29312 LAKE CHAPLAIN RD SEPA 017 - 002 - CULVERT REPLACEMENT UNDER LAKE CHAPLAIN Land Use Decision Documents 2025-04-17

agricultural land of long-term commercial significance and whether the proposal results in removing any of these soils. 'help' The United States Department of Agriculture(USDA)Natural Resources Conservation Service(NRCS) Web Soil Survey shows three soil units within the immediate vicinity of the culvert replacement site (USDA-NRCS,2016). These soils include Tokul gravelly medial loam, 8 to 15 percent slopes,Tokul gravelly medial loam, 10 to 30 percent slopes,and Tokul-Winston loam,25 to 65 percent slopes(USDA- NRCS,2016). d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. Jhelpl Yes,high flow events of Woods Lake Creek result in overtopping the roadway embankment and erosion on the downstream side which is threatening the stability of the roadway. e. Describe the purpose, type, total area, and approximate quantities and total affected area of any filling, excavation, and grading proposed. Indicate source of fill. Jhelpl • Excavation of road prism and existing culvert will cause 3,885 cubic yards of fill and 237 cubic yards of riprap. • Backfill of Road prism will cause 3,633 cubic yards of fill. • Fill to create proposed channel at culvert will cause 200 cubic yards of fill • Excavation to footing elevation below the OWHM will have 282 cubic yards of excavation • Place streambed sediments through entire reach below the OHWM will cause 530 cubic yards of fill. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Jhelpl Erosion is not expected to occur because appropriate BMPs will be used during construction. g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)?[help' The roadway will not change footprint site and there will not be a change in impervious surfaces resulting from the roadway work. However,the culvert is going from a 6-foot wide,62-foot-long pipe to a 22.9 open bottom arch culvert that is 80 feet long(an increase of 1,584 square feet). h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: 'help.' Examples of proposed BMPs to reduce or control erosion are catch basin filters,dust control(spraying) and a stabilized construction entrance.In addition,construction timing(when stream levels are low during the summer)and phased timing of actions will reduce the chance of sediments leaving the construction sites. 2.Air Jhelpl a. What types of emissions to the air would result from the proposal during construction, operation, and maintenance when the project is completed? If any, generally describe and give approximate quantities if known. Jhelpl It is anticipated that there might be a temporary increase from construction machinery emissions,dust, will increase during active construction. Upon completion,emissions will return to pre-project conditions. SEPA Environmental checklist(WAC 197-11-960) July 2016 Page 5 of 18