2701 ROCKEFELLER AVE NIMBUS Geotech Report 2023-12-29

Opportunity Zone Development LLC JN 19162 June 6, 2019 Page 14 designed by a specialty consultant familiar with the expected subsurface conditions and proposed construction. Plate 9 presents typical considerations for foundation drains at shoring walls. Footing drains placed Inside the building, outside of the building, or behind backfilled walls should consist of 4-inch, perforated PVC pipe surrounded by at least 6 Inches of 1-inch-minus, washed rock wrapped in a non -woven, geotextile filter fabric (Mirati MON, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 Inches below the level of a crawl space or the bottom of a floor slab, and It should be sloped slightly for drainage. All roof and surface water drains must be kept separate from the foundation drain system. In any un-shored areas, footing drains outside of the building should be used where: (1) crawl spaces or basements will be below a structure; (2) a slab is below the outside grade; or, (3) the outside grade does not slope downward from a building. A typical footing drain detail is attached to this report as Plate 10. Clean -outs should be provided for potential future flushing or cleaning of footing drains. It the structure includes an elevator, It may be necessary to provide special drainage or waterproofing measures for the elevator pit. If no seepage into the elevator pit is acceptable, it will be necessary to provide a footing drain and free -draining wall backflll, and the walls should be waterproofed. It the footing drain will be too low to connect to the stone drainage system, then It will likely be necessary to install a pumped sump to discharge the collected water. Alternatively, the elevator pit could be designed to be entirely waterproof; this would Include designing the pit structure to resist hydrostatic uplift pressures. As a minimum, a vapor retarder, as defined in the Slabs -On -Grade section, should be provided in any crawl space area to limit the transmission of water vapor from the underlying soils. Crawl space grades are sometimes left near the elevation of the bottom of the footings. As a result, an outlet drain is recommended for all crawl spaces to prevent an accumulation of any water that may bypass the footing drains. Providing a few Inches of free draining gravel underneath the vapor retarder Is also prudent to limit the potential for seepage to build up on top of the vapor retarder. No groundwater was observed during our field work. If seepage is encountered In an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping It from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final she grading In areas adjacent to a building should slope away at least one to 2 percent, except where the area is paved. Surface drains should be provided where necessary to prevent ponding of water behind foundation or retaining walls. A discussion of grading and drainage related to pervious surfaces near walls and structures Is contained in the Foundation and Retaining Walla section. SLABS -ON -GRADE The building floors can be constructed as slabs -on -grade atop non -organic native soil, or on structural fill. The subgrade soil must be in a firm, non -yielding condition at the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced wHh select, Imported structural fill. GEOTECH CONSULTANTS, INC.