4620 SEAHURST AVE 2020-05-20 - Laserfiche WebLink

March 7, 2011 Mr. Paul ThompsonlKolbear, Inc. L&A Job No. 11-001 • Page 5 season, but generally encountered no or just a speck of groundwater. Therefore, the impact of groundwater on proposed development of the new residences should be minimal. GEOLOGIC HAZARDS AND MITIGATION Landslide Hazard The site is generally flat to very gently sloped, except the western half of Lot 3 which is moderately steep to steep. The site is underlain by fresh, very-dense till and dense advance outwash deposits. These deposits are of high to very-high shear strength and have high resistance against slope failure. Therefore, the potential for deep-seated slides to occur on the site should be minimal. Erosion Hazard The surficial topsoil, occasional fill and weathered soil are of low resistance against erosion, while the underlying fresh till and advance outwash soils are of moderately high resistance against erosion. There is a remote chance that erosion may occur in the weaker surficial soils over the steeper, western half of Lot 3 of the site if it is devoid of vegetation cover and overly saturated. Progressive erosion can lead to shallow, skin-type mudflows in the steeper area. To mitigate such erosion hazard, vegetation outside of construction limits should be preserved and maintained. Unpaved exposed finished ground within the site resulted from construction activities should be re-seeded and re-vegetated as soon as possible. Concentrated stormwater should not be discharged uncontrolled onto the ground within or adjacent to the site. Stormwater over impervious surfaces, such as roofs and paved driveway, should be captured by an underground drain line system connected to roof downspouts or by catch basins installed in paved driveway. Water collected by these drain line systems should be tightlined to discharge into a storm sewer or suitable stormwater disposal facilities, such as rain gardens or surface • LIU & ASSOCIATES, INC.