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Lake Susan Hills West 9th: Approve Quote for Sanitary Sewer Repairs CITY OF CHANHASSEN 7700 Market Boulevard PO Box 147 Chanhassen, MN 55317 Administration Phone: 952,227,1100 Fax: 952,227.1110 Building Inspections Phone: 952,227,1180 Fax: 952,227,1190 Engineering Phone: 952,227.1160 Fax: 952,227.1170 Finance Phone: 952,227,1140 Fax: 952,227,1110 Park & Recreation Phone: 952,227,1120 Fax: 952,227.1110 Recreation Center 2310 Coulter Boulevard Phone: 952,227,1400 Fax: 952,227.1404 Planning & Natural Resources Phone: 952,227.1130 Fax: 952,227,1110 Public Works 1591 Park Road Phone: 952,227.1300 Fax: 952,227,1310 Senior Center Phone: 952,227.1125 Fax: 952,227.1110 Web Site www.ci.chanhassen.mn.us .1~ MEMORANDUM TO: FROM: DATE: September 28, 2009 a~ SUBJ: Lake Susan Hills West 9th Addition, Project No 93-5-1: Approve Quote for Sanitary Sewer Repairs PROPOSED MOTION "The City Council approves a quote in the amount of $39,400.00 with Parrott Contracting, Inc. for work to be performed on the Lake Susan Hills West 9th Addition Sanitary Sewer Repairs." City Council approval requires a simple majority vote of the City Council present. BACKGROUND During the course of the annual sewer cleaning operations, the Utility Department discovered a full pipe sag in the gravity sewer located in the street at 820 Lake Susan Hills Drive. Staff discussed this issue with the residents at this location and the sewer system apparently has been surcharging back into the lateral service pipe. Staff has had problems with this sewer pipe before. In 2005 this section of pipe was repaired and relayed. This fix involved placing aggregate bedding underneath the pipe for additional foundation support. After finding out about the sag this time, staff enlisted the services of a soils engineering firm to take soil borings and recommend a fix. The soil borings show there is swamp deposited organic silt material approximately of 22 to 34 feet below the pavement. The organic soil is believed to be consolidating which is causing the pipe and a manhole to settle. RECOMMENDATIONS FOR IMPROVEMENTS The City has several options it can consider. First, the City can do nothing. This option would need to include having the Utility department jet and clean the pipe monthly to reduce the likelihood of sewer backups. This, however, is not a good long-term fix because eventually, if the sewer keeps settling, sewer backups will occur. This option will also tax the Utility department and would not be feasible during winter months. The second option is to add additional aggregate foundation under the sewer pipe and manhole similar to what was done in 2005. The cost for this option would be approximately $25,000. This option is not Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow Todd Gerhardt Lake Susan Hills West 9th Addition Sanitary Sewer Repairs September 28, 2009 Page 2 recommended as a long-term solution because it has been proven to be a temporary fix. The third option is to remove the organic, compressible soils that are causing the problem. This option is not cost effective and would severely impact the residents during construction. Due to site confinement and excavation depth, the soils engineer has recommended the installation of helical piling supports for the 160' of settled sewer pipe and manhole. Piling-supported, rigid pipe and structures will maintain positive slope on the pipe while allowing for any future settlement of the surrounding soils. This piling support technique has been used successfully on other City projects. City staff cannot complete this type of work and would need to hire a contractor who has expertise in this type of construction. PROJECT LOGISTICS To reduce out of pocket costs, City forces will be used as much as possible. The City will purchase directly the materials needed for the project to avoid contractor material markups. City forces will also truck aggregate material for the project and bypass pump the sewer during construction. It is planned that the contractor will install the City-purchased helical piling and rigid sanitary sewer. The contractor will backfill and reconstruct the street to the gravel base level. City forces will pave the bituminous street section and complete the restoration. QUOTES A request for quotes was submitted to four contractors on September 10, 2009. Three quotes were received. The quotes received are as follows: Kusske Construction Com an Min er Construction, Inc. Parrott Contractin , Inc. $66,450.00 $48,760.00 $39,400.00 The fourth contractor was not able to submit a bid. Parrott Contracting submitted the low bid. This contractor has worked on several projects for the City in the past. Their work has been acceptable. The project should start October 5, 2009 with substantial completion by October 14, 2009. Bids were wide spread and can be attributed to work load of the contractors, time line when the work needs to be completed, and comfort level on completing the work. g:\eng\projects\k-o\lshw.9th\2009 sanitary sewer repairs\award contract 092809.doc Todd Gerhardt Lake Susan Hills West 9th Addition Sanitary Sewer Repairs September 28, 2009 Page 3 The cost for the City furnished materials and restoration is estimated at $46,600.00. The estimated cost of the sewer fix is $86,000.00 with the contractor furnished work, city purchased materials and restoration. This project was not budgeted for in 2009 since the problem was not identified. Staff is requesting the funds for the work be taken out of the sanitary sewer fund account. Attachments: 1. Repair Area Map 2. Soils Report c: Kevin Crooks, Utility Superintendent g:\eng\projects\k-o\lshw.9th\2009 sanitary sewer repairs\award contract 092809.doc Geotechnical Evaluation Report Proposed Manhole Repair Manhole Structure and Sanitary Sewer Repair Near 823 Lake Susan Hills Drive Chanhassen, Minnesota Prepared for City of Chanhassen Professional Certification: I hereby certify that this plan, specification, or report was prepared by me or under my direct supervision and that I am a duly Licensed Professional Engineer under the laws of the State of Minnesota. ~ \\,llltl""I/ \',db / :7!: ,\ \-\v.' l. 1(/1-'> //.