2207 GIBSON PL 2022-10-28 - Laserfiche WebLink

• • August 18,2014 Gibson Bluff L&A Job No. 14-056 Page 7 • • GEOLOGIC HAZARDS AND REMEDIATION Erosion Hazard • The bench top area of the site is underlain at shallow depth by medium-dense to dense, fine to medium to coarse sand deposits of the Esperance sand soil unit, overlain by topsoil and fme sand weathered soil. These soil deposits are all of moderate to high permeability, and would allow storm runoff to seep through easily. The bench top is very gently sloped. Therefore, the bench top of the site is not prone to erosion hazard. To further mitigate erosion hazard, areas disturbed and devoid of vegetation from construction activities should be vegetated and landscaped as soon as possible for erosion protection. Concentrated stormwater should not be discharged uncontrolled onto the ground within or adjacent to the site. Storm runoff over impervious surfaces, such as roofs and paved road/driveways, should be captured with underground drain lines connected to roof downspouts and by catch basins installed in the road/driveways. Stormwater collected by such drain line systems should be tightlined to'discharge into a stoma sewer or suitable stormwater disposal facilities. Landslide Hazard Where the Whidbey formation soil unit of extremely low permeability is exposed on • slopes or man-made cuts, groundwater seepage would occur. High groundwater seepage in winter can cause soil erosion in and above the seepage zone. Progressive erosion can cause soil sloughing and landslides. This is groundwater seepage and erosion induced, upward working landslides The Whidbey formation soil unit was encountered by only one of the three test borings at 31.0 feet. Therefore, the Whidbey formation soil unit is • LIU & ASSOCIATES, INC.