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Home My WebLink AboutFile Documents.134 E Bleeker St.0102-2020-BRES (39) I( Kumar&Associates,Inc.° Geotechnical and Materials Engineers 5020 County Road 154 and Environmental Scientists Glenwood Springs,CO 81601 phone: (970)945-7988 fax:(970)945-8454 email:kaglenwood@kumarusa.com An Employee Owned Company www.kumarusa.com Office Locations: Denver(HQ),Parker,Colorado Springs,Fort Collins,Glenwood Springs,and Summit County,Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED FULL BASEMENT & CRAWLSPACE UNDER EXISTING HOUSE 134 EAST BLEEKER STREET ASPEN, COLORADO PROJECT NO. 20-7-375.01 JUNE 14, 2021 PREPARED FOR: BRET HIRSH do EIGELBERGER ARCHITECTURE +DESIGN ATTN: NICK CHAN 350 MARKET STREET, SUITE 309 BASALT, COLORADO 81621 nchan(&,ei2elber2er.com RECEIVED 07/23/2021 ASPEN BUILDING DEPARTMENT TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 1 - FIELD EXPLORATION - 1 - SUBSURFACE CONDITIONS - 2 - DESIGN RECOMMENDATIONS - 2 - FOUNDATIONS - 2 - FOUNDATION AND RETAINING WALLS - 3 - FLOOR SLABS - 4 - UNDERDRAIN SYSTEM - 4 - SLOPE STABLIZATION - 5 - SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS TABLE 2 - PERCOLATION TEST RESULTS RECEIVED 07 /23 /2e21 Kumar&Associates,Inc.° Project No.20-7-375.01 ASPEN BUILDING DEPARTMENT PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed full basement and crawlspace addition under an existing residence to be located at 134 East Bleeker Street, Aspen, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our proposal for geotechnical engineering services to Eigelberger Architecture +Design dated May 15, 2020. An exploratory boring was drilled to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed basement and crawlspace will be constructed under the existing two-story residence. Basement floor will be structural over crawlspace. Grading for the structure is assumed to involve cut depths up to about 15 feet. We assume relatively light to moderate foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The subject site was developed with a two-story residence with a basement and detached garage with a living area above the garage. The ground surface was relatively flat. Vegetation consists of irrigated grass, small Blue Spruce and large Cottonwood trees. FIELD EXPLORATION The field exploration for the project was conducted on May 27, 2021. One exploratory boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted 45B drill rig. The boring was logged by a representative of Kumar&Associates, Inc. 21 Kumar&Associates,Inc.° Project No.20-7-375.01 \SPEN BUILDING DEPARTMENT -2 - Samples of the subsoils were taken with a 1%-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 Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about 1/2 foot of topsoil overlying dense, slightly silty sand and gravel down to the maximum explored depth of 26 feet. The soils were more sandy with depth. Laboratory testing performed on samples obtained from the boring included natural moisture content and gradation analyses. Results of gradation analyses performed on small diameter drive samples (minus 11/2-inch fraction) of the coarse granular subsoils are shown on Figure 3. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the new basement be founded with spread footings bearing on the natural granular soils. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural granular soils should be designed for an allowable bearing pressure of 3,000 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. 2) The footings should have a minimum width of 16 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided CEIVED adequate soil cover above their bearing elevation for frost protection. Pla 07/23/2021 Kumar&Associates,Inc.° Project No.20-7-375.01 ASPEN BUILDING DEPARTMENT - 3 - of foundations at least 42 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be well reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing area should then be moistened and compacted. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site granular soils. Cantilevered retaining structures which are separate from the residence (if any) and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at a moisture content near optimum. Backfill in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill. Backfill should not contain organics, debris or rock EIVED k GC than about 6 inches. 07/23/2021 Kumar&Associates,Inc.° Project No.20-7-375.01 ASPEN BUILDING DEPARTMENT -4 - The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.50. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 425 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a granular material compacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of old fill and topsoil, are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4-inch layer of free-draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50%retained on the No. 4 sieve and less than 2%passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill 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 minimu ° o a suitable gravity outlet. Free-draining granular material used in the underdrain system s`o r 07 /23 /nn21 Kumar&Associates,Inc.° Project No.20-7-375.01 ASPEN BUILDING DEPARTMENT - 5 - contain less than 2%passing the No. 200 sieve, less than 50%passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep. SLOPE STABLIZATION The City of Aspen requires an engineered excavation slope stabilization plan if proposed foundations are within 15 feet of neighboring structures or public travel ways. The plan is not required if excavations are less than 5 feet below the existing grade or further than 15 feet from travel ways and less than 15 feet deep. Slope bracing could be required depending on the addition location, size and excavation depth. Slope bracing through use of a variety of systems such as grouting, micro piles and soil nails should be feasible at the site. A shoring contractor should provide design drawings to support the proposed excavation slopes where needed. Other City requirements may also be applicable. DRYWELL Drywells and bio-swales are often used in the Aspen area for site runoff detention and disposal. The Natural Resources Conservation Service has identified four hydrologic groups (HSG) in the Aspen area and the site is located in Type B soil having a moderate infiltration rate. The results of percolation testing performed in Boring 1,presented in Table 1, indicate an infiltration rate of about 1 minute per inch. The bedrock is generally known to be relatively deep in this area and groundwater level was not encountered to the boring depth of 26 feet. The drywell should have solid casing down to at least basement level and perforation below that level. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the proposed construction has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 2'/2 inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with at least 2 feet of the on-site soil l E IVE D reduce surface water infiltration. 1 07/23/2021 Kumar&Associates,Inc.° Project No.20-7-375.01 ASPEN BUILDING DEPARTMENT - 6 - 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. LIMITATIONS This study has been conducted in accordance with 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 boring drilled at the location indicated on Figure 1, the proposed type of construction and our experience in the area. 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. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory boring 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 design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. 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, Kumar& Associates,Inc =cQ,00 l E6/S '‘ i James H. Parsons, P.E. s Reviewed by: .., Daniel E. Hardin, P.E. JHP/kac cc: Eigelberger Architecture—Hannah Hunt Moeller—(hannahhunt@eigelberger.coRE C E IVE D KL&A—Brett McElvain—(bmcelvain@klaa.com) 07/23/2021 Kumar&Associates,Inc.® Project No.20.7-375� PEN BUILDING DEPARTMENT / / . Two.RYPJ /tio,,,, \ \ \ CAN TRASH .p er \ FED.RYP.)� -' a:ENCLOSURE • 4•"L£A,39'6 - *' '—RICIRIC Ai,.. ) as REBAR FOUND CI• R•YP.) _-0..699.RC65 BEARSS66°16'31"W 1.97 S Gj�� w 1. ELEC N� L 1.1 METER ` . —' RS REBAR R CAP FOUND I • \ LS.IRL1EGIBLE St RIDGE RIDGES .. R/ �, `�79IS9' TORY r.• ;) pK I ��!i�,i�- TWOUSE W GARAGE 1.`, G d HOUSE WITH GARAGE y l• / 4.6 Bu44 RIDGE WATER / I -"pNCS 791F.F' F . • d,�—.._ METER I -1X7E CHIMNEY j91.80' . SEWER / •�1➢'� 7919.2'~� / ODRFJEWAY� CLEANOUT ., / d ' GAS M / •i I d c c METER 1 ,. I / 134 c 1 � `°yr I IRIDGE EAST 7691.6' r aTREETf / 7919.9.Gh� �(ff-`fR.J� •77„ SIGN /a '`_ I 8/7. ' E.E. / I _ L / , W I/2 LOT R O I / 7994 7922IA,EY X3 I ig 7891.8 'a�# ILJ1 .� ��T]� 'W lWgyi'� �$ /YS WELL / ' SSTONEIDEW_ /SHE SmEwALRITILEEI - //STONE / ,:...._ ..: -,' / PATIO /y �. /I `°, HALF '-I'� , WOOD/METAL /1 r/ / • / CK 65 / FENCE TRANSITION x LJe r 6,5005.FW / )g9$ /^S` TWO STORY WOOD /RIDGE FRAME HOUSE } I r `/>�' / 7916I /IW1TH BASEMENTRIDGEI {r,11 �ir I134 ESTBLFF¢FR STREET 7916.3' / + 6�JjLy iFF.Wn!. �/ 1 789s.78' . ' i .. 3F FENCE TRANSRION L 0/ 1894 (§ / ` � NI +7D , T� pg. Rmc� %i I az i REBAR FOUND 7916.7 • �/ r IeLOW GROUND . / • xI .0' J�09g 7895. / �r`_ �,.