Loading...
HomeMy WebLinkAboutDRB150144_Soils Test_1430233140.pdf MAY-29-2002 10:38 H-P GEOTECH P.01/18 GL271SteCh HEPWORTH. PAWL .GEOTECHNICAL, INC. 5020 County Road 154 Glenwood Springs,Colorado 81601 Phone: 970-945-7988 Fax: 970-945-8454 e-mail: hpgeo@hpgeotech.com FAX TRANSMITTAL FORM DATE: j I 9 /0 c2_, PROJECT NO.: 11/ 336" TO: Pr' �'U'?S��EG �vs� FAX NO: 970 - 70/.3 .6)>1_12(2/-7 FROM: D.<' fly. 3St,re A /Q/, NUMBER OF PAGES: MESSAGE: The original of this transmittal will be sent by: Ordinary Mail Itgl Overnight NEN Fax Only la Other lel The information contained in this facsimile message is confidential and intended for the sole use of the individual named above. If you are not the intended recipient, received this communication in error, or if problems occur with transmission, please notify us at 970-945-7988. Sent By; MAY-29-2002 1038 H-P GEOTECH r.ez%ic SUBSOIL STUDY FOR FOUNDATION DESIGN LOT 30, WESTHAVEN CIRCLE GLEN LYON SUBDIVISION TOWN OF VAIL EAGLE COUNTY, COLORADO Prepared For: Geoff Meagher 900 East Pine Street Seattle, WA 98122 Job No. 4 335 85 September 17 , 1985 MAY-29-2002 1039 :,-P GEOTECH P.03/18 TABLE OF CONTENTS CONCLUSIONS 1 SCOPE OF STUDY 1 PROPOSED CONSTRUCTION 1 SITE CONDITIONS 2 SUBSURFACE CONDITIONS 3 FOUNDATION RECOMMENDATIONS 4 FLOOR SLABS 5 EXCAVATION AND SITE GRADING 6 UNDERDRAIN SYSTEM 7 SURFACE DRAINAGE 8 LIMITATIONS 8 FIGURE 1 - LOCATION OF EXPLORATORY PITS FIGURE 2 - LOGS OF EXPLORATORY PITS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - GRADATION TEST RESULTS FIGURE 5 - GRADATION TEST RESULTS TABLE I - SUMMARY OF LABORATORY TEST RESULTS MAY-29-2002 10 39 H-P GEOTECH H.04/it CONCLUSIONS The residence constructed on the lot should be founded with spread footings placed on the natural subsoils and designed for a maximum soil bearing pressure of 3000 psf. Design and construction criteria relating to subsoil conditions encoun- tered at the site are presented in this report. Once more specific building and construction plans have been developed, we should be notified for geotechnical review. SCOPE OF STUDY This report presents the results of a subsoil study for a residence to be located on Lot 30, Westhaven Circle, Glen Lyon Subdivision, Town of Vail , Eagle County, Colorado. We understand the findings of this report will be considered in the purchase/sale of the lot. This report has been prepared to summarize the data obtained from the field and laboratory work and to present our conclusions and recommendations based on the assumed construction and the subsurface conditions encountered. Recommended design parameters and a discussion of geotechnical engineering considerations related to construction of the residential structure are included. Geologic aspects such as debris flow and snow avalanche which could potentially impact development on the site are beyond the scope of this study. PROPOSED CONSTRUCTION At the time of this report, building plans had not been developed. We assume the structure will be two to three stories MAY-29-2002 10 39 H-P GEOTECH -2- of wood frame construction with foundations and floor levels stepped to help reduce excavation depths. A maximum cut depth of one level ( 10 to 12 feet) into the hillside is assumed. Founda- tion loadings are assumed to be light to moderate, typical for this type construction and use. When more specific building plans have been determined, we should be notified for geotechnical review and to re-evaluate the recommendations contained in this report. SITE