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Home My WebLink About2010-07-07 PACKET 04.F.REQUEST OF CITY COUNCIL ACTION COUNCIL AGENDA MEETING ITEM # DATE 07/07/201 Engineering ORIGINATING DEPARTMENT Jennifer Levitt STAFF AUTHOR COUNCIL ACTION REQUEST Authorize the preparation of plans and specifications for the repair of the deteriorated 66" from Hefner to Hamlet Park Pond as outlined in Option #3. STAFF RECOMMENDATION It is recommended the Council authorize the preparation of plans and specifications for the repair of the deteriorated 66" from Hefner to Hamlet Park Pond as outlined in Option #3. ADVISORY COMMISSION ACTION DATE REVIEWED APPROVED DENIED ❑ PLANNING ❑ ❑ ❑ ❑ PUBLIC SAFETY ❑ ❑ ❑ ❑ PUBLIC WORKS ❑ ❑ ❑ ❑ PARKS AND RECREATION ❑ ❑ ❑ ❑ HUMAN SERVICES /RIGHTS ❑ ❑ ❑ ❑ ECONOMIC DEV. AUTHORITY ❑ ❑ ❑ ❑ ❑ ❑ ❑ SUPPORTING DOCUMENTS ® MEMO /LETTER: Jennifer Levitt, June 30, 2010. ❑ RESOLUTION: ❑ ORDINANCE: ❑ ENGINEERING RECOMMENDATION: ❑ LEGAL RECOMMENDATION: ❑ OTHER: CITY OF COTTAGE GROVE J MINNESOTA To: Honorable Mayor and City Council Ryan Schroeder, City Administrator From: Jennifer M. Levitt, P.E., City Engineer Date: June 30, 2010 Re: 66" Deteriorated Pipe from Hefner to Hamlet Park Pond Authorize Preparation of Plans and Specifications Background As a part of the original Thompson Grove Estates 1st Addition development, a 66" diameter concrete storm sewer pipe was designed and constructed in 1960. It was identified as the West Trunk Storm Sewer. It's currently located within the street right -of -way on Hefner Avenue, extending west under East Point Douglas Road, Highway 61, West Point Douglas Road, and along the north side of the Park and Ride parking lot, continuing further west under the railroad tracks and discharging into the southerly portion of Hamlet Park Pond. From West Point Douglas Rd to Hamlet Park Pond, it's located within a drainage and utility easement. In addition, a 48" storm sewer pipe parallels the 66" pipe 10 feet to the south. The 48" pipe provides storm sewer service to West Point Douglas Road and adjacent properties. This pipe was designed and installed in 1974. Recently, as part of their storm sewer inspection efforts, Public Works identified a pipe deterioration problem within the 66" concrete storm sewer pipe. City staff walked through the pipe and took pictures of the deterioration, please see attached 66" Concrete Pipe Deterioration Photos. Based on these inspections, it appears that the deterioration problem exists from the 66" flared end section at Hamlet Park to approximately 1,000 feet upstream (or between the north bound lane of Highway 61 and East Point Douglas Road). See the attached record plan drawing. There is a varied degree of pipe deterioration and it is inconsistent in location. The deterioration ranges from the concrete pipe material appearing to be in an exposed aggregate condition, to having the steel reinforcement exposed to a significant depth. At this time the pipe has not deteriorated to the point in which there is no concrete pipe remaining, but it is close. There are several possible reasons for this deterioration: 50 years of normal wear and tear /use of the pipe, possible quality control issues of the original manufacturing of the concrete pipe, significant volumes and velocities of storm water running through this pipe over 50 years, the abrasiveness of sediment carried through this pipe over the years, and possible exposure to foreign materials /chemicals. Discussion Several options for the repair of the pipe deterioration have been evaluated and are listed below with preliminary estimated costs: Concrete Patching of Existing 66" Concrete Pipe Estimated Construction Cost - $115,000, includes 5% contingencies Total Project Costs - $149,500, includes 30% indirect costs In this option estimates that 60% of the 1,000 feet of deteriorated pipe would require concrete patching. An access point would be constructed by adding a storm sewer manhole structure approximately 500 feet upstream from the 66" flared end section. This option should be viewed as a short to intermediate term solution and would require regular monitoring. Full Length CIPP Pipe Liner — Estimated Cost $550,000 Estimated Construction Cost - $550,000, includes 5% contingencies Total Project Costs - $715,000, includes 30% indirect costs This option includes a cast in place pipe liner for the entire 1,000 foot length of deteriorated 66" concrete pipe. This will require providing two access points to perform this work. Two storm sewer manhole structures will be constructed permanently at both of the access points. Prior to the lining of the pipe, the existing pipe will require a minimum level of concrete patching to allow the CIPP to be successful. The existing 66" flared end would be removed and replaced. Open Cut Pipe Replacement in conjunction with a CIPP Liner Estimated Construction Cost - $350,000, includes 5% contingencies Total Project Costs - $455,000, includes 30% indirect costs This option includes the installation of the CIPP liner within the 66" pipe that is under the railroad, Highway 61, and West Point Douglas Road. The remaining 700 feet of 66" pipe would be replaced in an open cut. Two storm sewer manhole structures would be constructed permanently providing access to the pipe system. PVC Liner Estimated Construction Cost - $ 525,000, includes 5% contingencies Total Project Costs - $682,500, includes 30% indirect costs A fourth option reviewed was the installation of a PVC liner within the existing 66" concrete pipe. The actual material cost of a PVC pipe large enough to be used within the existing pipe (60 ") is significant, and the reduction in the size of the pipe by inserting another pipe would restrict flows and could create upstream drainage problems without further analysis of the storm water model. Staff's recommendation would be the third option, Open Cut Pipe Replacement in Conjunction with a CIPP Liner, for the following reasons: 1. This option is cost - effective, only utilizing the more expensive lining rehabilitation method on the portions of pipe in which surface disturbance is not desirable (railroad and street crossings). 2. This pipe has had an effective service life of 50 years. Areas of pipe replacement would restart the clock on the pipe's useful life. 3. The life expectancy of the concrete patching option is difficult to predict due to the significant flows and velocities the pipe experiences, in addition to being challenging to construct. It is an effective short term solution, however at a significant cost. Financial Impact This pipe replacement( repair does not appear in the current CIP and as such this project is an unbudgeted expenditure. Due to the extensive deterioration and loss of structural integrity we should proceed with a repair rather than wait for a complete structural failure. The pipe is a part of the trunk storm sewer system and services large sub - watershed district. As the pipe serves an area -wide benefit and has met its life expectancy, funding for this project would come from the storm water area fund. No specific policy addresses this situation or prevents the use of area funds for a project of this nature and sufficient funding exists in the storm water area fund to support this expense. Recommendation It is recommended the Council authorize preparation of plans and specifications for the repair of the deteriorated 66" Concrete Pipe from Hefner Avenue to Hamlet Park Pond as outlined in Option #3. 66" Concrete Pipe Deterioration Photos e r I —� I �— j r.. v I 11 � C �I � I Lin : 1 Wmr... -. ., .. � -! ,. v y w S 'r 1 i `) ' t ( L�vl q � y \S I Z . I ,i.. fI ' 4 i r r � I ef 6 � r