Noise Wall Report 08-09-2013Report of Geotechnical Investigation Noise Wall Preserve at Rice Lake Chanhassen, Minnesota August 9th, 2013 ITCO Project 13009B INTRODUCTION ______________________________________________________________________________ Findings, conclusions and recommendations are repor ted herein for the above geotechnical investigation performed by ITCO Allied Engineering Company. The investigation was made with respect to generally applicable engineering practic e at this time within the geographic area. The investigation was performed generally according to the scope of our verbal service proposal on July 12, 2013. Mr. John Knoblauch orally authorize d the investigation on behalf of Knoblauch Builders. The report is for exclusive use by Knobl auch Builders and other authorized parties. The investigation is limited to: · Subsurface exploration and soil boring logs · Construction considerations · Excavation and earthwork methods · Foundation analysis · Foundation recommendations THE PROJECT ______________________________________________________________________________ Our understanding of the project is based on conver sations with Shirley Walker of Walker Engineering and the proposed noise wall plans provi ded. The project calls for the construction of nearly 1200 feet of noise wall (Type 2- Wood Planki ng Noise Barrier) to be constructed on the North side of Highway 212, East of County Road 101, which will extend the existing noise wall Eastward. We assume the following conditions will p revail with respect to noise wall construction: · Noise wall foundation consists of 12” x 18” pre-cas t concrete piles, spaced 8 feet on center, having a minimum compressive strength of 4000 psi. · Noise wall heights range from 7 to 20 feet with an average around 11 feet. Depth of post embedment range from 9 to 13 feet with an average a round 11 feet.
ITCO Project 13009B August 7 , 2013 2 · Wood planking will be used above ground to connect the piles and be used as a means of absorbing or reflecting nearby traffic noise levels . · Proposed cut and fill construction to develop final grades around and below the walls will be up to 4 feet. SITE CONDITION ______________________________________________________________________________ The project site is in Chanhassen, Minnesota. The p roposed noise wall begins roughly 1 mile East of the Highway 212 and County Road 101 intersection , where it will extend the existing noise wall on the North side beginning at station 1179+60 and ending at station 1191+35. The noise wall is to be constructed as part of the proposed Preserve at Rice Creek development that will be taking place on the North side of the proposed wall. The w all itself will sit on top of two partial fill and native soil berms, with a shallow area near the mid dle and far East end of the proposed wall. SUBSURFACE EXPLORATION ITCO Allied Engineering Company received a prelimin ary soil boring location plan from Walker Engineering proposing seven (7) soil borings rangin g from 15 to 20 feet in depth. The actual soil boring locations varied slightly from the proposed locations. Actual borings locations are shown on the Boring Location Plan in Appendix A. ITCO Allie d Engineering interpolated ground surface elevations at the borings using spot elevations and contours indicated on the site-grading plan prepared by Walker Engineering. Elevations are not ed on the Boring Logs in Appendix B. Accuracy of the boring locations and elevations sho uld be considered with respect to the methods used in their establishment. Borings were drilled to depths indicated on Boring Logs in Appendix B. Borings were drilled with hollow stem augers on dat es indicated on the boring logs using a track-mounted CME-45 drill rig. Independent Testing Techn ologies, from Waite Park, MN, conducted the borings under separate contract. Standard Penetrat ion Testing (SPT) was used to obtain soil specimens and N values. A specimen was obtained by driving the SPT sampler 1.5 feet into the bottom of the boring according to ASTM D1586 (Penetration Test and Split-Barrel Sampling of Soil ). The sampler interval is noted as SS on the Boring L ogs in Appendix B along with its N value. The N value is the number of SPT hammer blows needed to drive the sampler 12 inches into the bottom of the boring. Soil specimens obtained from the split spoon sampler are noted on the Boring Logs. These soil specimens were sealed and labeled in glass jars for subsequent review and classification.
