3628 UPLAND AVE 2016-01-01 MF Import

- : Mr.Dave Shar}� � � October 7, 1997 On September 17, 1997, we visited the site to observe existing conditions and verify information as presented in the above referenced geotechnical report. Our observations of the site confirmed conditions as described, and it is our opinion that geotechnical recommendations prosented in the referenced report are valid for the proposed cons[ruction. Review of the project drawings notes that foundation drains and roof downspouts will be tightlined to a dry well located at the northeast corner of the lot. The dry well is located 40 to 50 feet away from the top of the slope, and has planned dimensions of four feet by fifteen feet, and a depth of four feet. We would note that the native soil conditians into which the dry well will be cons!ructed consist of very dense silty sand with gravel. This soil will have a limited abiliry to infiltrate collected stortnwuter. The infiltration rate of the soils will likely be on the order of one tenth of an inch per hour, or less. It is our upinion that the positioning of tlie dp� well is satisfactory and we do not expect it would have any impact on the current stability of the west-facing s?ope. However,given the limited ability of the native soils to infiltrate water, we suspect that the size of the dry well is insufficienc to handle the volume of water which will be discharged to it during a significant stortn event. We recommend verifying the volume of the dry well to handle the stortnwater runoff, using a soil infilVation rate of one tenth of an inch per hour. A storage volume equivalent to 30 percent of the volume of the rock used to backfill the dry well can also be used. If required, the size of the dry well should be increased, or altematively,the dischargc should be tightlined to existing stormwater facilities in the adjacent residential street, if available. A representative of Terra Associates should observe foundation excavations to verify that soil conditions exposed are ns expected and will be suitable for support of the residential foundations as designed. We should also observe the installation of subsurface drainage to verify that it is completed in accordance�vith recommendations outlined in the referenced report and approved design drawings. We trust the information presented is sufficient to meet your curtent needs. Should you have any que:,tions or require additional information,please call. Sincerely, .$ J.S .E TERRA S � , A � � e �. � � :. : y ,� . lU--7—`�7 T eo ore ��.E �„ Principal En �c:��o �,4• . :0,1•rS,t'+`'v TJS:kh -�' Fxr�ss E!; Project No.T-3788 Page No.2