�y / BbftpMcg� tj t/ Sa9°26'Ot`W * //-- "�to II' 24s265' T T2 T3 r•.9 BORING- 1 — i STREET . I.O.A.GPS N]S= ✓5 1 x l 7895.0' SIGN :.G. 40NUMENT a7 a /1•W A1EP (;] 13 p r 40NUMENT 47 q ^J. 4 7d95.3'� 45,p0. _ 'I 47;A _ aS REBARd CAP FOUND / STONE / '�S L.S.f11LLEGIB / -� STREET SIDEWALK J` 7BM EL=7894.J5' // 7� SIGN E,yz MONUMENT a." �oy_R£7ET sae -r} �g�� y t is, 4-0`1ST�EE7 - / i fri e. E 10 0 1 0 G ao RECEIVED „� APPROXIMATE SCALE—FEET " 07L23/2021 20-7-375.01 Kumar & Associates LOCATION OF EXPLORATORY BORING Ig. 1 ,o ASPEN BUILDING DEPARTMENT BORING 1 EL. 7 89 5' LEGEND 0 .' TOPSOIL; CLAY, SANDY, ORGANIC, FIRM, MOIST, DARK BROWN. 32/12 GRAVEL (GP-GM); SANDY, SLIGHTLY SILTY, COBBLES, TRANSITIONING TO GRAVELLY SAND WITH DEPTH, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST TO MOIST, TAN. 5 ,. : 14/12 DRIVE SAMPLE, 1 3/8-INCH I.D. SPLIT SPOON STANDARD PENETRATION TEST. 64/12 WC=1.6 32/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 32 BLOWS OF +4=48 A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED :.:. : 200=12 TO DRIVE THE SAMPLER 12 INCHES. 10 50/1 NOTES L' 1. THE EXPLORATORY BORING WAS DRILLED ON MAY 27, 2021 L WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. = 15 64/12 2, THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED 0 o APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN 20 PROVIDED. 27/12 4. THE EXPLORATORY BORING LOCATION AND ELEVATION SHOULD BE 0 CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE WC=3.9 METHOD USED. +4=25 : 0 -200=5 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY �� BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES 25 o BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE 53/12 GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: 30 WC = WATER CONTENT (%) (ASTM D 2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 6913); -200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 21 E..2 r 20-7-375.01 Kumar &Associates LOG OF EXPLORATORY BORING 0 /�3?2021 ASPEN BUILDING DEPARTMENT HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 HRS 100 45 MIN 15 MIN 6OMIN 19MIN 4MIN 1MIN #200 #100 #50#40#30 16 #10#8 #4 3/8" 3 4" 1 1 2" 3" 5"6" 8"0 90 10 80 20 70 - 30 60 40 G 50 - 50 z1 a 40 60 E 30 70 20 80 10 90 0 I I I I I I I I I I I I III I I I I III I I I I I III I I I I I I III 100 .001 .002 .005 .009 .019 .037 .075 .150 .300 .600 1.18 2.36 4.75 9.5 19 38.1 76.2 127 200 .425 2.0 152 DIAMETER OF PARTICLES IN MILLIMETERS CLAY TO SILT SAND GRAVEL COBBLES FINE MEDIUM COARSE FINE COARSE GRAVEL 48 % SAND 40 % SILT AND CLAY 12 % LIQUID LIMIT PLASTICITY INDEX SAMPLE OF: Slightly Silty Gravel and Sand FROM: Boring 1 0 7.5' HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 HRS 100 45 MIN 15 MIN 60MIN 19MIN 4MIN 1MIN #200 #100 #50#40#30 #16 #10#8 #4 3/8" 3/4" 1 1 2" 3" 5I 6" 8"0 I 90 10 80 20 70 30 60 1 40 IQ - tz 50 1 50 40 - 60 30 70 20 - 80 I 10 - 90 0 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I T 100 .001 .002 .005 .009 .019 .037 .075 .150 .300 .600 1.18 2.36 4.75 9.5 19 38.1 76.2 127 200 v .425 2.0 152 DIAMETER OF PARTICLES IN MILLIMETERS SAND GRAVEL CLAY TO SILT COBBLES FINE MEDIUM COARSE FINE COARSE ry GRAVEL 25 % SAND 70 % SILT AND CLAY 5 % LIQUID LIMIT PLASTICITY INDEX These test results apply only to the E SAMPLE OF: Slightly Silty Gravelly Sand FROM: Boring 1 0 20' & 25' samples which were tested. The testing report shall not be reproduced, 2 except in full, without the written Ls approval of Kumar & Associates, Inc. lE Sieve analysis testl is performed in accordance with A D6913, ASTM D7928, i g ASTM C136 and/or TM D1140. 20-7-375.01 Kumar & Associates GRADATION TEST RESULTS 0 7%132021 ASPEN BUILDING DEPARTMENT I( i Kumar&Associates,Inc.° Gumar&Aland Materials Engineers and Environmental Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No.20-7-375.01 SAMPLE LOCATION NATURAL NATURAL GRADATION ATTERBERG LIMITS UNCONFINED MOISTURE DRY GRAVEL SAND PERCENT PLASTIC COMPRESSIVE BORING DEPTH CONTENT DENSITY (%) (%) PASSING 200 S EVE LIQUID LIMIT INDEX STRENGTH SOIL TYPE (ft) (%) (pcf) (%) (%) (psf) 1 7'/z 1.6 48 40 12 Slightly Silty Gravel and Sand 20 & 25 3.9 25 70 5 Slightly Silty Gravelly combined Sand RECEIVED 07/23/2021 ASPEN BUILDING DEPARTMENT I( A Kumar&Associates,Inc.® Gumar&Aland Materials Engineers and Environmental Scientists TABLE 2 PERCOLATION TEST RESULTS PROJECT NO.20-7-375.01 HOLE NO. HOLE DEPTH LENGTH OF WATER DEPTH WATER DEPTH DROP IN AVERAGE (INCHES) INTERVAL AT START OF AT END OF WATER LEVEL PERCOLATION (MIN) INTERVAL INTERVAL (INCHES) RATE (INCHES) (INCHES) (MIN./INCH) 76 64 12 64 54 10 54 483/4 5'/4 B-1 184 5 483/4 43 53/4 43 38 5 38 331/2 4'/z 1 Note: Percolation tests were conducted in a 4-inch diameter boring drilled on May 27, 2021. The average percolation rate was based on the last three readings of the test. RECEIVED 07/23/2021 ASPEN BUILDING DEPARTMENT