9001 AIRPORT RD SNO ISLE SKILL CTR EXPANSION 2009 Geotech Report 2018-01-02 MF Import

il I Subswfact Expbsation. Ceobgic Haza�d, and Sro-L1e Skiltr Center Addition Prdiminary Gtoachnicd Engintering Reporr Ereren. Washingron Geobgic Hawrds and Mitigations Irequired measures for an azea to be "buttoned-up" will depend on the time of yeaz and the dwation the azea will be left un-worked. During the winter months, azeas tLat aze I to be left un-worked for more than 2 days should be mulched or covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the I subgrade. Such measi:res will aid in the contractor's ability to get back into a work area after a storm event. 1'he stabilization process also includes establishing temporary storm water conveyance channels tluough work azeas to route runoff to the approved Itreatment facilities. 4. All dismrbed azeas should be revegetated as soon as possible. If it is outside nf the I growing seasoa, the disturbed azeas should be covered with mulch, as recoaunendea in the erosion conuol plan. Straw mulch p:ovides the most cost-effective cover measure and can be made wind-resistant with the application of a tackifier after it is placed. I5. Surface runoff and discharge should be conuolled during and following development. Uncontrolled discharge may promote erosion and sediment uansport. Under no Icircumstances should concentrated dischazges be allowed to flow over the top of steep slopes. I6. Soils that aze to be reused azound ihe site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but aze not I limited to, covering with plastic sheeting, the use of low stockpiles in flat azeas, or the use of straw bales/silt fences azound pil� perimeters. During the period between October la and Mazch 31�, these measures aze required. ( 7. On-site erosion control inspections and turbidity monitoring (if required) should be performed in accordance with the Ecology requirements. Weekly and monthly ( reporting to Ecology should be performed on a regulazly scheduled basis. TFSC I monitoring should be part of the weekly conscruction team meetings. Temporary and permanent erosion control and drainage measures should be adjusted and maintained, as � necessary, at the time of construction. � It is our opinion that with the proper implementation of the TESC plans and by field-adjusting appropriate mitigation elements (BMPs) during construction, as recommended by the erosion conuol inspector, the potential adverse impacts from erosion hazards on the project may be Imitigated. I i � i ( ✓une t�. 2008 ,+ssocurso Euerri sc��vices.nvc. 12 f EG/W-FF.l.tlDZi3A3-ProjraxiXMNOIl31FEIWP Page 9