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HomeMy WebLinkAboutStormwaterGruye Stormwater Management Minimum Requirement #2 For Bridge Proposal on Parcel 901193004 Construction Stormwater Pollution Prevention Twelve Elements 1. Mark Clearing Limits There is no clearing proposed for this project. Four small (12-inch) holes will be dug within an existing roadbed for footings. The retired truck scale will be laid upon the footings, spanning the wetland. 2. Establish Construction Access Construction will take place in the immediate vicinity of where the bridge will be placed. A concrete truck will pump into the footing forms from a pullout adjacent to Eaglemount Road. The bridge bed will be moved into place by a professional heavy equipment operator using a crane from the Eaglemount pullout. 3. Control Flow Rates This element does not apply to this small project. 4. Install Sediment Controls Straw wattles will be placed between the footings and the wetland to avoid sediment entering the wetland during construction as per BMP C235. • Use wattles: o In disturbed areas that require immediate erosion protection. o On exposed soils during the period of short construction delays, or over winter months. o On slopes requiring stabilization until permanent vegetation can be established. • The material used dictates the effectiveness period of the wattle. Generally, Wattles are typically effective for one to two seasons. • Prevent rilling beneath wattles by properly entrenching and abutting wattles together to prevent water from passing between them. Design Criteria • Install wattles perpendicular to the flow direction and parallel to the slope contour. • Narrow trenches should be dug across the slope on contour to a depth of 3- to 5-inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall, the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the wattle. • Start building trenches and installing wattles from the base of the slope and work up. Spread excavated material evenly along the uphill slope and compacted using hand tamping or other methods. • Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. • Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. • Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. • If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. • Wooden stakes should be approximately 3/4 x 3/4 x 24 inches min. Willow cuttings or 3/8-inch rebar can also be used for stakes. • Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding above the wattle. 5. Stabilize Soils There will be no freshly exposed soil on the site. Small holes will be excavated for forms. And the bridge bed will be placed over the top. 6. Protect Slopes The project will take place on level ground. 7. Protect Drain Inlets There are no drain inlets on or near the site. 8. Stabilize Channels and Outlets There will be no temporary channels or ditches associated with the project. 9. Control Pollutants BMP C131 for concrete handling will be followed. • Wash concrete truck drums at an approved off-site location or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground (including formed areas awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP C154: Concrete Washout Area for information on concrete washout areas. o Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated concrete washout areas as allowed in BMP C154: Concrete Washout Area. • Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheelbarrows) into designated concrete washout areas or into formed areas awaiting concrete pour. • At no time shall concrete be washed off into the footprint of an area where an infiltration feature will be installed. • Wash equipment difficult to move, such as concrete paving machines, in areas that do not directly drain to natural or constructed stormwater conveyance or potential infiltration areas. • Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly (without detention or treatment) to natural or constructed stormwater conveyances. • Contain washwater and leftover product in a lined container when no designated concrete washout areas (or formed areas, allowed as described above) are available. Dispose of contained concrete and concrete washwater (process water) properly. • Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters. • Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment requirements. 10. Control Dewatering It is unlikely that groundwater will be encountered during this project as the holes will be relatively shallow and placed within an existing roadbed. 11. Maintain BMPs App appropriate BMP’s will be installed prior to the work and will be removed within 30 days of the commencement of work. 12. Manage the Project The BMP Manual, Best Management Practices from Current Edition of Ecology Stormwater Management Manual, will be reviewed prior to the onset of work and all BMPs that apply will be put into place prior to the start of work.