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HomeMy WebLinkAbout1.07 Geotechnical ReportGEOTECHNICAL REPORT Gtech Hepworth - Pawlak Geotechnical, Inc. 5020 Couiify Road 154 Glenwood Springs, Colorado 81601 Phone: 970-945-7988 Fax: 970 - 945 -8454 hpgeo@hpgeotech.com PRELIMINARY GEOTECHNICAL STUDY PROPOSED T. O. RANCH SUBDIVISION ROAD 100 AND HIGHWAY 82 GARFIELD COUNTY, COLORADO JOB NO. 100 661 DECEMBER 19, 2000 PREPARED FOR: MARY ANN HYDE P.O. BOX 1557 ASPEN, COLORADO 81612 HEPWORTH - PAWLAK GEOTECHNNICAL, INC. December 19, 2000 Mary Ann Hyde P.O. Box 1557 Aspen, Colorado 81612 Job No. 100 661 Subject: Report Transmittal, Preliminary Geotechnical Study, Proposed T.O. Ranch Subdivision, 100 Road and Highway 82, Garfield County, Colorado Dear Ms. Hyde: As requested, we have conducted a geotechnical study for the proposed subdivision. The property is suitable for the proposed development based on geologic and geotechnical conditions. Potential storm water impacts from uphill drainage on the property should be considered in the development. Subsurface conditions encountered in the exploratory borings drilled in the proposed development area consist of about 2 to 15 feet of sandy clay and silty sand overlying dense river gravel alluvium. Groundwater was not encountered in the borings to the drilled depths of 6 to 18 feet. The upper soils were moist to very moist with depth. Spread footings placed on the natural subsoils and designed for an allowable bearing pressure in the range of 1,000 psf to 1,500 psf appear suitable for building support. Footings that bear entirely on the underlying dense gravels can be designed for 3,000 psf. Infiltration septic disposal systems appear feasible. The system may need to extend through the clay soils and into the underlying river gravel alluvium at Lot 1. The report which follows describes our exploration, summarizes our findings, and presents our recommendations suitable for planning and preliminary design. It is important that we provide consultation during design and field services during construction to review and monitor the implementation of the geotechnical recommendations. If you have any questions regarding this report, please contact us. Sincerely, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Steven L. Pawlak, P.E. Rev. by: DEH SLP/ksw TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY 1 PROPOSED DEVELOPMENT 1 SITE CONDITIONS 2 GEOLOGIC SETTING 2 FIELD EXPLORATION SUBSURFACE CONDITIONS GEOLOGIC SITE ASSESSMENT STORM WATER AND DEBRIS MANAGEMENT 4 SINKHOLES 5 REGIONAL EVAPORITE DEFORMATIONS 5 MOISTURE SENSITIVE SOILS 6 CONSTRUCTION RELATED SLOPE INSTABILITY 6 EARTHQUAKE CONSIDERATIONS 6 PRELIMINARY DESIGN RECOMMENDATIONS 7 FOUNDATIONS 7 FLOOR SLABS 7 UNDERDRAIN SYSTEM 8 SITE GRADING 8 SURFACE DRAINAGE 8 PERCOLATION TESTING 9 LINIITATIONS 9 REFERENCE 10 FIGURE 1 - GEOLOGY MAP FIGURE 2 - EXPLORATORY BORING LOCATIONS FIGURE 3 - LOGS OF EXPLORATORY BORINGS FIGURE 4 - LEGEND AND NOTES FIGURES 5 & 6 - SWELL- CONSOLIDATION TEST RESULTS TABLE I - SUMMARY OF LABORATORY TEST RESULTS TABLE II - PERCOLATION TEST RESULTS PURPOSE AND SCOPE OF STUDY This report 'presents the results of a preliminary geotechnical study for the proposed T.O. Ranch Subdivision located at Road 100 and Highway 82, Garfield County, Colorado. The project site is shown on Figs. 1 and 2. The purpose of the study was to evaluate the geologic and subsurface conditions and their potential impacts on the project. The study was conducted in accordance with our proposal for geotechnical engineering services to Mary Ann Hyde, dated May 4, 2000. A field exploration program consisting of a reconnaissance and exploratory borings was conducted to obtain information on the site and subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for project planning and preliminary design. This report su nmarizes the data obtained during this study and presents our conclusions and recommendations based on the proposed development and subsurface conditions