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HomeMy WebLinkAboutSubsoil Studyffi CTLITHOMPSON GEOTECHNICAL ENG]NEERING INVESTIGATION 49I HIGH ASPEN DRIVË, PHASE 2 GARFIELD COUNTY, COLORADO Prepared For: GREEN LINE ARCHITECTS 64 North 4th Street, Suite 5 Carbondale, CO 81623 Attention: Steve Novy, Project No. GS06 546.AA1-125 July 12,2022 CTllThompson. lnc. Colorado Sprinos, Gle¡lggodj$pdngg, Pueþlo, $ummit County - Colorado Cheyenne, lÁ/yoming and Bozeman, Montana Denvêr, Fort Collins, ffi TABLE OF CONTENTS scoPE...... SUMMARY OF CONCLUS¡ONS SITE CONDIÏIONS PROPOSED CONSTRUCTION . SITE GEOLOGYAND GEOLOGIC HAZARDS SUBSURFACE CONDIT¡ONS.......... SITE EARTHWORK..... Excavations Subexcavation and Structural Fill.. Foundation Wall 8ackfi11................ BUtLDtNG FOUNDATIONS.................. Footings on Structural Fill ................. Drilled Piers ................. SLAB-ON-GRADE CONSTRUCTION .. CRAWL SPACE CONSTRUCTION...... FOUNDATION WALLS... suBsuRFACE DRA|NAGE.................. SURFACE DRAINAGE CONCRETE CONSTRUCTION OBSERVATIONS ... GEOTECHN]CAL RISK LtMlrATloNS ................ FIGURE 1-VIC¡NITYMAP FIGURE 2 - AERIAL PHOTOGRAPH FIGURE 3 - PROPOSED CONSTRUCT¡ON FIGURES 4 AND 5 - SUMMARY LOGS OF EXPLORATORY BOR¡NGS FIGURES 6 AND 7 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 8 - FOUNDAT¡ON WALL DRAIN CONCEPT TABLE I - SUMMARY OF LABORATORY TESTING GREEH LI¡¡E ÁRC¡{ITECTS 49I I{IGH ASPEN DRIVE, PHASE 2 CTLIT PROJECT NO. GS06546.00t-125 1 1 2 3 3 4 5 5 Þ 6 7 7I I ........10 ........11 ........12 ........12 ........ t3 ........'34 ........ f4 ........15 ffi SCOPE CTllThompson, lnc. (CTLIT) has completed a geotechnicalengineering in- vestigation for Phase 2 af construction at 491 High Aspen Drive within High Aspen Ranch in Garfield County, Colorado. We conducted this investigation to evaluate subsurface conditions at the site and provide geotechnical engineering recommen- dations for the proposed construction. The scope of our investigation was set forth in our Proposal No. GS 22-0'139. Our report was prepared from data developed from our field exploration, laboratory testing, engineering analysis, and our experi- ence with similar conditions. This report includes a description of the subsurface conditions observed in our exploratory borings and provides geotechnical engi- neering recommendations for design and construction of foundations, floor sys- tems, below-grade walls, subsurface drainage, and details influenced by the sub- soils. A summary of our conclusions is below. SUMMARY OF CONCLUSIONS Subsurface conditions encountered in our exploratory borings at the site generally consisted of surficial layer of topsoil ar 2 to 3 feet thick- ness of existing fill, underlain by natural sandy clay to the total ex- plored depth of 30 feet. Free groundwater was measured at a depth af 29 feet in TH-1 at the time of drilling. 2.The natural sandy clay atthis site has potential for significant expan- sion when wetted under building loads. Without mitigation, expansion of the clay soil is likely to result in differential heave and damage to the buildings. We judge the buildings can be constructed on footing foundations, provided the soils are subexcavated to a depth of at least 4 feet below footings and replaced with densely-compacted, structural f¡l¡. A drilled pier foundation is a positive alternative that would further mitigate risk of building movement. We recommend subexcavation of the soils below interior floor slabs to a depth of at least 4leet and replacement with densely-com- pacted, structural fillto mitigate potential slab heave. Subexcavatíon and replacement with structural fill to at least 1.5 feet is recom- mended below driveways, concrete flatwork, and playing courts. GREEN LINE ARCHITECTS 49I HIGH ASPE¡I DRIVE, PHASE 2 cTLlf PROJEGT ¡tO. GS86546.001 -1 25 1 3. I ffi A foundation wall drain should be constructed around the perimeter of the crawl space below the residence to mitigate water that infil- trates backfill soils adjacent to the residence. Site grading should be designed and constructed to rapidly convey surface water away from the buildings. SITE CONDITIONS The subject site is at 491 High Aspen Drive (a.k.a. Lot 31, High Aspen Ranch) in Garfield County, Colorado. A vicinihT map with the location of the site is included as Figure 1. The subject property is a 35.35-acre parcel that is northwest of the intersection of High Aspen Drive