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HomeMy WebLinkAboutSoils Report 02.24.2004HEPWORTH-PAWT_AK GEOTECHNJCAL Hepwo n-FawI k Geotechnical, Inc. 5020 Count; Road 154 Glenwood Springs, Colorado 81601 Phone: 970-945-7988 Fax: 970-945-8454 email: hpgeo®hpgeotech.com PRELIMINARY SUBSOIL STUDY PROPOSED BIG R COMMERCIAL PARK 28485 HIGHWAY 6 . EAST OF RIFLE GARFIELD COUNTY, COLORADO JOB NO. 104 106 FEBRUARY 24, 2004 PREPARED FOR: RIFLE SKI CORPORATION ATTN: BOB REGULSKI P.O. BOX 9 RIFLE, COLORADO 81650 Parker 303-841-7119 0 Colorado Springs 719-633-5562 Silverthorne 970-468-1989 TABLE OF CONTENTS - PURPOSE AND SCOPE OF STUDY - I - PROPOSED DEVELOPMENT - 1 - SITE CONDITIONS - 2 - FIELD EXPLORATION - 2 - $f nj SUBSURFACE CONDITIONS - 2 - PRELIMINARY DESIGN RECOMMENDATIONS 3 - FOUNDATIONS _ 3 -` FLOOR SLABS - 4 - UNDERDRAIN SYSTEM _ 4 _ SURFACE DRAINAGE - 5 - LIMITATIONS - 5 - FIGURE 1 LOCATION OF EXPLORATORY BORINGS FIGURES 2 and 3 - LOGS OF EXPLORATORY BORINGS FIGURE 4 - LEGEND RAND NOTES FIGURE 5, 6 and 7 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1.- SUMMARY OF LABORATORY TEST RESULTS a. PURPOSE AND SCOPE OF STUDY proposed Big Rro the pp This report presents the results of a preliminary subsoil study for Colorado. Commercial Park located at 28485 Highway 6, East of Rifle, Garfield County, The project site is shown on. Figure 1. The purpose of the study was to evaluate the conducted in subsurface conditions and their impact on the project. The study was general accordance with our agreement for geotechnical engineering when the servicesto Rifle Ski conducted Corporation, dated January 7, 2004. Percolation testing well be performed ground thaws. A field exploration program consisting of exploratory borings was conducted to obtain information on the site and subsurface conditions. Samples of the subsoils obtain ed during the field exploration were tested in the laboratory to determine their classification, fi compressibility or swell and other engineering characteristics. The results of theeld exploration and laboratory testing were analyzed to develop recommendations for project planning and preliminary' design. This report summarizes the data obtained during this study and presents our conclusions and recommendations based on the proposed development and subsurface conditions encountered. PROPOSED DEVELOPMENT The proposed development consists of a 16 lot commercial subdivision as shown on Figure 1. The proposed buildings in the development will likely consist of large steel frame, metal skin buildings with slab -on -grade floors. The development will be serviced with individual wells and septic disposal systems. If development plans change significantly from those described, we should be notified to re-evaluate the recommendations presented in this report. -2 - SITE CONDITIONS The site was vacant and covered with about 6 inches of snow at the time of our field exploration. Existing commercial buildings are located on Lots 2 through 6 of the development. The ground surface on the property is relatively flat with a slight slope down to the southwest. Irrigation ditches are located along the northern side of the property. Vegetation consists of scattered brush and trees; grass and weeds. FIELD EXPLORATION The field exploration for the project was conducted on January 16, 2004. Six exploratory borings were drilled at the locations shown on Fig. 1 to evaluate the subsurface conditions. The borings were advanced with 4 inch diameter continuous flight auger powered by a truck -mounted CME -45B drill rig. The borings were logged by a representative of Hepworth-Pawlak Geotechnical, Inc. Slotted PVC pipe was placed in each of the borings to allow for monitoring of future water levels. Samples of the subsoils were taken with a 2 inch I.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing: SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils consist of about 1 to 2 feet of topsoil overlying stiff and slightly moist to soft and very moist, sandy clay and silt with stratified silty sand layers. Relatively dense, Job No. 104 106 Gtech -3 - slightly clayey silty sandy gravel containing cobbles and probable boulders was encountered beneath the clay and silt at depths between about 22 and 31Y2 feet. Drilling in the dense gravel with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, unconfined compressive strength testing and finer than sand size gradation analyses. Results of swell -consolidation testing performed on relatively undisturbed drive samples of the upper clay and