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Kerber Pond Slope Stabilization: Approve Quote0 CITY OF CNANHASSEN 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 7901 Park Place Phone: 952.227.1300 Fax: 952.227.1310 Senior Center Phone: 952.227.1125 Fax: 952.227.1110 MEMORANDUM TO: Todd Gerhardt, City Manager FROM: Paul Oehme, Director of Public Works /City Engineer .q' py—T e - --, DATE: April 23, 2012 SUBJ: Kerber Pond Slope Stabilization, Project No. 11 -09: Approve Quote PROPOSED MOTION "Approve Quote in the amount of $64,310.00 to Parrot Contracting, Inc. for Kerber Park Pond Stabilization Improvements." City Council approval requires a simple majority vote of the City Council present. BACKGROUND In 2008, the City reconstructed Laredo Drive and constructed a rain garden feature and stormwater pond in Kerber Park Pond. These improvements were made to help treat the stormwater runoff before it entered Lotus Lake. The construction of the stormwater pond took place on a steep hillside which required excavation and regrading to construct the pond. The work was completed the fall of 2008. Starting in the spring of 2009 the slope of the north facing hillside has slowly been moving. The contractor for the Laredo Drive project has been out several times to try to correct the problem but the hillside keeps moving. Staff hired a geotechnical firm to complete a soils investigative report to try to figure out why the slope is moving and what can be done to correct the problem. A site survey and soil borings were also taken on the slope. The report identified several potential causes %J the failure. One of the main causes of the problem is a sand lenses at the bottom of the hillside Web Site that was unknown prior to the slope failure. This sand lenses acts as a relief for www.ci.chanhassen.mn.us ground water in the hillside. During wet times of the year, ground water flows out of the hillside and made the newly placed soil on the hillside unstable. The pond area required soils to be removed to construct the pond. The soils that were planned to be removed consisted of organic soil that was suitable and planned to be Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow Todd Gerhardt Kerber Pond Slope Stabilization: Approve Quote April 23, 2012 Page 2 used as topsoil for on the street project. Underneath the organic soil some clay material was also necessary to be removed. However, it was found after start of the excavation of the pond the organic soils and some of the clay contained a small amount of asphalt. These soils were not suitable for the contractor to use on the project. Since the soils could not be used on the project, the material would have needed to be trucked to a dump site which would have cost $40 /cubic yard to dispose of or a $160,000 change order. Instead of trucking the material off site it was determined the best course of action was to use this material on the north side of the stormwater pond next to Kerber Pond. Because of the change in soil placement, more soil material was needed to be graded around the pond. During the construction of the pond, the moisture content of the material brought in from the street project was over optimum moisture content because of the rain fall that took place during construction and consequently had lower soil strength. Staff did discuss trying to dry out the material before it was placed however this option was dismissed because of the time involved drying the material and there was no guarantee there would be good weather to completely dry the material. Also staff did discuss with the contractor replacing the material with offsite drier fill. The contractor price for this work was excessive and staff did not think the price was worth the cost at that time. In hindsight, if the change order for new dry material was approved to be placed, the slope may still have failed due to ground water seeping out of the hillside. Several corrective measures were reviewed to address the problem. These options included: 1. Full or partial slope reconstruction with normal weight fill. 2. Full or partial slope reconstruction with light weight fill. 3. Fill pond and regrade hillside. 4. Sheet piling. Staff is recommending replacing the full slope failure area with normal weight fill that has low moisture content. Based on the geotechnical report, this option has the greatest safety factor and therefore the best chance of success. This option is also less costly then options 2 -4. This option also includes constructing a drainage layer with drain tile so ground water can discharge out of the hillside without causing soil failure. Staff has received two quotes for the recommended fix. The quotes received are as follows: Parrott Construction, Inc. $64,310.00 Minger Construction, Inc. $77,935.00 Parrott Construction, Inc. has worked on several City projects. Their work has been acceptable. The project has been budgeted for in 2012 CIP (SWMP #43). Funding is proposed to be split equally between the Street Pavement Management Fund and the Surface Water Utility Fund. The work is anticipated to start mid July. Attachments: Resolution & CIP Sheet g: \eng \public \_2000 -2009 public projects \_2008 projects \08 -01 2008 street improvements \bkgd apry quote kerber pnd slope.doc CITY OF CHANHASSEN CARVER AND HENNEPIN COUNTIES, MINNESOTA DATE: April 23, 2012 RESOLUTION NO: 2012- MOTION BY: SECONDED BY: A RESOLUTION APPROVING A QUOTE FOR THE KER13ER POND SLOPE STABILIZATION PROJECT NO. 11 -09 WHEREAS, quotes were received for the Kerber Pond Slope Stabilization Project No. 11- 09; and WHEREAS, it appears the quote from Parrott Contracting, Inc. in the amount of $64,310.00 is the lowest responsible quote. NOW THEREFORE, BE IT RESOLVED by the Chanhassen City Council: 1. The mayor and clerk are hereby authorized and directed to enter into a contract with Parrott Contracting, Inc. in the name of the City of Chanhassen for the Kerber Pond Slope Stabilization Project No. 11 -09, according to the plans and specifications therefore approved by the City Council and on file in the office of the city clerk. Passed and adopted by the Chanhassen City Council this 23` day of April, 2012. ATTEST: Todd Gerhardt, City Manager Thomas A. Furlong, Mayor YES NO ABSENT Capital Improvement Program 2012 thru 2016 City of Chanhassen, MN Project # SWMR043 Project Name Kerber Park Storm Pond Slope Stabilization Imp Account #1 720 - 7025 -xxxx Account #2 Account #3 Account #4 Department Surface Water Management Contact Paul Oehme Type Improvement Useful Life Category SWMP Priority n/a lieseriptton ' Total Project Cost: $115,000 This project would stabilize the slope next to the storm water pond. The project includes removing the unstable soils from the slope, installing draintile and replacing them with better materials. Justification The slope next to the storm water pond is not stable at this time. This pond was constructed along with the Laredo Drive Street Improvement project. The contractor which constructed the pond tried several times to stabilize the slope unsuccessfully. Do to the nature of the soil, unexpected springs and groundwater, wet weather since the pond was completed and lack of mature vegetation, the slope never stabilized. If the slope is not stabilized soon, the movement of soil could impact private property. Expenditures Total aenance 2012 2013 2014 2015 2016 115,000 115.000 Total 115,000 115,000 Funding Sources 2012 2013 2014 2015 2016 Total Street Pavement Management 57,500 57,500 Surface Water Utility Fund 57,500 57,500 Total 115,000 115,000 118