( -..-..' 00:.....,' "":.\~ 'l ~ ).~. '0 ~ shua L. Kirk, PE ~;' (.q,ISED.... ~ - . Llw'~"~ '_ Project Engineer :: : rROFESSI~NAL: :: License Number: 45005 ENGINEeR ,: ::: ... . . "("... August 28, 2009 ~tP~" 45005 ..t;~ ",'.,n', .'~~ ",,~7l'." ......~-....... ,,/ I$' ....H..:.\~V,... 1'1 OF Mh" ", 1111111\\\\\\ Project Bl-09-03401 Braun Intertec Corpor13tion BRAUN INTERTEC Braun Inlertec Corporation 1100 1 Hampshire Avenue S Minneapolis, MN 55438 Phone: 952.995.2000 Fax: 952.995.2020 Web: broullintertec.com August 28, 2009 Project BL-09-03401 Mr. Kevin Crooks City of Chanhassen 7700 Market Boulevard PO Box 147 Chanhassen, MN 55317-8363 Re: Geotechnical Evaluation Manhole Structure and Sanitary Sewer Repair Near 823 Lake Susan Hills Drive Chanhassen, Minnesota Dear Mr. Crooks: We are pleased to present this Geotechnical Evaluation Report for the proposed repair of the manhole structure and associated sanitary sewer pipes near 823 Lake Susan Hills Drive. A summary of our results, and a summary of our recommendations in light ofthe geotechnical issues influencing design and construction, is presented below. More detailed information and recommendations follow. Summary of Results Based on information provided by you, it is our understanding the existing sanitarY sewer lines entering and exiting the manhole structure are not properly flowing, and are likely the result of ongoing soil consolidation issues. This manhole has previously settled and been repaired, and is again experiencing settlement. Based on discussions with you, the manhole structure is approximately 11 feet deep. One boring to a nominal depth of 40 feet was completed on Lake Susan Hills Drive, approximately 5 feet from the manhole structure. The boring encountered sandy lean clay fill to a depth of about 22 feet, where organic silts were encountered to a depth of about 34 feet. Beneath the organic soils, alluvial lean clay was encountered to a depth of 39 feet, where glacial till sandy lean clay was encountered to the boring termination depth. Groundwater was initially encountered during drilling at a depth of 11 feet beneath the surface. This may represent a perched condition as the boring was being completed, water was observed at a depth of 25 feet with 39 1/2 feet of auger in the ground. We anticipate the static groundwater level will be near that of the organic soils, however long term monitoring would be necessary to confirm this. Groundwater monitoring was not included in our scope of services. Seasonal and annual fluctuations in the groundwater level should be anticipated. o Providing engineering and environmental solutions since 1957 City of Chanhassen Project BL-09-03401 August 28, 2009 Page 2 Summary of Recommendations It appears that the organic silt soils are the main cause of the past and current settlement of the manhole structure. These soils are generally weak, and prone to settlement over time. We anticipate that these soils will continue to consolidate and settle over time. Due to the depth of the soils and the confined area for construction, it is our opinion that the manhole and associated pipes should be supported using helical anchors. Please read the attached report for more detailed results and recommendations. Remarks Thank you for making Braun Intertec your geotechni~al consultant for this project. If you have questions about this report, or if there are other services that we can provide in support of our work to date, please call Josh Kirk at 952.995.2222 or Ray Huber at 952.995.2260. Sincerely, BRAUN INTERTEC CORPORATION ~ qa L Kirk, PE h~~~ct Engineer ~t Associate-Senior Engineer Geo Report-Lake Susan Hills Manhole Repair BRAUN INTERTEC I Table of Contents Description Page A. Introductio I) ................................. ........... ..... ............... ....................................... .............................. 1 A.l. Project Description ..... ............... ....... ......... ................ .... ......... ......... ............... ............... ..... 1 A.2. Purpose......... ........... ...................... ....... ...... ........................................... ........... .................. 1 A.3. Background Information and Reference Documents......................................................... 1 A.4. Site Conditions........ ......... ......... ..... ......... ........................ .............. ......... ............................. 1 A.S. Scope of Services...... ......... ........ ................. .................... ................ ................ .................... 1 Results.. ............ ................... .................... .............. ....... ............ ...................... ............... ................... 2 B.l. Exploration Logs.. ................ ......... ............ .................. .......... ................................... ........ .... 2 B.1.a. Log of Boring Sheets .............................................................................................. 2 B.l.b. Geologic 0 rigins......... ......... ........ ................................. ....... ............... ..... ............... 2 B.2. G eologi c Profile.... ....... .......... ...... ....... ..... ............................................. ........... ..... ............... 3 B.2.a. Geologic Materia Is ........... ..... ........... .................. ... ........... ..... ............. .................... 3 B .2.b. Groundwater .............. ........... ...................... ........................... ............. .................. 