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HomeMy WebLinkAboutObservation of Pit Excavation 08.21.2019VE:iii n dd x&ei1i' $®+exY? pit pibs[®b *Elf.v mepty $tI i nifIL II: c$ Kix: (970) 945-8454 mail: kazienwood(kumarusa.com C§1. � CDVIya y Www.kumarusa.cQmrtiCftlf(riuiwJIL Springs, CC) mow phone: (970) 915.7988 Anima s>1 Oflee Locations: Denver (HQ), Parker, Colorado Springs, l'on Collins, Glenwood Springs, and Summit County, Colorado F X144 August 21, 2019 Tim Lucas P.O. Box 1506 Glenwood Springs, CO 81602 (dbldr'05(ragmai ) Subject: Tim: Project No. 19-7-420 Observation of Pit Excavation, Proposed Garage of Main Residence, Lot 15, Mountain Springs Ranch, Mountain Springs Road, Garfield County, Colorado As requested, a representative of Kumar & Associates, Inc. observed the pit excavation at the subject site on August 13, 2019 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. These services were performed supplemental to our agreement for professional engineering services to you, dated July 8, 2019. We previously conducted a subsoil study for design of foundations at the site and presented our findings in a report dated July 17, 2019, Project No. 19-7-420. We also observed the excavation for the residence at the site and presented our findings in a report dated August 6, 2019. The garage will be attached to the main residence and have a slab -on -grade floor. At the time of our visit to the site, a pit excavation 7 feet deep had been dug just south of the proposed garage area. The soils exposed within the excavation mainly consisted of sandy clay with rock fragments. Results of swell -consolidation testing performed on a sample taken from the pit, shown on Figure 1, indicate the soils are slightly compressible under light loading and exhibited collapse potential (settlement under constant load) when wetted. This sample may have been partly disturbed which could have caused the collapse. No free water was encountered in the pit and the soils were slightly moist to moist. The soils exposed in the pit excavation are mainly clay and could be used for support of spread footings designed for the recommended allowable bearing pressure of 2,000 psf with a risk of differential movement if the bearing materials were to become wetted. As an alternative, with a lower movement risk, shallow spread footings placed on at least 2 feet of road base and sized for HP. ►► <a , , )ooc0 UU Had+-Ls+-Ls+A=© 1111 -1--1- ♦♦ ,TC, 91@ 9ZI1Z+++++++++ -iZA$TMZ+++++++++anaa xx OZZ®ZIONUu 154JUL �� H[1+++++++++ $AiiaAiiz$A O Tim Lucas August 21, 2019 Page 2 an allowable bearing pressure of 2,000 psf can be used. The base course should be compacted to at least 98% of standard Proctor density at near optimum moisture content. An underdrain is not needed where the foundation walls do not retain earth such as on the downhill side. Other recommendations presented in our previous report which are applicable should also be observed. The recommendations submitted in this letter are based on our observation of the soils exposed within the pit excavation and the previous limited subsurface exploration at the site. Variations in the subsurface conditions below the excavation could increase the risk of foundation movement. We should be advised of any variations encountered in the excavation conditions for possible changes to recommendations contained in this letter. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. If you have any questions or need further assistance, please call our office. Sincerely, Kumar & Associates, Inc. SLP/ljf Attachment: Figure 1 — Swell -Consolidation Test Results cc: Kaup Engineering — Dale Kaup ( :ie(ir=ltaupefgineering.cotn * ATH, MMMM== ♦i 2ftalbHlo.---w=PdLl=v•d=igizug- U3 ■a qc OFVii J J A Kumar & Associates, Inc. Project No. 19-7-420 1E CONSOLIDATION - SWELL — 2 — 4 — 6 — 8 —10 —12 —14 SAMPLE OF: Sand and Clay FROM: Garage Area Pit ® 4.5' WC = 14.4 %. DD = 90 pcf Them teat re,u>d opy' only to she rh a t t.et,dryp- 14uC:41,11'4neepptor fvU, , tk tlarrtllen op.prwel of m Mvor ono bsva]otra. 1na. Swell ccur/oMTh Wallop pwrerm in occordoeea h #SDA 6-6-4548.8.d. i 11 ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE - KSF 10 100 19-7-420 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 1