Laserfiche WebLink
<br />'" <br /> <br />.J <br /> <br />STRATUM GROUP <br />1451 Grant Street, Bellingham, W A 98225 <br />Phone (360) 714-9409 <br /> <br />July 31, 2005 <br /> <br />Michael Havens <br /> <br />Re: Clearing and Storm Water Impacts <br />Tax Parcel 701153016, Toandos Road <br />Jefferson County, Washington <br />rru.",QS _ ~ Pl.-V 0<0- oo"-i7"l <br />Dear Mr. Havens: <br /> <br />Clearing of trees from the site as described by you in your email to me will have no impact on <br />storm water. Most of the site is underlain by sand and gravel (advance glacial outwash and/or <br />transition beds). These soils are very well draining with very rapid permeability. Clearing of trees <br />from areas underlain by these well-drained soils will not lead to any increase in storm water flow <br />on the surface. The ravine on the north side of the propertY and the ravine south of the property <br />are dry ravines with no indication of flowing water at any time. These features appear to be <br />remnant outwash ravines and no longer transmit water even during extreme rainfall events. <br /> <br />The following recommendations are made to ensure that the clearing will not have any negative <br />impacts to storm water or to slope stability. The first recommendation is the same as the <br />recommendation I made in my initial report. The other recommendations are based on my <br />understanding of the geology of the site and slopes on the site. <br /> <br />Ground cover vegetation within the ISO-foot landslide buffer should not be disturbed. <br />Trees within the buffer may be thinned or limbed for view purposes. However, if the trees <br />are thinned, trees should be left on at least 30-foot centers. The mature trees on the slope <br />are hydrologically mature and as such will greatly reduce the risk of the upper slope from <br />becoming saturated. The trees also playa significant role in landslide deposit stability. <br />That is large wood debris greatly slows the rate at which erosion of a landslide debris pile <br />at the base of the bluff in the event that another landslide takes place. <br /> <br />No clearing of trees should take place within the pipe stem portion of the east end of the <br />property as this area is underlain by glacial till and clearing in this area may lead to an <br />increase in storm water flow. Clearing in this area may be appropriate subject to further <br />on-site review. <br /> <br />No clearing of tress should take place on the steep slope between the access road and the <br />southeast comer of the property without additional review as to the potential storm water <br />impacts. If this area is underlain by till (I did not look specifically at this slope), increased <br />run off down the slope could lead to erosion and slope stability problems. <br />