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HomeMy WebLinkAboutBEST WESTERN TRANSMISSION PUD LOT 1 PRELIMINARY LOT 2 PRELIMINARY AND FINAL - 15 93 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTv a EAST •'J STREET AND SOUTH COLIEGE AVENUE1 •'J COLZINS,•• •'/• Top of Grrnmd- Depth of PVC Pipe Depth to Water Product Monitoring Elevation Water (1) Elevation on Water Well odor (ft.) (ft.) (ft.) (ft.) MR-1 None 97.4 12.4 85.0 0 MW-2 Very Slight 97.0 12.8 84.8 0 MW-3 Slight 97.2 11.8 85.4 0 MW-4 None 98.2 12.7 85.5 0 (1) Depth to Grater measured from top of PVC pipe. Chen &Associates TABLE I Dissolved Aromatic Hydrocarbon Concentrations in Water Samples, Proposed Amoco Service Station, Fort Collins, Colorado Collected August 8, 1988 Ethyl— Total Benzene Toluene benzene xylenes Well No. --------------------------- mg/l --------- I ND ND ND ND 2 0.12 0.01 0.01 0.03 3 ND ND 0.03 ND 4 ND ND ND ND Total Dissolved Aromatic Hydrocarbons ND 0.17 0.03 ND ND = Not detected at or below 0.001 mg/l. Statistically reproducible _ detection Limit 0.01 mg/l. . RDS:mph 88245ART0056 I':GEND: [a Asphalt, thickne. es indicated. Base course, thickness as indicated. ® Fill, sand, clayey to silty, moist, dark brown. QClay (CL), silty to sandy, stiff, slightly moist to moist, brown to dark brown, slightly calcareous. Sand (SC), clayey to slightly clayey, loose to dense, slightly moist to moist, light brown to brown. 10/12 1 NOTES: 1. 2. 3. 4. 5. Sand and gravel (SM-GM), fine to coarse sand with gravel, clean to slightly silty, dense to very dense, slightly moist to moist, brown. Sandstone, fine grained, hard to very hard, slightly moist to moist, brown, cemented. Drive sample, two-inch I.D.CCalifornia liner sample. Drive sample, Standard Penetration Test, 1 3/8-inch split spoon sample. Drive sample blow count. Indicates that 10 blows of a 140-pound hammer falling 30 inches were required to drive the California or SPT sampler 12 inches. Depth to water level and number of days after drilling measurement was made. Depth at which test hold caved. Exploratory borings were drilled on July 25, 1988 with a four -inch diameter continuous flight power aug'er.an&a seven-inch diameter continuous flight power hol,Fow stem power auger and on August 9, 1988, with a four -inch diameter continous flight power auger. Loca Lions of exploratory borings were measured approximately by pacing from features shown on the site plan provided. Elevations of exploratory borings were measured by instrument level and refer to the bench mark on Figure 1. The exploratory boring locations and elevations should be.considered accurate only to the degree implied by the method used. The lines between materials shown on the exploratory boring logs repoesent the approximate boundaries between material types and the transitions may be gradual. 6. Ground -water -levels shown on the logs were measured at the time and under conditions indicated. Fluctuations ,in the water-1 evel may occur, w.ith time. 16 061 88 1 Chen & Associates I LEGEND AND NOTES Fls. 6 LEGEND: [a Asphalt, thickness as indicated. ® Base course, thickness as indicated. ® Fill, sand, clayey to silty, moist, dark brown. ©Clay (CL), silty to sandy, stiff, slightly moist to moist, brown to dark brown, slightly calcareous. Sand (SC), clayey to slightly clayey, loose to dense, slightly moist to moist, light brown to brown. ®Sand and gravel (SM-GM), fine to coarse sand with gravel, clean to slightly silty, dense to very dense, slightly moist to moist, brown. Sandstone, fine grained, hard to very hard, slightly moist to moist, brown, cemented. Drive sample, two-inch I.D.lCallfornia liner sample. ` Drive sample, Standard Penetration Test, 1 3/8-inch split spoon sample. r Drive sample blow count. Indicates that 10 blows of a 140-pound hammer 10/12 falling 30 inches were required to drive the California or SPT sampler 1 12 Inches. Depth to water level and number of days after drilling measurement was made. — o- Depth at which test hold caved. NOTES: 1. Exploratory.borings were drilled on July 25, 1988 with a four -inch diameter continuous flight power auger.and,'a seven-inch diameter continuous flight power holaow stem power auger and on August 9, 1988, with a four -inch diameter continous flight power auger. 2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory borings were measured by instrument level and refer to the bench mark on Figure 1. 4. The exploratory boring locations and elevations should be'considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the exploratory boring logs represent the approximate boundaries between material types and the transitions may be gradual. 