ITCO Project 13009B August 7 , 2013 3 Soil specimens were reviewed and classified in the soil laboratory by the engineer or qualified technician. Boring Logs were prepared with respect to ASTM D2488 (Description of Soils: Visual and Manual Procedure ). Soil strata lines shown on the Boring Logs are approximate boundaries between different soil types. Transition between s oil types may be gradual. SUBSURFACE CHARACTER GROUND DESCRIPTION At the boring locations, organic topsoil materials were generally encountered to depths ranging from 0 to 10 inches. In borings B-1 thru B-5, which were put down in the Western portion of the site near the existing noise wall, topsoil layers were u nderlain by relatively medium to stiff consistency cohesive soils having N values of 6 blows per foot or more. The majority of soils present in Borings B-1 thru B-5 were classified as Sandy Clay (CL) usi ng the USC (United Soil Classification) system. Boring B-2 had what appeared to be an organic clay layer to a depth of 5.5 feet. A sample of this material taken at 4.5-5.5 feet of depth was tested for organic content and was found to be only slightly organic. Test results are in Appendix C. Boring B-6 was put down on top of the second smalle r berm towards the East side of the noise wall. B-6 contained 10” of topsoil underlain by brown cla yey sand (SC) to 5-1/2 feet of depth, with N-values ranging from 7 at 2 to 3 feet of depth and 4 at 4-1/2 to 5-1/2 feet of depth. Below the brown clayey sand, a brown sandy clay (CL) was found to a t least 10 feet in depth, that contained N –values ranging from 3 to 7. A layer of organic buri ed topsoil (OL) was discovered from 11-1/2 to 12-1/2 feet of depth. Below the buried topsoil lens, s tiff brown and grey sandy clay (CL) was encountered until termination of boring depth, 20 f eet. Boring B-7 was conducted on the Eastern end of the project, in a low lying area approximately 40 feet from the end of the proposed noise wall. Borin gs showed dark brown organic clay (OL) until at least 3 feet of depth, brown and sandy clay (CL) fr om 4-1/2 feet to 15 feet of depth. GROUND WATER Observations to detect water in the Borings are not ed on Boring Logs in Appendix B. Observations made during drilling indicate no ground water was p resent. Borings B-5 and B-7 were left open to monitor any groundwater infiltration since the bori ngs were conducted. A subsequent observation was made on August 7, 2013. At this date, Boring B-5 was dry down to cave-in depth of 9 feet. Boring B-7 had a cave-in depth of 7.5 feet and was wet at 6 feet. It is believed the water found in B-7 had infiltrated or ran into the open borehole d uring the previous days rain event.
ITCO Project 13009B August 7 , 2013 4 CONSTRUCTION CONSIDERATIONS ______________________________________________________________________________ GROUND WATER IMPACT The ground water surface within an unconfined aquif er is generally a subdued reflection of the ground surface. Groundwater flows from recharge ar eas in higher ground to discharge areas in lower ground and water bodies such as wetlands, str eams, rivers and lakes. Ground water and perched water surfaces at the project site may vary or fluctuate due to ground surface drainage, site topography and climate. Seasonal or longer pe riods of drought or excess precipitation cause such variation and fluctuation too. Based on the bo rings conducted, no groundwater impact would occur as a result of this project. FOUNDATION ANALYSIS ______________________________________________________________________________ Three computer programs (COM624P, CLM 2.0, and LLP9 9) were used to calculate and check max deflections based on the soils encountered duri ng exploratory drilling. An assumed horizontal wind load of 25 psf was used for a design parameter. Based on this wind load, the post spacing, and the wall height; the ho rizontal shear and overturning moments were calculated at the posts. These values are shown in TABLE A below. Design of post embedment depths depends primarily u pon the allowable horizontal deflections at ground level, which will limit the noise wall defle ctions to 1” for every 10 feet of wall height. Based on the soils encountered, two