2127 100TH ST SE 2024-06-14 - Laserfiche WebLink

3.3.2 Soils Criteria and Mapped Description The manuals define hydric soils as those that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Field indicators are used for determining whether a given soil meets the definition for hydric soils. NRCS Web Soil Survey maps the soils on the project site as Alderwood-Urban land complex, 0— 8 percent slopes. Aldenvood-Urban land complex, 2 to 8 percent slopes is described as consisting of about 60 percent Alderwood gravelly sandy loam and about 25 percent urban land. Included in this unit are small areas of McKenna and Norma soils and Terric Medisaprists in depressional areas and drainageways on plains. Also included are small areas of soils that are very shallow over a hardpan; small areas of Everett, Indianola, and Ragnar soils on terraces and outwash plains;and soils that have a stony and 5oulder surface layer. Included areas make up about 15 percent of the total acreage. The Alderwood soil is moderately deep over a hardpan and is moderately well drained. It formed in glacial till. Typically the surface layer is very dark grayish brown gravelly sandy loam about 7 inches thick. The upper part of the subsoil is dark yellowish brown and dark brown very gravelly sandy loam about 23 inches thick. A weakly cemented hardpan is at a depth of about 35 inches. Permeability of this soil is moderately rapid above the hardpan and very slow through it. Available water capacity is low. 3.3.3 Hydrology Criteria The 2010 Regional Supplement defines wetland hydrology as "areas that are inundated (flooded or ponded) or the water table is less than or equal to 12 inches below the soil surface for 14 or more consecutive days during the growing season at a minimum frequency of 5 years in 10." During the early growing season, wetland hydrology determinations are made based on physical observation of surface water, a high water table, or saturation in the upper 12 inches. Outside of the early growing season,wetland hydrology determinations are made based on physical evidence of recent inundation or saturation (i.e. water marks, surface soil cracks, water-stained leaves). Long-Term Rainfall Records Month Normal/ 30%Chance Will Have Observed Condition(Dry, Condition Month Weight Product(Condition Average Less Than More Than Precipitation Normal,Wet) Value* Value Value,Month Value) May 2.59 1.8 3.09 1.7 Dry 1 1 1 June 2.29 1.44 2.77 0.91 Dry 1 2 2 July 1 0.9 0.32 1.06 1 0.29 Dry 1 3 3 WETS Station:EVERETT,Period of Record:1992-2022 Total 6 Observed Precipitation Station:EVERETT 2.0 N,WA Form Adapted From NRCS Engineering Field Handbook,Chapter 19,Hydrology Tools for Wetland Determination LSum is: Then: *Condition Value: 6-9 Prior Period Has Been Drier Than Normal Dry=1 0.14 Prior Period Has Been Normal Normal=2 5-18 Prior Period Has Been Wetter Than Normal Wet=3 Figure 6 AgACIS WETS table indicating drier than average conditions. 2127100th Street SE 5 WRI#23188 Critical Area Study and Mitigation Plan October 9, 2023