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1 <br />1 <br />PENSKE TRUCK LEASING EVERETT ONSITE IMPROVEMENTS <br />CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN <br />Sitts & Hill Engineers, Inc. <br />Job Number 17,710 <br />BMP C101: Preserving Natural Vegetation <br />Purpose <br />The purpose of preserving natural vegetation is to reduce erosion wherever practicable. <br />Limiting site disturbance is the single most effective method for reducing erosion. For <br />example, conifers can hold up to about 50 percent of all rain that falls during a storm. Up <br />to 20-30 percent of this rain may never reach the ground but is taken up by the tree or <br />evaporates. Another benefit is that the rain held in the tree can be released slowly to the <br />ground after the storm. <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />Conditions of Use <br />Natural vegetation should be preserved on steep slopes, near perennial and intermittent <br />watercourses or swales, and on building sites in wooded areas. <br />. As required by local governments. <br />. Phase construction to preserve natural vegetation on the project site for as long as <br />possible during the construction period. <br />Design and Installation Specifications <br />Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and <br />vines. <br />The preservation of individual plants is more difficult because heavy equipment is gen- <br />erally used to remove unwanted vegetation. The points to remember when attempting to <br />save individual plants are: <br />. Is the plant worth saving? Consider the location, species, size, age, vigor, and the <br />work involved. Local governments may also have ordinances to save natural veget- <br />ation and trees. <br />. Fence or clearly mark areas around trees that are to be saved. It is preferable to <br />keep ground disturbance away from the trees at least as far out as the dripline. <br />Plants need protection from three kinds of injuries: <br />• Construcbon Equipment- This injury can be above or below the ground level. <br />Damage results from scarring, cutting of roots, and compaction of the soil. Placing <br />a fenced buffer zone around plants to be saved prior to construction can prevent <br />construction equipment injuries. <br />. Grade Changes - Changing the natural ground level will alter grades, which affects <br />the plant's ability to obtain the necessary air, water, and minerals. Minor fills usu- <br />ally do not cause problems although sensitivity between species does vary and <br />should be checked. Trees can typically tolerate fill of 6 inches or less. For shrubs <br />2014 Stormwater Management Manual for Western Washington <br />Volume 11- Chapter 4 - Page 266 <br />SITTS & HILL ENGINEERS, INC. 17 <br />TACOMA, WASHINGTON <br />