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Home My WebLink AboutSoils ReportGtech HEPWORTH-PAWLAK GEOTECHNICAL November 19, 2014 Porforio Revilla 105 Summit Drive, Unit B Carbondale, Colorado 81623 Hep v rth-Pawlak GcutrLhnic.tl, int. 5020 County Por.td 154 Glenwood Springs, Culor:ulu 81601 Phone: 970-945-7988 Fax: 970-945-8454 cmati: hpgcu@hrgeotech.unn s-41 •,r LLj%%%jjJj�. Y s /it. 12/1 1 I .}tea NAV II /1914 � �tr7 �:frYr_-1.1:►:1}� i l_ Job No. 114 496A Subject: Observation of Excavation, Proposed Jaime Residence, 3911 County Road 100, Garfield County, Colorado Dear Mr. Revilla: As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the excavation at the subject site on November 3, 2014 and performed backfill compaction testing on November 14 and 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. The services were performed in accordance with our agreement for professional engineering services to you, dated November 4, 2014. The proposed residence will be a single story double -wide modular home supported on a spread footing foundation. The foundation has been designed based on an assumed allowable soil bearing pressure of 2,000 psf. At the time of our initial visit to the site, the foundation excavation had been cut in one level from 0 to 4 feet below the adjacent ground surface and filled about 2 feet deep at the west end. The soils exposed at design footing elevation consisted of natural sandy silt and clay in the majority of the excavation and recently placed, relatively soft sandy silt and clay fill at about the westernmost 10 feet of the building area. No free water was encountered in the excavation and the soils were slightly moist. Results of swell - consolidation testing performed on two relatively undisturbed samples of the natural sandy silt and clay, presented on Figure I, indicate relatively low compressibility under existing low moisture conditions and light Ioading, a low to moderate collapse potential (settlement under constant load) when wetted, and high compressibility potential under additional loading. A large bulk sample of the on-site sandy silt and clay fill was obtained and tested for standard Proctor to provide a reference value for compaction testing. The Proctor test results are presented on Figure 2. Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989 Porforio Revilla November 19, 2014 Page 2 We recommended to you to remove the existing fill from below footing areas and bear on the underlying natural soils or replace it with structural fill, compacted to at least 98 percent of standard Proctor density to re-establish design footing grade. The fill at the west end of the building area was reportedly re -worked and on November 14 we performed a nuclear gauge compaction test at the west footing line. The test indicated relatively low compaction at moisture content about 4 percent below optimum. The upper foot of under footing fill was then removed and the exposed fill surface was reportedly re -compacted using a walk -behind double drum vibratory roller. The top foot of fill was then replaced with compacted 3.i inch aggregate base course. A nuclear gauge test performed on November 18 in the compacted aggregate base course below the west footing line indicated the material was compacted to 98 percent compaction as recommended. Our field compaction test reports are attached for reference. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natural soil or suitably compacted structural fill designed for an allowable soil bearing pressure of 2,000 psf can be used for support of the proposed residence with a risk of settlement due to the variable bearing conditions. The exposed soils tend to compress when wetted and there could be post - construction settlement of the foundation if the bearing soils become wet. The settlement could be 1 to 2 inches assuming a limited depth of wetting and compressible soils of about 10 feet. Footings should be a minimum width of 20 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be compacted. The bearing soils should be protected against frost and concrete should not be placed on frozen 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 14 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for on-site soil as backfill. It will be critical to keep the bearing soils dry to prevent settlement and building distress. Backfill placed around the structure should be compacted and the surface graded to prevent ponding within at least 10 feet of the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads should not be located within 10 feet of the foundation and preferably only consist of xeriscape. Job No. 114 496A Porforio Revilla November 19, 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. If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Thomas J. Westhoff, CET Reviewed by: Steven L. Pawlak, P.E. TJW ksw Attachments Figure 1, Swell -Consolidation Test Results Figure 2, Proctor Compaction Test Report Earthwork Compaction Test Reports dated 11`14, 1814 Job No. 114 496A Compression Compression % 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 __,0 