Volume 2: Draft Gorst Planned Action Environmental Impact Statement

GORST PLANNED ACTION EIS | AFFECTED ENVIRONMENT, SIGNIFICANT IMPACTS, AND MITIGATION MEASURES• Indianola loamy sands occur in the southwest portion of the UGA, and include a large portion of the highintensity development in this area. The soil is easily excavated, and in flat areas can support high densitydevelopment and on-site sewage disposal systems.• Kilchis very gravelly sandy loams occur in the hills in the north portion of the UGA, and are mapped as having30 to 70 percent slopes. They are shallow soils, with depth to basalt bedrock of 16 to 20 inches. The shallowdepth to bedrock and steep slopes present severe limitations for development.• Ragnar fine sandy loams occur in flat areas within the northwest portion of the UGA. These deep, well-drainedsoils are well suited to urban development.• Norma fine sandy loams occur in the floodplain of Gorst Creek, and in other low areas in the south half of theUGA. These hydric soils have a high water table and pond runoff, making them poorly suited to developmentand on-site sewage systems.Based on the soil survey for the area, approximately 28 percent of the Gorst UGA is mapped as having a slope ofgreater than 15 percent. In these areas, moderate to steep slopes present challenges to constructability (USDA SoilConservation Service 1980).Table 3.1-1Soil Types in the Gorst Creek Watershed and Gorst UGA, and Their Associated ConstructionLimitations and Erosion Hazard PotentialMap UnitAlderwood Very GravellySandy LoamKilchis Very Gravelly SandyLoamAcres inWatershed 1Acres inUGA1,109 01,006 50Ragnar Fine Sandy Loam 986 33 SlightHarstine Gravelly SandyLoamSchneider Very GravellyLoam737 25Indianola Loamy Sand 332 53Kitsap Silt Loam 317 28Constructability ofUGA Soils(Limitations forBuilding and StreetDevelopment)Slight to severe,depending on slopeSevere (shallow depthto rock)Moderate to severe(wetness)356 0 Severe (steep slopes)Slight to severe,depending on slopeModerate to severe(wetness)Dystric Xerothents 249 4 Severe (steep slopes) HighIndianola-Kitsap Complex 256 5See information forIndianola and Kitsapmap units.Neilton Gravelly Loamy Sand 255 0 Slight to severe, SlightErodibility/Erosion HazardSlight – less than 15 percentslope; moderate – 15 to 30percent slopeModerate to severe (rapidrunoff)Moderate – less than 6 percentslope; severe – greater than 6percent slopeSlight – less than 15 percentslope; moderate – 15 to 30percent slopeSevere (rapid runoff)Slight – less than 6 percentslope; moderate – 6 to 10percent slopeSlight – less than 8 percentslope; moderate – 8 to 15percent slope; severe – greaterthan 15 percent slopeSee information for Indianolaand Kitsap map units.Draft | June 2013 3-6