3 6.3. Laboratory Test Results ........ .......... ................................... ......... ......... ...... ..... ....~ ....... ........ 4 Basis for Recommendations . ..........:~.................. .................. .......... ......... .................... ............ ........ 4 C.l. Design Deta i Is ....... ..... ........... ..... ....... ..... ......... .............................. ....... ........... .................... 4 C.2. Design Considerations ............... ..................... ......... ....... ............ .................. ...........:.. ........ 4 C.3. Construction Considerations ....... ..... ....... ....... ............................ .................. ...................... 5 Recommendations............ ..... ............ .......... ...... ............ ......... ..................... ................ ................;... 6 D.l. Helical Anchor Foundation System ............................................ ......................................... 6 D.2. Soil Parameters... ..... .............. ........ ........... ..................... ..... .... .......... ............ ...... ................ 7 D.3. Pave ments ......... ...................... ............. ........ ...................................... ...... ....... ............... .... 7 D.3.a. Utility Trench Backfill............... ................. ............................ ....... .......................... 7 D.3.b. Subgrade Proof-Ro II............ ..... .......... ....... ........ ................. ..... ......... ...................... 7 0.3.c. Design Sections.... ................ ...... ...................... ............... ................. ................ ...... 7 0.3.d. Materials and Compaction .................................................................................... 8 D.4. Construction Quality Control..... ..... ............ ....... .......... ................ ................ .............. ......... 8 D.4.a. Excavation Observations ............ .......... ...... ....... ....... ............. ;... ....... .............. ....... 8 D.4.b. Helica l'Anchor Observations. ........................ .... .......... .................. ................. ....... 8 D.4.c. . Materia Is Testing ..................... ............... ....................... ....... ........... ............. ......... 8 D.4.d. Pavement Subgrade Proof-RoiL......... ................. .......... ....... ........... .......... ............. 8 D.4.e. Cold Weather Precautions. ................. ....................... ........ ..................... ....... ........ 9 Proced ures...................................... ..... ......... ...... ..... .............................~. ....... ....... ......... ............ ...... 9 E.l. Penetration Test Borings .......... ..... ..... ........................ ........... ........... ......... ............ ............. 9 E.2. Material Classification and Testing......... ....... ...... ................. ......... ....... ..................... ......... 9 E.2.a. Visual and Manual Classification ...........................................................................9 E.2.b. La boratory Testing ............. ....... ............. .......................... .............. ........................ 9 E.3. Groundwater Measurements ......................... ...... .............. ............ ...................... ..... ........ 10 B. C. D. E. Table of Contents (continued) Description Page F. Qua lifications........... ......... ............................ ............ ...................... .............. ................................. 10 F.1. Variations in Subsurface Conditions ................................................................................. 10 F.1.a. Material Strata...... ..... ......... ............ ................. ....... ....... ..... ........................ ......... 10 F.1.b. Groundwater Levels............................ ....... ...... ....... ....... ..... ........... ............. ......... 10 F.2. Continuity of Professional Responsibility .........................................................................11 . F .2.a. Pia n Review... ............... ............. ... ....... ............. ....... ......... .................................... 11 F.2.b. Construction ObserVations and Testing ..............................................................11 F .3. Use of Report.... ...................... ....... ....... ...... .................. ................ .................... ................. 11 F .4. Sta ndard of Ca re ... .................. .............. ..... ................ ................... ........................... ......... 11 Appendix Log of Boring Sheet Descriptive Terminology BRAUN INTERTEC A. Introduction A.l. Project Description This Geotechnical Evaluation Report addresses the proposed repair to the manhole structure and sanitary sewer pipes that are experiencing settlement near 823 Lake Susan Hills Drive in Chanhassen, Minnesota. The key design, construction or performance component of this project is the presence of swamp deposited soils at depth beneath the manhole and its effect on the long term performance of the structure and associated pipes. A.2. Purpose The purpose of this geotechnical evaluation is to evaluate the cause of the apparent manhole settlement and to present recommendations for repair of the structure. A.3. Background Information and Reference Documents To facilitate our evaluation, we reviewed the following information: · A discussion with Kevin Crooks regarding the current state of the structure and issues from the past regarding settlement. · Geologic atlas showing the expected soil types in this area. A.4. Site Conditions The manhole structure in question is in Lake Susan Hills Drive, near the house located at 823 lake Susan