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HomeMy WebLinkAboutFile Documents.535 E Cooper Ave.0004.2019 (19).ACBK RECEIVED 1/7/20 9 H-P--- KUMAR 5020 County Road 154 ASPEN Glenwood Springs, CO 81601 BUILDING DEPARnical Engineering I Engineering Geology g als Testing I Environmental Phone: (970)945-7988 Fax: (970)945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Denver(HQ), Parker, Colorado Springs, Fort Collins,Glenwood Springs,Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED STEIN ERIKSEN BUILDING ADDITION 529-535 EAST COOPER AVENUE ASPEN, COLORADO PROJECT NO. 18-7-522 SEPTEMBER 24, 2018 PREPARED FOR: NJ STEIN,LLC do ANDREW HECHT ATTN: DON CARPENTER 625 EAST HYMAN AVENUE,#201 ASPEN, COLORADO 81611 don@projectresourceco.com RECEIVED 1/7/2019 ASPEN BUILDING DEPARTMENT TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 1 - MINE SUBSIDENCE - 2 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 3 - FOUNDATION BEARING CONDITIONS - 3 - DESIGN RECOMMENDATIONS - 3 - FOUNDATIONS - 3 - FOUNDATION AND RETAINING WALLS -4 - FLOOR SLABS - 6 - UNDERDRAIN SYSTEM - 6 - SURFACE DRAINAGE - 7 - DRYWELL - 7 - LIMITATIONS - 7 - 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 H-PvKUMAR Project No. 18-7-522 RECEIVED 1/7/2019 ASPEN BUILDING DEPARTMENT PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed addition to the Stein Eriksen building located at 529-535 East Cooper Avenue, 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 NJ Stein, LLC dated July 30, 2018. 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 building addition will be a 1 story structure attached to the north side of the building. Ground floors will be structural over crawlspace and slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about 3 to 5 feet. We assume relatively light 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 a developed lot with apartments and commercial sections at the time of our field exploration. The ground surface is graded mostly flat about 2 feet below the alley elevation. Elevation difference across the building addition area is about 2 feet. Vegetation consists of landscaped trees, bushes and shrubs. H-PvKUMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 2 - ASPEN MINE SUBSIDENCE BUILDING DEPARTMENT Portions of the Aspen area are underlain by mine workings. The workings are primarily underground tunnels between Aspen and Smuggler Mountains southeast and east of the downtown area. The works consist of numerous tunnels beginning a few hundred feet below the ground surface becoming shallower to the south. Under certain conditions these workings may collapse and cause surface subsidence. Glory Hole Park, which is about three blocks southeast of the subject site, is believed to have been caused by the collapse of one or more tunnels. The subject site appears to be west of these main tunnel works. Our borings were relatively shallow and for foundation design only, however, no indications of subsurface voids were found at the subject site. We believe the risk of subsidence due to the collapse of underground mine works throughout the service life of the proposed development to be low. If further evaluation of the mine works subsidence potential is desired, we should be contacted. FIELD EXPLORATION The field exploration for the project was conducted on September 12, 2018. 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 CME-45B drill rig. The boring was logged by a representative of H-P/Kumar. 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. H-PyKUMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 3 - ASPEN SUBSURFACE CONDITIONS BUILDING DEPARTMENT A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about 6 inches of concrete over 4 inches of base course overlying silty sand and gravel fill to 5 feet underlain by medium dense to dense, slightly silty sand and gravel with cobbles to the drilled depth of 16 feet. Laboratory testing performed on samples obtained from the boring included natural moisture content and gradation analyses. Results of gradation analyses performed on a small diameter drive sample (minus 11h inch fraction) of the coarse granular subsoils are shown on Figure 4. 