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A. Minnetonka Middle School Well Project Update 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 WII'II.ci .chanhassen.mn. us A MEMORANDUM TO: Todd Gerhardt, City Manager FROM: Paul Oehme P.E., Dir. of Public Works/City Engineer -? fJ. ,,~ . DATE: February 25,2005 SUBJ: Minnetonka Middle School Well Project No. 08-08: Update BACKGROUND Staff has been working on the possibility of converting the City-owned Minnetonka Middle School well into a municipal well. As you are aware, the City recently lost the use of two water supply wells during heavy irrigation pumping last summer. Currently, the City is in the process of drilling two new wells, Wells 12 and 13, to replace the lost well production. The school well improvement is proposed to add additional capacity to the system needed to meet demand in the short term from new developments coming on line such as the Chanhassen High School. The school well was drilled in 1963 before the current well code was in force and was turned over to the City in the 1970's after the school hooked up to City water. The pump and motor currently in the well can only pump 250 gallons per minute (gpm) and does not have the required chemical treatments available to pump into the distribution system. The City test pumped the well last fall to determine if it could yield more than the current 250-gpm capacity. Also, in conjunction with the test pumping, Barr Engineering completed a groundwater model of the west well field to identify any well field interference issues. Based upon this information, it was determined the well could yield between 700-800-gpm with no interference issues. The aquifer into which the well is constructed could yield more, however, there is a 6" casing at the bottom of well which limits the yield of this well. The City also received a preliminary evaluation of the well from a well contractor last fall regarding redeveloping the well. DISCUSSION Staff met with the Minnesota Department of Health (MDH) and explained the City's water needs to them and asked permission to make modifications to the school well and use it as a regular well during peak days. On February 4, 2008, the MDH commented on staff's request. Unfortunately, the well was not constructed to current well code requirements and it would be very difficult and expensive to have this well fixed to comply with current well code. However, the MDH did say it would give the City permission to use the well on a regular basis under certain conditions which are detailed below. The following criteria would need to be met in order for the Middle School well to be used as a municipal water supply: The City of Chanhassen · A growing community with clean lakes, quality schools, a channing downtown, thriving businesses, winding trails, and beautiful parks. A great place to live, work, and play. Todd Gerhardt Minnetonka Middle School Well Project February 25, 2008 Page 2 1. A complete water quality analysis for this particular well has not been conducted in some time due to the well being used only as an "emergency backup"; water analysis for VOC's, radionuclides, radon, TOC, nitrate and coliform bacteria must be run at a minimum. All samples must meet the requirements of the Safe Drinking Water Act. 2. The well must be located at least 50 feet from potential sources of contamination as specified in Minnesota Rules Chapter 4725. A well site survey by a representative of the Minnesota Department of Health must be conducted. 3. The well owner must obtain an appropriations permit from the Minnesota Department of Natural Resources. 4. A preliminary wellhead delineation worksheet must be completed for this well and submitted to the MDH for review. 5. The well owner must provide written documentation that they own or legally control all land within 50 feet of the well. The City would need to obtain an easement from the School District for this requirement. The easement would have a sunset clause. 6. A copy of the downhole camera videotape must be provided to the MDH for reView. 7. After December 31,2009, the well will not be allowed to be used as a community water supply well to meet average day demands. If the City would like to keep the well as an "emergency back-up" well, then the MDH will allow this designation until the year 2012. An "emergency back-up" well designation significantly reduces the allowable pumping of the well. By December 31,2012, the well should be sealed in accordance with Minnesota Rules Chapter 4725. 8. The MDH may revoke the approval to use this well if the well is found to be vulnerable to contamination during the time period specified, or if the property ownership or legal easement changes. Staff feels the City can comply with the MDH requirements assuming that the School District is willing to work with the City and grant the required easements. The main issue is the requirement to cap the well by the end of 2012. The school well would be used as a peaking well during high demand periods in the summer and would function primarily as a backup well throughout the remainder of the year. With respect to the requirements, staff feels the necessary improvements are cost effective even with the conditions set forth by the MDH since the necessary improvements would be planned in such a way to allow for a future well to be drilled nearby replacing the school well when it is sealed. The new well would be able to G:\ENGIPUBLIC\_2008 Projects\08-08 School well No. 14\bkgd 022508 Council worksessiol1.doc Todd Gerhardt Minnetonka Middle School Well Project February 25,2008 Page 3 utilize a majority of the infrastructure installed to connect the school well to the distribution system. The plan is to connect the school well to the City's system by direct boring a raw watermain from the school well to Well No. 7 located at the comer of Lake Lucy Road and Lake Harrison Circle. The raw watermain would be placed on the site where a new well could be drilled in the future. The water from the school well will receive chemical treatment at Wellhouse No.7 and then be directed down to the low zone system via an existing raw watermain pipe intended for future use as water supply main for the proposed west treatment plant. If the project moves forward, the improvements would be designed to plan for drilling a future well after 2012. This is roughly the same time when the City is planning to consider building the west water treatment facility. The electrical system serving the school well and most of the raw water piping would be sized so that it could be used by the anticipated future replacement well and so would not be lost once the school well is abandoned and sealed. In addition, it may be possible to size the new pump and motor for the school well so that they too would be usable in the future though this is not yet known. The only infrastructure that would not be reused by a new well is approximately 300' of 12" raw watermain pipe, the pitless adaptor on the well itself, and some of the electrical wiring that would run from the electrical vault to the school well. The cost of infrastructure that would not be reused by a new well but is necessary for the school well is estimate at this time to be between $50,000-$90,000. Staff is planning to review this information with the Council and get direction on whether they think the project should move forward. Attachments: CIP Page Drawings c: Brian LeMon, Barr Engineering G:\ENGIPUBLICI_2008 Projectsl08-08 School well No. 141bkgd 022508 Council worksessioIl.doc Capital Improvement Program City of Chanhassen, MN 2008 thru 2012 I Account # 3 Contact Department Water System Improvements Type Unassigned Useful Life Category Utilities P.'iority nJa I Project # W-045 Project Name West Junior High School Well Account # 1 Account #2 I Total Project Cost $715,000 I Description I This improvement will convert the school well from a stand by well into a regular producing municipal well. Currently, the well can only produce 250 gpm. It is anticipated the well could produce as much as 800 gpm. The project consists of a new submersible pump and using some electrical components from well #5 that are anticipated to be decommissioned. A new water main is necessary to be extended to well #7 well house for chemical treatment. Valve improvements are also anticipated to have the ability to bleed this water out ofthe high zone pressure area. I I Justification I To meet the current water demand of the city. I I Expenditures Construction 2008 715,000 715,000 2009 2010 2011 2012 Total 715,000 715,000 I Total I Funding Sources Water Utility Fund 2008 715,000 715,000 2009 2010 2011 2012 Total 715,000 715,000 I Total I I Operational Impact/Other I I I I I I 132 I 25 I (:) o Feet 25 75 I 50 - BARR Figure 1 School Well Site City of Chanhassen Chanhassen, MN