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Home My WebLink AboutREDTAIL RESIDENTIAL - FDP - 26-01A - REPORTS - GEOTECHNICAL (SOILS) REPORTGeotechnical Engineering Supplemental Report Retail — Proposed Mixed Use Development Fort Collins,.Larimer County, Colorado Project No. 20015260 Page 2 Terracon was encountered at approximate depths of '/2 to 7-1/27feet below site within these -two (2) locations or approximate mean sea level elevation of4984 to 4987. The stratification boundaries shown on the enclosed boring/piezometer logs represent the approximate locations of changes in soil types; in -situ, the transition of materials may be gradual. The soil profile for this study is generally consistent with the soil and bedrock conditions presented in our previous subsurface exploration report. GROUNDWATER CONDITIONS Groundwater was encountered in these two borings/plezometers at.approximate depths of 6 to 7-1/24det. below existing site. grades or approximate elevations of 4983 to 4984. These observations represent only the current groundwater conditions, and may not be indicative of other times or at other locations. Groundwater levels can be expected:to fluctuate with varying•seasonal and weatherconditlon%,as well as volumwof.each pond. GEOTECHNICAL ENGINERING RECOMMENDATION • Earthwork- Embankment Recommendations for Roadway.Alignment Within Pond.ln-Fill The civil engineering consultants for the project, North Star Design, and the project developer, Lagunitas Companies, have requested Terracon to provide supplemental, geotechnical'engineedng recommendations for earthen embankments to be installed/constructed within the northwestern pond as depicted in the attached schematic sent to Terracon via electronic mail from North Star Design. The embankment fill materials should consist of relatively homogeneous material which is placed and compacted in uniform lifts, moisture conditioned to plus or minus 2 percent of optimum moisture content and mechanically compacted to at least 98 percent of Standard Proctor Density(SPD) ASTM D698. Temporary dewatering:and stabilizationofthe underlying sof /compressible soils within the existing pond will' be necessary. For stabilization purposes, we suggest excavating approximately 2-feet into the underlying bedrock formation to allow for placement of: additional fill material. After temporary dewatering methods are in -place and the excavation into the bedrock has been completed we recommend placement of.a 42 to 18- inch layer of granular fill material such as 3-inch. minus pit run or 1-1/24nch washed aggregate as a stabilization mechanism. It may also be necessary to place a geogrid geotextile in combination with the structural fill/stabilization material. The need for geotextile as well as the stabilization zone will need to.be determined based upon.field conditions; however, the contract documents should contain a budget provision if this procedure is necessary. The embankment fill material should consist of an approved fill material and should be placedInuniform`8 to 12-inch lifts; moisture conditioned to plus or minus 2. percent of optimum moisture content,. and mechanically compacted to 98 percent of SPD ASTM D698. During the placement and compaction procedures field density tests should be taken to verify compliance. The proposed embankments should be constructed on minimum slopes of 2-112:1 (horizontal to vertical) or flatter on both the upstream and downstream faces. Additional pavement recommendations for this portion of the site have been provided in the original geotechnical engineering report on Page 8. It is our understanding the internal roadway will be a LOG OF BORING NO. PZ-5 Page 1 of 1 CLIENT ARCHITECT / ENGINEER Lagunitas Companies SITE Cameron Park Second Filing PROJECT Fort Collins, Colorado Redtail Mixed Use Development SAMPLES TESTS DESCRIPTION J m > ,r `p a U x N m w K H F z zH ZZ d = Ufw o > o w zm ctW w I—z Uwd Approx. Surface Elev.: 4989 ft o Z) z a3 n o 3 n z0 Z)rn 0.5 6" TOPSOIL 4988.5 WEATHERED SANDSTONE Tan, gray, moist, poorly cemented 2 4987 SANDSTONE Tan, gray, moist, cemented to well cemented 5 1 10 12 4977 