encountered. PROPOSED DEVELOPMENT The 17 acre TO Ranch will be subdivided into three single- family residential lots, see Figs. 1 and 2. The lots will be between 4 and 7 acres. Specific building types and locations had not been determined at the time of this study. It is expected that the residences will be relatively large, 2 to 3 story buildings. In addition to the residences, outbuildings and other axillary structures may also be built on the lots. The residences will have individual wells and sewage disposal facilities. Primary access to the lots will be a common driveway located along the northern boundary of Lot 1. If development plans change significantly from those described above, we should re- evaluate the recommendations presented in this report. H -P GEOTECH L� SITE CONDITIONS The TO Ranch is located near Catherine's Store in the Roaring Fork valley about 3 miles upstream of Carbondale. The property covers parts of the northern half of Section 31, T. 7 S., R. 87 W. Highway 82 borders the property on the south and County Road. 100 borders the property to the east. The Roaring Fork River is located about 3,000 feet south of the highway. The topography on the property is shown on Figs. 1 and 2. Slopes on the property are nearly level to gently sloping, in the range of 1% to 5%. The property is on two alluvial fans that developed at the mouths of two tributary drainages with basins on the northern valley side, see Fig. 1. The drainage basin upslope of the western fan is large and covers more than 2,500 acres. The drainage basin upslope of the eastern fan is considerably smaller and covers about 30 acres. The streams that drain these two basins are ephemeral and only have flow following intense precipitation. At the time of our field work, the property was an irrigated pasture and hay field. Residences, commercial facilities and ranches are located on the adjacent properties. GEOLOGIC SETTING The general geologic features at the TO Ranch and vicinity are shown on Fig. 1. The property is on the fourth river terrace level (Qt4) above the Roaring Fork River. In this part of the valley the fourth terrace lies about 20 feet above the river and the higher fifth terrace (Qt5) is about 100 feet above the river. A steep escarpment separates the fourth and fifth terrace levels. Alluvial fans (Qaf) have developed at the mouths of the tributary drainages along the base of the escarpment. Alluvial aprons (Qaa) are present at the base of the escarpment between the alluvial fans. The fourth terrace level (Qt4) is underlain by glacial outwash that correlates with the late Pleistocene Pinedale glacial period (Kirkham and Widmann, 1997). The exploratory borings show that the alluvial fan deposits near the borings are between 2 to 15 feet thick and overlie glacial outwash. The fan deposits are a low to medium plasticity silty sand and sandy clay with scattered angular rock fragments. The H -P GEOTECH -3 underlying outwash consists of rounded gravel, cobbles and boulders in a silty to clean sand matrix. The fans are geologically young and are largely the product of sediment deposited by infrequent flash foods and associated debris flows and debris floods. Regional geology mapping shows that formation rock in the project area is the Pennsylvanian age Eagle Valley Evaporite (Kirkham and Widmann, 1997). The evaporite crops out on the valley sides to the north and south of the project area, but is covered by surficial soils at the project site. The Eagle Valley Evaporite is a gray to tan gypsum, anhydrite and halite with interbedded siltstone, claystone, shale and dolomite. Bedding in the rock is usually complexly folded because of flow of the plastic evaporite. The gypsum, anhydrite and halite are soluble in fresh water. Subsurface voids and related sinkholes are sometimes present in areas where the Eagle Valley Evaporite is near the ground surface. Regional geologic mapping shows that sinkholes are present on the older alluvial fans about 1000 feet to the north of