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1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />PENSKE TRUCK LEASING EVERETT ONSITE IMPROVEMENTS <br />CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN <br />and other plants, the fill should be less. <br />Sitts & Hill Engineers, Inc. <br />Job Number 17,710 <br />When there are major changes in grade, it may become necessary to supply air to <br />the roots of plants. This can be done by placing a layer of gravel and a file system <br />over the roots before the fill is made. A file system protects a tree from a raised <br />grade. The tile system should be laid out on the original grade leading from a dry <br />well around the tree trunk. The system should then be covered with small stones to <br />allow air to circulate over the root area. <br />Lowering the natural ground level can seriously damage trees and shrubs. The <br />highest percentage of the plant roots are in the upper 12 inches of the soil and cuts <br />of only 2-3 inches can cause serious injury. To protect the roots it may be neces- <br />sary to terrace the immediate area around the plants to be saved. If roots are <br />exposed, construction of retaining walls may be needed to keep the soil in place. <br />Plants can also be preserved by leaving them on an undisturbed, gently sloping <br />mound. To increase the chances for survival, it is best to limit grade changes and <br />other soil disturbances to areas outside the dripline of the plant <br />. Excavations -Protect trees and other plants when excavating for drainfields, <br />power, water, and sewer lines. Where possible, the trenches should be routed <br />around trees and large shrubs. When this is not possible, it is best to tunnel under <br />them. This can be done with hand tools or with power augers. If it is not possible to <br />route the trench around plants to be saved, then the following should be observed: <br />Cut as few roots as possible. When you have to cut, cut clean. Paint cut root <br />ends with a wood dressing like asphalt base paint if roots will be exposed for <br />more than 24-hours. <br />,, Backfill the trench as soon as possible. <br />b Tunnel beneath root systems as close to the center of the main trunk to pre- <br />serve most of the important feeder roots. <br />Some problems that can be encountered with a few specific trees are: <br />. Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir <br />do not readily adjust to changes in environment and special care should be taken <br />to protect these trees. <br />. The windthrow hazard of Pacific silver fir and madrona is high, while that of <br />Western hemlock is moderate. The danger of windthrow increases where dense <br />stands have been thinned. Other species (unless they are on shallow, wet soils <br />less than 20 inches deep) have a low windthrow hazard. <br />. Cottonwoods, maples, and willows have water -seeking roots. These can cause <br />trouble in sewer lines and infiltration fields. On the other hand, they thrive in high <br />moisture conditions that other trees would not <br />. Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, <br />2014 Stormwater Management Manual for Westem Washington <br />Volume 11- Chapter 4 - Page 267 <br />SITTS & HILL ENGINEERS, INC. 18 <br />' TACOMA, WASHINGTON <br />