and Stover Valley Road. Previously, CTLIT performed a geotechnical engineering investigation for a new clubhouse and pool in the northeast part of the property (Project No. GS06546.000-125; report dated April 16, 2A21'). A pond is in the northwest part of the site. A barn, stable/resi- dence, and gravel parking area are currently located at the site. îhese structures are shown on the aerial photo attached as Figure 2. Ground surface at the site generally slopes at less than 5 percent down to the east and northeast. A photo- graph of the site at the time of our subsurface investigation is below. Looking northeast across site with drill rig at ïH-1 GREEN LltlE ARCHITECTS 49I HIGH ASPEFI ÞRIVË, PHASE 2 GTLIT PROJECT HO. GS06546.0ûr-r25 4 2 ffi PROPOSED CONSTRUCTION We reviewed schematic design plans for the project by Green Line Archi- tects (dated May 31 ,2A221. Existing buildings at the site will be deconstructed. New construction will include a two-story ranch manager's residence with an at- tached garage, a single-story officelgarage building, a tennis court, and a pickle- ball court. Paved access drives and parking areas are planned. A site plan with the proposed construction is shown on Figure 3. The plans indicate the lower-level floor of the residence will be structurally-supported with a crawl space below. Slab- on-grade floors are anticipated in the garage/office building and within the garage of the residence. We expect excavation depths of less than 10 feet for the proposed con- struetion, including the recommended -Íeel subexcavation below footings and floor slabs. Foundation loads for the buildings are expected to be less than 3,000 pounds per linear foot of foundation wall with maximum interior column loads of less than 50-kips. The tennis and pickleball courts are anticipated as post-ten- sioned slabs. We should be provided with architectural plans, as they are further developed, so we can provide geotechnicallgeo-structuralengineering input. SITE GEOLOGY ANÐ GEOLOG¡C HAZARDS As part of our geotechnical engineering investigation, we reviewed geologic mapping by the Colorado Geological Survey (CGS) titled, "Geologic Map of the Carbondale Quadrangle, Garfield County, Colorado", by Kirkham and Wídmann (dated 2t08r. The mapping indicates that trachyandesite bedrock {Pliocene Epoch) is at or near the ground surface at the site. We did not encounter bedrock in our exploratory borings. The natural sandy clay soils we found in our borings are likely part of the undivided deposits of alluvium and colluvium (Holocene and Late Pleistocene Epochs) that are mapped to the north and west of the subject site. GREEÍ{ LINE ARCI{ITECTS 49' HIGH ASPEN ORIVE, PIIASE Z cr|-fT pRoJEcT NO. 6506546.601-128 3 ffi We also reviewed the CGS map "Collapsible Soils and Evaporite Karst Haz- ard Map of the Roaring Fork Valley, Garfield, Pitkin and Eagle Counties", by Jona- than L. White (dated zAWr. This map indicates unconsolidated deposits in the ar- eas adjacent to the subject site. These deposits are described as including collu- vium, sheetwash, and alluvium. The map descriptions indicate these types of soils are geologically recent and typically loosely-packed, porous, and dry. These soil deposits are often prone to collapse when wetted, especially under applied building loads. Our laboratory testing on samples from our exploratory borings indicate the soils at this site have potential for expansion and not collapse. We judge that ex- pansion of the soils is the primary hazard for structures at the site. SUBSURFACE CONDITIONS Subsurface conditions were investigated by directing drilling of four explora- tory borings (TH-1 through TH4) at the site. The borings were drilled on April 18, 2022 with a track-mounted drill rig and solid-stem auger at the approximate loca- tions shown on Figures 2 and 3. Exploratory drilling operations were directed by our engineer, who logged subsurface conditions encountered and obtained repre- sentative samples of the soils. Graphic logs of the soils encountered in our explor- atory borings are included as Figures 4 and 5. Subsurface conditions encountered in our exploratory borings at the site generally consisted of surficial layer of topsoil ar 2 to 3 feet thickness of existing fill, underlain by natural sandy clay to the total explored depth of 30 feet. Free groundwater was measured at a depth of 29 feet in TH-1 at the time of drilling. PVC pipe