CONDITIONS At the time of our field work the site was vacant and vege- tated with native grasses and aspen trees. The property is situated on the lower northwesterly facing side of Vail Valley at about 8200 feet elevation and overlooks the Gore Creek Valley bottom. Grades across the proposed building area are moderately steep to steep sloping, about 25% to 35%, and increase to about 40% towards the upper (southeast) part of the lot . Elevation difference across the assumed building area (between the pit locations shown on Fig. 1 ) is about 20 to 25 feet . A steep road cut of about 6 to 10 feet height has been made between Westhaven Circle and the lower edge of the site. A shallow ephemeral drainage which crossed the steep to very steep evergreen vege- tated slope of Tract D above the site to the southeast outlets onto the upper extremes of the lot and is presently dry. An existing, multiple story wood frame residence above a buried parking level is located on the adjoining Lot 29 to the south- west. The residence excavation was reportedly cut into multiple levels to reduce excavation depth. MAY-29-2002 10:39 H-P GEOTECH p.0s/le -3- SUBSURFACE CONDITIONS The general subsurface conditions at the site were evaluated by excavating three exploratory pits at the approximate locations shown of Fig. 1 . The steep road cut , together with the site grade and soft topsoil layer, required the use of a track-mounted backhoe to access and traverse the site. The exploratory pit locations were determined from building setback requirements and discussion with Ron Byrne, regarding the probable residence loca- tion. Graphic logs of the subsoil profiles encountered are pre- sented on Fig. 2. As indicated by the logs the subsoil profile is relatively uniform and consists of a 1 to 2 foot topsoil depth above relatively dense silty to clayey sand, gravel and cobble deposit with occasional boulders. Boulders to about 4 foot size were encountered, but larger boulders may be present at other locations. The upper 2 to 4 foot depth of this granular stratum was noted to contain porous fine-grained soil. Generally, less silt and clay and a greater number of cobbles and boulders were encountered with depth in the pits. The larger material encoun- tered with depth caused practical excavation refusal with the light duty track hoe at 13 foot depth in Pit 1 . The depth achieved at the maximum reach of the backhoe was 16 feet in Pits 2 and 3. Results of gradation analysis performed on the minus 3- inch to minus 5-inch size fraction of bulk samples taken at selected depths within the pits are shown on Figs. 4 and 5 . Results of these and other laboratory test results are summarized on Table I . MAY-29-2002 1039 H-P GEOTECH P.07/18 _4_ No free water was encountered in the exploratory pits during excavation and the granular subsoils were generally moist. FOUNDATION RECOMMENDATIONS Considering the subsurface conditions encountered in the test pits and the assumed construction, we recommend the residence constructed on the site be founded on spread footings placed on the natural granular subsoils. The following design and construction criteria should be observed for a spread footing foundation system: 1 ) Footings placed on the natural granular subsoils below all topsoil and upper porous silty to clayey soils may be designed for a maximum soil bearing pressure of 3000 psf. Settlements are expected to be about 1 inch maximum for the assumed type construction. 