different soil property analyses were conducted. Borings B-1 thru B-5 and B-7 contained generally the same type of soils and correlations and assumptions were made to define several soil properties. The ge otechnical parameters that were arrived at and used for inputs into the deflection programs are li sted in TABLE B below. Lateral earth pressures were also assumed for the LLP99 program. Active Ear th Pressure, At-Rest Earth Pressure, and Passive Earth Pressure coefficients were taken as 0 .5, 0.7 and 2 respectively. Boring B-6, which was on the smaller berm towards t he East, contained some less dense soil layers as well as a layer of buried organic topsoil . This boring analysis was conducted separately. It is assumed that the same or similar type of soils w ould be found along the rest of the berm. TABLE A: LOAD CASES VS. WALL HEIGHTS Wall Height (Feet) Horizontal Shear (kips) Overturn ing Moment (ft-kips) 8 1.6 6.4 13 2.6 16.9 18 3.6 32.4 22 4.4 48.4
ITCO Project 13009B August 7 , 2013 5 TABLE B: GEOTECHNICAL PARAMETERS USED IN ANALYSIS Layer Depth to Bottom of Soil Strata (ft) Soil Type (USCS) Unit Weight (PCF) Friction Angle Cohesion (PSF) Modulus of Subgrade Reaction 1 5 CL, OL 100-120 0 - 10 0-200 10 2 10-12 CL 120 25 500 100 3 12-20 CL 125 28 1800 500 The results of our foundation analysis agree with t he embedment depths for the piles as listed in Appendix C of this report, with the exception of po sts 114-143, for which we recommend a minimum embedment to elevation 901.1 feet. RECOMMENDATIONS ______________________________________________________________________________ SITE PREPARATION Project design and site preparation may require aba ndonment or relocation of buried utilities, including utilities discovered during construction. Utilities must be completely removed, capped, or fully grouted. Utility excavation must be filled a ccording to the STRUCTURAL BACKFILL section of this report. EXCAVATION AND EARTHWORK CLEARING AND GRUBBING Clearing and grubbing must remove all trees, bru sh, stumps, roots, and designated removal structures within clearing l imits. Stump holes and removed structures should be replaced with structural backfill to prev ent localized subsidence in planned construction areas. TOPSOIL REMOVAL AND REUSE All natural topsoil, replacement topsoil and buri ed topsoil (all with undecomposed organic matter) must be completel y stripped away and removed from project areas designated for fill. These organic bearing s oils must not remain beneath structural fill or structural backfill. These soils can potentially d ecay when they are exposed to bacteria and oxygen (air), which may cause excessive ground surf ace subsidence beneath the above built features during their lives. These soils can be re used as topsoil replacement in designated landscape areas, wasted onsite, or exported offsite . UNSUITABLE SOIL Subgrades of structural fill must be properly pr epared to support applied loads. Remove unsuitable soil beneath the fill are a and replace it with structural backfill up to design subgrades of features.
ITCO Project 13009B August 7 , 2013 6 Unsuitable soils generally include: organic soil (p eat, muck and OL and OH types with faint to strong odor); natural topsoil, buried topsoil or re placement topsoil (all with grass, roots, decaying vegetation, humus and otherwise undecomposed organi c matter with faint to strong odor); soil with excessive moisture; very soft to soft compressible cohesive soil (clayey and silty); debris and rubble; soil mixed with debris and rubble; potentia lly collapsible metastable soil (loess, sand with honeycombed grain structure) and other kinds of soi l defined by the engineer. STRUCTURAL FILL SUBGRADE The subgrade surface that will support structura l fill should be relatively flat. In sloping ground, the subgrad e surface should be benched as flat steps along sloping ground. The subgrade, especially in flatte r areas with no benching, should be prepared to provide reliable bonding across the interface betwe en structural fill and underlying subgrade ground. Reliable bonding will reduce interface wea kness and increase shearing resistance against sliding along the interface. Remove