BOTTOM OF BORING ' 10-feet of 4-inch diameter PVC casing installed approximate Top of Casing Elevation = 4989.5 N A Z O QU K WK F The stratification lines represent the approximate boundary lines g between soil and rock types: In -situ, the transition may be gradual. g WATER LEVEL OBSERVATIONS, ft 1 rerracon BORING STARTED 7_8_02 oWL DRY WD 6 AB BORING CCME 7ASR RIG 75EDOREMAN WL $ Water Level Checked on 7/17/2002 APPROVED DAR JOB # 20015260 LOG OF BORING NO. 1 Page 1 of 1 CLIENT ARCHITECT / ENGINEER Lagunitas Companies SITE Cameron Park Second Filing PROJECT Fort Collins, Colorado Redtail Mixed Use Development SAMPLES TESTS O o DESCRIPTION co r o F Lu z U a= m > z�n o w Z zz � j a U M a 0 �0 Lu Fz > OOx �� X Approx. Surface Elev.: -9+77•ft `%911, 2-)E w o U)D Z) z w X a� U) m a0 3 0 X 0 8- zi- D (n 0Z) U) co 0.3 3" GRAVEL ROAD BASE 41.091.6 1 SS 12 16 18.0 FILL MATERIAL Sandy Lean Clay trace Gravel Brown, tan, gray, rust, moist, stiff to very 3 stiff SANDY LEAN CLAY 2 ST 12 1 28.0 97 3050 Tan, gray, moist, calcareous, medium stiff 3 SS 12 1 4 23.7 to soft 5 7.5 F% 0.0011 4 ST 12 21.3 105 570 WEATHERED SANDSTONE _ 5 SS 12 24 19.8 Tan, gray, moist, poorly cemented 10 V f. 2 _9*16 10 SANDSTONE. Tan, gray, moist, cemented to well cemented 14.5 6 SS 6 50/0.5 19.2 BOTTOM OF BORING e a 0 0 i 0 U 6 K K W H The stratification lines represent the approximate boundary lines m between soil and rock types: in -situ, the transition may be gradual. N N R WATER LEVEL OBSERVATIONS, ft Irerracon BORING STARTED 12 4-01 WL W 7.5 WD i 7.3 Al RING COMPLETED 12-4-01 WL 2 Q RIG E 55 FOREMAN GW W col WL Water Level Checked on 12/11/2001 APPROVED DAR JOB # 20015260 m III ®�---- - N 1 I j UIO . I I — . 0.2 I �.2 TDR LE __; ..—...—. ._� N0; �9 \...� 0.5 OA I i II I NO.11 !! \\`-=--- ------ - �1 II I I =1i .7=1 Nb12Ii Kin,z TBM = RIM ELEVATI �J / -OF SEWER MANHOLE\ \ I ldlbl ?AM IS FOR GENERAL LOCATION ONLY, IS NOT INTENDED FOR CONSTRUCTION PURPOSES. LEGEND APPROXIMATE TE5T BORING LOCATION TB NO. 2 NOT DRILLED DUE TO PREVIOU5LY fX15TlNG TE5T BORINGS O TB N05. 14 2 DRILLED IN 1995, PROJECT NO. 20955155 TE5T BORINGS FOR 5UPPLEMENTAL EXPLORATION FIGURE 1 : 51TE PLAN REDTAIL MIXED U5E DEVELOPMENT NORTH OF F0551L CREEK OFFICE PARK 8 WE5T OF CAMERON PARK OFFICE FORT COLLIN5, COLORADO Project Mng, DAR 1 re r ra e o n 301 N. Howes Street Fort Colhn5, Colorado 8052 1 Project No. 200152G( Designed By: DAR scale: I " = IOC Checked By: DAR Date: 3/23/0`. Approved B, DAR Drawn By: \le Name: NEW LAYOUT 3-23-05 Figure No. 1 'aMER OOUNTY ZONED FA1 i �I I InpEmi I 9 I � 1 I ' FOR GENERAL LOCATION ONLY, INTENDED FOR CONSTRUCTION PURPOSES �mbQ CAM OFW CAAIER011 1 I LEGEND APPROXIMATE TEST BORING LOCATION TB NO. 2 NOT DRILLED DUE TO PREVIOUSLY EXISTING TEST BORINGS O TB NOs. 1 # 2 DRILLED IN 1995, PROJECT NO.20955185 o T BORJNGS FOR SUPPLEMENTAL EXPLORATION I LL Y I I i a I i IFossu LWW PARMAY FIGURE 1: SITE PLAN ! i REDTAIL MIXED USE DEVELOPMENT NORTH OF FOSSIL CREEK OFFICE PARK 4 WEST OF CAMERON PARK OFFICE FORT CO W NS, COLORADO 5000 4990 EXISTING "PO SPILLWAY 49 NORMAL "P, WSEL 4 4980 DATUM ELEV 4975.00 • • I• ' - r 7%'OPOSED LP .,D -•.Q 1.' • --•-• l GRADE -21 u � • I886.32_ `e•-, TYPE H ...,. • PAST TO • 32" DEEP 0+00 )R =4992.57 INSULATE TOP OF BOX 10 ON BOTH SIDES OF CBC 1O0YR PROPOSED p "POND A" WSEL 7:1 4988.33 FF m SUPPORT FOR CBC SHALL BE DESIGNED BY GEOTECHNICAL & STRUCTURAL ENGINEER No Text Geotechnical Engineering Supplemental Report Terracon Retail— Proposed Mixed Use Development: Fort Collins,:LarimerCounty; Colorado Project No. 20015260 Page 6 and dewatering requirements are the responsibility of others. In the event that changes in; the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report.in writing. We appreciate the opportunity to be of service, to you on this . phase 'of your project. If you have any, questions concerning this report, or if we may be of further:service to:you,,please .do snot hesitate to.contact Us. Sincerely TFRRAGRln,.11f a Geotechnical €"' rtrnent Manager Enclosures; SchematicSite Plan of Proposed-RoadwayrAlignment from North Starrpesign; Inc. SchematiccCross-Sectional Diagram of