Hills Drive. The street is part of an existing residential neighborhood. The neighborhood is fully. developed, with a bituminous road surface and curb and gutter in place. The Lake Susan Hills West Park borders the eastern portion ofthe development, and appears to consist mainly of wetland areas. A.S. Scope of Services Our scope of services for this project was originally submitted as a Proposal for Geotechnical Evaluation dated August 5, 2009. We received authorization to proceed from you on August 11, 2009. Tasks performed in accordance with our authorized scope of services included: · Performing a reconnaissance of the site. City of Chanhassen Project BL-09-03401 August 28, 2009 Page 2 . Staking and coordinating the clearing the area of underground utilities. . Performing 1 penetration test boring to a nominal depth of 40 feet below grade. . Performing laboratory moisture content and organic content tests on selected penetration test samples. . Preparing this report containing a summary of the geologic materials encountered, results of laboratory tests, and recommendations for methods to support the existing structures. Our scope of services was performed under the terms of our General Conditions, dated June 15, 2006 B. Results B.l. Exploration logs B.l.a. Log of Boring Sheets Log of Boring sheets for our penetration test boring is included in the Appendix. The log identifies and describes the geologic materials that were penetrated, and present the results of penetration resistance tests performed within them, laboratory tests performed on penetration test samples retrieved from them, and groundwater measurements. Strata boundaries were inferred from changes in the penetration test samples and the auger cuttings. Because sampling was not performed continuously, the strata boundary depths are only approximate. The boundary depths likely vary away from the boring locations, and the boundaries themselves may also occur as gradual rather than abrupt transitions. B.l.b. Geologic Origins Geologic origins assigned to the materials shown on the logs and referenced within this report were based on: (l) a review of the background information and reference documents cited above, (2) visual classification of the various geologic material samples retrieved during the course of our subsurface exploration, (3) penetration resistance (4) laboratory test results, and (5) available common knowledge of the geologic processes and environments that have impacted the site and surrounding area in the past. BRAUN I NTE RTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 3 B.2. Geologic Profile B.2.a. Geologic Materials The general geologic profile at the boring location consists of (proceeding down from the ground surface) a pavement section, fill, organic silts, and alluvial and glacially deposited clays to the boring termination depth. The existing pavement section consisted of 6 inches of bituminous pavement over 12 inches of aggregate base. The aggregate base layer can become contaminated with the underlying subgrade soils over time and it can be difficult to determine the actual thickness. As a result, aggregate base thicknesses should be considered approximate. Beneath the pavement section, fill soils consisting of sandy lean clay were encountered to a depth 21 feet beneath the surface. The penetration resistance of the fill soils ranged from 4 to 12 blows per foot (BPF). Organic silt was encountered beneath the fill to a depth of 34 feet beneath the surface. The organic silt contained occasional layers of fibers and contained shells throughout. The penetration resistances encountered in the swamp deposit soils ranged from Weight of Hammer (0) to 7 BPF. Alluvial lean clay was encountered beneath the organic soils. The lean clay contained silt and silty sand lenses throughout. The penetration resistance in the lean clay was 5 BPF, indicating a rather soft consistency. . Glacially deposited sandy lean clay was encountered at a depth of 39 feet and extended tothe termination depth of the boring. The sandy lean clay contained trace amounts of gravel. The penetration resistance in the sandy lean clay was 7 BPF, indicating a medium consistency. B.2.b. Groundwater Groundwater was initially encountered during drilling at a depth of about 11 feet beneath the surface, and again at a depth of 25 feet with 391/2 feet of auger in the ground. The groundwater encountered at 11 feet was likely a perched condition within the fill. We anticipate the static groundwater level will be near that of the organic soils, however long term monitoring would be necessary to confirm this. Groundwater monitoring was not included in our scope of services. Seasonal and annual fluctuations in the groundwater level should be anticipated. BRAUN I NTE RTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 4 B.3. laboratory Test Results The moisture content of the selected samples was determined to vary from approximately 17 to 85 percent, indicating that the material was near or above of its probable optimum moisture content. Several of the samples were selected from the swamp deposited soils, and had elevated moisture contents (above 50 percent). This is due to the presence of organic matter. Our organic content tests indicated that the swamp deposited soils contained 4 to 11 percent organic material by weight, indicating the soils were considered slightly organic to moderately organic. C. Basis for Recommendations C.l. Design Details Based on conversations with the project team, we understand that the manhole will remain in its present location, and will be raised to re-establish its design invert elevation. Similarly, the sanitary sewer pipes that have been affected by the settlement of the manhole, will also be raised to their design elevations. C.2. Design Considerations It appears that the organic silt soils