the property. FIELD EXPLORATION The field exploration for the project was conducted on November 22 and December 15, 2000. Three 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 Longyear BK -51HD drill rig. The borings were logged by a representative of Hepworth - Pawlak Geotechnical, Inc. Samples of the subsoils were taken with 1% inch and 2 inch I.D. spoon samplers. The samplers were 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, Fig. 3. The samples were returned to our laboratory for review by the project engineer and testing. H -P GEOTECH r. 4 SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Fig. 3. Below about 1 foot of topsoil, the subsoils consist of medium to stiff sandy clay and loose to medium dense silty sand overlying dense, slightly silty sandy gravel, cobbles and boulders. Drilling in the dense gravel alluvium with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit at depths of 6 feet to 18 feet. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, finer than sand size gradation analyses and liquid and plastic limits. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the upper clays and silty sands, presented on Figs. 5 and 6, indicate moderate compressibility under conditions of loading and wetting. The clay soils are low to medium plasticity and medium to stiff consistency. The laboratory testing is summarized in Table L No free water was encountered in the borings at the time of drilling or when checked 3 days later. The upper soils were moist to very moist with depth. 1 GEOLOGIC SITE ASSESSMENT There are several conditions of a geologic nature that should be considered in project planning and design. These conditions and their expected influence on the proposed development are discussed below. STORM WATER AND DEBRIS MANAGEMENT The alluvial fans in the project area are geologically young and are potential sites of debris flows and debris floods associated with thunderstorms. The existing drainage channels on the fans are shallow and usually poorly defined. A hydrologist should evaluate if the existing fan channel system has the capacity to convey the appropriate design flash floods and associated debris flows and debris floods. If the appropriate design flash flood cannot be contained in the existing channel system then H -P GEOTECH 5 channel improvements should be considered. If it is not possible to route the design flash floods through the project in the existing or improved channels, then other mitigation options could be deflection berms and building flood proofmg. The appropriate mitigation method will largely depend on the building locations, the size of the design flash flood and risks acceptable to the developer and home owners. SINKHOLES Evidence of sinkholes were not observed on the property, however sinkholes are known to be present in the region. The sinkhole risk on the property is viewed to be low and no greater than that present in other parts of northwestern Colorado where the evaporite is near the surface. The potential for shallow subsurface voids that could develop into sinkholes should be considered when planning site specific geotechnical studies at the building sites. If conditions indicative of sinkhole related problems are encountered, the building site should be abandoned or the feasibility of mitigation evaluated. Mitigation measures could include: • Stabilization by Grouting • Stabilization by Excavation and Backfitlling • Deep Foundation Systems • Structural Bridging • Mat Foundations • Set -back from the Sinkhole Water features such as landscape ponds are not recommended near building sites unless evaluated on a site specific basis. Home owners should be advised of the sinkhole potential, since early detection of foundation distress and timely remedial actions are important in reducing the cost of remediation, should a sinkhole start to develop after construction. REGIONAL EVAPORITE DEFORMATIONS The project site is in an area where broad regional ground deformations have been associated