6. Ground -water .levels shown on the logs were measured at the time and under conditions indicated. Fluctuations -in the water level may occur with time. 6 061 88 1 Chen & Associates I LEGEND AND NOTES I F*, 6 i Oats of Installation 8/9/88 Drilling Company Chen S Assoc. Drilling Method 4" SFA Fief Engineer R. Treat Depth Log Do=iption ° 1 M 12/12 5 20 - 25- 30- 6/12 50/1 20/0 Ground surface Eleaalion 98.5' Elevation of Top of Riser Pipe 98.2' I.D. of Protective Casing 0 - 5' Type of Protective Casing Metal cast , l h i gh traffic rated Depth to Bottom of Vault 0. 7' 1.0. of Riser Pipe 2" Tyre of Riser Pipe Sch. 40 PVC Olometer of Borehole 411 Type. of Sookfill Concrete 0-2' Depth to ibis of Sool 7' Ty" of Seel Ben ton i to rl- Dope% is lbp of Somd Pock 51 T/p of Sots/ pack 10- 7 n c i' l i r a ;and Delp* b Top of Sorwm 8.5' lea of WO scream 2" Type of well Smen Sch 40 PyC , 0.020" slotted OWh to SAW of Screen 23.6' Depth to Be"" of Borehole 25.0' Greemd water Level (Depth from Top of Riser) Date Depth 8/9/88 sealed 8/9/88 12.4' 8/18/88 12. ' 6 061 88 Chen & Anecietts I Report of Mtxtieorirtq Well MW-4 y, 5 Date of Installation 7/26 Drilling Comoony Chen & Aria -. Drilling Method 4" $FA Field Engineer R. Treat Depth Log Deeuiption 0 12/12 5 11/12 no 50/10 0 Ground Surface Elevation 97.5' Elevation of Top of Riser Pipe 97.2' I.D. of Protective Casing 0.5' Type of Protective Casing Meta I cast . h i qh traffic rated Depth to Bottom of Vault 0. 7' I.D. of Riser Pipe 2" Type of Riser Pipe —Sch. 40 PVr Diameter of Borehole 4" Type of a«tfiil Benton i to used from 0.8' down to 3.0' Depth to Tbo of Ssel 0.8' Type o{ seal Ben ton i to Depth so Tbp of sew Peat 3 . 0' Type ei Sew Peck 10'-70 ci 1 Tyra sand Dept to Top w smom 3. 5' I.D. of wdt secants 7" Typo of well Screw Sch _ 40 PVC - 0.070" slotted Depth to Sam .of Serwn 18.5' Depth to 1A An of floohole 19. 5' Groww Wo»r Level (Depth from Top of Riser) Oat* Depth 7/25/88 11.5' 7/25/88 18' 8/4/88 11.8' 16 061 88 I `bm & Assocaatees I Report of Mattittxitty well ►w-3 I ng. 4 I r••_r-r. >- Oat• of Installotiom 7/25/88 Drilling Company Chen & Assoc. Drilling Method_4" SFA Fielid Engineer R- Tr at )eplh Log Description 01 m 18/12 �� to/t2 5J 15� � 20/0 Ground Surface Elevation 08.0' Elevation of Top of Riser Pipe 97.6' L0. of Protective Casing 0.5' Typo of Protective Casing Meta t cast, h i ah traff is rated Depth to Bottom of Vault 0.71 I.O. of Riser Pipe 2" Type of Riser Pipe 5ch, 40 PVC Dieewter of Borehole 4" Type of Beokfill Concrete,'used 0-1 .5' Depth to Top of Seel 1 ' 5' Type of Seel. 8 Pn ton i r P Deptf to Tbp of Sad Peck 3 .0' Type of Soar Pock 10-70 <i 1 ica sand Doom to Top of Sersem 4 �' LD. 04 WON Sereew 2" Type of Well Screen 5ch. 40 PVC, 0.020" cl nrt-d Depth to Bottom of Screen 19.0' Depth to Bottam of Borahols 19.0' Ground Woter Level (Depth from Top of Riser) Date Depth 7/25/88 Trace 8/4/88 12.8' I 6 061 88 I Chen & Associates CAWM-5 Report of Monitoring Well MW-2 ft 3 Dott of Installation 7 /88 Drillinq Company Chan & ASSQ Drilling Method 2k" ID HSA Fi.l4d Engineer R. Treat Depth Log Description 0 10/12 5 7/12 10 35/12 15 55/5 ►TOI 50/2 Ground Surface Elevation - 97.7' Elevation of Top of Riser Pipe 97.4' I.D. of Protective Casing 0. 5' Type of Protective Casing Metal cast. high rraffir rarPd Depth to Bottom of Vaelt 0 • 7' 1.0. of Rise Pipe2" Type of Rises Pipe Sch . 40 PVC Diameter of Borehole T' HSA Type of BeakfHl CnnrrPre itaPd 0-1 S' Depth to Top of Seal . 1 • 5' Too of Seel Ben ton i t e DyM to lbp of sad Peek ' *716 of saw pack 10-10 ci?irn ;and Dgth to Top of SWOON - 4 S' LD: of WON Sere" 2" Typo of won Screen Sch, 40 PVC. 0.0 0" slotted Depth to Sol of amen 19.5' Depth to Bettlow a(Borehole - 19 . 5' Grornd Water level (Depth fran Top of Ries) Dote Depth 7/25/$$ -161 AA/RR tZ 4, -S Raport of MonitoriN we" MW-1 2 W z W a w 0 W J J O U x 0 N EAST STUART STREET I FUEL STORAGE j I I I EXISTING i I AMOCO I SERVICE j I STATION I I 1 I 1 I I i I LEGEND: B.M.: Property . Corner Pin and Cap Elev. = 100.0' (Assumed) APPROXIMATE SCALE: 1"=30' I W-4 -- --� I /I 1 EXISTING VACANT MOTEL I 1 bo 1 6 I b 1 MW-3 MW-1 /� j / 1 I I I APPROXIMATE DIRECTION OF GROUND -WATER FLOW / EXISTING ONE- � I STORY WITH I I I I BASEMENT I I / 1 ---J I 1 � MW-2 --- • MW-1 = monitoring well PROPERTY BOUNDARY .. --Ground-water contours, elevation in feet 6 061 88 Chen & Associates LOCATION OF MONITORING WELLS Fig. 1 Amoco Corporation August 26, 1988 Page 2 schedule 40 PVC pipe. During removal of the augers in wells Mw-1 through Mw- 3, the soils sloughed into the boring. Permanent protective covers were installed on the monitoring wells, nearly flush with the existing pavement. The permanent covers were grouted in place and the pavement adjacent to the covers was patched. Subsequent to monitoring well placement, the wells were developed. On August 4, 1988, monitoring wells 1 through 3 were sampled. Monitoring well 4 was sampled on August 18, 1988.