7401 LARIMER RD 2021-12-21 - Laserfiche WebLink

• • B. Environmental Elements f HELP1 1. Earth [help] a. General description of the site: (circle one): g, rolling, hilly,steep slopes,mountainous, other b. What is the steepest slope on the site(approximate percent slope)? The study area is generally flat,with slopes occurring from Larimer Road down to the farmland and within the drainage ditches(NRCS 2019).There are variable slopes associated with the existing drainage ditches on the site,with the steepest slopes being approximately 70%and less steep slopes being approximately 40%. c. What general types of soils are found on the site(for example,clay, sand,gravel, peat, muck)? If you know the classification of agricultural soils,specify them and note any agricultural land of long-term commercial significance and whether the proposal results in removing any of these soils. The predominant mapped soil type in the study area is Mukilteo muck(NRCS 2019). The site also includes Terric Medisaprists,Alderwood-Everett gravelly sandy loams, and Puget silty clay loam. Mukilteo muck soils are often found in areas used for hay production, livestock grazing, and wildlife habitat(USDA 2018). The Mukilteo series consists of very deep, poorly drained soils formed in glacial uplands, glacial drift plains, and river valleys.Soils observed on site do not match the Mukilteo description;these soils are either other soils or the years of farming have altered the upper soil profile,resulting in a more uniform, sandy loam that is well drained. Soils observed on site are primarily very well- drained sandy loams and resemble the Puyallup soil series or Mukilteo subsoil profile. d. Are there surface indications or history of unstable soils in the immediate vicinity? If so,describe. There is some erosion occurring along the slopes of the drainage ditches that were rerouted as part of the Project. This erosion is due to the lack of stabilization of the slopes with vegetation and the steepness of the slopes. No erosion is evident outside of that associated with the newly dug ditches. 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. As part of the work that was already completed, upland grading activities were limited to excavating approximately 600 cy of topsoil to assist with drainage ditch rerouting activities. High spots were targeted across the property to use as fill material. Only on-site material was used to support grading activities; no material was imported to or exported from the property. Soil augmentation to a depth of 6 inches on the Tonnes property will include importing and distributing a`60/40 topsoil mix across areas that have been filled. The topsoil will then extend another 25 feet onto the Tonnes property and will taper in depth from 6 inches to 0 inches where it meets the existing grade.The estimated amount of fill for soil augmentation is 1,355 cy. The topsoil area will then be seeded with a pasture mix. Grading related to ditch modification activities is described in Section 3.a. 4