sand soils, presented on Figures 5, 6 and 7,.indicate low to moderate compressibility under conditions of loading and wetting. The shallow clay samples showed a low to moderate expansion potential when wetted under a constant light surcharge with swelling pressures measured in the range of about 2,000 to 6,000 psf. Unconfined compressive strength testing was performed on two of the more moist clay and silt samples with measured strengths of about 1,400 and 1,950 psf. The laboratory testing is summarized in Table L Groundwater was measured in the borings at depths between 9 and 23 feet. The upper subsoils were slightly moist to very moist with depth. PRELIMINARY DESIGN RECOMMENDATIONS The conclusions and recommendations presented below are based on the proposed development, subsurface conditions encountered in the exploratory borings and our experience in the area. The recommendations are suitable for planning and preliminary design but site specific studies should be conducted for individual lot development. FOUNDATIONS Bearing conditions will vary depending on the specific Location ofthe building on the property. Spread footings placed on the natural shallow silt and clay soils appear suitable with some risk of settlement/heave due to loading and wetting of the bearing soils. We Job No. 104 106 Gtech -4- ' expect the footings can be sized for an allowable bearing pressure in the range of 1,500 psi to 2,500 psf. Bearing levels should not be deeper than about 5 feet below the existing Expansive clays encountered in building areas may need to be removed or the footings designed to impose a minimum dead load pressure to limit potential heave. A deep foundation system, such as driven piles or helical piers, may be needed if highly expansive clays are encountered. Foundation walls should be designed to span local anomalies and to resist lateral earth loadings when acting as retaining structures. Below grade areas and retaining walls should be protected from wetting and hydrostatic loading by use of an underdrain system. The•footings should have a minimum depth of 36 inches for frost protection. ground surface. FLOOR SLABS Slab -on -grade de construction should be feasible for bearing on the non -expansive natural soils below the topsoil. There could be some post construction slab movement at sites with soils that tend to heave or settle when wetted. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints. Floor slab control joints should be used to reduce damage due to shrinkage cracking. A minimum 4 inch. thick layer of free -draining gravel should underlie basement level slabs to facilitate drainage. In more expansive clay areas, a structurally supported floor may be warranted to limit possible distress caused by wetting of the expansive clays. UNDERDRAIN SYSTEM Although free water was encountered below expected excavation depths, it has been our experience in the area and where clays are present that local perched groundwater can develop during times of heavy precipitation or seasonal rnnoff. An underdrain system. should be provided to protect below -grade construction, such as retaining walls and basement areas from wetting and hydrostatic pressure buildup. The drains should consist of drainpipe surrounded above the invert level with free -draining granular material. The -5 - drain should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet or sump and pump. Typically buildings with slab -on -grade floor at near the exterior surrounding grade should not require an underdrain system. SURFACE DRAINAGE The grading plan for the development should consider runoff from adjacent lots through the project and at individual sites. Potential overflow from irrigation ditches should also be considered in the drainage plan. Water should not be allowed to pond which could impact foundations. To limit infiltration into the bearing soils next to buildings, exterior backfill should be well compacted and have a positive slope away from the building for a distance of 10 feet. Roof downspouts and drains should discharge well beyond the Limits of all backfill and landscape irrigation should be restricted. LIMITATIONS This study has been conducted according to generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory borings located as shown on Figure 1, the proposed type of construction and our experience in the area. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for planning and preliminary design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued Job No. 104 106 GecPtedh -6 - consultation, conduct additional evaluations and review and monitor the implementation of our recommendations. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fillby a representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK GEO Jordy Z. Adamson, Jr. P.E Reviewed by: ( \D-k.Q„ Daniel E. Hardin, P.E. JZA/ksw Job No. 104 106 Gtech APPROXIMATE SCALE 1"=250' 5360 5370 5365 5375 BORING 3 © BORING 4 19`\ • \ • 0 BORING 5 LEGEND: • EXPLORATORY BORING 0 LOT NUMBER 0 BORING 1 � 16 5375 • BORING 2 0 d BORING 6 L _ J EXISTING \ BUILDINGS (TYPICAL) L.._J 0 5370 / 5360 J 5365 ACCESS EASEMENT 104106 HEP WORTH--PAWLAK GEOTECHNICAL, INC. LOCATION OF EXPLORATORY BORINGS Figure 1 0 5 10 15 20 25 30 BORING 1 ELEV.= 5377' 15/12 WC=11.7 DD=110 4/12 W0=18.3 DD=107 —200=74 UC=1400 4/12 4/12 BORING 2 ELEV.= 5372' 12/12 6/12 WC=120 DD+112 WOH WOH BORING 3 ELEV.= 5373' 14/12 7/12 WCC15.0 DD=110 —200=86 3/12 1/12 0 5 10 15 20 25 30 35 35 Note: Explanation of symbols is shown on Figure 4. FYI Depth — Feet 104 106 HEPWORTH—PAWLAK I LOGS OF EXPLORATORY BORINGS GEOTECHNICAL, INC. Figure 2 BORING 4 ELEV.= 5371' 12/12 10/12 WC=5.3 DD=120 —200=29 WOH WOH BORING 5 ELEV.= 5367' 11/12 WC=9.5 OD=112 5/12 WC=18.8 DD=103 —200=91 UC=1950 2/12 3/12 BORING 6 ELEV.= 5367' Note: Explanation of symbols is shown on Figure 4. 13/12 7/12 WC=8.2 DD=107 —200=64 10/12 10/12 11/12 0 5 10 15 20 25_ 30 Depth — Feet 104 106 HEPWORTH—PAWLAK GEOTECHNICAL, INC. LOGS -OF EXPLORATORY BORINGS Figure 3 a fLEGEND: r--• ti/ -7 15/12 0,1 WOH TOPSOIL; sandy silty clay, organics, firm, moist, brown, upper 8 inches frozen. CLAY AND SILT (CL—ML); sandy, silty sand layers, strotified, stiff and slightly moist to soft and very moist with depth, wet below groundwater level, brown. GRAVEL (GM); silty, sandy, slightly clayey, with cobbles and possible boulders, dense, wet, brown, subrounded to rounded rock. Relatively undisturbed drive sample; 2—inch I.D. California liner sample. Drive sample blow count; indicates that 15 blows of a 140 pound hammer falling 30 inches were required to drive the California sampler 12 inches. Free water level in boring and number of days following drilling measurement was token. Weight of hammer pushed sampler 12 inches. (No blows) Depth at which boring had caved when checked on January 17, 2004. Practical drilling refusal. Indicates slotted PVC pipe installed in boring to depth shown. NOTES: 1. Exploratory borings were drilled on January 16, 2004 with a 4—inch diameter continuous flight power auger. 2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. 3. Elevotlons of exploratory borings were obtained by interpolation between contours on the site plan provided. Logs are drawn to depth. 4. The exploratory boring locations and elevations should be considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the exploratory between material types and transitions may be grcdu 6. Water level readings shown on the Iogs were made at Fluctuation in water level may occur with time.. 7. Laboratory Testing Results: WC = Water Content ( % ) DD = Dry Density ( pcf ) —200 = Percent passing No_ 200 sieve UC = Unconfined Compressive • Strength (psf) 104 105 1 HEPWORTH—PAWLAK GEOTECHNICAL, INC. boring logs represent the approximate boundaries al. the time and under the conditions indicated. LEGEND AND NOTES Figure 4 Expansion % Compression Compression -- Expansion 1 0 1 2 1 0 1 2 Moisture Content = 11.7 percent Dry Density = 110 pcf Sample 'of: Sandy Silty Clay From:Boring 1 at 1 Foot Expansion upon wetting 0.1 1.0 10 APPLIED PRESSURE — ksf 100 0.1 Expansion upon wetting Moisture Content = 12.0 percent Dry Density = 112 pcf Sample of:Sandy Silty Cloy From:Boring 2 at .3 Feet J .0 10 APPLIED PRESSURE — ksf 100 104 106 HEPWORTH—PAWLAK GEOTECHNICAL, INC_ SWELL—CONSOLIDATION TEST RESULTS Figure 5 0 1 3 U Com pression 4 0 1 2 3 4 Moisture Content = 18.0 percent Dry Density = 110 pcf Sample of: Sandy Silty Clay From:Boring 3 at 5 Feet Nc No movement upon wetting \) 0.1 1.0 10 APPLIED PRESSURE — ksf 100 Moisture Content = 5.3 percent Dry Density = 120 pcf Sample of: Silty Sand From:Boring 4 at 5 Feet Compression upon wetting NcN 0.1 1.0 10 APPLIED PRESSURE — ksf 100 104 106 HEPWORTH—PAWLAK GEOTECHNICAL, INC. SWELL—CONSOLIDATION TEST RESULTS Figure 6 Compression — Expansion 2 1 0 1 2 c 1 0 0 a w 0 O • 1 0 0 G) E 0 U 0.1 Moisture Content = 9.5 percent Dry Density = 112 pcf Sample of: Sandy Silty Clay From: Boring 5 at 1i Feet .0 0 APPLIED PRESSURE — ksf 100 Moisture Content = 8.2 percent Dry Density = 107 pcf Sample bf: Very Sandy Silty Clay From:Boring 6 at 5 Feet 0.1 Expansion upon wetting 1.0 10 APPLIED PRESSURE — ksf 100 104 106 GEOTECHNICAL, INC. HEPWORTH—PAWLAK SWELL—CONSOLIDATION' TEST RESULTS I Figure 7 • - irs..