment and flooding problems. Area of Concern Disturbed areas or slopes that drain toward adjacent properties Stabilizing area after grading has been completed Off site flows that enter the constructions site Concentrated flows that leave the construction site Site Perimeter Control Continuous berms, silt fences, sandbags Mulching, seeding, planting, emulsifiers, or a combination of two or more Continuous berms, earth dikes, drainage swales and lined ditches Outlet control measures that will dissipate velocities Additional controls within the interior of construction site should supplement perimeter controls once rough grading is complete. 2.4 Internal Erosion and Drainage Design Once the perimeter controls have been selected, the issue of internal erosion and drainage controls must be addressed. Internal practices are typically more time consuming and labor intensive since they will be used in close proximity of construction activities. They are required early in the project until permanent practices can be implemented. Some of the internal erosion and drainage design practices to be used include: Check dams, geotextile mats, and under extreme circumstances concrete channel lining. 2-2

3 Terracing at regular intervals. Slope benches or ditches. Surface roughening or temporary seeding. 2.5 Maintenance and Inspection Constant inspection and maintenance of the selected practices are critical towards the success of preventing erosion and sediment transport. Maintaining a daily or weekly checklist of practices to inspect for deficiencies of those practices are critical to the success of preventing erosion and sediment displacement. A good way to ensure that all practices will be properly utilized is for the contractor to arrange a pre-construction meeting with the City of Bowling Green s Stormwater Inspector. This meeting should take place after the Notice to Proceed, but prior to the mobilization of equipment. One of the most critical aspects of maintaining the construction site s BMPs is to have a plan on when sediment should be removed from the utilized practices, and where should it be placed. The BMPs in this manual often suggest when sediment should be removed from structures, but the contractor should demonstrate sound judgment in maintaining the structures more frequently if necessary. A sound inspection and maintenance strategy should include the following: 1. Verify that sediment-laden stormwater is directed to temporary sediment traps or basins. Verify that sediment basins and traps are at low points below disturbed areas. 2. Protect all existing or newly installed storm drainage structures from sediment clogging by providing inlet protection for area drains and curb inlets. Stormwater inlet protection can utilize sand bags, sediment traps, or other similar devices. 3. Excavate permanent stormwater detention ponds early in the project, use them as sedimentation ponds during construction, remove accumulated sediment, and landscape the ponds when the upstream drainage area is stabilized. 4. Inspect temporary sediment barriers such as silt fences, rock filters, and continuous berms after every rainfall. These barriers should only be used in areas where sheet flow runoff occurs. They are ineffective if the runoff is concentrated into rill or gully flow. 5. Internal outfalls must also be protected to reduce scour from high velocity flows leaving pipes or other drainage facilities. 2-3

4 2.6 EPSC Preparation Guidance The EPSC Plan will consist of a site plan sheet at a scale suitable for illustrating the elements that will control erosion and sediment, and a set of directions in narrative form within the contract documents. The Owner of the development or project will be responsible for preparing the EPSC Plan. Whether it is the Owner, designer or a subcontractor to develop the plans, the matter is left up to the Owner. The plans will illustrate which practices shall be used and their placement within the project. The narrative will explain decisions concerning erosion and sediment control, and when required, show why those measures were selected, either by calculations or sound engineering judgment. This will allow the reviewer to make informed decisions on the efficiency and practicality of the BMPs selected. The level of detail shown on the drawings depends on the magnitude of the project. For single lots, a sketch may be all that is required to show the inspector. However for larger developments, such as a shopping center or industrial park, a plan sheet at an appropriate scale shall be submitted to the City for review. Here is a list of typical notes that should be added to every EPSC plan, large and small. 1. As a minimum, all erosion and sediment control practices will be constructed and maintained according to the standards located in the City of Shelbyville s BMP Manual, Stormwater Ordinances, and as required by state and federal laws. 2. A copy of the approved Erosion Prevention and Sediment Control Plans shall be maintained at the project site at all times. This copy shall be presented to the City of Shelbyville s representatives upon request. 3. Prior to commencing land-disturbing activities in any area not on the approved erosion and sediment control plan, the contractor shall submit a supplementary erosion control plan to the City of Shelbyville for review and approval. 4. All erosion and sediment control measures are to be placed prior to or as the first step in clearing and grading. The contractor is responsible for any additional erosion control measures necessary to prevent erosion and sedimentation as determined by the City of Shelbyville. 5. During dewatering operations water must be pumped through an approved filtering device. The City of Shelbyville may suspend dewatering operations if pollution is observed. 6. The contractor shall inspect all erosion and sediment control devices at least once a week and at least once a day during rainfall events. The contractor shall perform any repairs or maintenance immediately in order to ensure effective erosion and sediment control. 7. The contractor shall maintain a record of all inspections and maintenance activities at the project site. This record shall be made available to the City of Shelbyville upon request. 2-4

5 2.7 Storm Water Pollution Protection Plan Requirements of the Storm Water Pollution Protection Plan (SWPPP) are discussed in Appendix C BMP Plans. 2-5