are the main cause of the past and current settlement of the manhole structure and adjacent pipes. These soils are generally weak, and prone to settlement over time. We anticipate that these soils will continue to consolidate and settle over time. Due to the depth of the soils and the confined area for construction, it is our opinion that the manhole and associated pipes should be supported using helical anchors. This is based on the following considerations: · The swamp deposited organic silt was encountered approximately 22 feet beneath the surface, extending to about 34 feet. An excavate/ backfill approach including the removal of all of the organic soils beneath the structure is not feasible due to the confined work area and presence of existing utility lines and homes. BRAUN INTERTEC City of Chanhassen Project Bl-09-03401 August 28, 2009 Page 5 · Sheet piling or driven piles are also likely not feasible due to the confined work space, and the possible presence organic soils in surrounding areas that may become unstable from vibrations. The vibrations generated from sheet piling or driven piles will also be highly intrusive to the neighboring homeowners. · If a partial correction of the organic soils beneath the structure is considered, there is a minor risk of continued settlement due to the continued consolidation of the organic soils. This risk should be assumed by the owner, and may result in periodic maintenance of the pipe. C.3. Construction Considerations From a construction perspective, the project team should also be aware that: . The helical anchors will need to extend through the organic soils and alluvial clays into the glacial till soils. . We recommend encasing the helical anchor shafts in grout. The grout will provide additional stiffness for lateral support of the a nchor, and reduce the corrosion potential of the anchor shaft due to the presence of organic soils. . The sanitary sewer pipes extending away from the manhole will also need to be supported by helical anchors. The weight of the soil on top of the pipe should also be considered when designing helical anchor capacity. . If the haunch supporting the pipe is larger than the diameter of the pipe, the soil mass above the exposed portions of the support structure should also be considered during helical . anchor design. . It is our understanding that the sanitary sewer pipe will be welded to the haunch. By welding the two pieces together, the potential for pipe corrosion is introduced. Steps to prevent corrosion of the pipes should be implemented. . It appears that there are several other underground utilities present beneath the roadways. Careful consideration should be taken if portions of the roadway are excavated, as this may disturb the soils supporting the existing utilities. BR.AUN INTERTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 6 D. Recommendations Based on conversations with the design team, it appears that a system of helical anchors will be designed to extend into the native glacial till soils to support the manhole structure and associated pipes. The following sections provide recommendations regarding the design and construction of the helical anchors and the reconstruction of the roadway. It is our understanding that final design of the helical anchors will be conducted by a specialty contractor that will also install the anchors. 0.1. Helical Anchor Foundation System Helical anchors appear to be the most suitable approach to support the manhole structure. The installation ofthe anchors can be performed in relatively confined areas and will not produce excess vibrations that could disturb or destabilize any organic soils that may be present in the surrounding area, and will be less intrusive to neighboring homeowners. Based on the results of the boring, it appears that about 10 feet of fill and 10 feet of organic soils are present beneath the manhole, with an additional 5 feet of rather soft alluvial clays. These soils will need to be penetrated by the helical anchors and embedded into the glacial till soils to attain the desired capacity. The final design of the helical anchor system will be conducted by others; however, based on the results from the boring, we anticipate the anchors will extend to a depth of at least 50 feet. The specialty contractor doing the installation should calculate the final design length, capacity and number, size and spacing of the helical anchors. A number of helical anchors will likely be placed beneath the manhole structure and at prescribed distances along the pipe alignment to support the weight of the pipe and the overlying fill soils. A structural slab or grade beam may also be constructed beneath the manhole to support it. Haunches will likely be constructed at the top of the anchors to act as a cradle for the pipe. We understand the pipe will be welded to the haunch. We recommend using a rigid sanitary sewer pipe with flexible connections to reduce the risk of pipe cracking or shearing of the pipe at the transition between the a nchor supported pipe and the ground supported pipe. BRAUN INTERTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 7 Organic soils can also be corrosive to the helical anchor shafts, as such, we recommend the shafts be encased in grout during installation. The grout will also provide increased lateral stiffness to the anchors. Additionally, if the pipe is welded to the haunch, the corrosion potential that the location of the weld has been increased. We recommend the necessary corrosion protection measures be taken. 