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Project No. 9929.G Geotechnical Investigation/Vineyard Avenue, Pleasanton 8 August 2003 52. Active conditions occur when the top of the wall is free to move outward. It should be noted that the effects of any surcharge or compaction loads behind the walls must be accounted for in the design of the walls. 53. If keyed or interlocking non-mortared walls such as Keystone or Earthstone walls are utilized, the following soil parameters would be applicable for design using on-site, native materials within the reinforced fill zone: Internal Angle of Friction: 25 degrees Cohesion: 0 p.s.f. Bulk Unit Weight: 125 p.c.f. These walls should be designed and constructed in accordance with the manufacturers recommendations. 54. The above criteria are based on fully drained conditions. If drained conditions are not possible, then the hydrostatic pressure must be included in the design of the wall. A linear distribution of hydrostatic pressure of 63 p.c.f. should be adopted. 55. In order to achieve fully-drained conditions, a drainage filter blanket should be placed behind the wall. The blanket should be a minimum of 12 inches thick and should extend the full height of the wall to within 12 inches of the surface. If the excavated area behind the wall exceeds 12 inches, the entire excavated space. behind the 12-inch blanket should consist of compacted engineered fill or blanket material. The drainage blanket material may consist of either granular crushed rock and drain pipe fully encapsulated in geotextile filter fabric or Class II permeable material that meets CalTrans Specification, Section 68, with drainage pipe, and optional fabric. A 4-inch perforated drain pipe should be installed in the bottom of the drainage blanket and should be underlain by at least 4 inches of filter type material. A 12-inch cap of native soil material should be placed over the drainage blanket. 56. Piping with adequate gradient shall be provided to discharge water that collects behind the walls to an adequately controlled discharge system away from the structure foundation. TERRASEARCH, inc Page 26 of 53