• The wells were each purged of ap- proximately three well volumes until the rare' and specific con- ductance of the ground water stabilized. Water samples were obtained using a Teflon bailer and were placed in 40 milliliter glass vials containi m a freon fixative supplied by the Amoco Corporation Ground Water Management Section. The samples were express mailed to Amoco's laboratory in Tulsa, Oklahoma, for analysis. A summary of the field measurements during sampling are presented in Table I. The monitoring wells were installed and constructed as discussed with the client for purposes of monitoring potential petroleum hydrocarbon contamina- tion at the site. Information submitted in this report isbased upon the data obtained from the exploratory borings drilled at the locations indicated on the exploratory boring plan and the monitoring wells installed. The nature and extent of subsurface and contaminant variations across the site may not be evident based on information from the exploratory borings. As requested, our services were monitoring well installation, gourd -grater sampling, and sam- pling to verify the classification and engineering characteristics of the soil encountered. We understand that Amoco Corporation will make recommendations regarding monitoring well usage or abandonment. If you have any questions or if we may be of further service, please contact our office. ,�p0 R EGIS t:�0;:•'ORI 0,* Sincerely, �L. CEIEcY & ASSOCIATES, INC. 20462 00 By ', ,rS� •..... goyG Norman F. Lewis NFWeac Rev. By: JAS Encs. cc: Mr. Bruno Procopio Chen & Associates Chen &A wiates Consulting Geotect.—cal Engineers 96 South Zuni Casper Denver, Colorado 80223 Colorado Springs 303/744-7105 Ft. Collins Glenwood Springs Phoenix Rock Springs Salt lake City San Antonio August 27, 1988 Subject: Monitoring Well Installation, Proposed Amoco Service Station, Fast Stuart Street and South College Avenue, Fort Collins, Colorado Job No. 6 061 88 Amoco Corporation Ground Water Management Section 7201 Fast 38th Street, Space 7253 Tulsa, Oklahoma 74138 Attention: Mr. Ray Stcelting Gentlemen: As requested, Chen & Associates, Inc., installed four monitoring wells and obtained samples of ground water at the site of the proposed Amoco located at the southeast corner of East Stuart Street and South College Avenue in Fort Collins, Colorado. We were requested -by Mr. Bruno Procapio of Amoco Oil Company to install four wells at the subject site. The wells were installed in order to obtain samples of groundwater for analysis by the Amoco Oil Company and to provide information for.ifoundation.recommendations for the proposed construction. The monitoring wells, MW-1 through MW-3, were installed on July 25, 1988. Monitoring well MW-4 was installed on August 91 1988, as a result of new building locations and the results of the initial drilling. The approximate locations of the monitoring wells is shown on Figure 1. Subsurface conditions encountered in the exploratory borings drilled for installation of the monitoring wells generally consisted of a layer of asphalt pavement underlain by five to 8.6 feet of clayey sand and sandy clay, and 1.5 to 4.5 feet of silty sand and gravel overlying sandstone bedrock to the maxi- mum depth of drilling, 25 feet. Summaries of the boring logs are presented on Figures 2 through 5. At the time of drilling, ground water was encountered at approximately 16 to 20 feet in the exploratory borings. During the drilling operation, samples of subsurface soils were obtained at approximate five-foot intervals for head space analysis with a photoioniza- tion detector (Photovac Tip 1). The results of these analyses were presented in the field parameter summaries submitted with the ground -water samples. Petrochemical odor was noticed in the bedrock in boring MW-3. - Subsequent to completing each of the exploratory borings, a monitoring well was installed for ground -water sampling. Details of the monitoring well installations are shown on Figures 2 through 5. The monitoring wells are constructed of two-inch diameter, threaded, flush -jointed, schedule 40 PVC pipe. The screen section is constructed of 0.020-inch, machine slotted, 0 Chen &Associates Consulting Geolechnical Engineers TABLE I SUMMARY OF LABORATORY TEST RESULTS 6 061 88 SAMPLE LOCATION NATURAL MOISTURE CONTENT (%) NATURAL DRY DENSITY (Dd) GRADATION PERCENT PASSING NO 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH (Dil) AASNTO CLASSIFICATION (GROUP INDEX) SOIL OR BEDROCK TYPE MOLE DEPTH (lost) GRAVEL (%) SAND (%) LIQUID LIMIT 1%) PLASTICITY INDEX (%) MW-1 .1 15.5 111.4 59 39 22 A-6(10) Very Sandy Clay MW-2 1 9.1 107.1 59 30 16 A-6 (6) Very Sandy Clay 4 9.1 103.3 57 30 14 A-6 (6) Very Sandy Clay MW-3 1.5 9.6 112.3 47 26 11 A-6 (2) Clayey Sand 4 21.3 97.6 80 37 17 Sandy Clay MW-4 4 14.5 A10.1 57 31 16 Very Sandy Clay I 1 PIVOT LINE 11 a � r 10 10 so _ O 7t 200 s s a0 ps 300. 