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Home My WebLink About16-7-596.01 (11-06-18) Secondary Unit ExcObs signed.pdf H-P-.KU mAR5020 County Road 154 Glenwood Springs,CO 81601 Geotechnical Engineering I Engineering Geology Phone:(970)945-7988 Materials Testing I Environmental Fax:(970)945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs,and Silverthorne, Colorado November 6,2018 Paragon Homes Attn: Ed Venerable 6460 S. Quebec St. #400 Centennial, Colorado 80111 ed@paragonhomesdenver.com Project No. 16-7-596.01 Subject: Observation of Excavation, Proposed Secondary Unit of Duplex Residence, Lots 14A and 14B,Bighorn Fifth Addition,4872 Meadow Lane, Vail, Colorado Dear Ed: As requested, a representative of H-P/Kumar observed the excavation at the subject site on October 29 and November 1 and 6, 2018 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for are presented in this report. The services are supplemental to our agreement for professional services to Paragon Homes dated August 21, 2018. We previously observed the primary (north) duplex unit excavation at the site and presented our findings in a report dated August 23, 2018 under the above project number. We previously conducted a subsoil study for design of foundations at the site and presented our findings in a report dated February 7, 2017, Project No. 17-7-596. The proposed construction is similar to that discussed in that report. The secondary residence is the southern unit of the duplex at the site and has been designed to be supported on spread footings using an allowable bearing pressure of 2,000 psf based on recommendations provided in the subsoil study report. On October 29, the excavation was well underway and nearly complete, and had been cut generally at two levels up to about 40 feet below the adjacent ground surface daylighting to the northwest. The soils exposed in the bottom of the excavation consisted of relatively dense, silty sand and gravel with cobbles. The results of a gradation analysis performed on a sample of the silty sand and gravel with cobble soils (minus 3-inch fraction) obtained from the site are presented on Figure 1. Groundwater was encountered in the excavation and we recommended the groundwater be controlled by trenches to a sump and pump system or to gravity outlet as feasible. The soils were moist to wet. On November 1, a construction dewatering drain system had been installed consisting of a series of perimeter and interior drain pipes placed in shallow trenches with gravel below design footing elevation with the pipes out-letting to a perforated concrete manhole to the northwest of the excavation. The drains appeared to be adequately controlling the groundwater; however, a few Paragon Homes November 6, 2018 Page 2 wet areas of footing subgrade were observed. On November 6, we observed the excavation subgrade in all footing areas to be firm and the groundwater being adequately controlled, and the footing subgrade areas were not frozen. The footing areas were formed at this time. The soil conditions exposed in the excavation are generally consistent with those previously encountered on the site and suitable for support of spread footings designed for the recommended allowable bearing pressure of 2,000 psf. There could be some differential settlement due to the variable cut depths and assumed variable foundation loading. Loose and disturbed soils should be removed in the footing areas to expose the undisturbed natural coarse granular soils and the subgrade compacted. The water seepage into the excavation should continue to be collected and diverted away from the footing areas and any softened soils and mud removed before concrete placement. The bearing soils should be protected from frost and concrete should not be placed on frozen soils. 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 foundation 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, �i t IT et CI Z �s 32 13 f 7 David A. Young, ` oits&bi t DAY/kaciZYNAL r-rto�� attachments Figure 1 - Gracfation Test Results cc: Vail Construction Group—Jay Nobrega(iay@vailconstructiongroup.com) H-Pk4KUMAR Project No. 16-7-596.01 HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S.STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 MRS 100 45 MIN 15 MIN 60MIN 19MIN 4MIN 1MIN 6 00 1100 450 440 630 410 I10 8 44 3 6" 3 4' I I/2 3" 5.6. 6+0 I I 90 t I i H 180 IIPF I - 20 70 t r I ` I I 30 I 40 0 1 50 I I -- I 50 III 40 IIIIIM � r E I 60 30 IPi I 70 zo I 1 I I 1 i eo I — I io 1 - I r I I so 0 I I 11 1 I 1 1 1 1 1 1 1 11 t II 1 till I i 111111 I 1 .001 .002 .005 .009 .019 .037 .075 .150 .300 I .600 1.16 12.36 4.75 9.5 19 36.1 1 176.2 t 127 20000 I .425 152 DIAMETER OF PARTICLES IN MILLIMETERS CLAY TO SILT SAND GRAVEL FINE MEDIUM COARSE FINE COARSE COBBLES GRAVEL 46 % SAND 34 X SILT AND CLAY 20 SAMPLE OF: Silty Sandy Gravel FROM: Bottom of Southwest Portion of Secondary Unit Excavation, 10-29-18 •i Zi i i 1 I I i al1 I ;1 I i 1 These test results apply only to the ksamples which were tested. The testing report shall not be reproduced. except in full, without the written approval of Kumar& Associates. Inc. Sieve analysis testing is performed in accordance with ASTM D422, ASTM C136 and/or ASTM 01140. e ,6 1l' 16-7-596.1 H-P�KUMAR GRADATION TEST RESULTS Fig. 1