with evaporite solution and flow. An evaporite related subsidence trough has been identified on the outwash terrace about one mile to the east of the H -P GEOTECH LJ L. L 6 project area (Kirkham and Others, 1998). The trough is about 4,500 feet long and 1000 feet wide. It is uncertain if geologic processes that produced this subsidence trough and others in the region are still active or if deformation has stopped. If regional ground deformations are still occurring their rates are low and differential movements over short distances are unlikely. Because of this, the risk of regional deformation problems to residential buildings in the project area is considered to be low. We are unaware of problems associated with possible broad evaporite deformations in the region. MOISTURE SENSITIVE SOILS It has been our experience that the alluvial fans in the Roaring Fork River valley can be moisture sensitive and have the potential for relatively large differential compression if the deposits are relatively deep and wetted after construction. Preliminary recommendations for foundations on the alluvial fans are presented in the Preliminary Design Recommendations section of this report. The potential for moisture sensitive soils should be evaluated on a site specific basis during development on the lots. CONSTRUCTION RELATED SLOPE INSTABILITY We do not expect major problems with construction related slope instability if grading is engineered and extensive grading is not needed for the residences. Preliminary recommendations for site grading are presented in the Preliminary Design Recommendations section of this report. EARTHQUAKE CONSIDERATIONS The project area could experience moderately strong earthquake related ground shaking. Modified Mercalli Intensity VI ground shaking should be expected during a reasonable service life for the residences, but the probability for stronger ground shaking is low. Intensity VI ground shaking is felt by most people and causes general alarm, but results in negligible damage to structures of good design and construction. Occupied structures should be designed to withstand moderately strong ground shaking with little or no damage and not to collapse under stronger ground shaking. The region is in the H -P GEOTECH 7 Uniform Building Code, Seismic Risk Zone 1. Based on our current understanding of the earthquake hazard in this part of Colorado, we see no reason to increase the commonly accepted seismic risk zone for the area. 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 could vary depending on the specific building location and excavation depth on the property. Based on the nature of the proposed construction, spread footings placed on the natural subsoils should be suitable for building support. We expect the footings can be sized for an allowable bearing pressure in the range of 1,000 psf to 1,500 psf. Footings that bear entirely on the underlying dense gravel alluvium can be designed for an allowable bearing pressure of 3,000 psf. There could be locally soft wet soils that need to be removed or stabilized in footing areas. 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 Ioadnng by use of an underdrain system. The footings should have a minimum depth of 36 inches for frost protection. FLOOR SLABS Slab -on -grade construction should be feasible for bearing on the natural soils below the topsoil. There could be some post construction slab movement at sites with hydrocompressive soils. 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 craclanng. A H -P GEOTECH -8 minimum 4 inch thick layer of free - draining gravel should underlie basement level slabs to facilitate drainage. UNDERDRAIN SYSTEM Although free water was not encountered in the exploratory borings, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. 