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40 <br />Q H <br />>Hrn <br />Him <br />yx0 <br />H 'Oil <br />xx O H <br />G7OE <br />H t7 <br />OH((�� <br />HH M O <br />ry,V qng <br />r HH <br />t7 to <br />O H <br />C]t7 rn <br />r <br />IHrn <br />HOrn <br />e sf <br />1� <br />In general, the site is overlain by up to one foot or forest duff rich in organic material and <br />loosely consolidated. Fallen trees and decaying vegetation litter patches of the forest floor, soil <br />borings (shown in Appendix A) completed to depths up to 7 ft at locations shown on Plate 1 <br />indicated varying conditions, which are described below. No wetland soils were found in any of <br />the area proposed for wetland creation. <br />The gully located on the western edge of the site is underlain by clayey sRnds to well - <br />graded silty sands or sandy silts. Decreasing amounts of fines occur at increasing depth. In the <br />upper reaches of the gully, a poorly -graded sand was encountered. These results suggest that the <br />site is located near the boundary between the Vashon till, a relatively impermeable layer and the <br />water -bearing Esperance Sand. <br />The eastern gully is underlain by silty sand material in the upper reaches. In the extreme <br />upper reach, the silty sand is underlain by clayey sand, whereas midway down the gully a gravelly <br />sand occurs belo%; the silty sand. At a lower elevation the poorly -graded sand exists near the <br />surface underlain by silty sand. In general, the lower permeability till soils are more prevalent <br />in the higher elevation areas. Within the gullies, more well drained and more permeable sails (less <br />fines) exist. <br />The western gully headland soils consist of dense silty sand containing up to 40% silt and <br />clay beneath about six inches of forest duff. Low soil moisture content of 11% and high <br />percentage of fine material indicates the soil is derived from till. Elevations range from 550 to <br />570 feet with shallow slopes of 10%. A large puddle, 200 square feet, pooled on the ground <br />surface at a bend in the road, indicating low permeability soils in this area. <br />Moisture content in the soils varied across the site, ranging from 3.7 percent in the poorly - <br />graded sand to 18.8 percent in the silty sand. Ground water was encountered at 4 1/2 ft in boring <br />HA6. No evidence of flowing surface water was observed in the gullies, though ponded water <br />occurred on the dirt roads and in areas near lborings HA13, indicating localized low permeability <br />zones that perch water after a rainfall event. Permeability test conducted in the lab on <br />recompacted soil samples from HA13 and HA14 indicated very low values, with hydraulic <br />conductivities on the order of I x 10-7 cm/s. <br />1.1.2.2 Surface Water Conditions <br />As previously mentioned, evidence of active erosion or flow of surface water was not <br />observed within the gullies on site. Ponded surface water was observed on compacted dirt road <br />surfaces and in the areas of boring HA-13. The ponded surface water indicates that low <br />permeability soils and poor drainage exist in areas of higher elevation and flatter terrain. <br />The overall water balance for the site can be estimated from general climatologic and <br />runoff statistics. Average annual precipitation for the area is approximately 35 inches, and <br />average annual evaporation is approximately 20 to 25 inches annually (based on information from <br />the Pacific Northwest River Basins Commission, Vol. VI Water Resources, 1970). Adjustment <br />of the evaporation data to reflect natural evapotranspiration indicates that there is excess <br />4 <br />DAMES & MOORE <br />