all unsuitable material beneath structural f ill and replace it with structural backfill. For subgrade with excessive moisture, scarify subgrade soil to remove excessive moisture. Compact scarified soil into subgrade as structural backfill . Water content of structural backfill should be controlled and maintained to achieve the stability and the required compaction requirements. Compact structural backfill into the subgrade accor ding to TABLE C. Remove all ground in the subgrade which does not meet requirements herein, a nd replace it with structural backfill up to the designated subgrade level of the structural fill. Where the subgrade ground has excessive water content, consideration can be given to aerating it by spreading it, scarifying it or blending it with drier ground. STRUCTURAL FILL Structural fill can be obtained from onsite, impo rted, or over-excavated material. Structural fill must be non-expansive in organic cohesive material (clayey) or granular cohesionless material (sandy and gravelly) relative ly well graded. Poorly graded granular material with uniform grain size (for example uniformly grad ed “pea gravel”) should not be used as structural fill when structural fill thickness exce eds 1 foot. Cohesive material must have a Liquid Limit less than 45 and a Plasticity Index less than 20. Cohesive and other materials with over 20 percent fines passing #200 sieve must be placed in loose lifts 6 to 8 inches thick using a sheepsfoot, vibratory roller, or pneumatic tire rol ler making several passes. Cohesionless (granular) structural fill must be placed in loose lifts 10 to 12 inches thick using smooth vibro-rollers making several passes. Use a power tamper or vibro-plate compactor to place structural fill in confined areas using loose lifts up to 4 inches thick compac ted by making several passes. Water content of structural fill must be controlled and maintained t o achieve the stability and the required compaction requirements. Aerate or add water as ne cessary. Compaction of structural fill must meet recommendations in TABLE C. Before compaction, structural fill material should be mixed thoroughly to make its water content uniform and within optimum water content range. If this material’s water content is excessively wet and above this range, this material should be dried . Aerate this wetter material by spreading it out
ITCO Project 13009B August 7 , 2013 7 or scarifying it to make it suitable as structural fill meeting this range. Blending this wetter mate rial with drier material to make suitable structural fil l meeting this range may be considered. If structural fill material water content is excessive ly dry below optimum range, the material’s water content should be adjusted upward to make it suitab le structural fill meeting this range. Blending this drier material with wetter material to make su itable structural fill meeting this range may be considered. CONSTRUCTION MONITORING AND DRAINAGE Excavation and earthwork construction must be monitored periodically to evaluate compliance wi th recommendations in this report. Monitoring should be performed by an engineering technician fr om our company with engineering supervision. Drainage must be provided to prevent surface water run-off from wetting, accumulating, and standing in open excavations. Gravity drainage dit ches or other methods can be considered. TABLE C: COMPACTION REQUIREMENTS FOR STRUCTURAL FI LL Construction Applications Standard Proctor ASTM D698 (%) · Structural Fill for noise wall support not exceeding 10 feet in height 95 · Top 10 feet of Structural Fill for noise wall exceeding 10 feet in height 100 FOUNDATION DESIGN AND CONSTRUCTION We recommend supporting the noise wall on pre-cast pile foundations as shown in the preliminary plan provided by Walker Engineering. The post holes used to install the pre-cast piles should be backfilled with a select granular material and comp action achieved through wetting with the exception of posts # 110 through #151 where a concr ete mix should be used to backfill the post holes. We also recommend posts #114 through #143 should ha ve the depth of embedment increased to reach a minimum elevation of 901.1feet.