2) Spread footings should have a minimum width of 16 inches for walls and 2 feet for columns. 3) Exterior footings or footings constructed in nonheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Four feet is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span an unsupported length of a least 10 feet. 5) Foundation walls acting as retaining structures should be designed to resist a lateral earth pressure based on an equivalent fluid weight of 45 pcf. Backfill should consist of granular soils such as those encountered on-site and MAY-29-2002 10.40 H-P GEOTECH P.03/18 -5- should be compacted to at least 90% of standard Proctor density (ASTM D698) . The backfill surface should be sloped away from the structure a distance equal to the backfilled depth but at least 10 feet. An underdrain should be provided to prevent hydrostatic pressure buildup behind the wall. 6) Areas of loose or soft material and any existing fill , porous fine-grained soils and topsoil encountered within the founda- tion excavations should be removed and the footing bearing level extended down to firm natural subsoils. Voids result- ing from boulder removal below foundation excavations should be backfilled with concrete. 7) Footing excavations should be observed by a representative of the soil engineer prior to concrete placement. FLOOR SLABS The natural on-site soils exclusive of topsoil are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement, nonstructural floor slabs should be separated from bearing walls and columns with an expansion joint which allows unrestrained vertical movement. Floor slabs should be provided with control Joints to reduce damage due to shrinkage cracking and the slabs should be ade- quately reinforced. We suggest that control joints be provided on the order of 15 feet on center. A minimum 4-inch free draining gravel layer should be placed immediately beneath floor slabs. This material should consist of aggregate with less than 5% passing the No. 200 sieve and more than 50% retained on the MAY-29-2002 10:40 H-P GEOTECH P.09/18 -6- No. 4 sieve. The underslab gravel should connect to the under- drain system (described below) . EXCAVATION AND SITE GRADING Due to the moderately steep to steep slope of the lot, unstable slope conditions could develop as a result of construc- tion excavation. Excavation should be kept relatively shallow to reduce the risk of slope instability. Permanent unretained cuts should not exceed 10 feet in vertical height and should be graded at 2 horizontal to 1 vertical or flatter. Stepping or benching the foundation excavations into the slope will reduce cut depths and improve slope stability. If fill sections are constructed for driveways, embankment heights of up to 10 feet can be used if the fill slopes do not exceed 2 horizontal to 1 vertical and the fills are properly compacted and drained. The ground surface underlying fill sections should be prepared by removing all organic matter, scarification to about 8-inch depth and recom- pacting to 95% of the maximum standard Proctor density prior to fill placement. Fill should be benched into slopes exceeding 5 horizontal to 1 vertical. Subsequent fill can consist of the on- site soil exclusive of organic matter and oversized rock compacted to at least 95% of the maximum standard Proctor density (ASTM D698) at a moisture content near optimum. Good surface drainage should be provided around all permanent cut and fill slopes to direct surface runoff away from the slope faces. Slopes and other stripped areas should be