was installed in TH-1 and TH-4 to facilitate subsequent checks of groundwater.TH-Z and TH-3 were backfilled immediately after exploratory drilling was completed. Samples of the soils obtained from our exploratory borings were returned to our laboratory for pertinent testing. Four samples of the sandy clay selected for GRËEhI LI¡¡Ë ARCHITECTS 49I HIG}I ASPEN DRIVE, PHASE 2 crllT PROJEeT NO. GS06546.601-125 4 ffi one-d¡mensional, swell-consolidation testing exhibited 1.6 to 3.9 percent swell when wetted under an applied pressure of 1,000 psf. Engineering index testing on two samples showed high plasticity with liquid limits of 72 and 58 percent, plastic- ity indices of 35 and 31 percent, and 96 and 92 percent silt and clay (passing the No. 200 sieve). Two samples of soil tested had water-soluble sulfate contents of 0.09 percent. Swell-consolidation test results are shown on Figures 6 and 7 . La- boratory testing is summarized on Table l. SITE EARTHWORK Excavations We expect excavation depths of less than 10 feet for the proposed construc- tion, including the recommended 4-feet subexcavation below footings and floor slabs. Based on our subsurface investigation, excavations at the site can be made with conventional excavating equipment. Sides of excavations need to be sloped or braced to meet local, state and federal safety regulations. The sandy clay at the site will likely classiñ7 as a Type B soil based on OSHA standards governing exca- vations. From a "trench" safety standpoint, temporary slopes deeper than 5 feet that are not retained should be no steeper than I to 1 (horizontalto vertical) in Type B soils. Contractors are responsíble for maintaining safe excavations. Contractors should identifu the soils encountered and ensure that O$HA standards are met. We do not expeet that excavations for the proposed construction will pene- trate a free groundwater table. Excavations should be sloped to a gravity dis- charge or to a temporary sump where water from precipitation and seepage can be removed by pumping. GREEN LI¡¡EARCH'TECTS 49I FI¡GH ASPEN DRIVË, FT{ASE 2 cTLfT PROJECT NO. GS06546.0Aí125 5 ffi Subexcavation and Structural Fill Our laboratory testing and engineering experience indicate the natural sandy clay at the site has significant potentialfor expansion when wetted under building loads. We judge that the buildings can be constructed on footing founda- tions with slab-on-grade floors, provided soils below the buildings are subexca- vated to a depth of at least 4 teet below footing and slab elevations. The subexca- vated soils should be with densely-compacted, structuralfill. The subexcavation process should extend laterally at least 2 feet beyond the perimeter of the building footprints. The excavated soils from the site can be reused as structuralfill, provided they are free of rocks larger than 4 inches in diameter, organÍc matter, and debris. Structural fill soils should be moisture-conditioned to within 2 percent of optimum moisture content, placed in loose lifts of I inches thick or less, and compacted to at least 98 percent of standard Proctor (ASTM D 69g) maximum dry density. Mois- ture content and density of structuralfill should be checked by a representative of our firm during placement. Observation of the compaction procedure is necessary. Foundation Wall Backfill Proper placement and compaction of foundation wafl backfill is important to reduce infiltration of surface water and settlement from consolidation of backfill soils. This is especially important for backfill areas that will support driveways, pa- tios, and sidewalks, The natural sandy clay soil can be used as backfill, provided it is free of rocks larger than 4-inches in diameter, organics, and debris. Backfill should be placed in loose lifts of approximately 10 inches thick or less, moisture-conditioned to within 2 percent of optimum moisture content and compacted to at least 95 percent of maximum standard Proctor (ASTM D 698) dry GREE}I LINE ARCH¡TECTS 4Sl H|GH ASPEiI DRTVE, P¡{ASE 2 cTrfT pRoJEcT !