6300 MERRILL CREEK PKY BASE FILE 2018-01-01 MF Import

i � � JN 97092 � Quadrant Pa9e Z � August 13, 199T �. The test pits were excavated on March 7, 1997 with a trackhoe provided by the client. The , undersigned associate of Geotech Consultants, Inc. observed the excavation process, logged the ; test pits, and obtained representative samples of the soil encountered. "Grab" samples of selected subsurtace soil were collected from the trackhoe bucket. The Test Pit Logs are attached to this report as Plates 3 through 9. Except for the previous wetland area, the test pits revealed a thin mantle of topsoil overlying 2 to 4 feet of loose to medium-dense, weathered glacial till that consists of gravelly, silty sand. The upper approximale 6 to 24 inches of the weathered glacial till c:,ntained a significant amount of roots. The weathered glacial till overlies dense to very dense, unweathered glacial till. Our firm has been involved with many other sites in the near vicinity and have found this glacial till soil throughout the ; area. The middle of the site is bare because organic soils in a former wetland were removed and subse- quently replaced with on-site soil. Last fall, GeoEngineers observed the removal of the organic soils and the replacement with compacted on-site soil durng five site visits. Four of their site visits { were between September 30 and October 4, 1996, while the remaining visit was made on October 23. Density tests perfomied during the first four visits indicated that compaction near or above 95 percent was achieved in the southern portion of the excavated area. However, no tests were per- , formed on the northern portion where it appears that up to about 9 feet of excavation was made. Our recent Test Pit 10 was excavated on apparently the southem end of the wetland excavation, and 6 feet of inedium-dense, competent fili soil was revealed overlying dense native soil. However, about 9 feet of loose fill wzs revealed in Test Pit 1. We returned to the site during ihe initial phase of earthwork in July of 1997. Numerous test pits were excavated by the grading contractor in the and the earlierlfiP was adequatehy cohmpa ted except n�the as aeof T s't pi�1�und the test pit area, The final logs represent our interpretations of the field logs and laboratory tests. The stratification liro:s on the logs represent the approximate boundaries between soil types at the exploration loc:ations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. The relative densities and moisture descriptions indicated on the test pit logs are interpretive descriptions based on the conditions observed during excavation. Groundwater Some groundwater seepage was observed at a depth of 2 to 4 feet in the test pits in March perched on the dense glacial till. This perched groundwater is typical in areas of glacial till during the wet winter and spring months in the Puget Sound region. However, seepage has not been observed during the recent earthwork. CONCLUSIONS AND RECOMMENDATIONS General The native, glacial till soil that was revealed in most of the earlier test pits and recent observations is typical for the Seaway Center and the Puget Sound region. Glacial till soil has a high shear GEOT�(:H CONSULTAT7I'S,INC.