7 Z 100 O too a Oo a e Too 200 o a � z A a 00 y� m i Y 400 1 q 1 I 1 1 i goo 6 061 88 Chen dz ASSOCiatcs NOMOGRAPH FOR M1410 PAVEMENT DESIGN WITH fled.6i Fig.6 9 70 eo e x W 60 7 QQ it 40 6 5 CO j 30 W 5�U ; 20 ' y 4 ' 1Q 5 3 I SERVICEAPILITY INPEX - 2.0 B I 6 4 cc 1.000 500 3 � uo 100 50 2 2.0 6 F 5.0 2 4 6 16 161 83 I Chen & Associates ::.SPHAL ` PAVEML DESIGN OMOOROH ft. 5 CA-1-79 chen and assoc' des, inc. 5 as 0 0 4 " 0 iMoisture Content 9. 1 percent From: MW-2 at depth 41 Ulm ai Nolilillimmullimmillil Nolilillimmullilmmillill mlmiiiimllmiimmilii U.1 _ l.0 lU 1UU APPLIED PRESSURE — ksf moisture Content 21 .3 percent Sampieof: Sandy Clay From: MW-3 at depth 4' HIM U.l 1.0 w 1uU APPLIED PRESSURE — ksf 6 061 98 SWELL -CONSOLIDATION TEST RESULTS Fig. 4 .. - LEGEND: ! V Asphalt, thickness as indicated. Base Course, thickness as indicated. Fill, sand, clayey to silty, moist, dark brown. Sand and Clay (SC-CL), sand, clayey to slightly clayey, loose to dense, slightly moist to -moist, light brown to brown, interbedded with clay, silty to sandy, stiff, slightly moist to moist, brown to dark brown. ®Sand and gravel (SM-GM), fine to coarse sand with gravel, clean to slightly silty, dense to very dense, slightly moist to moist, brown. ®Sandstone, fine grained, hard to very hard, slightly moist to moist, brown, cemented. Drive sample, two-inch I.O.CCalifornia liner sample. Drive sample, Standard Penetration Test, 1 3/8-inch split spoon sample. Drive sample blow count. Indicates that 10 blows of a 140-pound hammer 10/12 falling 30 inches were required to drive the California or SPT sampler 1 12 inches. Depth to water level and number of days after drilling measurement was made. —► Death at which test hole caved. NOTES: I. Exploratory borings were drilled on July 25, 1988 with a four -inch diameter continuous flight power auger and a seven-inch diameter continuous flight hollow stem power auger and on August 9, 1983 with a four -inch diameter continuous flight power auger. 2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory borings were measured by instrument level and refer to the bench mark on Figure 1. 4. The exploratory boring locations and elevations should be, considered accurate only to the degree implied 'by the method used. 5. The lines between materials shown on the exploratory boring logs represent the approximate boundaries between material types and the transitions -may be gradual. 6. Ground -water .levels shown on the logs were measured at the time and under conditions indicated. Fluctuations in the water level may occur with time. -. 6 061 88 Chen & Associates LEGEND AND NOTES. 3 Mw-3 t11'-1 MW-2 (BW-1) mw-4 'E1.=98.0E1.=98.0' E1.=97.5' E1.=96.5' Assumed Finished Floor Level 100 100 2.25" 2" 10/12 3.0" 3' DD=111.4 18/12 2.0" 2.511 -200059 DD=WC-907.1 12/12 4.5" LL=3: °1=22 - 200= 200=59 wC=9.6 DD=112.3 12/12 95 Pt=16 -200=47 Q3 LL=26 7/12 10/12 PI=11 6/12 we=9.1 )01 we=14.5 DD=103.3 11/12 wC=qt.3 DD=110.1 -200-57 LL=30 D�0�86 -zoo=57 QO PI=t4 90 LL=37 F 35/12 50/6 PI=17 ,- W w 50/10 50/11 W W U- - 10 10 10 z g5 - = - 0,0 85 0 55/5 20/0 _ 20/0 a W o 75/1 W J J W � W 80 0 80 25/0 30/1 50/2 50/1 75 75 20/0 70 70 6 061 88 Chen & Associates T LOGS OF MONITORING WELLS Fig. 2 EAST STUART STREET I FUEL L STORAGE j B.M.: Property Corner Pin and Cap Elev. = 100.0' (Assumed) Flu II � EXISTING I AMOCO I I SERVICE I I APPROXIMATE SCALE: 1"=30' STATION I I I I I 1 I I t /*MW - 4 -- - r� jl EXISTING VACANT MOTEL I � I eb. L--------------------� I I I • MW-3 MW-1 I . j I I / I I I I APPROXIMATE DIRECTION OF GROUND -WATER FLOW r I I I EXISTING ONE- I I STORY WITH I 1 1 BASEMENT I I� I • MW-2 ---- , PROPERTY" BOUNDARY' LEGEND: • MW-1 = monitoring well Ground -water contours, elevation in feet 6 061 88 Chen & Associates LOCATION OF MONITORING WELLS F1s. 1 pavement subgrade should be proofrolled with a heavily loaded pneumatic -tired vehicle. Pavement design procedures assume a stable subgrade. Areas which deform excessively under heavy wheel loads are not stable and should be removed and replaced to achieve a stable subgrade prior to paving. Drainace: The collection and diversion of surface drainage away from paved areas is extremely important to the satisfactory performance of pavement. Drainage design should provide for the removal of water from paved areas and prevent the wetting of the subgrade soils. ji1WtY : Y �� This report has been prepared .in accordance with generally accepted soil and foundation 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 borings drilled at the locations indicated on the exploratory boring plan, and the proposed type of construction. The nature and extent of subsurface variations across the site may not become evident until excavation is performed. If during construction, fill, soil, rock or water conditions appear to be different from those described herein, this office should be advised at once so reevaluation of the recommendations may be made. We recommend on -site observation of excavations and foundation bearing strata by a representative of the soil engineer. 