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HomeMy WebLinkAboutPermit Field Test & Inspection Report 2005-5-16 I, =, J" ..-/ 05/16/05 Walter Custom Homes 2863 Riverwalk Lp, ,Eugene, OR 97401 :>";; 'C;~F7j~~:Ul ~ : fl. \' i "I 7""''' -. ~ _\.h;:) HILL&DALE ENGINEERING, LLC 74 EAST 18TH AVENUE, SUITE #5 EUGENE, OREGON 97401 (541) 868-0667 FAX: (541) 868-0888 L~~.\..:.:.._..:;.~-...::.:____~~.::: RE: Lot 29 Mountainl1'ate Subdivision, Snringfield ,- Level II Preliminary soil report - Job #264-05 As you requested, a preliminary site soil investigation was performed at the above noted site on 05/12/05, The investigation was performed by digging test pits as recommended by the Boire Associates INC supplemental report dated 0211 0/05. Lot 29 is in an area oflots that were investigated as a group, That group consisting oflots 27, 29-33, Lot 29 is on the upslope portion of the cul-de-sac that backs to a steep ridge, The soil in this area is a layer of top, soil approximately 6"-12" in depth over a layer of brown, moderately stiff silty clay approximately 12" in depth over a layer of soft gray clay that is at least 24" in depth, It is likely that this clay layer is over decomposed sandstone at an undetermined depth in this area, Due to the ridge beyond, and the impervious soil conditions, surface water flowing downslope from the ridge is flowing and standing over the lot. Soft fill soil conditions exist at the street apron of the lot, likely performed at time of street construction, This lot is considered to be buildable with the following recQ.Iflhl~ationSoior-site preparation and foundation design, ' .. . ..' : ...... . The proposed residence for this lot has been designed and engineered by Cedar Creek Design ~..: . Construction, I have reviewed the plan, site plan and foundation to determine if the P'll12 ~~ consiSl;ql" with the conditions at the site, The plan includes high wall foundation that is appropriate for the' ..' : proposed structure placement and design for this 101, and appears to have been desigMa:sp;:cifically for this lot. The site plan appears to be consistent with site conditions, No extraordinlll)' .fl'~ation.M:Il~u, other then retaining walls, is recommended to be installed at this time, Retaining WaJJ./Iii1!$n. is to)i~ .. performed using a minimum of 35psf equivalent lateral earth pressure, for high walls designed wttb.. : backfill under 8' in height. Retaining walls designed using restraint at the top and bottom that have backfill in excess of 8' in height are,to use 60psf equivalent lateral earth pressure, The foundation design is to be based on 1500 psf soil bearing pressure, This designer has used 60psf equivalent lateral earth pressure for non-top restrained high walls with backfill less than 8' in height and 1500 psf soil bearing pressure, which is satisfactory, 0\~ . COP\{ ~I-- HL.'E ..... . . ..... ...... . . .. ...... . . .. ...c.. . . .. .. .... . . . ... . ...... . . .... J:'" ...-J . Due to the preliminary level IT investigation of the conditions at this lot, it is recommended that a representative from this office be on site at time of excavation to determine actual soil ,conditions at the site and make final recommendations for the site preparation, These recommendations will likely be to remove the soft clay to decomposed sandstone, which will be an appropriate building material for the proposed foundation, If removal of the clay layer is not feasible, the likely recommendation will be to excavate to solid clay, and install a layer of compacted crushed rock a minimum of 12" in depth over the clay layer for the installation of the proposed foundation, This procedure is to provide an acceptable building surface for the proposed foundation and to maintain the clay soil moisture content that is , designed to mitigate the shrink and swell potential of the clay layer, Additional clay soil moisture content maintenance may be recommended should these procedures be required as determined by the soil conditions encountered at time of excavation, All of these determinations are better made at time of excavation when full site exploration may be performed, In addition, it is likely that the soft fill soil at the street apron of the lot at the proposed driveway will have to be removed to native soil and built back up with compacted crushed rock, This will also be determined at time of excavation. It is recommended that perimeter footing drains be installed at the upslope side of the structure and directed to an approved outlet, to divert the surface water away from the foundation footprint, and not cause impact on adjacent lots, These drains are to be a minimum of3" diameter perforated drain pipe placed at the base of the footings in clean round rock, An additional diversion trench to be placed at the back of the lot may also be recommended to be installed, to be determined at time of excavation, dependent on the extent of subsurface water that may be present, A report stating the required site preparations and verification that these recommendations have been performed will be provided by this office and is to be provided to the City of Springfield building department prior to the footing inspection to be performed by the City of Springfie4c1~MJiector t.,aollow .. .. . concrete to be poured for the footings, ...... ... . The excavation and erosion control requirements of the City of Springfield are adequate for thii~m;. Measures recommended at time of excavation for site preparation and for drainage,ffte.tt>.be perWnd such that there will be no adverse impact on the adjacent sites. .., . ..' : ...... . . .. Thank you for this opportunity to be of service, If you have any questions regardintlothii .epo~ M~ract .. .... me at 868-0667, .. .. . ... . .. .. . Sincerely, Pamela S. Hillstrom, P,E, I ~M om: wi,lios] _ ......._......-..~............l......,""',;;:.~\ . ..... . . ..... ...... . . .. ...... . . .. ...... . . .. .. .... . . . .. .. ...... . . ....