0.2. Soil Parameters The soils present above the pipe will likely consist of the existing sandy lean clay fill encountered by the boring. The soil mass will act on the pipe and should be accounted for in the design of the helical anchors. We have assumed a wet density of 125 pounds per cubic foot (PCF) for the soil, with a friction angle of 26 degrees. The volume of soil supported by the pipe was assumed to extend up and away from the pipe at a 1:1 angle, or a 45 degree angle from vertical. Based on these parameters, we anticipate the pipe will carry a weight of approximately 15 kips (15,000 pounds) per linear foot of pipe. 0.3. Pavements D.3.a. Utility Trench Backfill After the installation of the helical anchors to support the manhole structure and pipes, we recommend compacting the soils in the utility trench to re-establish roadway subgrade elevations. We recommend spreading backfill and fill. in loose lifts of approximately 8 to 12 inches and the compacting the backfill to at least 95 percent of the standard Proctor density to within 3 feet of the subgrade elevations, and to 100 percent in the upper 3 feet of the subgrade. The moisture content ofthe fill should be maintained between 1 percentage point below to 3 percentage points above the soils optimum moisture content. The existing fill soils encountered by the borings appear suitable for re-use as engineered filt. D.3.b. Subgrade Proof-Roll After the installation of the helical anchors, backfilling of the utility trench, and prior to placing aggregate base material, we recommend proof-rolling the pavement subgrade to determine if the subgrade materials are loose, soft or weak, and in need of further stabilization, compaction or subexcavation and recompaction or replacement. A second proof-roll should be performed after the aggregate base material is in place, and prior to placing bituminous pavement. D.3.c. Design Sections We recommend placing a pavement section similar to that in the surrounding street. Based on the result of our boring, it appears that the existing pavement section consists of approximately 6 inches of bituminous pavement and 12 inches of aggregate base. BRAUN INTERTEC City of Chanhassen Project BL-D9-03401 August 28, 2009 Page 8 D.3.d. Materials and Compaction We recommend specifying crushed aggregate base meeting the requirements of Minnesota Department ofTransportation (Mn/DOT) Specification 3138 for Class 5. We recommend that the bituminous wear and base courses meet the requirements of Specifications 2360. We recommend that the aggregate base be compacted to a minin;um of 100 percent of its maximum standard Proctor dry density. We recommend that the bituminous pavement be compacted to at least 92 percent ofthe maximum theoretical density. 0.4. Construction Quality Control O.4.a. Excavation Observations We recommend having a geotechnical engineer observe all excavations related to subgrade preparation. The purpose of the observations is to evaluate the competence ofthe geologic materials exposed in the excavations in areas that will be ground supported. D.4.b. Helical Anchor Observations We recommend a geotechnical engineer or engineering technician observe the insta lIation of the helical anchors. The installation documentation should include the type of pier, the depth, the gauge pressure and the torque that is achieved during installation. 0.4.c. Materials Testing We recommend density tests be taken on the soils placed for the utility trench backfill to determine if the compaction efforts meet the minimum project specifications. We also recommend slump, air content and strength tests of Portland cement concrete during curb and gutter replacement. 0.4.d. Pavement Subgrade Proof.RolI We recommend that proof-rolling of the pavement subgrades be observed by a geotechnical engineer to determine if the results of the procedure meet project specifications, or delineate the extent of additional pavement subgrade preparation work. BR.AUN INTERTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 9 DA.e. Cold Weather Precautions If construction is anticipated during cold weather, all snow and ice should be removed from the excavations prior to placing fill. No fill should be placed on frozen subgrades. No frozen soils should be used as fill. Concrete delivered to the site should meet the temperature requirements of ASTM C 94. Concrete should not be placed on frozen subgrades. Concrete should be protected from freezing until the necessary strength is attained. Frost should not be permitted to penetrate below footings. E. Procedures E.l. Penetration Test Borings The penetration test boring was drilled with a truck-mounted core and auger drill equipped with hollow-. stem auger on August 21,2009. The boring was performed in accordance with A5TM D 1586. Penetration test samples were taken at 2 l/2-or 5-foot intervals. Actual sample intervals and corresponding depths are shown on the boring logs. E.2. Material Classification and Testing f.2.a. Visual and Manual Classification The geologic materials encountered were visually and manually classified in accordance with ASTM Test Method D 2488. A chart explaining the classification system is attached. Samples were sealed in jars or bags and returned to our facility for review and storage. E.2.b. Laboratory Testing The results of the laboratory tests peiformed on geologic material samples are noted on or follow the appropriate attached exploration logs. The tests were performed in accordance with ASTM or AASHTO procedures. BRAUN I NTE RTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 10 E.3. Groundwater Measurements The drillers checked for groundwater as the penetration test borings were advanced, and again after auger withdrawal. The boreholes were then backfilled or allowed to remain open for an extended period of observation as noted on the boring logs. F. Qualifications F.l. Variations in Subsurface Conditions F.l.a. Material Strata Our evaluation, analyses and recommendations were developed from a limited amount of site and subsurface information. It is not standard engineering practice to retrieve material samples from exploration