Henness Ridge Yosemite Institute Assimilitive Soils Analysis

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This project is to assess the hydraulic assimilative capacity of onsite soils for treated wastewater effluent. Based on the preliminary review of the site and the alternative campus layouts, a potential disposal area has been identified and are shown on the attached map. It is anticipated that the following field activities will be undertaken to evaluate site assimilative capacity: 1)soil survey of potential disposal area identifying soil type, texture, qualitative permability, slope, drainage, vegetative cover, depth to an impermeable layer, depth to seasonal high water table and bedrock outcrops; 2) up to eight test pits in each potential disposal area; 3) each disposal area will have long-term hydraulic assimilative capacity tests; 4) Up to five (5) piezometers installed to a maximum depth of 20 feet below ground surface in the preferred precise disposal area. This will require excavation of up to 20 soil test pits and the drilling of up to five (5) groundwater monitoring points. The test pits will be distributed between the potential disposal areas. Ideally the test pits wll be combined with an archeological study on the Site (Conduct archeological investigations at a historic-era archeological site in the general vicinity of the proposed campus site. Investigations will include intensive surface inspection, mapping and documentation of all archeological resources, and controlled excavations. These excavations will be carried out in a series of shovel probes (50cm diameter excavations up to 100 cm deep) and test excavation units (1 X 1m or 1 X 2m, estimated to extend between 50 and 100cm deep. A total of not more than 50 shovel probes and 5 excavation units are anticipated. All soils will be screened for archeological components, and artifacts collected for analysis. All soils will be returned to the excavations. All collected materials will be analyzed, and diagnostic items will be cataloged and accessioned into the Yosemite Museum collections. Results of research will be presented in a technical report of findings). The groundwater monitoring wells will be installed in the area with the most advantageous conditions for future construction of a disposal field. The soil pits will be excavated using a rubber tire mounted backhoe with a 24 inch bucket. The total number and specific location of test pits will be determined in the field based on the results of the initial test pit findings. Test pit will vary in size and the maximum size wil be 6-feet deep/ 2 feet wide/10 feet long. Top soil will be segregated and preserved for restoration of each test pit site. Ingress and egress will be limited to specified corridors leading to each of the potential disposal fields. Where possible, tests will be excavated outside of the drip line of the trees. Up to three of the test pits will be utilized for a long term hydraulic capacity test. This will involve backfilling the base of the test pit with washed pea gravel and the placement of a plywood box to provide a resevoir for a constant head of water on the simulated drainfield. The test procedure, developed by Steve Wert. This constant head test will be run for a period of 2 to 5 dyas depending on acceptance rates of the soils. The groundwater monitoring wells will be constructed of 2-inch diameter PVC and will be installed to a maximum depth of 20 feet below ground surface (bgs). Drilling will be accomplished using a rubber tire truck mounted hollow-stem auger. One well will be sited to intercept groundwater upgradient of the disposal field and three/four wells will be installed to monitor potential impacts downgradient of the dipsosal field. Soil boring, well construction and well development will be conducted in accordance with NPS guidelines. If access is restricted due to tree density alternative methods of excavation will be utilised (hand augers).