P�oposed'Roadwayfrom North 'StarDesign; .Inc. Figure No. 1 — Test Boring' Location Diagram—Terracon1nitial Report dated'July 2, 2002 Revised Site Plans—Figure'No. 1 illustrating,New-Layout, Test Boring No. 1 - Drilled December 4, 2001 and Piezometer No. 5 Drilled July 8, 2002 Copies: Addressee (3) North Star Design(2): Patricia Kroetch, P.E. Weeks and Associates (1): Mr. Gary Weeks, P E. r Geotechnical Engineering Supplemental Report Retail -Proposed Mixed Use Development Fort Collins, Larimer County, Colorado Project -No. 20015260 Page 5 Terracon Fill against grade beams and retaining walls should be compacted to densities specified in Earthwork. Compaction of each lift adjacent to walls should be accomplished with hand -operated tampers or other lightweight compactors. Overcompaction may cause excessive lateral earth pressures, which could result in wall movement. For retaining walls exceeding 8-feet in heights, Terracon should be notified so additional recommendations can be provided, if necessary. Retaining Wall Drainage To reduce hydrostatic loading on retaining walls, a subsurface drain system should be placed behind the wall. The drain system should consist of free -draining granular soils containing less than five percent fines. (by weight) passing a No: 200 sieve placed adjacent to the wall. The freeAraining granular material should be graded to prevent the intrusion of fines or encapsulated in a suitable filterfabric. A drainage system consisting of either weep holes or perforated drain lines (placed near the base ofthe wall) should be used to intercept and discharge water, which would tendto saturate the backfill. Where used, drain lines should be embedded in a uniformly graded filter material and provided with adequate clean -outs for periodic. maintenance. An impervious soil should be used in. the upper.layerof backfill to reduce the potential for water infiltration. As an alternative, a prefabricated drainage structure, such as geocomposite maybe used'. as a substitute for the granular backfill adjacent to he wall. GENERAL COMMENTS Terracon should be retained.to review -the finaldesign plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in .the design and specifications. Terracon also should be retained to provide testing and observation. during excavation,. grading, foundation and construction phases of the project. The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and frorri 'other information .discussed <in this report. This report does not reflect variations,that may occur between borings, across the site; or due to the modifying effects of weather. The nature and extent of -such variations may not become evident until during or after construction. If variations appear; we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or .by implication any environmental assessment of the site or identification of contaminated or 'hazardous materials or conditions. If the owner is concerned about the potential for such contamination, other studies should.be undertaken. This report' has been prepared for the exclusive use of .our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are, intended or made. Site safety, excavation support, Geotechnical Engineering Supplemental Report Retail— Proposed Mixed Use Development Fort Collins, Larimer County, Colorado Project No. 20015260 Page 4 Terracon The geotechnical engineer should observe foundation excavations to verify compliance with the project specifications. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required. Lateral Earth Pressures — (for wall less°than 8-feet in height) For soils above any free water surface, recommended equivalent fluid pressures for unrestrained foundation elements are: Active: Cohesive soil backfill (on -site clay) ....................................................... 50 psf/ft Cohesionless soil backfill (imported granular material) ........................ 