14 Chen &Associates reaction for rigid pavements. Both values are empirically related to strength. Sabgrade Materials: Based on the results of the field and laboratory studies, the subgrade materials at the site classify as A-6 with gib itxiices between 2 and 10 in accordance with the American Association of State Highway and Transportation Officials (AASRTO) classification as shown on Table I. For design purposes, a soil support value of 4.5 was selected for flexible pavements and a modulus of subgrade reaction of 100 pci was selected for rigid pavements. An EDLA (18 kip equivalent daily load application) of five was assumed for design purposes. The IDLA was based upon an assumed average daily traffic mix at the site consisting of approximately 2,400 automobiles per day and one combination truck per day. This converts to an IDLA of about 2, but the value of 5 was chosen to allow for the effects of trucks turning. Pavement Desicrn: The .pavement for the site should consist of six inches 'of high quality aggregate base course and three inches of asphalt surface. As an alternative, a full -depth asphalt section of five inches may be used. Trash pickup points and other areas where truck turning movements are concentrated should be paved with five inches of portland cement concrete. The concrete pavement should contain sawed or formed joints to one quarter the depth of the slab at a maxim= spacing of 15 feet on center. Sibgrade Preparation: Existing pavement should be removed completely from the areas to be paved. Prior to placing the pavement section, the entire subgrade area should be scarified to a depth of eight inches, adjusted to near optim m, and compacted to 95 percent of the maximim, standard Proctor density. The 13 Chen &Associates STORAGE TANK INSTA7Ta'CN Installation of the proposed underground storage tanks will require an excavation approximately 12 feet deep. Excavation of two to three feet of sandstone bedrock may be required to achieve this depth. In our opinion, excavation of the near surface bedrock and overburden soils should be possible with heavy duty conventional excavation equipment. PAVEMENT Tr DESI(R1 Pavement reccnmendaticns presented herein are based on an evaluation of -- subsurface conditions at the vacant motel site. Subsurface and pavement - conditions at the existing Amoco service station were not evaluated. It was assumed that due to the extent of construction on the motel site that all existing pavement would be removed. The existing pavement section for the motel site, as well as the existing service station site could be utilized with an cverlayment. If any overlayment is considered, we are prepared to evaluate the pavement section at the existing service station and to provide recommendation for overlayment. A pavement section is a layered system designed to .distribute con- centrated traffic loads to the subgrade. Performance of the pavement _ structure is directly related to the physical properties of the subgrade soils and traffic loadings. Soils are represented for pavement design purposes by means of a soil support value for flexible pavements and a modulus of-subgrade 12 Chen &Associates r- (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 minianmt slope of six inches in the first ten feet in unpaved areas and a minimum slope of three inches in the first ten feet in paved areas. (4) Roof downspouts and drains should discharge well beyond the limits of all backfi11. (5) Landscaping which requires typical irrigation and lawn sprinkler heads should be located at least five feet from foundation walls. An analysis of the presence of hydrocarbons within the soil and bedrock at the.site was conducted in order to. evaluate the potential for petrochemical contamination of the subsurface profile. The soil and bedrock encountered in the .exploratory borings were sampled at approximate five-foot intervals for head space analysis with a photoionization detector (Photovac TIP I). Petrochemical odor was noticed in boring MW-3 at fourteen feet. Subsequent to ccapleting each of the exploratory borings, a monitoring well was installed for ground -water sampling. The wells were developed after placement. Details of well placement and sampling are discussed in a separate letter to Mr. Gene Schmidt of Amoco Corporation's Ground Water Management Section in Tulsa, Oklahoma. R4 Chen &Associates natural soil and bedrock encountered at shallow depths is suitable for use in conr-acted fills beneath floor slabs. The above recommendations assume that floor slabs will be placed only upon the natural soils or upon thin sections of properly compacted structural fill. At the west end of the car wash building, deep fills in excess of three feet may be required due to the basement in the existing building. Settlement of fill material due to seepage from the car wash may occur even with properly compacted