protected againt erosion by revegetation or other methods. Boulders will be VW-29-2002 10 40 H-P UEOTECH P.10/le -7- encountered in the excavations and should not be included in the fill sections. We estimate oversized rock (approximately greater than 6-inch diameter) may range from about 10 to 30% . Generally, the amount of oversized rock appears to increase with depth but should be expected to vary at other parts of the site . UNDERDRAIN SYSTEM Although free water was not encountered during our investi- gation, it has been our experience in mountain areas such as this that local perched groundwater may develop during times of heavy precipitation or seasonal runoff. Therefore, the lower level or each level cut into the hillside should be protected from wetting by installation of an underdrain system. The underdrain system should consist a perforated pipe installed in a gravel-filled trench placed along the building perimeter and at the base of interior steps in grade. The drain invert should be at least 12 inches below the lowest adjacent grade and sloped on a minimum 1% grade to a suitable gravity outlet . The underslab gravel should be connected to the perimeter drain. The gravel drain material should consist of aggregate with less than 5% passing the No. 200 sieve and at least 50% retained on the No. 4 sieve with a maximum size of about 2 inches. The drain should also act to prevent buildup of hydrostatic pressures behind foundation and basement walls. MAY-29-2002 10:410 H-P GEOTECH P.11/18 -8- SURFACE DRAINAGE The following drainage precautions should be observed during contruction and maintained at all times after the facility has been completed: 1 ) Excessive wetting or drying of the soils exposed in the foundation excavations and underslab areas should be avoided during construction. 2) Miscellaneous exterior backfill should be moistened or dried to near optimum and compacted to at least 90% of maximum standard Proctor density. 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. 4} Roof downspouts and drains should discharge well beyond the limits of all backfill. LIMITATIONS This report has been prepared in accordance with generally accepted geotechnical engineering practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on the exploratory pit plan. The nature and extent of variations between the exploratory pits may not become evident until excavation is performed. If during constrtuction, existing fill , soil, rock or water conditions appear to be different from MAY-29-2002 10:41 H-P GEOTECH P.1d/1b -9- those described herein, this office should be advised at once so re-evaluation of the recommendations may be made. We recommend on-site observation of exavations and foundation bearing strata by a soil engineer. The steep to very steep slopes to the southeast above the proposed building site may have a potential for debris flow or avalanche which could impact a residence on the lot. Although the likelihood of such an occurence appears remote, we recommend that geologic conditions which could potentially impact the site be evaluated as part of the design work. Previous geologic work concerning potential impacts has been performed by Arthur Mears Associates. CHEN AND ASSOCIATES, INC. By Stephen A. Down Reviewed By Steven L. Pawlak, P.E. SAD/ec PHT-G7-GlOOG Ib•41 n-r ULuIcLLn Westhaven Circle i Ph ne Box 011 . %/ — ' - '-';''<';--.'-'-'.'l:7.l,/ -. -- --- -<--..-.