35 psf/ft On -site bedrock materials.........................................not recommended for use • Passive: Cohesive soil backfill (on -site clay)....................,................................250 psf/ft Cohesionless.soil backfill (imported granular material)......................350, psf/ft Where the design includes restrained elements, the following equivalent fluid pressures are recommended • At rest: Cohesive soil backfill (on -site clay)......... .............................................. 65 psf/ft Cohesionless, soil backfill (imported granular material) ........................ 50 psf/ft On -site -bedrock materials.........................................not recommended for use The lateral earth pressures presented above do not include any factor of safety and are not applicable for submerged soils/hydrostatic loading. For submerged conditions- the following lateral earth pressures should. be applied: Active: Submerged Soils/Hydrostatic Loading Cohesive soil backfill (on -site clay) ........................................ :.............. 90 psf/ft Cohesionless soil backfill (on -site or imported.granular material) ........ 80 psf/ft • Passive: Submerged Soils/Hydrostatic Loading Cohesivesoil*backfill (on -site clay) ....... .............................................:.125 psf/ft , :., Cohesionless soil backfill (imported granular material) ...................... 175 psf/ft At rest: Submerged Soils/Hydrostatic Loading Cohesive soil backfill (on -site clay) ....................................................... 95 psf/ft Cohesionless soil backfill (imported granular material) ........................ 90 psf/ft Geotechnical Engineering Supplementa1.Report Retail— Proposed Mixed Use Development Fort.Collins, Larlmer County, Colorado Project.No. 20015260 Page 3 Terracon jurisdictional City of Fort Collins roadway. Therefore, after completion of the embankment fill, and "rough - final subgrade" preparationa follow up geotechnical engineering exploration should be completed in general accordance with. the Larimer County Urban.Area Street Standard (LCUASS) Pavement Design Criteria. For estimating/planning or budget purposes, the recommendations for "main -traffic" corridors contained in our original report could be used, .which indicated a: minimum of 4-inches of HotMixAsphalt,(HMA) underlain by a minimum of 7-inches of aggregate base course. Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the aggregate road base: section. Soft or weak areas delineated by the proofrolling operations should be undercut or stabilized in -place to achieve the appropriate subgrade support. General "earthwork" recommendations for the project pertaining to site and subgrades preparation, imported materials, placement and compaction criteria and excavation construction procedures are included, in original report under the "Earthwork" section on page 11 through 13. Slope Protection The slopes of these. two embankments should be protected. from wave action, wind erosion. and general weathering. It is recommended the face of the embankments be rip -rapped, consisting of a durable rock adequately sized or an equivalent such. as a fabric map to reduce erosion. The riprap shouldbe properly, bedded with gravel or separated from the embankment by filter fabric to minimize the washing out of fines below the riprap. If elected, the fabric mat should be installed in accordance with the manufacture's recommendations. The top of the embankment slope should be provided with,a minimum of 6'inches of gravel base course surfacing for future truck access. Foundation Systems - Spread Footings or Pads for Box Culvert, Wing Walls and Retaining Walls Based on the anticipated loads for the proposedconcrete box culvert structure and associated wing walls, and any retaining wall for this portion of the project, it is our opinion. the use of a spread footing/pad foundation system bearing upon approved embankment fill material may be utilized to support -these structural elements. Footings, should be placed on a minimum 3-foot layer of approved fill material placed and compacted as previously described. The subsurface soils at or near the groundwater interface maybe soft or loose, and compressible or settlement prone; exhibiting a relatively low bearing capacity and potentially unstable characteristics. Therefore, it may be necessary