fill. Settlement may result in differential movement and cracking of the floor slab. Settlement of the fill materials may be reduced by Limiting seepage from the car wash by using flexible membrane liners beneath the floor slab or by other measures which will reduce seepage into the subgrade materials. Alternatively, the car wash should be located to minimize the depth of fill underlying the floor slab. The following drainage precautions should be observed during construction and maintained at all times after the facility has been completed. (1) Excessive wetting or drying 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 90 percent of the maximum standard Proctor density in landscape areas and to at least 95 percent of the maximum standard Proctor density in pavement areas. 10 Chen & Associates replaced with nonPxpansive fill material compacted to 100 percent of the max== standard Proctor density near the optimun moisture content. New fill should extend down from the edges of the footings at a one horizon- tal to one vertical projection. (7) Excessive wetting or drying of the foundation excavations should be avoided during construction. (8)' A representative of the soil engineer should observe all footing excava- tions prior to concrete placement. The natural on -site soils, exclusive of topsoil, are suitable to support lightly to moderately 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. We suggest joints be provided on the order of 15 feet on center. The requirements for slab reinforcement should be es- . tabli.shed by the designer based on experience and the intended slab use. Fill placed beneath floor slabs should be a nonexpansive, granular material. The soil engineer should evaluate the suitability of proposed fill materials. Fill should be placed and campectedto at least 95 percent of the maxim= standard Proctor density near cptim:= moisture content. Some of the E Chen & Associates soread Footing Foundation system: Spread footing foundations bearing on the natural soils.are considered as an alternative for the cashier and car wash buildings. These buildings do not have the uplift and lateral loads as- sociated with the canopy, therefore, they need not be founded on piers. The design and construction criteria presented below should be observed for a spread footing foundation system. The construction details should be con- sidered when preparing project documents. (1) Footings placed on the undisturbed natural soils should be designed for an allowable soil bearing pressure of 2,000 psf. (2) Based on experience, we estimate total settlement for footings designed and constructed as .discussed in this section will be approximately one (3) Footings -placed on the.soils should have a minimun.width of,16 inches for continuous footings and of 24 inches for isolated pads. (4) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protec- tion. Placement of foundations at least 30 inches below the exterior grade is typically used in this area. (5) Continuous foundation walls should be, reinforced top and bottom to span an unsupported length of at least ten feet. (6) Areas of loose or soft material or deleterious substances encountered within the foundation excavation should be removed and the footings extended to adequate natural bearing material. As an alternate, the:,'I loose or soft material or deleterious substances may be__removed _ and 8 Chen &Associates (7) Concrete used in the piers should have a mina' = slimip in the range of five to seven inches. (8) Based on the results of our field exploration, laboratory testing and our experience with similar properly constructed drilled pier foundations, we estimate pier settlement will be low. Generally, we estimate the settlement of a pier up to 24 inches in diameter will be on the order of 1/2 inch when designed according to the criteria presented herein. (9) Pier holes should be properly cleaned prior to the placement of concrete. (10) The presence of water in some of the exploratory borings indicates the use of casing or dewatering equipment in the pier holes may be required to reduce water infiltration. The requirements for casing and dewatering equipment can sometimes be reduced by placing concrete immediately upon cleaning and observing the pier hole. In no case should concrete be placed in more than three inches of water. (11) The drilled shaft contractor should mobilize equipment of sufficient size and -operating condition to achieve the required penetration in the sandstone bedrock. (12) concrete should be placed in piers the same day they are drilled. The Presence of water or caving soils may require that concrete be placed immediately after the pier hole is completed. Failure to place concrete the day of drilling will normally result in a requirement for additional bedrock penetration. (13) A representative of the soils engineer should observe pier drilling operations on a full-time basis. 