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 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. SITE GRADING The risk of construction - induced slope instability at the site appears low provided cut and fill depths are limited to about 10 feet. More extensive grading may be feasible and should be studied on a site specific basis. Structural fills should be compacted to at least 95 % of the maximum standard Proctor density near optimum moisture content. Prior to fill placement, the subgrade should be carefully prepared by removing all vegetation and topsoil. The fill should be benched into slopes that exceed 20 % grade. The on -site soils excluding oversized rock and topsoil should be suitable for use in embankment fills. Some of the clays are very moist and could require drying before use as structural fill. Permanent unretained cut and fill slopes should be graded at 2 horizontal to 1 vertical or flatter and protected against erosion by revegetation, rock riprap or other means. SURFACE DRAINAGE The grading plan for the subdivision should consider runoff from steep uphill slopes through the project and at individual sites. Water should not be allowed to pond which could impact slope stability and foundations. To limit infiltration into the bearing soils next to buildings, exterior backfill should be well compacted and have a positive H -P GEOTECH -9 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. PERCOLATION TESTING Percolation tests were conducted on November 28 and December 18, 2000 to evaluate the feasibility of infiltration septic disposal systems at the site. One percolation hole was drilled next to each of the three exploratory borings at locations as shown on Fig. 1. The test holes were drilled with 6 inch diameter auger and were soaked with water one day prior to testing. The soils encountered in the percolation holes are similar to those encountered in the exploratory borings shown on Fig. 2 and consist of stiff sandy clay and silty sand. The percolation test results are presented in Table II and indicate variable percolation rates. Based on the subsurface conditions encountered and the percolation test results, the tested areas appear suitable for conventional infiltration septic disposal systems. Due to possible slow percolation rates in the clay soils encountered at Lot 1, the disposal system may need to be extended down into the underlying gravel alluvium. A civil engineer should design the infiltration septic disposal system for each lot. LINIITATIONS 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 expressed or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the field reconnaissance, review of published geologic reports, the exploratory borings located as shown on Figs. 1 and 2, 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 H -P GEOTECH - 10 - 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 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 fill by a representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK ; = "` :..� CAL, INC. Steven L. Pawlak, P. Reviewed by: Daniel E. Hardin, SLP/ksw cc: Land Design Partners - Attn: Ron Liston REFERENCE Kirkham, R.M. and Widmann, B.L., 1997, Geology Map of the Carbondale Quadrangle, Garfield County, Colorado: Colorado Geological Survey Open File 97 -3. Kirkham, R.M. and Others, 1998, Geology Map of the Leon Quadrangle, Eagle and Garfield Counties, Colorado: Colorado Geological Survey Open File 98 -3. H -P GEOTECH Qafo Qt5 Qaa too I f 1 1 �-- 1 l 1 I 1 l 1 � �3 1 j <�Qafo I ` Qafo fo / '~ -.... __'� '% Qt5 .. Qt5 _ ▪ �� 1 • i r-- ,� �, Qaa Qaf 7 I• Lot 3 • B4 Ale P-2 32 dot 2 Qt4 Catherine's Store EXPLANATION; Qaf - Alluvial Fan Qafo Old Alluvial Fan Qaa - Alluvial Apron Qt4 - Fourth Terrace Level Qt5 - Fifth Terrace Level — — — Contact (approx.) • Baring (approx.) 0 Perciolalion Test (approx.) 0 300 ft Scale 1 In. = 30011 Contours 1 ft. • 1 0 001] HEPWORTH- PAWLAK 100 GEOTECHNICAL, Inc TO Ranch - Exploratory Boring Locations 10 15 20 BORING 1 ELEV. =6286' RI 1B /12 WC =16.8 DD =110 -200=86 LL =28 PI =12 BORING 2 BORING 3 ELEV. =6289' ELEV. =6291' 13/12 WC =8.0 DD =103 - 200 =61 7/12 WC =11.2 DD =110 7/12 5/2,15/0 26/12 9/12 WC =11.7 DD =110 .