ITCO Project 13009B August 7 , 2013 8 FOUNDATION EMBEDMENT PROTECTION BACKFILL CAP AND WATER RUN-OFF Foundation backfill must be capped with at least 1 foot of impermeable cohesive soil (CL) to minimize infil tration of surface water run-off into backfill. Direct all such water run-off away from the pilings and other structures. MINIMUM EMBEDMENT DEPTHS Bearing grades of all foundations subjected to fr eezing temperatures must be embedded beneath ground surfac es for frost penetration protection. Minimum embedment depths are specified in State of Minnesota building codes or local building codes. The greatest embedment depth of these codes should be used for protection. In general accordance with these codes, use a 48” minimum reco mmended embedment depth for frost protection. FROST HEAVE AND ADFREEZING PROTECTION All foundations subject to freezing must be designed against detrimental effects from frost pen etration. Frost penetration can cause frost heave and adfreezing. Frost penetration may occur if three conditions exist: freezing temperatures, frost-susceptible soil, and capillary water “wickin g” to the bottom of the freezing zone. Frost-penetrated soil expands in volume. It may heave th e ground surface upward. Adfreezing occurs when soil freezes to foundation surfaces. Adfreezi ng induces upward acting shear strain along vertical foundation surfaces, which may potentially drag foundation surfaces upward (heaving). Foundations must be properly designed against frost heave and adfreezing to minimize the potential for structural distress (cracking and dis tortion). Methods described below should be considered in designing foundations to resist poten tially adverse effects from frost penetration. CONCLUSIONS ______________________________________________________________________________ Remove all topsoil from all areas that are to be re -graded and/or filled. Generally the topsoil ranged from 0 inches to 10 inches except in the are a of soil boring B-7 where topsoil was encountered until 3 feet of depth. Based on these b orings there were no areas where organic soils would need to be removed and replaced. However, if organic soils are encountered below the topsoil layers during construction, they would need to be removed and replaced following the guidelines for replacing unsuitable soils. Based on the preliminary plan that was forwarded to our office, the proposed post embedment depth should rest on soil with adequate bearing cap acity and fulfill the max deflection requirements after corrections are made to ensure pile #114 thru #143 post embedment reach a minimum elevation of 901.1 feet. Backfill around the posts should be a select granular material with the exception of post #110 through #151 where a concret e mix should be used in place of the sand. Backfill sand for the posts should be compacted in accordance with the compaction requirements for structural fill.
ITCO Project 13009B August 7 , 2013 9 CHANGED CONDITION AND OBSERVATION ______________________________________________________________________________ Analyses, conclusions and recommendations in this r eport are invalid if any changes are made to the project’s nature, planning, design, and locatio n of structures or construction. Upon such changes, the Engineer must be given an opportunity to review such changes. Following the review, the analyses, conclusions, and recommendations in t his report can be modified and verified in writing. Analyses, recommendations and conclusions in this r eport are based partially upon subsurface conditions encountered in the exploratory soil bori ngs. The nature and extent of any variation of subsurface conditions across the site may not becom e evident until the project’s construction stage. If any variation in subsurface conditions becomes e vident, the Engineer must be provided an opportunity to review such variation. Following th e review, the analyses, conclusions, and recommendations in this report can be modified and verified in writing. The Engineer must be provided an opportunity to rev iew designs and specifications for the project. Following the review, the analyses, conclusions and recommendations in this report can be properly interpreted and implemented with respect t o the designs and specifications. We recommend engaging the Engineer to provide conti nuous engineering service during the project, especially with respect to excavation, ear thwork and construction of foundations and pavement. During construction, on-site presence by the Engineer will be to observe compliance with design concepts, specifications and recommenda tions in this report. Observation provides an opportunity to modify design concepts, specificatio ns, and recommendations in this report in the event that subsurface conditions differ from antici pated conditions. Respectfully Submitted, Itco Allied Engineering Company Prepared By: Reviewed By: Joseph Carlson, E.I.T. Robert Sullentrop , P.E. Project Engineer Professional Engineer MN Reg #144634 MN Reg #17823
CONTENTS INTRODUCTION .............................................................................................................................1 THE PROJECT ...............................................................................................................................1 SITE CONDITION ...........................................................................................................................2 SUBSURFACE EXPLORATION ......................................................................................................2 SUBSURFACE CHARACTER .........................................................................................................3 GROUND WATER...................................................................................................................3 CONSTRUCTION CONSIDERATIONS ...........................................................................................4 GROUND WATER IMPACT.....................................................................................................4 FOUNDATION ANALYSIS ..............................................................................................................4 RECOMMENDATIONS ...................................................................................................................5 SITE PREPARATION...............................................................................................................5 EXCAVATION AND EARTHWORK..........................................................................................5 FOUNDATION DESIGN AND CONSTRUCTION.....................................................................7 FOUNDATION EMBEDMENT PROTECTION..........................................................................8 CONCLUSIONS ..............................................................................................................................8 CHANGED CONDITION AND OBSERVATION ..............................................................................9 APPENDIX A BORING LOCATION PLAN APPENDIX B BORING LOGS APPENDIX C LABORATORY TEST RESULTS APPENDIX D NOISE WALL PLANS