7 Chen &Associates i loads to a stratum of high bearing capacity. They have the additional advantage of providing the necessary means to resist uplift and lateral loads. The natural soils at the site have adequate bearing capacity for the as- sociated buildings; however, it may be more economical and convenient to found them on piers as well. Drilled Pier Foundation System: The design and construction criteria presen- ted below should be observed fora straight -shaft pier foundation system. The construction details should be considered when preparing project documents. (1) Piers should be designed for an allowable end bearing pressure of 30,000 psf and a skin friction of 3,000 psf for the portion of the pier in bedrock. Uplift due to structural loadings on the piers can be resisted by using 75 percent of the allowable skin friction value plus an al- lowance for pier weight- (2) - A.m;nimim, dead load pressure is not required. (3) Piers should penetrate at least three pier diameters into bedrock. (4) Piers should be designed to resist lateral loads using a modulus of horizontal subgrade reaction in the sandy clay soils of 60 tcf and a modulus of horizontal subgrade reaction of 300 tcf in the bedrock. The modulus value given is for a long one -foot wide pier and must be cor- rected for pier size. (5) Steel reinforcement to resist tension caused by swelling materials will not be necessary. (6) A void is not necessary beneath grade beams. 6 Chen &Associates Ground water was encountered at depths of 16 to 20 feet at the time of drilling. All borings were completed as monitoring wells to monitor the ground water and obtain samples of ground water for evaluation of the presence of hydrocarbons. Samples obtained from the exploratory borings were returned to our laboratory for visual classification and testing. The laboratory testing was conducted in accordance with applicable ASTM standards. Laboratory testing included standard property testing, including natural moisture content, dry density, minus 200 sieve fraction, liquid and plastic limits, and swell - consolidation characteristics. Swell -consolidation tests conducted on samples Of sandy to very sandy clay indicate that the material has a nil swell - - potential and -consolidates slightly upon loading. Results of the laboratory testing program are shown on Figures 2 and 4 and in the attached s mmiary of Laboratory Test Results, Table I. Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recc=end the build- ings and canopy be founded on straight -shaft piers drilled .into the bedrock. As an alternate, the buildings, but not the canopy, may be founded on spread footings bearing on the natural soils. Straight -shaft drilled piers for support of the canopy have the advantage Of providing separate high -capacity piers. for transferring the structural 5 Chen &Associates occupied by an existing Amoco service station. The southern half of the property was occupied by an estimated 40-year old vacant motel and a separate one-story building with basement. The majority of the area around the service station and motel was asphalt paved. Topography was nearly level, with a gentle slope to the south. SUBSURFACE COND=ONS The subsurface conditions were investigated by drilling four exploratory borings at the approximate locations shown on Figure 1. Two borirxgs were drilled within the approximate footprint of the proposed gasoline facility, _ one hole was drilled in the approximate location for the underground storage _ tanks and one hole was drilled in the approximate location of the proposed car wash.building. Graphic logs of the exploratory borings are shown on Figure 2 with a legend and notes on Figure 3. The subsurface profile encountered in the borings generally consisted of a thin layer of asphalt, with base course, underlain by 5 to about 8.5 feet of clayey sand and sandy clay, and 1.5 to 4.5 feet of silty sand and gravel. the overburdened soils were underlain by sandstone bedrock extending to the maximum depth drilled, 25 feet. Standard penetration tests performed during drilling indicated that the consistency of: the clayey sand and sandy clay was medium to very stiff while the silty sand and gravel was medium dense to very dense. The sandstone bedrock was very hard. 4 Chen &Associates a discussion of geotechnical engineering considerations related to construc- ticn of the proposed Amoco facility are included in the report. Amoco Oil Company has proposed to build a new self-service station and car wash facility. The facility will consist of an approximate 17- by 20- foot cashier building, a 24- by 152-fcat free-standing canopy over the cashier building and gasoline pump islands, and an 18- by 44-foot drive -through car wash building. Plans are still preliminary but the canopy will most likely be supported by five columns. The car wash and