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 to moist. FOUNDATION BEARING CONDITIONS The upper 5 feet of subsoils encountered at the site consists of man placed fill that is unsuitable for foundation and floor slab support. The underlying relatively dense, slightly silty sand and gravel with cobbles soils possess moderate bearing capacity and low settlement potential. At proposed excavation depths for the foundation, we expect the subgrade will consist of the natural slightly silty sand and gravel soils. Shallow excavations may need to be deepened to expose natural coarse granular soils and the sub-excavated depth backfilled with compacted structural fill. A spread footing foundation system should be feasible for foundation support of the structure with a low risk of differential movement. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building addition be founded with spread footings bearing on the natural granular soils or compacted structural fill. H-PWUMAR Project No. 18-7-522 RECEIVED 1/7/2019 -4 - ASPEN, ign and construction criteria presented below should be observed for a spread footing BUILDING DEPAR � b foundation system. 1) Footings placed on the undisturbed natural granular soils or compacted structural fill should be designed for an allowable bearing pressure of 2,500 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 18 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 42 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 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) The existing fill, debris and loose 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. Structural fill used to reestablish design bearing level should consist of a relatively well graded granular material compacted to at least 98% of standard proctor density at near optimum moisture content. 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 H-P-WUMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 5 - ASP E n and can be expected to deflect sufficiently to mobilize the full active earth pressure BUILDING DEPAMIE condition (if any) 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 95% of the maximum standard Proctor density at a moisture content near optimum. Backfill placed 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 larger than about 6 inches. 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 0.45. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 450 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. H-P <UMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 6 - ASPE(� BUILDING DEPARR SLABS The natural on-site granular soils, exclusive of man placed fill, 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 minimum 1% to a suitable gravity outlet, sump and pump, or drywell. Free-draining granular material used in the underdrain system should 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 feet deep. H-P-WUMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 7 - ASPPII�T Tpp ACE DRAINAGE BUILDING DEPArfl IST The following drainage precautions should be observed during construction and maintained at all times after the addition 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 21/ inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site, finer graded, soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 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 2, indicate an infiltration rate between about 2 to 5 minutes 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 16 feet. The drywell should have solid casing down to at least basement level and perforation below that level. 