1136 GRAND AVE A&B 2016-01-01 MF Import

. . ' I August 25,2006 Mr. Scott Anderson L&A Job No. 6A126 Page 4 Groundwater Condilions The fresh till soils at very shallow depth are practically impervious,while the underlying advance outwash soils are of moderately high permeabiliry. Stormwater infiltrating into the surficiel more pertneable soils would perch on the suri'ace of the underlying fresh till soils. This near-surface perched groundwater may dry up completely in the dryer summer months and accumulate and rise in thc wet winter months. The groundwatcr would flow down-gc�adient along the sutface of the fresh till soils where in contact,and seep easily into the underlying advancc:outwash soils and perch over a fine sandy to clayey silt deposit underl_ring the advance outwash soif unit. It is our opinion shallow perclied groundwater will have any significant impact on the stability of the steep slope within and bclow the site. The vegetation cover on the stcep slope, however, should be maintained fbr erosion protection of the topsoil and weathered till soils overlying the fresh till soils. SITE STARILITY EYALUATION AND RECOMMENDATIONS The site is most likely undedain by fresh till soils at shallow depth. The fresh till soils and the advancc outwash deposits undcrling the till soils are of vcry-high to high shear strength and have exccllent resistanee against soil movement and slope failure. Therefore, the potential for deep- seuted landslides to occur on the site should be minimal. The surficiai topsoil and weathered till soils draping the steep slope can be eroded if devoid of vegetetion cover and overly saturated. Progressive erosion can result in shallow, skin-type mudflows on the steep slope. To mitigate such hazard, thc vegetation covered on the slope should be maintained and concentrated stormwater should not be discharged onto the slope or anywhere within the site. Storm runoff over impervious surfaces, such as roofs and paved driveway should be captured with underground drain linc system ticd to roof downspouts a��d by catch basins installed in paved LIU & ASSOCIATES, INC.