2621 ROCKEFELLER AVE Geotech Report 2022-10-25

The pipes should be laid with minimum sl opes p s opes of one-half percent and discharge into the stormwater collection system to convey the water off site. The pipe installations should include a cleanout riser 11 with cover located at the upper end of each pipe run. The cleanouts could be placed in flush mounted access boxes. Collected downspout water should be routed to appropriate discharge points in separate pipe systems. Other Considerations Exterior retaining systems used to achieve grade transitions or for landscaping, can be constructed using traditional structural systems such as reinforced concrete, CMU blocks, or rockeries. Alternatively, retaining walls can consist of reinforced soil and block facing structures. In recent years, the latter structural system has proven to be an economically reasonable alternative to more traditional retaining wall systems. We can provide additional design recommendations for reinforced soil and block facing structures,if requested. 11 SLAB-ON-GRADE FLOOR Subgrade Preparation We recommend that the concrete slabs-on-grade be constructed on a gravel layer to provide uniform support and drainage, and to act as a capillary break. We expect that slab-on-grade floors can be supported on the dense to very dense glacial soils encountered in our test pits or on properly compacted structural fill extending down to these materials. Prior to placing the gravel layer, the subgrade should be proofrolled as described previously in the Earthwork section of this report. Existing fill located under the east side of the building should be removed as described in the Earthwork section. If necessary,the subgrade should be recompacted to a firm and unyielding condition. Design Parameters The gravel layer below slabs-on-grade should consist of 6 inches of clean crushed gravel, with a maximum particle size of 1 l inches and negligible sand or silt. For slabs designed as a beam on an 14 elastic foundation, a modulus of subgrade reaction of 200 pci may be used for subgrade soils prepared as recommended above. 111 If water vapor migration through the slab is objectionable, the gravel should be covered with a heavy plastic sheet, such as 10-mil plastic sheeting,to act as a vapor retarder. This will be desirable where the slabs will be surfaced with tile or will be carpeted. The contractor should be made responsible for 11 maintaining the integrity of the vapor barrier during construction. It may also be prudent to apply a sealer to the slab to further retard the migration of moisture through the floor. PAVEMENT SUBGRADE RECOMMENDATIONS We recommend that the subgrade soils in new pavement areas be prepared and evaluated as described in the Earthwork section of this report. In cut areas, we recommend that the upper 12 inches of the existing site soils be compacted to at least 95 percent of the maximum dry density per ASTM D 1557 prior to placing pavement section materials. Where old fill exists,the upper 2 feet should be compacted to at least 95 percent. If the subgrade soils are loose or soft, it may be necessary to excavate the soils 11 and replace them with structural fill,gravel borrow,or gravel base material. Based on our explorations, the majority of the pavement subgrade soils are expected to consist of fill on the east side of the building. Pavement subgrade conditions should be observed and proof-rolled during construction to 11 File No.12547-001-00 Page 13 GEOENGINEERS/ I February 3,2006