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. H-PtiKUMAR Project No. 18-7-522 RECEIVED 1/7/2019 - 8 - ASPEN'tneclusions and recommendations submitted in this report are based upon the data obtained BUILDING DEPARI 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, H-P,z,KUMAR 974,/ James H. Parsons, E.I. Reviewed by: _ 4 '' �f . 16222 Steven L. Pawlak, JHP/kac "" H-P-KUMAR Project No. 18-7-522 RECEIVED 1/7/2919 ` ASPS G 1 BUILDING DEPA TMENT WESTERLY 25'OF LOT G I I ASPEN GROVE 1 BUILDING I—II '1L:' 1 = j . t.s, .e �,p.t ■E. • wrv�o �� >6 RW ®!!: - •1'•°O• EASTERLY S.OF LOT G SO 5 '^I t�6V / N - v 2 75 \ L a AVAIL I ��'°wil LOTN I *A �Y5 a a ce CONCRETE i u O l' �'; (� so SLOPE. BORING 21 - 2 \,=� i17 (61F �,Ea `., BOWMAN �' �� BUILDING ALEY >.. I..R.LO.W., NAV !III! I I a 3 w ,� R PARK IGN O 10 — (0...„,.) 0,... — ea,6 PROPERTY LJNE {} 1 a17 w.E a.rz ENTRY ENTRY LIGHT POLE CONCRETE S oEWALK i a�1 \/7�1 \---� ..., , I \tom 1 f�l 1.r :`��:_��-47Z�ice.��:= I\ I\. ;I OIL 0 • 'W' HUNTER STREET I. 1��� 10 0 10 20 APPROXIMATE SCALE—FEET 18-7-522 H-PtiKIJMAR LOCATION OF EXPLORATORY BORING Fig. 1 RECEIVED 1/7/2019 BORING 1 LEGEND ASPEN BUILDING DEPA' 11 61 T (6) CONCRETE, THICKNESS IN INCHES SHOWN IN PARENTHESES TO /6) 1111111111 LEFT OF THE LOG. 11 • (4) BASE COURSE, THICKNESS IN INCHES SHOWN IN PARENTHESES :4. 8/121: TO LEFT OF THE LOG. r4. FILL: SAND AND GRAVEL, SILTY, LOOSE, MOIST, DARK 5 0#70' 35/12 BROWN. SAND AND GRAVEL (SM—GM): SLIGHTLY SILTY, COBBLES, WC=1.4 MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, BROWN GRAY, —200=7 ROUNDED ROCK. w ' = 10 DRIVE SAMPLE, 1 3/8—INCH I.D. LINER SAMPLE. 50/3 o_ w 8/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 8 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. 15 30/6, 50/4 WC=4.0 +4=47 NOTES —200=9 1. THE EXPLORATORY BORING WAS DRILLED ON SEPTEMBER 12, 2018 WITH A 4—INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 20 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422); —200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 18-7-522 H-P- -KUMAR LOG OF EXPLORATORY BORING Fig. 2 RECEIVED 1/ I / O I w9 HYDROMETER ANALYSIS SIEVE ANALYSIS 1 TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 HRS 100 45 MIN 15 MIN 6OMIN 19MIN ♦MIN 1MIN COO f100 /50/40/30 /1 1 /8 /4 3/8" 3/4" 1 1 2" 3" 5"6" 8"0 ASPEN , BUILDING JEPARTMI)NT +- 1__ _ - 1 , 1 - 70 80 20 70 30 f I 60 ( I 40 t rg C, I �— —I 50 8` a 40 60 30 _ r ( 70 zo i __T — — — ! — I _ —_ — 1 ! ao 10�-- I --- I i — I 90 o I I .001 .002 i (.005i .009 .0119 .037 1 I.0751 I .150 I .300 I I I.600 I 1 11.18 !2.361 14.75 I 1 19.5 19 1 38.1 I 176.2t 1127 200 .425 2.0I DIAMETER OF PARTICLES IN MILLIMETERS 152 I CLAY TO SILT SAND GRAVEL FINE MEDIUM COARSE FINE COARSE COBBLES GRAVEL 47 X SAND 44 X SILT AND CLAY 9 X SAMPLE OF: Slightly Silty Sand and Gravel FROM: Boring 1 0 15' These test results apply only to the samples which were tested. The testing report shall not be reproduced, except In full, without the written approval of Kumar & Associates, Inc. Sieve analysis testing Is performed In accordance with ASTM D422, ASTM C136 and/or ASTM D1140. 18-7-522 H-PtiKUIVIAR GRADATION TEST RESULTS Fig. 3 RECEIVED N 1/7/201 °d NI. "c1 -- r ASPEN 00 r 0 BUILDING DEPARTgENT a = � c a o •o co �n v) L. d >, >, y .an tu v, C7vDC7 a W>2 Oaf S Fes-- ZoN U D a QD o 17) J az w ix m 2 . W =~ ° k a- O Q J J L!J Ix J ® Zz0W 0WQ Z CO ci CI) 0-1 0 ON IIIIIIII III I zo d O 0 �r a 2 Q J (1) Q c x 0 J cc)-m cc - V F-O W a Z O HW I . _J�Z QQZ o . O <00 Z m 0 Z 2 O N 111 V 0 If) •- O v J d Z 0 m RECEIVED 1/7/2019 ASPEN H-PKUMAR BUILDING DEPARTMENT TABLE 2 PERCOLATION TEST RESULTS PROJECT NO. 18-7-522 HOLE NO. HOLE LENGTH OF WATER WATER DROP IN AVERAGE DEPTH INTERVAL DEPTH AT DEPTH AT WATER PERCOLATION (INCHES) (MIN) START OF END OF LEVEL RATE INTERVAL INTERVAL (INCHES) (MIN./INCH) (INCHES) (INCHES) B-1 106 2 48 34 14 0.14 34 30 4 0.5 30 28 2 1 4 28 27 1 4 5 27 25 2 2.5 25 23 2 2.5 23 22 1 5 22 21 1 5 21 20 1 5 20 19 1 5 Note: The percolation test was conducted in the completed 4-inch diameter borehole on September 12, 2018.