locations continuously with depth, and therefore strata boundaries and thicknesses must be inferred to some extent. Strata boundaries may also be gradual transitions, and can be expected to vary in depth, elevation and thickness away from the exploration locations. Variations in subsurface conditions present between exploration locations may not be revealed until additional exploration work is completed, or construction commences. If any such variations are revealed, our recommendations should be re-evaluated. Such variations could increase construction costs, and a contingency should be provided to accommodate them. F.l.b. Groundwater Levels Groundwater measurements were made under the conditions reported herein and shown on the exploration logs, and interpreted in the text of this report. It should be noted that the observation period was relatively short, and groundwater can be expected to fluctuate in response to rainfall, flooding, irrigation, seasonal freezing and thawing, surface drainage modifications and other seasonal and annual factors. BRAUN INTERTEC City of Chanhassen Project BL-09-03401 August 28, 2009 Page 11 F.2. Continuity of Professional Responsibility F.2.a. Plan Review This report is based on a limited amount of information, and a number of assumptions were necessary to help us develop our recommendations. It is recommended that our firm review the geotechnical aspects of the designs and specifications, and evaluate whether the design is as expected, if any design changes have affected the validity of our recommendations, and if our recommendations have been correctly interpreted and implemented in the designs and specifications. F.2.b. Construction Observations and Testing It is recommended that we be retained to perform observations and tests during construction. This will 'allow correlation of the subsurface conditions encountered during construction with those encountered by the borings, and provide continuity of professional responsibility. F.3. Use of Report This report is for the exclusive use of the parties to which it has been addressed. Without written approval, we assume no responsibility to other parties regarding this report. Our evaluation, analyses and recommendations may not be appropriate for other parties or projects. FA. Standard of Care In performing its services, Braun lntertec used that degree of care and skill ordinarily exercised under similar circumstances by reputable members of its profession currently practicing in the same locality. No warranty, express or implied, is made. BRAUN INTERTEC Appendix BRAUNSM INTERTEC Braun Project BL-09-03401 GEOTECHNICAL EVALUATION Sanitary Sewer Investigation 823 lake Susan Hills Drive Chanhassen, Minnesota DRilLER: C, Powers I METHOD: 3 1/4" HSA, Autohammer Depth feet ASTM 0.0 Symbol PAV - 1.5 FILL ~ c_ o fii '>- Q) .Q .0 ro- 15 c_ .Q ro c_ e{' '9 )( al- - .e 1l- .c VI ~- o (5 c 'E -- al t- CIl >- ~ G- t/) al Cl CIl- CIl !:9_ 888 21.0 OH ..... 0- .:.i ... g)- c0- N c0- b \!) gi- I .. => q:- '" cO Q. - l!) rl ~ '" - o l!) z_ a: o cO ::J- l!) 9 B L -09-03401 BORING: LOG OF BORING ST-1 LOCATION: Lake Susan Hills Drive, in front of 823 lake Susan Hills Drive DATE: Description of Materials (ASTM 02488 or D2487) 6 inches of Bituminous over 12 inches of Aggregate Base. - Fill: Sandy Lean Clay, with a trace of Gravel, with occasional _ Poorly Graded Sand lenses, brown, wet. - - ORGANIC SILT, with traces of fibers, with shells, black and dark brown to 27 feet, then brown and gray, wet. _ (Swamp Deposit) - Braun Intertec Corporation - - - - - - - - - - - - - - - - - - - - - - - - 8/20/09 I SCALE: BPF WL mc qp % tsf 4 5 4 5 17 :sz. 12 10 11 8 23 3 .!. 3 85 7 51 1"=4' Tests or Notes An open triangle in the water level (WL) column indicates the depth at which groundwater was observed while drilling. A solid triangle indicates the groundwater level in the bOring on the date indicated. Groundwater' levels fluctuate. oc = 11% oc = 4% 5T-1 page 1 of 2 BRAUNIM INTERTEC Braun Project BL-09-03401 GEOTECHNICAL EVALUATION Sanitary Sewer Investigation 823 lake Susan Hills Drive Chanhassen, Minnesota DRILLER: C. Powers METHOD: 31/4" HSA, Autohammer LOG OF BORING BORING: ST-1 (cont.) LOCATION: Lake Susan Hills Drive, in front of 823 Lake Susan Hills Drive DATE: 8/20/09 SCALE: 1" =4' Depth Description of Materials feet ASTM BPF WL me qp Tests or Notes 32.0 Symbol (ASTM 02488 or D2487) % tsf ORGANIC SILT, with traces of fibers, with shells, black and dark brown to 27 feet, then brown and gray, wet. 0 34.0 (Swamp Deposit) (continued) CL LEAN CLAY, with frequent Silt and Silty Sand lenses, gray, wet, rather soft. (Alluvium) 5 1/2 fJl .~- ~ 39.0 ~ CL .a ro- '0 c 41.0 .9 1il t:_ .JS! 'C '-'- Vi a o Q)- Q) en .... c- ,:.; ... 8_ ...... 00 ~ ... c ~ . cd _ ~I :::> ;2- 00 ~ a._ ~ ,..; o ;;l;- <> C> 2_ C2 o '" .... - o \!l 9 BL-09-03401 SANDY LEAN CLAY, with a trace of Gravel, gray, wet, medium. (Glacial Till) 7 1 1/4 END OF BORING. Water observed at 11 feet with 11 1/2 feet of hollow-stem auger in the ground. Water observed at 25 feet with 39 1/2 feet of hollow-stem auger in the ground. Boring immediately backfilled with bentonite grout. Braun Intertec Corporation ST-1 page 2 of 2 BRAUN INTERTEC Descriptive Terminology of Soil ::8 ~!~rJgl!~~ Standard 0 2487 . 00 Classification of Soils for Engineering Purposes {Unified Soil Classification System} Particle Size Identification Boulders ..................,.....,...... over 12" Cobbles ..,...,......,..,..............3"to 12" Gravel Coarse ............................ 314" to 3' Fine ................................. NO.4 to 3/4" Sand Coarse ............................ NO.4 to No, 10 Medium ........................,.. No. 10 to No. 40 Fine ................................. No. 40 to No. 200 Silt ..........................,..,......... -< No. 200, PI< 4 or below "A" line Clay .......................,.....,.......