------ - 7 // � r-8160 'f— � j 8)50 +-� _ - 4/ . — -- '/f- gla Aanro xim ate -------' - j ___,-- 8t40 8160J / ,---"7 _�� �'� 1 �2~ � ..i� �--� t 11 � - `- . • � 8170 ._--/T,.,, - Scale !„ _ 30' Electric Transformer -� '" • 8180 aooA".„/ 7 --- -- //2kj72 ->---_________- 'r ,-- .------- \ t 3 '---------- l• / 8140 >---;,.....,.. ce 811 \ - �<---"---- r- f —�i _f�- 8200 - I l iY, �_,,r ' E}�c^iet /i - 8190 / -------% /`- 8210 V., ---- -.:------ " _ A/ ;_--- /- _______ ------;;CI 8200 Xj //�-- /' /_--- — 8220 8210 -----'� 82 CO -------- / �~ \?ropert - Boundary f335-83 _.. :.c::a- rn �:. '.ora -:• ?;- -Chen end associates, inc. .. �:: . -�:�_ ; ,:, Im° IRY-29-20102 10:41 11-rutuiCLn ' Pit 1 Pit 2 T 3 8185 Elev, 8161 Elev. = 8167' 1._ _v. = 8181 ' 8185 —. a8180 •-- 8180 ill a: _ �1 I 8175 — 8175 _ II 8170s • 1 1.'C=4.8 8170 --- • I + #4=58 - '" i -200=11 110 I -1pa gpi, i 4,4 CU C.I CJ L� _ - �dC=13.2 e" j 8165 — 1 5 1 LL=28 - rti.4 I PI= 9 .,°., #4=27 - o co ,••1 -200=30 > , - v o) di/ 8160 -- w 8160 r.•`� , - ' WC=6.8 . • 1 -200=21 !W. 8155 -1 °": 8155 — i WC--.6 ., ; • #4=52 .r '� I -200=15 •a.• '4 I — �� 8150 8150 • .. I _.• J 8145 8145 4-335-8:I cites and associates, inc. Logi. of Ex771oratory .`.'its Fig.2 MAY-29-2002 10:41 H-P GEOTECH r.lD,lo Legend: ElTopsoil; organic, low density, silty to clayey, soft, moist, dark brown, with roots. F•r , Gravel (GM-GC); sandy with subangular cobbles and occasional boulders, roo silty to clayey, medium dense to dense, moist, brown to light brown, zones of porous fines, slightly calcarous. Disturbed Bulk Sample. Practical refusal with light duty track hoe. Notes: 1) Exploratory pits were excavated on September 10 and 11, 1985 with a light duty track hoe. 2) Location of exploratory pits were measured approximately by pacing from features shown on the site plan provided. 3) Elevations of exploratory pits were obtained by interpolation between contours on the plan provided and checked by hand level. 4) The exploratory pit locations and elevations should be considred accurate only to the degree implied by the method used. . 5. The lines between materials shown on the exploratory pit logs represent the approximate boundaries between material types and the transitions may be gradual. 6. Laboratory Testing Results: WC = Water Content (%) DD = Dry Density (pcf) -200 = Percent Passing No. 200 Sieve + #4 = Percent retained on No. 4 Sieve. LL = Liquid Limit (%) Pi = Plasticity Index (%) 4-335-85 cis and =sedates, Inc. Le"•e_d arta Notes Fig. 3 11AY-29-2002 1041 H-P GtUItLH ' •-- _.. CA-2-79 .lien and associates, inc. HYDROMETER ANALYSIS SIEVE ANALYSIS r TIME READINGS I U.S.STANDARD SERIES CL FAN.y01.:.►HE UPENIN(35 I { 24 MR 7Hl4 45 MIN 1SM'N. 60 MIN 19MIN.4MIN. 1 MIN '2(1(1 '100 '!50'40'30 '18 I'e A" w._ vi.' 3" S•'6` I' 1011 • 0 10 J \,, 10 ao 4 j .. i 20 ` T .30 70 ` _ r I 4 - 1 t 1 = Z� • - , _ .. i 140 W F . ••••"..----..ut 1 W If .. SO i r— t 30 ti z _ ''. - t I z W I _ 4 � ti-_. f W U a . J 7 { 11. n. 30. i T ` ��� 11 I 201 ## 80 0< j f u r r '.IrI t I II 1 f II I 14r IIII I' r I it 1 “f1 4 . r r.1.. I I 001 002 005 uu4 .019 037. Ora .149 .tyl I >S0 •'S '2 3E 4.76 3!.,2 19.1 38.1 78.2 127 2611 042 2.0 191 I DIAMETER OF PARTICLE IN MILLIMETERSI SAND GRAVEL COBBLES CLAY'U SIL? FINE r MCDIUM ICOARS6 FINE I COARSE _ GRAVEL 53 % SAND 26 % SILT ANO CLAY 21 % LIQUID LIMIT PLASTICITY INDEX 'b / SAMPLE OF silty to clayey FROM Pit 1 at 4 feet to 6 feet sandy gravel [ HYDROMETER ANALYSIS SIEVE ANALYSIS I TIME REAOINt;S V S SrANI)AHUS HIES CLLAII SQUARE JPENINGS 74,414714H 1(I _4 y, 1,,, 1,0� 3' 5..8"49 14 174 1S MIN 60 M1N. 19 MIN.4 MIN. 1 MIN. '200 '100 '50 '40'30 '16 5 100 —4wN.4_=—=w r 4.111041111111M4�—4_4�4�- •���I �Ii--mo_mas—mi5imiuminsamir_Me 10 90 .