600 RIVERSIDE RD Geotech Report 2022-10-25

Landau Associates The foundation backfill material should be underlain by a woven geotextile, such as Marafi 50OX or equivalent, and thoroughly compacted to provide a firm subgrade for the proposed pump stations. Buried pump stations and vaults will be subjected to upward buoyancy forces when the groundwater level around the structure is higher than the fluid level inside the structure. Such structures should, therefore, be designed to resist this upward force to prevent possible heave and cracking of their bottoms. Lateral earth pressures against the proposed below -grade pump stations will depend upon the inclination of any adjacent slopes, type of backfill, degree of wall restraint, method of backfill placement, degree of backfill compaction, drainage provisions, and magnitude and location of any adjacent surcharge loads. At -rest soil pressure is exerted on a subsurface structure or wall when it is restrained against rotation. In contrast, active soil pressure will be exerted on a subsurface structure or wall if its top is allowed to rotate or yield a distance of roughly 0.001 times its height or greater. For this project, we assume that the walls of the proposed below -grade pump stations will be restrained against rotation and that the structures will have level backfill. We also assume that the backfill placed around the below -grade pump stations will consist of properly compacted impermeable fill as to prevent contaminant migration across the muciflat aquitard. Due to the impermeable nature of this material, below grade structures should be designed for a horizontal at -rest equivalent fluid pressure of 95 pcf for the full height of the structure. This value includes hydrostatic pressure. The above recommendation regarding at -rest earth pressures assumes that there will be no adjacent surcharge loads. If the below -grade pump stations will be subjected to the influence of surcharge loading within a horizontal distance equal to or less than the height of the walls, the walls should be designed for the additional horizontal pressure. The additional lateral earth pressure from surcharge loads can be estimated as a uniform pressure distribution equal to the surcharge pressure multiplied by a lateral earth pressure coefficient of 0.5. 3.8 Pavement Design The following sections provide geotechnical recommendations for design and construction of new pavement sections for the proposed access road and trails. 3.8.1 Access Roads For the proposed access roads, including 8th Street, we recommend a pavement section that consists of 5 inches of hot mix asphalt (HMA) over 6 inches of crushed surfacing base course (CSBC) over 6 inches of compacted gravel borrow. The upper two inches of CSBC may be replaced by two inches of crushed surfacing top course (CSTC). Prior to placement of the recommended pavement section, the Geotechnical Engineering Report 0121030.010.011 Riverside Business Park March 22, 2018 Public Access Trails and Roadway Improvements 3-11 ri 1 11 I