- 200 =50 6/12 WC =15.5 DD =111 16/5,10/0 Note: Explanation of symbols is shown on Fig. 4. 10 15 20 100 661 HEPWORTH- -PAWLAK 1 LOGS OF EXPLORATORY BORINGS GEOTECHNICAL, INC. Fig. 3 LEGEND: ElTOPSOIL; organic sandy silty and clay, slightly moist, dark brown. 1 L CLAY (CL); sandy, silty, medium to stiff, moist to very moist, brown, low to medium plasticity. SAND (SM); silty to very silty, gravelly layers, scattered cobbles, loose to medium dense, moist to very moist, brown. GRAVEL, COBBLES, AND BOULDERS (GM-GP); slightly silty sandy, dense to very dense, slightly moist, brown, rounded rock. Relatively undisturbed drive sample; 2-inch I.D. California liner sample. Drive sample; standard penetration test (SPT), 1 3/8 inch I.D. split spoon sample, ASTM D - 1586. Drive sample blow count; indicates that 18 blows of a 140 pound hammer 18/12 falling 30 inches were required to drive the California or SPT sampler 12 inches. Practical drilling refusal. NOTES: 1. Exploratory borings were drilled on November 22 and December 15, 2000 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. Elevations 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 boring logs represent the approximate boundaries between material types and transitions may be gradual. 6. No free water was encountered in the borings at the time of drilling or when when checked 3 days later. 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 ) LL = Liquid Limit ( % ) PI = Plasticity Index ( % ) 100 661 HEPWORTH- PAWLAK GEOTECHNICAL, INC. LEGEND AND NOTES Fig. 4 aQ 0 1 0 2 co a) O 3 U 4 0 as 0 CI) 2 • 3 U 4 5 0.1 1.0 10 APPLIED PRESSURE - ksf 100 Moisture Content = 11.2 percent Dry Density = 110 percent Sample of :Very Silty Sand From:Boring 2 at 5 Feet Compression upon wetting 0.1 1.0 10 APPLIED PRESSURE -- ksf 100 100 661 HEPWORTH —PAWLA GEOTECHNICAL, INC. . SWELL CONSOLIDATION TEST RESULTS Fig. 5 Moisture Content = 16.8 percent Dry Density = 110 percent Sample of:Sandy Clay From: Boring 1 at 1 Foot No movement upon wetting • M 0.1 1.0 10 APPLIED PRESSURE - ksf 100 Moisture Content = 11.2 percent Dry Density = 110 percent Sample of :Very Silty Sand From:Boring 2 at 5 Feet Compression upon wetting 0.1 1.0 10 APPLIED PRESSURE -- ksf 100 100 661 HEPWORTH —PAWLA GEOTECHNICAL, INC. . SWELL CONSOLIDATION TEST RESULTS Fig. 5 1 2 3 0.1 1.0 10 APPLIED PRESSURE - ksf 100 100 661 HEPWORTH- PAWLAR GEOTECHNICAL, INC. SWELL CONSOLIDATION TEST RESULTS j Fi.g.6 Moisture Content = 15.6 percent Dry Density = 111 percent Sample of: Very Silty Sand From: Boring 3 at 10 Feet No movement upon wetting 0.1 1.0 10 APPLIED PRESSURE - ksf 100 100 661 HEPWORTH- PAWLAR GEOTECHNICAL, INC. SWELL CONSOLIDATION TEST RESULTS j Fi.g.6 HEPWORTH - PAWLAK GEOTECHNMCAL, INC. TABLE I SUMMARY OF LABORATORY TEST RESULTS JOB NO. 100 661+ SAMPLE LOCATION NATURAL MOISTURE CONTENT ( %} NATURAL DRY DENSITY (pcf} GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH (PS9 SOIL OR BEDROCK TYPE BORING DEPTH {feet) GRAVEL 1 %} - SAN» {961 LIQUID LIMIT ( %) PLASTIC INDEX 1 961 1 1 16.8 110 86 28 12 Sandy Clay • 2 2 Y2 8.0 103 61 Sandy Clayey Silt 5 11.2 110 Very Silty Sand 3 5 11.7 110 50 Very Silty Sand 10 15.6 111 Very Silty Sand • HEPWORTH - PAWLAK GEOTECHNICAL, INC. TABLE II PERCOLATION TEST RESULTS JOB'NO.100 661 HOLE NO. HOLE DEPTH {INCHES} LENGTH OF INTERVAL (MIN} WATER DEPTH AT START OF INTERVAL (INCHES) WATER DEPTH AT END OF INTERVAL (INCHES} DROP IN WATER LEVEL (INCHES} AVERAGE i PERCOLATION RATE (MIN. /INCH) P -1 32 15 9 7 '/4 1 1/4 30 73/4 7 % 7 6 '/4 a/4 6 1/4 5 % '/S 5'/4 5'/4 14 5 1/4 4 3/4 'A P -2 35 15 12 10 % 1 314 20 10 1/4 8 '/4 2 8 '44 7 1 3/4 7 5 'A 1 Yz 5 '/z 4 '/4 3/4 4'/4 4 . % P -3 32 15 refill 8 N.- 6 A 1 3/4 20 51/4 5 1'/4 5 4''A % 6 3/4 5 1 1/4 5 4 1/4 3/4 L 4 '/4 3 '/3 '/4 Note: Percolation test numbers correspond to adjacent exploratory boring number (see Fig. 1). The percolation tests were performed in 6 -inch diameter auger holes on December 19, 2000. The percolation rate is the average of the last 2 readings of each test.