{o. Gs06546.001-12 6 ffi density. Moisture content and density of the backfill should be checked by a repre- sentative of our firm during placement. Observation of the compaction procedure is necessary. BUILDING FOUNDATIONS The natural sandy clay at this site has potential for significant expansion when wetted under building loads. Without mitigation, expansion of the clay soil is likely to result in differential heave and damage to the buildings. We judge the resi- dence and office/garage building can be constructed on footing foundations, pro- vided the soils are subexcavated to a depth of at least 4 feet below footings and replaced with densely-compacted, structural fill. The subexcavation and structural fill should be in accordance with the Subexcavation and Structural Fill section. A drilled pier foundation is a positive alternative that would further mitigate risk of building movement. Drilled piers in expansive soils are designed and con- structed to resist uplift from heave by anchoring in the soils below the depth of po- tentialwetting. Typically, drilled foundations experience less movement, as com- pared to footing foundations. Recommended design criteria for footings and drilled piers are below. These criteria were developed from our analysis of field and laboratory data, as well as rur experience. Footinss on Structural Fill Footings should be supported on a minimum 3-feet thickness of densely-compacted, structuralfill. The structuralfill should be in ac- cordance with recommendations in the Subexcavation and Structural Fill section. Footings on the structuralfill can be designed using a maximum net allowable bearing pressure of 3,000 psf. The weight of backfill soil above the footings can be neglected for bearing pressure calculation. GREEN L¡NE ARCH'ÏECTS 49I HIGH ASPEN DRIVE, PHASE 2 CTLIT PROJECT NO. GS08546.001-125 1 2 7 ffi 3. 4. A friction factor of 0.35 can be used to calculate resistance to sliding between concrete footings and the structuralfill soil. Continuous wall footings should have a minimum width of at least 16 inches. Foundations for isolated columns should have minimum di- mensions aÍ 24 inches by 24 inches. Larger sizes may be required, depending upon foundation loads. Grade beams and foundation walls should be well-reinforced. We rec- ommend reinforcement sufficient to span an unsupported distance of at least 12feet. The soils under exterior footings should be protected from freezing. We recommend the bottom of footings be constructed at a depth of at least 36 inches below finished exterior grades. The Garfield County building department should be consulted regarding frost protection re- quirements. Piers should be designed for a maximum allowable end bearing pressure of 12,000 psf and an allowable skin friction value of 1,2A0 psf. Skin friction should be neglected for the portion of the upper 3 feet of pier below grade beams. Piers should be designed for a minimum deadload pressure of 50û psf based on pier cross-sectional area. lf this deadload cannot be achieved through the weight of the structure, the pier length should be increased beyond the minimum values specified in the next para- graph. The clay soil should be assigned a skin friction value of 1,24A psf for uplifr resistance. Piers should have minimum lengths of 25 feet. The pier length should not exceed about 30 times the pier diameter. Piers should be reinforced to full length with at least three No.5 (16mm), Grade 6t Ø2A Mpa) reinforcing bars (or the equivalent) to resist a potential uplift tension. Reinforcement should extend into grade beams and foundation walls. A 6-inch continuous void will be required beneath allgrade beams and foundation walls, between piers, to allow for potential soil heave and concentrate the deadload of the building on the piers. 5 6 Drilled Piers 2. GREE¡¡ LINE ARCH¡TECTS 491 HIGH ASPEN ÐRtVË, PHASE 2 crLlT pRoJEcT i¡o. Gs06545.001-125 1 3. 4. 5 8 ffi Piers should be carefully cleaned prior to placement of concrete. To reduce potentialfor problems during pier installation, we recommend that a "drill and pouf construction procedure be used, in which con- crete is placed in the pier holes immediately after the holes are drilled, cleaned and inspected by our representative. Concrete should not be placed by free fall in pier holes containing more than 3 inches of water. Concrete should have sutficient slump to fillthe pier holes and not hang on the reinforcement. We recommend a slump in the range of 5 to 7 inches. Formation of mushrooms or enlargements at the top of piers should be avoided during pier drilling and subsequent construction opera- tions. lnstallation of drilled piers should be observed by a representative of CTLIT to identiff the proper bearing strata. S LAB-ON.GRADE CONSTRUCTION Slab-on-grade floors are anticipated