*''''',,,_ Expansion upon wetting 0.1 Moisture Content = 9.5 percent Dry Density = 112 pcf Sample of: Sandy Silty Clay From: Boring 5 at 1i Feet .0 0 APPLIED PRESSURE — ksf 100 Moisture Content = 8.2 percent Dry Density = 107 pcf Sample bf: Very Sandy Silty Clay From:Boring 6 at 5 Feet 0.1 Expansion upon wetting 1.0 10 APPLIED PRESSURE — ksf 100 104 106 GEOTECHNICAL, INC. HEPWORTH—PAWLAK SWELL—CONSOLIDATION' TEST RESULTS I Figure 7 HEPWORTI-I-PAWLAK (L_,../TECHNICAL, INC. TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Joh No. 104 106 SAMPLE LOCATION NATURAL MOISTURE CONTENT (WO NATURAL DRY DENSITY (KO GRADATION PERCENT PASSING NO. 200 SIEVE A1TERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH {PSr) SOIL OR BEDROCK TYPE BORING DEPTH - ({t) GRAVEL n �u) SAND o �u) LIQUID LIMIT • (%) PLASTIC INDEX (%) 1 1 11.7 110 • Sandy silty clay 5 18.3 107 74 1400 Sandy clay and silt • 2 3 12.0 112Sway silty clay 5 18.0 110 88 Sandy silty clay 4 5 5.3 120 29 Silty sand 5 1% 9.5 112 Sandy silty clay 5• 18.8 103 91 1950 Slightly sandy silty clay 6 S 3.2 .107 - 64 Very sai.acly silty clay Gtech HEPWORTH - PAWLAK GEOTECHNICAL June 23, 2004 Rifle Ski Corporation Attn: Bob Regulski P.O. Box 9 Rifle, Colorado 81650 1-lepworth-Pawlak Geotechnical, Inc. 5020 County Road 154 Glenwood Springs, Colorado 81601 Phone: 970-945-7988 Fax: 970-945-8454 email: hpgeo®hpgeotech.com Job No. 104 106 Subject: Gamma Radiation Survey, Proposed Big R Commercial Park, 28485 Highway 6, East of Rifle, Garfield County, Colorado. Dear Mr. Regulski: As requested, we have performed a radiation survey at the subject site. The findings and conclusions of our survey are presented in this report. We previously conducted a preliminary subsoil study for the commercial development and presented our findings in a report dated February 24, 2004, Job No. 104 106. Proposed Development: The proposed development consists of a 16 lot commercial subdivision. The commercial buildings will likely consist of large steel frame, metal skin structures and will be serviced by individual wells and septic disposal systems. Site Conditions: The area of the proposed development is located to the east of Rifle and is bordered on the south side by Highway 6. Existing commercial buildings are located on Lots 2 through 6 of the development. The site consists of previously irrigated farmland with irrigation ditches along the northern side of the property. The ground surface on the property is relatively flat with a slight slope down to the southwest. Vegetation outside the developed areas consists of scattered brush and trees, grass and weeds. Radiation Survey: A gamma radiation survey was conducted in the development area on June 21 and 22, 2004. Gamma radiation measurements were taken on about 200 foot spacings throughout the property with additional measurements taken adjacent existing buildings to evaluate potential imported backfill using a Ludlum Model 3 survey meter Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthome 970-468-1989 Rifle Ski Corporation June 23, 2004 Page 2 and Ludlum Model 44-9 detector. The readings were taken about 2'/2 feet above the ground surface. The survey points and readings are summarized on Figure 1. The 56 readings ranged from 0.015 to 0.03 millirems per hour with an average of about 0.025 millirems per hour. Background readings taken approximately % mile to the east of the property were 0.02 millirems per hour. Conclusions: The gamma radiation readings taken at the site appear to be typical of natural background levels in the area. No mitigation of the radiation should be required. If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH — PAWLAK G !--`'";'�::�M., INC. 'V4. ADA . .[_ O.Sd Jordy Z. Adamson, Jr. Rev. by: SLP JZA/ksw attachment Figure 1— Location of Radiation Survey Points Job No. 104 106 GEtech APPROXIMATE SCALE 1" = 250' 104 106 .03 _025 �- 025 LEGEND: • .015 .02 .025 .03 .02 .03 .03 .025 .02 .02 .025 .025 .025 .015 025 .025 .02 .025 .025 -• _025 .025 _025 .02 _03 .025 .025 .03 EXISTING BUILDINGS (TYPICAL) 1- 1 025 .025 -- .025 s 25 ".0+1` \ .02 i .02 .02 i-. L - J 025 .025 025 C� x.025 -x.02 6�Z .02 S �`GkIlP`l V \•� .02 .03 .03 .025 .03 .025 .025 _015 RADIATION SURVEY POINT,READINGS IN MILLIREMS PER HOUR .025 ,1 31 ---- ACCESS 015 ' EASEMENT .025 HEPWORTH—PAWLAK GEOTECHNICAL, INC. LOCATION OF RADIATION SURVEY POINTS Figure 1