-< No. 200, PI ~ 4 and on or above "A" line Criteria for Assigning Group Symbols and Soils Classification Group Names Using Laboratory Tests · Group Symbol Group Name b c: Gravels Clean Gravels Cu a: 4 and 1 $. Co $. 3 c GW Well-graded graveld '" 0 More than 50% of 5% or less fines e =-0 Cu -< 4 andlor 1 > Co> 3 c GP Poorly graded gravel" o (t) coarse fraction t/J .S Q) a11.'l~ retained on Gravels with Fines Fines classify as ML or MH GM Silty gravel" ,~ c:~'" NO.4 sieve More than 12% fines' Fines classify as CL or CH GC Clayey gravel d19 'E ~g Sands Clean Sands Cu:2 6 and 1 :5. Co :5. 3 c SW Well-graded sand h ",,,, ('oj ~~o 50% or more of 6% or less fines I Cu < 6 andlor 1 > Cc::' 3 c SP Poorly graded sand h ...<:Z coarse fraction "'~ Fines classify as ML or MH Silty sand I 9 t, o~ passes Sands with Fines SM ()O E No.4 sieve More than 12% I Fines classify as CL or CH SC Clayey sand' p. ., Inorganic PI > 7 and plots on or above "A" line I CL Lean clav' i m (/):5 Silts and Clays PI -< 4 or plots below" A" linel ML :0::-0 Silt" m 0'" '" Liquid limit (l)fIl:> Liquid limit - oven dried OL Organic clay k 'm" '" ., less the n 50 Organic 0.75 "D co .- -< OL Organic silt' I m 0 .,c.'" Liquid limit - not dried .5 ~8 PI plOIS on or aoove "A' line CH Fat clav k I "' "'ON Inorganic l;,E . Silts and clays PI plots below "A' line MH Elastic silt k ' m . ~ 0 Liquid limit ~oZ u:~ 50 or more Organic Uquid limit - oven dried <: 0.75 OH Organic clay k , m p '" Liquid limit - not dried OH Organic silt' , m . Highly Organic Soils Primarily organic matter, dark in color and organic odor PT Peat a, Basedonthe malerial passing the 3-in{i5mm)sieve, b. If field sample contained cobbles or boulders. or both, add -with cobbles or boulders or both- to group name. c, Cu: D;oID" Co:~ 010 X D60 d, If soli contains~15% sand, add 'with sand' to group name. e. Gravelswilh 5 to 12% fines require dual symbols: GW.GM well-graded gravel with silt GW-GC well-graded gravel with clay GP.GM pooriy graded gravel with sill GP-GC poony graded gravel w~h clay f If fines classify as CL-ML, use dual symbol GC-GM or SC-SM. g. Iff,nes...-e organic. add "with organic fines' togroup name. h, If soil contains ~ 15% gravel. add "with gravel' to group name, Sands with 5to 12% rifles require dual symbols: SW-SM well-graded sand wilh silt SW-SC well-graded sand with clay SP..SM poorly graded sand with sin Sp.SC poorly graded sand with clay j. If Alterberg limits plol in hatct1ed area. soil is a CL.ML. silty clay, k If soil contains 10 1029% plus No. 200, add 'with saner or 'wilh gravel" whichever is predominant I. ~ soil contains ;;o3O"k plus No, 200, predominanlly sand, add 'sandy'togroup name. m, ~ wil contains~ 30% plus No. 200 predominantly gravel, add'graveDf to gruup name. n. PI ~ 4 and plolS on or above 'N line, o. PI < 4 or plOIS below "A' line. p, PI plots on or above "A' line. q, PI plots below "A" fine. 60 50 - ~ 40 X (Il "0 1: 30 .r:- 't) ; 20 III III 0:: 00 WD MC LL PL PI P200 10 7 . 4 o 0, 30 90 10 16 20 40 50 80 100 60 70 Dry density, pel Wet density, pcf Natural moisture content, % Liqiuid limit, % Plastic limit, % Plasticity index, % % passing 200 sieve Liquid Limit (LL} Laboratory Tests OC Organic content, % S Percent of saturation, % SG Specific gravity C Cohesion, psf o Angle of internal friction qu Unconfined compressive strength. pst qp Pocket penetrometer strength, tsf Relative Density of Cohesion less Soils Very loose ................................ 0 to 4 BPF Loose ....................................... 5 to 10 BPF Medium dense ......................... 11 to 30 BPF Dense .......".."......................... 311050 BPF Very dense ............................... over 50 BPF Consistency of Cohesive Soils Very soft ................................... 0 to 1 8PF Soft ....................................... 2to:l BPF Rathersott ............."................ 4to 5 BPF Medium .....".............."......"..." 6 to 8 8PF Rather stiff ............................... 9 to 12 BPF Stiff ....................................... 13 to 16 BPF Very stiff ................................... 17to 30 BPF Hard ..............m...................... over 30 8PF Drifling Notes Standard penetration test borings were advanced by 31/4" or 61/4" 10 hollow.stem augers unless noted otherwise, Jetting water was used to clean out auger prior to sampl.ing only where indicated on logs. Standard penetration test borings are designated by the prefix "ST' (Split Tuoe). AU samples were taken with the standard 2" 00 split-tube sa mpler, except where noted. Power auger borings were advanced by 4" or 6" diameter continuous- flight, solid-stem augers. Soil classifications and strata depths were in- ferred from disturbed samples augered to the surface and are, therefore, somewhat approximate. Power auger borings are designated by the prefix "6," Hand auger borings were advanced manually with a 1 1/2" or 3 1/4" diameter auger and were limited to the depth from which the auger could be manually withdrawn. Hand auger borings are indicated by the prefix "H," 110 BPF:. Numbers indicate blows per foot recorded in standard penetration test. also known as "N" value, The sampler was set 6" into undisturbed soil below the hollow-stem auger. Driving resistances were then counted for second and third 6" increments and added to get 6PF. Where they differed significantly. they are reported in the following form: 2/12 for the second and third 6" increments, respectively. WH: WH indicates the sampler penetrated soil under weight of hammer and rods alone; driving not required. WR: WR indicates the sampler penetrated soH under weight of rods alone; hammer weight and driving not required, TW indicates thin.walled (undisturbed) tube sample. Note: All tests were run in general accordance with applicable ASTM standards. Re. 7107