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Home My WebLink AboutB14-0153 Engineering letter Swt-o isl i ,ti ,'0,d,k t.i,',,,1101k;11, ills was 'IkNo.# 41wrA '4'au 1111'Wol?"III-I'AW1 AK ( I'o iI"CI INICA1 I ,-, ,,,,' .iw, , ,11 June24, 2014 ,„,,,I 1,1.,,,,i„i,i ,. , Mountain Air Builders LLC Attn: Mr. Roland Lee 1513 Birch Street Canon City, CO 81212 Job No. 414 151A Subject: Excavation Observation, Renovation/Addition to the Hoyt-Young Residence, 2764 South Frontage Road,Town of Vail, Colorado. Dear Mr. Lee: As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. (HP Geotech) observed the excavation at the subject site on June 18, 2014 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. HP Geotech previously provided a letter with recommendations for drain system for the referenced project under the same job number, dated 5/21/2014. The services were performed in accordance with our agreement for geoteclmical engineering services to Mountain Air Builders, dated May 15, 2014. We reviewed the structural plans prepared by KRM Consultants, Inc.,Job No. 1401-09, dated 6/13/14. At the time of our site visit, the superstructure of the existing single-family residence and been removed. The existing concrete foundation walls and spread footings remained. The lower level spread footings at the south elevation and continuous footings at the west elevation were cut to the footing subgrade level,approximately 4 to 61/2 feet below existing grade. The soils exposed in the base of the excavation consisted of silty sand (SM). The silty sand was loose to medium dense, slightly moist, and reddish brown to dark brown. The exposed soils offered minimal resistance when probed with a 3/8-inch T-probe with penetration depths of 12 to 18 inches to the underlying gravels in which were very dense with minimal penetration. Results of swell-compression testing performed on samples taken from the site, shown on Figure 1, indicate the soils are moderately compressible under conditions of loading and (Inwood Spri rw, 'ii& _1)-15r.i.', ,1 6 r irlsc r iL'i *11-71 19 ♦ ( ,IuF,kI„ ,i,riIirs 719-633-5562 Mountain Air Builders LLC June 24,2014 Page 2 wetting. No free water was encountered in the excavation and the soils were slightly moist. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natural silty sand designed for an allowable soil bearing pressure of 1,500 pounds per square foot (psi) can be used for support of the proposed addition at the south and west elevation. We should be contacted to observe the soils exposed for the addition foundations at the north, east, and southeast side. It appears the foundations immediately east of the east side of the existing foundation wall will be on up to 8 feet of man-placed foundation wall backfill. The fill soils will not be suitable shallow foundation support. We recommend one of the following options be incorporated for these foundations: I) man-placed fill be removed and replaced with structural fill compacted to 98 percent the standard Proctor dry density, 2) the foundations extended clown to the relatively undisturbed soil , or 3) the use of a deep foundation system consisting of helical piers with a minimum tip elevation below the man-placed fill materials. We can provide further recommendations upon request. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils and existing fill in footing areas should be removed and the bearing level extended down to the undisturbed natural soils. Exterior footings should be provided with adequate soil cover above their bearing elevations for frost protection. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pounds per cubic foot (pcf) for on-site soil as backfill. Job No.414 151A Ctech Mountain Air Builders LLC June 24,2014 Page 3 The recommendations submitted in this letter are based on our observation of the soils exposed within the foundation excavation and do not include subsurface exploration to evaluate the subsurface conditions within the loaded depth of foundation influence. This study is based on the assumption that soils beneath the footings have equal or better support than those exposed. The risk of foundation movement may be greater than indicated in this report because of possible variations in the subsurface conditions. In order to reveal the nature and extent of variations in the subsurface conditions below the excavation, drilling would be required. It is possible the data obtained by subsurface exploration could change the 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. Please call if we can be of any further assistance. Sincerely, HEPWORTH - PAWLAK GEOTECHNICAL, INC. O?jOOC t og.Chad M. Bringle, P.E. � ` . 0 1p10 fit Project Engineer �. : 41153 • ¢S 1 14411 Attachments: Figure I—Swell-Compression Test Result °It;' AL E\‘‘ Job No.414 15 I A Gabech 2.0 - - Moisture Content= 13.2 percent 1.0 - Dry Unit Weight=98 pcf Sample of:SAND (SM), silty 0.0 From: HD-2 at Footing Subgrade Level Percent Passing the No.200 Sieve=23 0 J -1.0 J w F— Moderate Compression -2.0 on wetting — z -3.0 - O i 00 -4.0 w a -5.0 2 0 -6.0 -7.0 . -8A - - 0.1 1 10 100 APPLIED PRESSURE (KSF) • II HEPWORTH-PAWLAK 2764 SOUTH FRONTAGE ROAD 414 151A GEOTECHNICAL, INC. SWELL-COMPRESSION TEST RESULTS FIG. 1 KR M CONSULTANTS, INC. RECORD P.O. Box 4572 • Vail,Colorado 81658 • 970-949-9391 TO: Roland Lee Mountain Air Builders DATE: 6/24/2014 JOB NUMBER: I q0 1 - 09 PROJECT: Hoyt-Young Remodel I RFI L MEETING NOTES RESPONSE n CLARIFICATION/CHANGE I This letter is in regards to the installation of the steel dowels in the footings at the locations identified as 3/S6, 4/S6, 6/S6, 7/S6 and similar areas. Since there will be no other steel in the footings in these areas at the time of the concrete pour, these dowels may be installed after the concrete is poured, while it is still wet. SIGNED: COPY TO: D:zAllfr- Joe M. .'Malley, 'E f p F�E:GIS7 ?tip REVIEW ►• �0._%....1EA+••°F9F0 4f. ;p�0 hwv.o t,, AIM. 4 Titer nnum, PE i e 1E4 jc.t 4 4 fit*``„{ - -<'` I