to stabilize the bearing stratum. with either 1-1/2-inch clean graded aggregate or 3-inch minus pit -run material. All footings bearing on a minimum 3-foot, layer of approved engineered, fill material could be design using a maximum net allowable bearing pressure of 2,000 psf. Footings should`be proportioned to reduce differential foundation movement. Proportioning on the basis of equal total movement is recommended; however, proportioning to relative constant dead -load pressure ,.will also reduce differential settlement between. adjacent footings. Total movement resulting from the assumed structural loads is estimated to be on the order of 1-inch. Exterior footings should be placed a minimum of 30 inches below finished grade for frost protection and to provide confinement for the bearing soils. Finished grade is the lowest adjacent grade for perimeter footings. August 12, 2005 Lagunitas Company 3944 JFK Parkway— Suite B200 Fort Collins, Colorado 80525 Attn: Mr. Jon Prouty Irerracon Consulting Engineers & Scientists Terracon Consultants, Inc, 301 North Howes Fort Collins, Cclorado 80521 Phone 970.484.0359 Fax 970.484.0454 w'ww.l ei'rda con. corn Re: Geotechnical Engineering Report— Addendum No. 2 Retail - Proposed Mixed Use Development - Cameron. Park 2nd Filing Supplemental Recommendations for Realignment of Roadway — Northwest Portion of Site Fort Collins, Larimer County, Colorado Terracon Project No. 20015260 Terracon conducted a geotechnical engineering exploration for Retail Property, a proposed mixed -use development project, located west of the Cameron/Fossil Creek Office Complex and College Avenue/US Highway 287, south of Fairway Lano, and east of the Burlington Northern & Santa Fe .Railroad tracks in south Fort Collins, in December of 2001. The primary purpose of the initial study was to evaluate the site for soil, bedrock and groundwater conditions; as well as to provide foundation, pavement, and earthwork design recommendations based on the subsurface conditions encountered. For further information and findings thereof, please refer to our "Geotechnical Engineering Report" December 20, 2001, Project No. 20015260. Terracon also provided a supplemental report dated July 26, 2002, in which additional information in regards to groundwater conditions relative to the adjacent ponds were addressed as well as recommendations for earthen embankments for a waterline and a roadway through the central portion of the site were provided. On July 23, 2003, we provided an addendum report which provided additional information regarding proposed finished floor and foundation grade elevations relevant to the groundwater level encountered throughout the site. We have recently been requested to provide supplemental geotechnical engineering design criteria for the proposed roadway alignment to be constructed along the western perimeter of the site which also traverses through an existing detention pond. The proposed intent is to earthen fill the central portion of this pond, creating two ponds connected by an approximate 3-foot by 5-foot concrete box culvert. SUBSURFACE CONDITIONS During our initial subsurface exploration activities, two (2) test borings were drilled in the general vicinity of the proposed "pond in -fill' roadway alignment area. 'Boring No. 1, drilled on December 4, 2001 to an approximate depth of 14-1/2-feet below site grade was located on the north side of the pond, while Boring/Piezometer No. 5, drilled on July 8, 2002, to an approximate depth of 12-feet below site grades was located to the south of pond. The subsurface soils encountered within these two related borings or piezometers generally consisted of an approximate 3-foot layer of existing fill material at the surface of Boring No. 1, underlain by the native sandy lean clay which extended to the bedrock below. At the surface of Piezometer No. 5 was an approximate 6-inch layer of silty topsoil underlain by the weathered sandstone bedrock below. Weathered sandstone bedrock transitioning to competent bedrock with increased depths Delivering Success .for Clients and Employees Since 1965 More Than 70 Offices Nationwide