cashier buildings will most likely be of masonry block construction with a brick veneer. The cashier building may alternatively be of pre -fabricated construction. Based on experience with similar :construction, we anticipate the foundation loads will be on the order of 1.5 to 2 kips per linealfoot for the buildings. canopy loads may be on the order of 20 to 25 kips per column axially, 2 to 3 kips laterally at the top of each column and 12 to 15 kips of uplift per column. If loadings, locations or conditions are significantly different from those described above, we should be notified to re-evaluate the reccmrtnenda- tions contained in this report. SITE CONDITIONS At the ,time of our field investigation, the northern half of the site was Chen & Associates PURPOSE AND SCOPE OF STUDY This report presents the results of a subsurface study for the proposed Amoco service station and car wash to be located at the southeast corner of East Stuart Street and South College Avenue in Fort Collins, Colorado. The subsurface study was conducted for the purpose of developing foundation recommendations, endations, evaluating potential petrochemical contamination of the subsoils and ground water, and determination of a pavement section for the site. The project site is shown on Figure 1. A field exploration program consisting of exploratory borings was conducted to obtain information on subsurface conditions. Samples obtained during the field exploration were examined for petrochemical odor and the exploratory borings were tested to determine the concentration of gas and percent of the lower explosive limit (UM). Samples obtained from the :exploratory borings were returned to the laboratory to determine the clas- sification and engineering characteristics of the on -site soil and bedrock. The results of the field exploration and laboratory testing were analyzed to develop rations for foundation types, depths and allowable pressures for the proposed building and canopy foundations, and to provide pavement recommendations. The results of the field exploration and laboratory testing are. presented herein. This report has been prepared to summarize the data obtained during this study and to present our conclusions and recommendations based on the proposed construction and the subsurface conditions encountered. Design parameters and 2 Chen &Associates A subsurface study for the purpose of developing soil and foundation reca mnendations and evaluating potential petrochemical contamination of the subsoils has been performed for the proposed Amoco gasoline and car wash facility located at East Stuart Street and South College Avenue in Fort Collins, Colorado. The subsurface profile at the site consists of a thin asphalt layer, a base course layer and five to 8 1/2 feet of sandy clay and clayey sand over sandstone bedrock to the maximum depth drilled, 25 feet. Ground water was encountered at depths of 16 to 20 feet at the time of drilling. It. is recommended that the buildings and canopy be founded on straight-- _._ 1 11shaft piers drilled into the bedrock and designed for a maximum allowable end bearing pressure of 30,000 psf and a skin friction of 3,00o psf. An alternate foundation recormendation of spread footings bearing on the natural soils and designed for an allowable bearing pressure of 2,000 psf is presented for the buildings. Pavement for the site should consist of either six inches of aggregate base course and three inches of asphalt surface, or five inches of full -depth asphalt. Heavy load areas should be paved with five inches of portland cement concrete. XCTrMan F. Lewis eeoewoe � :w c 20462 . •m P.E. Chen &Associates LIST OF FIGURES FIG. 1 - LOCATION OF MONITORING WELLS FIG. 2 - LOGS OF MNITORING WELLS FIG. 3 - LEGEND AND NOTES FIG. 4 - SWELL -CONSOLIDATION TEST RESULTS FIG. 5 - ASPHALT PAVEMENT DESIGN NOMGRAPH FIG. 6 - M40GRAPH FOR RIGID PAVEMENT DESIGN WITH SI=2.0 TABLE I - LABORATORY TEST RESULTS Chen & Associates v � • •• \iY�l\r1. EXECUTIVE SUMMARY PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS SUBSURFACE CONDITIONS FCUNDATION RECXZ21ENDATIONS ERTTTED PIER FOUNDATION SYSTEM SPREAD FOOTING FOUNDATION SYSTEM FLOOR STARS SURFACE DRAINAGE HYDROCARBONS UNDERGROUND SIORAGE TANK INSTALLATION PAVE = DESIGN SUBGRADE MATERIAT� PAVEMENT DESIGN SUBGRADE PREPARATION DRAINAGE LIMITATIONS 1 2 3 3 4 5 6 8 9 10 11 12 12• . 13 13 13 13 14 Chen &Associates • 5 Chen &Associates D South Zuni Casper Denver, Colorado 80223 Colorado Springs Consulting Geotechnical Engineers 3031744-7105 Ft. Collins Glenwood Springs Phoenix Rock Springs Salt lake City San Antonio SOIL AND FOUNDATION STUDY PROPOSED AMOCO SELF-SERVICE GASOLINE AND CAR 4� FACILITY EAST STUART STREET AND SOUTH COLZF.GE AVENUE FORT COLS.ZTiS, COLORADO PREPARED FOR: AMOCO • ■ CO. :0 SCU`I!H SYRACUSESTREET DENVER, •• • • •D• 80237 71 • I• BRUNO PROMPIO JOB NO. 6 061 88 AUGUST 30, 1988