2211 GIBSON PL Geotech Report 2023-04-06

August 18, 2014 Gibson Bluff L&A Job No. 14-056 Page 16 consist of compacted, clean, sandy soils. A 4-inch perforated PVC footing drain pipe, as recommended in the DRAINAGE CONTROL section of this report, should be provided for the foundation walls. The drain lines should be hydraulically connected to the drainage blanket behind the walls and tightlined to a storm sewer. Slab-on-Grade Floors Slab-on-grade floors, if used for the proposed residences, should be placed on firm subgrade soils prepared as outlined in the SITE PREPARATION AND GENERAL EARTHWORK and the STRUCTURAL FILL sections of this report. Where moisture control is critical, the slab-on-grade floors should be placed on a capillary break which is in turn placed on the compacted subgrade. The capillary break should consist of a minimum four-inch-thick layer of free-draining gravel or crushed rock containing no more than 5% by weight passing the No. 4 sieve. We recommend that a vapor barrier, such as a 6-mil plastic membrane, be placed over the capillary break to keep moisture from migrating upwards. Road/Driveways Performance of road/driveways pavement is critically related to the condition of the underlying subgrade soils. We recommend that the subgrade soils under the driveway/parking area be treated and prepared as described in the SITE PREPARATION AND GENERAL EARTHWORK section of this report. Prior to placing base material, the subgrade soils should be compacted to a non-yielding state with a vibratory roller compactor and proof-rolled with a piece of heavy construction equipment, such as a fully- LIU & ASSOCIATES, INC.