�� 4.r.�.r4M.� �rww .�4� " --�______5_.___ 41mmmmttmll111t1111N• IIMIMI 4MININ111111141•1■11.•114w..141. 14 1 111 14ti4ti. 3C 4411131•rw__ismulr unimmo .01=3114r_wmmmin.Inx. fa__s 20 7,, 5. , •44 •444 444,. ... 4144....4444.4..45mmmummaassimiWommlimmin ammo 45 , ss�IsraSe ==="0== ==== :=.1.40 lonammsamm..=.masotammimmiimmmagimitiamellnannibliommommiamoinalmama ..45444=== a: kia a. 1111= 11E 1111Eai ui 70 20— 1 __ M1. =sem 80 sll1lMs�eM1 _s: Nss ' >_i___s_____ Ali-�i-a OMEN=MEOW. °° 0 4t14.O.45..44tttr 41 ,s.....,,...r.r,rrUPI M........w.I._.....• _•1•14•11,.. 100 S41 I1(I.' 1)01 'Y9 u19 .037 .074 149 297 590 1.1936 476 9.,2 1(1I 38• 787 127 700 .042 2.0 `O I DIAMETER OF PARTICLE IN MILLIMETERS SAND VRAVEL COBBLES .'.LAY TO SILT FINE I MEDIUM (COARSE FINE I COARSE GRAVFI 27 'h SAND 43 lf% SILT AND CLAY 30 % C IOUIU LIMIT26 a, I'LASTICI TY INDEX 9 r SAMPLE OF Silty to clayey FROM Pit 2 at 2 feet to 4 feet _sand and gravel < 4-335-85 4 GRADATION TEST RESULTS Fig. MAY-29-2002 10:42 H-P UtUIhCH I •A1' �-4 CA-2-79 ...ien and associates, inc. HYDROMETER ANALYSIS SIEVE ANALYSIS 1 TIME READINGS U.S.STANDAR()SERIES I CLEAR SQUARE OPENINT•S 1 [A.IR. 7 HP '10 45 MIN Iti MIN d0 MIN 19 MIN 4 MIN 1 MIN '200 '100 '50 '40'30 •16 18 '4 Y." 1'6' T" 5"B' r 'fir 1. • .-- r 0 90 , + 1 . i 2 10 r ply Z61)i J . + t _ 7 t a 1 — C II i)a0 J i tri 1 �cr n - r 1 �� 1 A. 30 1 r . r 20 701 , •••- 80 0 a0 3 r -r rr t.A ? ,j I r n rr T 'r f fT� + 1 r . r,r f1 1 r '� t r r li, I 700 !7c1:� (10:� 009 1)17 037 074. 140. 297 I i590 I.19 •3o 4 14 9.52 19 1 AI 1 76.2 1277' .. Oc' 2.0 DIAMETER OF PARTICLE IN MILLIMETERS • SAND GRAVEL OQ88LE5 !:LAY TO 511 1 FINE 1 MEORJM !COARSE' FINE 1 COARSE ;RAVEL 52 % SAND 33 % SILT AND CLAY 15 % 01. 'i LIQUID LIMIT PLASTICITY INDEX SAMPLE OF silty to clayey FROM Pit 2 at 12 feet to 16 saudy'gravel feet h YQROMETER ANALYSIS SIEVE ANALYSIS I I IME HEADINGS U.S.STANDARD SERIES CLEAR tiOUANE OPENINGS 24 rill. 7 mit '10 45 MIN 15 MIN MI MIN. 19.MIN 4 MIN. 1 MIN '21.0 -100 '50 '40.30 "70 1'8 '0 k" y.. 1'k" 7" . 5"5" b )00 - N. 1 _ 'I ' E T p i/ ' 10 701 t r 30 l f 1 v _ - - t W Z'iM r r 7 �p2 '� I W SOX I - • W T f 1 33 • / r ;70 ',T I 10 •I . , , i , 1Yn[, '1 � t f r . . j , : rrrrik i.- 1 ft � 1,,.. '100 ((11 q077 001 t 5009 ,019 037 071 (49 .297 590 I.)0 12 38 A 76 9.s:' ,y 7 70.1 79.7 !Z/ 200 042 2.0 152 IDIAMETER OF PARTICLE IN MILLIMETERS SANfi cSi4AVr'1 („AY.()SILT FIND ] MEDIUM 'COARSE_ TINE I COARSE GV8BLE9 GRAVEL 58 % SAND 31 % SILT AND CLAY 11 's, LIQUID LIMIT 'q PLASTICITY INDEX 5AMPIEOF ,gandy gravel, slightly FROM pit 3 at 10 feet to 16 feet siJ1.ty to clayey, 4-335-85 5 GRADATION TEST RESULTS Fig._ f RY-29 -d 10;411—r ucu1CLn - .. -1 T H f0 IC I III oz 44-1 O.a N cuN N� 1' > T ), 7, 61 1 o" Klr -10- .T i u9 -8 0? �W CJ qJ.--I b {I COI m 2 u O,4 L N•+OG k O I I en TT ib7in OOU v ...44 G -fCr 0 kII 0)(t al RT MU C ,-4 CI) H aml J W W>_ CO z h v . n r , 17.W20 W O y a s LL j O H V N IQ U W O W W a i_- J Has a I . .. I 4 I. 4. • < 1— aO r . W C, CO U >. i p'p N �J� p _ ¢ (i) ai • V .r�l ~' Qh W C' — r-O .--I • m ni 20 N m ., I < m C.... Q 4 r ,C3r en -+ Z i,, N ..Y f^ Cl Z J o ILI g I LL. n W.. U O > l N. N to u-, N ..,1 •4-1 u } . . Cc ' Y 2a-C Q `oui S. M Z O 4]Z 4•..io-; CO N ,1* C3 "� • O v o 'D r.' in T .D ,O .i• ,p •T .-8 ..I f W l I I I 121 o� N N O 1 ,, { a 2 , a V) 1...1 r-I N CI TOTAL P.18