Moisture Content = 8.4 percent Dry Density = 95 pcf Sample af: Sandy Silt and Clay From: Bottom of Excavation at Northeast Corner, 11-3-14 Compression upon wetting 0.1 1.0 10 APPLIED PRESSURE - ksf 100 _„,3 Moisture Content = 9.1 percent Dry Density = 97 pcf Sample of: Very Sandy Silt and Clay From: Bottom of Excavation at East Side, 11-3-14 Compression upon wetting 0.1 1.0 10 APPLIED PRESSURE - ksf 100 114 496A H Hepworth—Pawlak Geotechnical SWELL -CONSOLIDATION TEST RESULTS Figure 1 ` COMPACTION TEST REPORT - 112.5 110 °, 1 1 .. I Will 1 107.5 • ,_ 0 a N c ru a' in 105( hh • 102.5 ZAV for Sp.G. = 2 40 9 100 10,5 12 13.5 15 16.5 18 19.5 Water content. Test specification: ASTM D 698-OOa Method A Standard Elevl Depth Classification Nat. Moist. Sp.G. LL PI % > #4 % < No.200 USCS AASHTO TEST RESULTS MATERIAL DESCRIPTION Maximum dry density m 110.0 pcf Optimum moisture = 13.5 % Sandy Silt and Clay Project No. 1 14496A Client: Porforio Revilla Project: 3911 County Road 100, Garfield County, Colorado o Location: Under Footing Fill Sample Number: 231-14 Remarks: Figure 2 Hepworth-Pawlak Geotechnical, Inc. Glenwood Springs, Colorado Tested By: KO Checked By: TJW Gtech HEPWORTH - PAWLAK GEOTECHNICAL 5020 County Road 154 Glenwood Springs, Colorado 81601 Phone: 970-945-7988 Fax: 970-945-8454 hpgeo a(�hpgeotech.com Earthwork Compaction Testing Report Client: Porforio Revilla 105 Summit Drive Unit B Carbondale, Colorado 81623 Job No.: 114496A Day: Friday Date: 11/14/14 Page: 1 of 1 Project: Proposed Jaime Residence, 3911 County Road 100, Garfield County, Colorado Weather: Cloudy, calm, snow overnight Temperature: 26° at 8:30 am Earthwork Contractor: Porforio Revilla Equipment Used: Mini -hoe, Wacker RT walk -behind double drum roller Description of Earthwork Fill below west footing line of proposed residence was tested. Results indicate Tested: unacceptable compaction at about 4 percent below optimum moisture. Verbal Communication: Porforio Revilla was informed of our test results. Placement and Compaction Procedure: Not observed by HP Geotech. Lift Thickness: Max. Rock Size: Compactor(s) Used: Test No. Location Moisture Conditioning: Number of Passes: Nuclear Gauge Moisture/Density Test Results Fill below west footing One Depth or Elev. Field Dry Density (pcf) Field Moisture Content Field Comp. (%) 1 5' N of SW building corner footing grade 93.8 9.5 85 Min. Comp. Req. (%) 98 Proctor Lab No. 231-14 Proctor Sample Reference: Lab No. Method Description Max. Dry Dens. (%) Opt. Moist. (%) 231-14 ASTM D 698 Sandy Silt and Clay 110.0 13.5 THIS rtcrun i rncaeNTS OPINIONS AS A RESULT OF OUR UBSERVATIONSOF FILL PLACEMENT, WE NAVE RELIED ON THE CONTRACTOR TO CONTINUE APPLYING THE RECOMMENDED COMPACTIVE EFFORT AND MOISTURE TO FILL DURING THE TIMES WHEN OUR OBSERVER IS NOT OBSERVING OPERATIONS THE NUCLEAR DENSOMETER METHOD OF TESTING WAS USED IN SUBSTANTIAL ACCORDANCE WITH ASTM D 6938 TJW/ Thomas J. Westhoff, CET Steven L. Pawlak, P.E. Field Technician Reviewed By Gtech HEPWORTH -PAWLAK GEOTECHNICAL Client: Porforio Revilla 105 Summit Drive Unit B Carbondale, Colorado 81623 Project: 5020 County Road 154 Glenwood Springs, Colorado 81601 Phone: 970-945-7988 Fax: 970-945-8454 hpgeo hpgeolech.com Earthwork Compaction Testing Report Job No.: 114496A Day: Date: Page: Tuesday 11/18/14 1 of 1 Proposed Jaime Residence, 3911 County Road 100, Garfield County, Colorado Weather: Clear, calm, dry Earthwork Contractor: Temperature: 35° at 2:00 pm Porforio Revilla Equipment Used: Description of Earthwork Tested: Verbal Communication: Mini -hoe, Wacker RT walk -behind double drum roller 314 inch aggregate base course placed as fill in the westernmost 10 feet of proposed building area was tested. Results indicate acceptable compaction at about 1.7 percent below optimum moisture. Porforio Revilla was informed of our test results. He stated that they had removed a foot of the fill and then compacted the exposed surface with several passes of the walk -behind roller. The top foot was then replaced with 314" aggregate base course compacted with the walk -behind roller. Placement and Compaction Procedure: Not observed by HP Geotech. Lift Thickness: Compactor(s) Used: Max. Rock Size: Moisture Conditioning: Number of Passes: Test No. Location Nuclear Gauge Moisture/Density Test Results Fill below west portion of building area Depth or Elev. Field Dry Density (pcf) Field Moisture Content Field Comp. (%) 1 Center of west footing line footing grade 130.2 5.8 98 Min. Comp. Req. (%) 98 Proctor Lab No. Typ. Proctor Sample Reference: Lab No. Method Description Max. Dry Dens. (%) Opt. Moist. (%) Typ. TYIC OL 6f1oT deccc..Tc. ASTM D 698 �n...,n.,.. . n . nwn•,. r w� w 314 Inch aggregate base course (typical value) ..... ..-�.�.-�� ... -. _ ��_ _-_ _ 134.0 7.5 COMPACTIVE EFFORT AND MOISTURE TO FILL DURING THE TIMES WHEN OUR OBSERVER IS NOT OBSERVING OPERATIONS THE NUCLEAR DENSOMETER METHOD OF TESTING WAS USED IN SUBSTANTIAL ACCORDANCE WITH ASTM O 6938 WE HAVE RELIED ON THE CONTRACTOR TO CONTINUE APPLYING THE RECOMMENDED TJW/ Thomas J. Westhoff, CET Steven L. Pawlak, P.E. Field Technician Reviewed By