in the garage/office building and within the garage of the residence. Driveways and concrete flatwork will likely be adjacent to the buildings. The tennis and pickleball courts are anticipated as post-tensioned slabs-on-grade. We recommend subexcavation of the soils below interior floor slabs to a depth of at least 4 feet and replacement with densely-compacted, struc- turalfillto mitigate potential slab heave. Subexcavation and replacement with struc- tural fill to at least 1.5 feet is recommended below driveways, concrete flatwork, and playing courts. The structural fill should be in accordance with the Subexcava- tion and Structural Fill section. Based on our analysis of field and laboratory data, as well as our engineer- ing experience, we recommend the following precautions to enhance potential per- formance of slab-on-grade construction at this site. Slabs should be separated from footings and column pads with slip joints that allow free vertical movement of the slabs. GRÉEN LIHE ARCH¡TECTS 49f H|GH ASPEiI DRIVE, PHASE 2 cTllr PROJECT NO. GS06546.001.125 6 7 I I 1 I ffi 2,The use of underslab plumbing should be minimized. Underslab plumbing should be pressure tested for leaks before the slabs are constructed. Plumbing and utilities which pass through slabs should be isolated from the slabs with sleeves and províded with flexible cou- plings to slab supported appliances. Exterior concrete flatwork should be isolated from the building. These slabs should be well-reinforced to function as independent units. Movements of these slabs should not be transmitted to the building. Frequent controljoints should be provided, in accordance with Ameri- can Concrete lnstitute (ACl) recommendations, to reduce problems associated with shrinkage and curling. CRAWL SPACE CONSTRUCT¡ON The plans indicate the lower-level floor of the residence will be structurally- supported with a crawlspace below. The minimum crawl space height depends on the materials used to construct the floor system above the space. Building codes normally require a clear space of at least 18 inches between exposed earth and un- treated wood components of the structuralfloor. For non-organic systems, we rec- ommend a minimum clear space oÍ 12 inches. This minimum clear space shoufd be maintained between any point on the underside of the floor system, including beams, plumbing pipes, and floor drain traps and the soils. Utility connections, including water, gas, air duct, and exhaust stack connec- tions to appliances on structural floors should be capable of absorbing some deflec- tion of the floor. Plumblng that passes through the floor should ideally be hung from the underside of the structural floor and not laid on the bottom of the excavation. lt is prudent to maintain the minimum clear space below all plumbing lines. Control of humidity in crawl spaces is ímportant for indoor air quality and per- formance of wood floor systems. We believe the best current practices to control humidity involve the use of a vapor retarder or vapor barrier (10 mil minimum) 3 4 GREEN LII¡E ARCHÍTECTS 4Sf ¡{tG¡{ ASPEN DRIVE, PHASE 2 CTLIT PROJECT iro. GS06546,0A1425 10 ffi placed on the soils. The vapor retarderlbarrier should be sealed at joints and at- tached to concrete foundation elements. lt may be appropriate to install a ventila- tion system that is controlled by humidistat. FOUNDATION WALLS Foundation walls which extend below-grade should be designed for lateral earth pressures where backfill is not present to about the same extent on both sides of the wall, such as in crawl spaces. Many factors affect the values of the de- sign lateral earth pressure. These factors include, but are not limited to, the type, compaction, slope, and drainage of the backfill, and the rigidity of the wall against rotation and deflection. ln general, for a very rigid wall where negligible or very little deflection will occur, an "at-rest" lateral earth pressure should be used in design. For walls that can deflect or rotate 0.5 to 1 percent of wall height (depending upon the backfill types), design for a lower "active" lateralearth pressure may be appropriate. Our experience indicates below-grade walls in typical buildings deflect or rotate slightly under normal design loads, and that this deflection results in satisfactory wall per- formance. Thus, the earth pressures on the walls will likely be between the "active" and "at-rest" conditions. For backfill soils conforming with recommendatians in the Foundation Wall Backfill section that are not saturated, we recommend design of below-grade walls at this site using an equivalent fluid density of at least 45 pcÍ. This value assumes deflection; some minor cracking of walls may occur. lf very little wall deflection is desired, a higher design value for the at-rest condition using an equivalent fluid pressure of 60 pcf is recommended. An equivalent fluid pressure of 300 pcf can be used for the "passive" earth pressure case. GREE¡I L¡¡¡E ÂRCHITECTS 49I HIGH ASPEN Í'R¡VE, PHASE 2 crllT PROJECT HO. GS06546.001-t25 l1 =ffi SUBSURFACE DRA¡NAGE Water from precipitation, snowmelt, and irrigation frequently flows through relatively permeable backfTll ptaced adjacent to a buitding and collects on the sur- face of less permeable soils at the bottom of the foundation excavation. This pro- cess can cause wet or moist conditions in below-grade areas, such as crawl spaces, and result in water pressure developing outside foundation walls. lf a structurally-supported floor system with a crawl space is utilized for the building, we recommend construction of a foundation wail drain around the perimeter of the crawl space. The exterior foundation wall drain should consist of 4-inch diameter, slotted, PVC pipe encased in free-draining gravel. A prefabricated drainage composite should be placed adjacent to foundation walls. Care should be taken during back- fill operations to prevent damage to drainage composites. The drain should dis- charge via a positive gravity outlet or lead to a sump where water can be removed by pumping. The gravity outlet should not be susceptible to clogging or freezing. lnstallation of a clean-out along the drainpipe is recommended. The foundation walldrain concept is shown on Figure 8. SURFA,CE DRAINAGE Surface drainage is critical to the performance of foundations, floor slabs, and concrete flatwork. Site grading should be designed and constructed to rapidly convey surface water away from the buildings. Proper surface drainage and irriga- tion practices can help control the amount of surface water that penetrates to faun- dation levels and contributes to heave of soils that support foundations, slabs, and other structures. Positive drainage away from foundations and avoidance of irriga- tion near foundations also help to avoid excessive wetting of backfillsoils, which GREE¡,¡ LINE ARCHITECTS 491 HÍGH ASPEN DRIVE, PHASE 2 CTLIT PROJÊCT NO. G806546-0Aí1Í5 12 ffi can lead to increased backfill settlement and possibly to higher lateral earth pres- sures, due to increased weight and reduced strength of the backfill. We recom- mend the following precautions. The ground surface surrounding the exterior of the buildings should be sloped to rapidly convey surface water away from the buildings in all directions. ìÂ/e recommend a constructed slope of at least 12 inches in the first 10 feet (10 percent) in landscaped areas around the buildings. Backfill around the foundation walls should be moisture-treated and compacted pursuant to recommendations in the Foundation Wall Backfill section. We recommend that the buildings be provided with roof gutters and downspouts. The downspouts should discharge well beyond the lim- its of all backfill. Splash blocks and/or extensions should be provided at all downspouts so water discharges onto the ground beyond the backfill. We generally recommend against burial of downspout dis- charge pipes. lrrigation should be limited to the minimum amount sufficient to main- tain vegetation; application of more water will increase likelihood of slab and foundation movements. Plants placed close to foundation walls should be limited to those with low moisture requirements. lrri- gated grass should not be located within 5 feet of the foundation. Sprinklers should not discharge within 5 feet of foundations. Plastic sheeting should not be placed beneath landscaped areas adjacent to foundation walls or grade beams. Geotextile fabric will inhibit weed growth yet still allow natural evaporation to occur. CONCRETE Concrete in contact with soil can be subject to sulfate attack. We measured a water-soluble sulfate concentration of 0.09 percent in two samples of the natural sandy clay from the site (see Table l). For this level of sulfate concentratlon, ACI 332-A8, "Code Requirements for Residential Concrete", indicates there are no special cement requirements for sulfate resistance in concrete that is in contact with the subsoils. 