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INTERWEST — EVERETT CONTRACTOR'S YARD INTERIM FILL PROJECT Sitts & Hill Engineers, Inc. <br />CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN Job Number 17,733 <br />' BMP C123: Plastic Covering <br />Purpose <br />' Plastic covering provides immediate, short-term erosion protection to slopes and dis- <br />turbed areas. <br />Conditions of Use <br />' Plastic covering may be used on disturbed areas that require cover measures for less <br />than 30 days, except as stated below. <br />' . Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: <br />The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable <br />for long-term (greater than six months) applications. <br />. Due to rapid runoff caused by plastic covering, do not use this method upslope of <br />areas that might be adversely impacted by concentrated runoff. Such areas include <br />steep and/or unstable slopes. <br />' . Plastic sheeting may result in increased runoff volumes and velocities, requiring <br />additional on -site measures to counteract the increases. Creating a trough with <br />wattles or other material can convey clean water away from these areas. <br />' . To prevent undercutting, trench and backfill rolled plastic covering products. <br />. While plastic is inexpensive to purchase, the added cost of installation, main- <br />tenance, removal, and disposal make this an expensive material, up to $1.50-2.00 <br />per square yard. <br />. Whenever plastic is used to protect slopes install water collection measures at the <br />base of the slope. These measures include plastic -covered berms, channels, and <br />pipes used to covey clean rainwater away from bare soil and disturbed areas. Do <br />not mix clean runoff from a plastic covered slope with dirty runoff from a project. <br />. Other uses for plastic include: <br />1. Temporary ditch liner. <br />' 2. Pond liner in temporary sediment pond. <br />3. Liner for bermed temporary fuel storage area if plastic is not reactive to the <br />type of fuel being stored. <br />4. Emergency slope protection during heavy rains. <br />5. Temporary drainpipe ("elephant trunk") used to direct water. <br />' 2014 Stormwater Management Manual for Westem Washington <br />' Volume II - Chapter 4 - Page 294 <br />SITTS & HILL ENGINEERS, INC. 41 <br />' TACOMA, WASHINGTON <br />