1920 MERRILL CREEK PKY 2018-01-01 MF Import

o�n cc-oti w�v �u�c� �i u:ttn ��na i nw i wfi Y111t f1U� CUb tl�b 43JU P, UZ • ; ' „� •.... Sietra Construcdon Serviccs, Inc. SHANNON�WILSON,iNC. ; Attn: �fr. George Constantine March 18, 1994 Page 2 saz►d and gravel �s Vashon lodgement tilt and od�ec glaciaily-consolidated, dll-like solls that are locally termed "hardpan." Soth the till and outwash aze very dense, having been werridden by about 3,000 fxt of ica Fotlowing deglaciation, natucal slope processes, such as eteep, erosion and landsliding, cmated colluvial deposits, and surface water produced alluvial deposits. The colluvium remains on or at thc toe of the steep siopcs, and the alluvium is present in the stream courses, such as Merrill Creek. These post-glacial deposits are usually loose to medium dense and of variable grdin-siu distribudon. The inIluence of human activity is evident at the Intrawest SwWay site. The eastcrn slope of Ute site was exploited for bortow materials in the past, such that limited areas of the excavated slopes have bcen lcft rn�ersteepened and other ar�as replaced wtth fill. Additionally, flll was noted both on the upper plateau and at the toe of the exisdng eastern slope. srrF RPCANNAiSSANCE AND SI�QJ'E GEOLOdY The geology of the slope is based on our field cuonnaissance conducted on February 28, 19a4. In general, flve different materials wese observed: 1) Vashon tiil, 2) Vaslion advance out�vash, 3) colluvium, 4) landslide deposits, and 5) 811. No groundwafer seepage was noted on the slope during our reconnaissance. Figure 1 ptssenu the results of our reconnaissance. 1. 1,�11. 1SI1 is relativcly impermeable, a�cept whene sandy mnes are encountered. Generally, the till forms an impervious laycr belrnv which surface water cannot penetrate. In genewl, eill soils can stand near vertically for many ��eais, as evidenced by bluffs at the site (see Figure 1), but the bluffs may cetteat by block falis of dll that are deflned by joints in the soll mass. Caving ar block failute coutd also occur in the till due to activity on adjac�nt property. Aesides block falls, flll is geneially stable, such that rotational instability or slumps are ruely seen. � 1 2. Qldt�sh. Similar to till, outwash soils can stand near-vertical fvr some time; houtver, the face will eeode much faster due to exposure fi the elements. Addidonally, it is subjeCt to enosion from werland water flow. These ane the W6693-01