1 2 3 4 GREEN L¡NE ARC}IITECTS 4gl H|GH ASPE¡| DRME, PHASË 2 CTLIT PROJECT ¡¡O. GS06546.001-125 t3 ffi ln our experience, superficial damage may occur to the exposed surfaces of highly-permeable concrete, even though sulfate levels are relatively low. To con- trolthis risk and to resist freeze-thaw deterioration, the water-to-cementitious ma- terials ratio should not exceed 0.50 for concrete in contact with soils that are likely to stay moist due to surface drainage or high-water tables. Concrete should have a tolal air content of 60/o +l- 1.ía/o. CONSTRUCTION OBSERVATIONS We recommend that CTLIT be retained to provide construction observation and materials testing services for the project. This would allow us the opportunity to verify whether soil conditions are consistent with those found during this investi- gation. lf others perform these observations, they must accept responsibility to judge whether the recommendations in thÍs report remain appropriate. lt is also beneficialto projects, from economic and practical standpoints, when there is con- tinuity between engineering consultation and the construction observation and ma- terials testing phases. GEOTECHNICAL RISK The concept of risk is an important aspect of any geotechnical evaluation. The primary reason for this is that the analytical methods used to develop ge- otechnical recommendations do not comprise an exact science. We never have complete knowledge of subsurface conditions. Our analysis must be tempered with engineering judgment and experience. Therefore, the recommendations pre- sented in any geotechnical evaluation should not be considered risk-free. We can- not provide a guarantee that the interaction between the soils and the proposed structure will lead to performance as desired or intended. Our recommendations represent our judgment of those measures that are necessary to increase the chances that the structures will perform satisfactorily. lt is criticalthat all recom- mendations in this report are followed. GREEN L¡NE ARCHITECTS 49I HIGH ASPE¡¡ DR¡VE, PHASE 2 crllT PROJECT ¡tO. GS08åt6,qAl-123 14 ffi This report was prepared for the exclusive use of the client. The infor- mation, conclusions, and recommendations presented herein are based upon con- sideration of many factors including, but not limited to, the type of structures pro- posed, the geologic setting, and the subsurface conditions encountered. The con- clusíons and recommendations contained in the report are not valid for use by oth- ers. Standards of practice continuously change in geotechnical engineering. The recommendations provided in this report are appropriate for about three years. lf the proposed buildings are not constructed within three years, we should be con- tacted to determine if we should update this report. LIMITATIONS Our exploratory borings provide a reasonable characterization of subsur- face condítions at the site. Variations in subsurface conditions not indicated by the borings will occur. We should be provided with architectural plans, as they are fur- ther developed, so we can provide geotechnicallgeo-structural engineering input. This investigation was conducted in a manner consistent with that level of care and skill ordinarily exercised by geotechnical engineers currently practicing under similar conditions in the locality of this project. No warranty, express or im- plied, is made. lf we can be of further service in discussing the contents of this re- port, please call. crLlrHoMPSoN, tNc.Reviewed by: E-ï,ìì Ë.t.7 Project Engineer GREEN LINE ARCHITECTS 49r ¡lrcll ASPEN DR¡VE, PHASE 2 CTLIT PROJECT NO. GS06646.00f-125 D ( Manager t5 7/2 ffi o 500 lfxlo NOTE: SC¡["E l' - 1ü10' GREEN UNEARCH¡TECI1g ¡r$t lgdH AgFEûl Þñfi/E, Fl{AgE 2 PRO.'ECT NO. GSO6546.OOï -1 2ı SATELLTTE IMAGE FROM MAXAR (CoPYRTGHT 2A21) Vicinity ñ,lap Fls. I LEGEND: TH_1 APPROXIMATE LOCATION OF@ EXPLORATORY BORING NOTE: ffi 0 50 r00 SC¡{LE: 1' - 1øA' GREEN LINEAHCHITECTS 4Bf HTGHASPEN DR|VE, P!{A8E2 PROJËCT NO. GSO65,46.OA1 -1 25 SATELLITE IMAGE FROM MAXAR (coPYRrcHT 2A22) Aerial Photograph Flg. 2 LEGEN D: TH_1 APPROXIMATE LOCATION OFO EXPLORATORY BORING NOTE: ffi o 50 1ü) SOÂLE: f'- l0O' GREEN UNEARCHÍTECTA ¡¡gl HffoHASËll DHI!|E, FflAgEa PRATECT NO. GSO6546.OO1 -1 25 BASE DRAWING BY GREEN LINE ARCHTTECTS (DATED MAY 31 , 2A22) TennÍs ond Pickleboll Courts r I TH-4t, posed Coretoker's Residence Garoge/oflice Proposed Construction {lr' TH-2 TH_1 1 Flg. 3 t- UJ 1¡Jfr tzot- l!J UJ ïH-1 EL.7679 7680 7675 33r12 7674 24t12 7665 7660 19t12 7655 7650 g 3712 7645 7644 GREEN LIÑËARCHÍTECTS 491 HIGH ASPEN DRIVE. PFIASE 2 PROJETT NO. GS06546.00t -125 ïH-2 E1.7676 TH-3 8L.7675 TH4 E,L.7672 13t't2 19t12 311'|.2 13t12 27t12 33t12 2 3U12 46t12 39112 1t12 7680 7675 7670 7665 7660 7655 7650 7645 764t Summary Logs of ExploratbryBoiings Frc 4 ffi F-lrJuIL zot- fi¡Jul ffi LEGEND: E n þ TOPSOIL, CI.AY, SANDY, ORGANICS, WET, DARK BROWN. FILL, GRAVET PARKING SURFACE, CI.AY, MEDIUM STIFF. MOIST, BROWN, DARK BROWN, GRAY, RUST. CLAY, SANDY, STIFF TO VERY STTFF, MOIST TO WET, GRAY, BROWN, RUST. (CH) DRIVE SAMPLE. THE SYMBOL 33112 INDICATES 33 BLOWS OF A I4GPOUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.s-INCH O.D. CALIFORNIA.BARREL SAMPLER 12INCHES, g GROUNDWATER LEVEL MEASURED AT TIME OF DRILLING. NOTES: EXPLORATORY BORINGS WERE DRILLED ON APRIL 18.2022 WITH A TRACKMOUNTED DRILL RIG AND 4.INCH D¡AMETER. SOLID-STEM AUGER. 2. PVC P¡PE WAS INSTALLED lN ïH-1 AND TH-4 TO FACILITATE SUBSEQUENT CHECKS OF GROUNDWATER. OTHER BORINGS WERE BACKFILLED ¡MMEDÙATELY AFTER EXPLORATORY DR¡LLING OPERATIONS WERE COMPLETED. 3. ELEVATIONS OF ËXPLORATORY SORINGS WERE ESTIMATED FROM GROUNÞ SURFACE ELEVAT¡ON CONTOURS ON FIGURE 3. 4, THESE LOGS ARË SUBJECT TO THE EXPI.ANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. SUNf,MARY LEGEND OF EXPLORATORY BORINGS 1 GREEN LIFIEARCHITE TS 4S1 HIGHASPEN DRI\/E' PI{ASE2 PROJECT NO. GSd6546.00f -f 25 F¡G. 5 ffi 2.0I cl,z{-rô-xl¡ts2-2o (t U'lll -.rÉ.fLEoo4 3 2 0 -2 0.1 APPLIED PRESSURE. KSF 1.0 10 DRY UNITWEÍGHT= MOISTURÊ CONTËNT= 105 PCFzta u 100 Somple of CLAY, SANDY (CH) From From TH.l AT 9 FEET zo-rız ft+u¡szO-t6tt,t¡¡ ff.eEo(t -7 0.1 APPLIED PRËSSURE - KSF Somple of cLAy, sANDY (cH) 10 DRY UNITWEIGHT= MOISTURE CONTENT= 100 95 PCF ZAJ T,TH-2 AT 14 FEET GREEN LINEARCHITËCTS HIGH ASPEN RÂNCH, PHASE 2 PROJECT NO. GS06546.t0", -l 25 Swell-Consolidation Test Results I tt tl I t I I r I . EXPANSION UNDER CONSTANT PRËSSURE DUE TO WETTING tt 5 \ \\ ,ì t ¿ itiil t t ttttti ' EXPANSION UNDER CONSTANT - PRESSURE DUE TO WEÏTING I I I I t I f It t tililit t tililrI\ \ \ L \ { \\\ Il \ Þ 1.0 FIG.6 ffi 0 -2 zot, -3z o.x UTs4zo ØatËUJ -J É.o-Eo(t€ 0.1 APPLIED PRESSURE - KSF 1.0 10 DRY UNITWEIGHT= MOISTURE CONTENT= 100 105 PCF Zt.ø "t" Somple of CLAY, SANDY (CH) From From ÏH-3 AT 19 FEET o -1 -2 zq 2.s 3Lxlrl ñazoıU' uJÉ-Ô o- =o(t .6 0.f APPL¡ET} PRESSURE. KSF Somple of cLAY, sANDY (cH) t0 DRYUNITWEIGHT= MOISTURE CONTENT= 1t0 ß1 PCF ZSS "/"TH.4 AT 9 FEET GREEN LINEARCHITECTS HIGHASPEN RÁNCH, PHASE 2 PROJECT NO. GS06546.001 -.l 25 Swell-Consolidation Test Results .u ¡rilr t l tttilt - EXPANSION UNDER CONSTANT PRESSURE DUE TO WËTTING \\ \ \ \ \ \ \\\ \" (,) ( / rrllt t t ltlilt . EXPANSION UNÐER CONSTANT PRESSURE DUE TO WETTING I \ \ \t \ \ \\\ I \ \ i \ I 1.0 FIG.7 tr 2-t SLOPE PER OSFIA COVER E}MRE WDTH OF BACKFI\ BELOTY-GRAOE WAI.I. SUP JOINÍ PREFAERICATE} DRA¡T.IAGE mHPOSm (H¡RAû}RA¡N Sft{¡O oR EOUMALSÍÍ) GRAI/EL WÍIT{ NON-TTOì/EN GEOTEfllE FABRIC (UIRAFI l¿[ON OR EquvÄrifl). ATTACH PI.ASIIC SHEEIING TO FOUNDAÏOT.I MINIMUM I'INIMUM OR BEÍOIIDl:f SI'IOPE FROM BgfTOM OF FOOIING(wl[cHRER F GREATER] 4-IHCH DIAilNER FERFORA1ED R¡E¡D ORruN PPE THE P¡PE SHOUU' BE PI¡Ctr} IN A'¡RS{CH W¡¡H A StroPE OF AT LEASr 118-${CH DROP PER FOOT OF DRAIN. ENCåSE F|PE t¡t 1/2'TO 1-t/2' SCREEIIEI' GRAI/EL ÞOg{D ERAf'Et I.ATERA¡..LY ÏO FOüNC AltD AT tEASr 1/2 Hne'*fir OF FOOT|H6. FtrL E}{NRE TRENCH WÍTH GRAì'E- t{$tE ÏHE BOTTO}' OF THE Í'RAIII SHOU[D BE AÏ I,.EAST 2 NCHES BELO¡T BOTTOM OF FOOIIÍ-IO AT THE H¡EHEST FOü{T ÅilD SLOPË DONYil¡TARD TO A POSM/E GRAVIIY(X,NE[ OR TO A SUMP WHME WATER CT¡I BE REMSVED ry PUMPIHG. GREEN UNEÂRCHITECTS¡l8t H¡gH ASP$¡ EAlvÊ, PI{AÊE 2 PROJECT NO. GSO6546.OO1-1 25 Foundation Wall Drain Concept Flg.8 TABLE ISUMMARY OF LABORATORY TESTINGPROJECT NO. GS06546.001 -1 25ffiDESCRIPTIONCLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)CLAY, SANDY (CH)PASSINGNO.200SIEVE(%)9692SOLUBLESULFATES(%\0.090.09-SWELL(o/o\1.63.62.83.9ATTERBERG LIMITSPLASTICITYINDEX(o/r\3531LIQUIDLIMIT(o/o\7258DRYDENSITY(PCF)1041059695109105101105MOISTURECONTENT(ø/o\21.221.627.828.119.921.623.922.1DEPTH(FEET)4I1o14I19I19EXPLORATORYBORINGTH.1TH.1TH.1TH.2TH.3TH.3TH-4TH-4* SWELL MEASURED UNDER 1-OOO PSF APPLIED PRESSURE.Page 1 of 1