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HomeMy WebLinkAbout10A - Report Regarding Well No. 10PRIp~ ti U ~ ~~INNSSO~/ 4646 Dakota Street SE Prior Lake, MN 55372 CITY COUNCIL AGENDA REPORT MEETING DATE: NOVEMBER 1, 2010 AGENDA #: 10A PREPARED BY: STEVE ALBRECHT, PUBLIC WORKS DIRECTOR PRESENTER: STEVE ALBRECHT AGENDA ITEM: CONSIDER APPROVAL OF A REPORT REGARDING WELL NO. 10 AND WATER SUPPLY OPTIONS DISCUSSION: Introduction The purpose of this agenda report is to review proposed Well No. 10 and potential water supply alternatives. History Prior to 2001 the City of Prior Lake only operated three municipal wells leaving the City vulnerable to water supply shortage during large fire events or hot summer days characterized by heavy lawn sprinkling. When use exceeded the City's supply capacity, the City utilized water from Savage (if available) or imposed watering restrictions to protect the system. Between 2001 and 2007 the City added Wells 6, 7, 8 and 9. By comparison to our neighboring communities, Prior Lake currently has about 33% less pump- ing capacity per capita than both Savage and Shakopee. Prior Lake's sto- rage capacity is 58% and 48% less per capita than Savage and Shakopee respectively. It should be noted that Shakopee does have a significant amount of commercial water use and that Savage, in addition to the above pumping capacity, has access to up to 700 MG of surface water from Burnsville. An adequate water system serves two very important purposes. The sys- tem should be able to provide water supply and fire protection to the com- munity simultaneously. This means that on a peak water supply day the City must be able to maintain a system pressure of at least 20 psi. The Fire Department needs between 2,000 and 3,500 gpm (house fire) and a minimum of 20 psi of system pressure to fight a fire. The City maintains system pressure by keeping adequate water supply in the City's two ele- vated water towers. When system demand exceeds supply the tower le- vels drop and system pressures can drop below 20 psi in several areas of town. Because a house fire can utilize up to 3,500 gpm and the City's wa- tersystem currently can only produce 5,000 gpm the City's ability to fight a fire could be compromised on high use days. Since 1998 the City has ex- perienced low pressure periods of below 20 psi on several occasions, the most recent being early last fall when due to a watermain break the City system pressures dropped to below 20 psi for about one hour. Annual water use in the City of Prior Lake has grown from under 500 MG in 1998 to nearly 900 MG in 2007. The peak day water use has grown from 3.75 MGD in 1998 to over 7.0 MGD in 2007. Over the last three years both C:IDocuments and SettingslcgreenlMy DocumentslSharePoint DraftslWell 10 Agenda.doc the total use and peak days have decreased due mainly to three factors: 1) Economy 2) Weather (Precipitation/Temp) and 3) Building Construction slow-down. In 2007 the City's peak day use jumped to 1 MGD more than the City had experienced in any previous year. This jump in use was a result of a very dry summer and new landscaping associated with the substantial number of new homes constructed over the previous years. On several occasions that summer the City had to open up the Savage interconnect to refill the City's water towers. The City was fortunate that Savage had adequate supply available and that no major fire events occurred on the days of shortage. The existing interconnect between Prior Lake and Savage is not automated and the flow cannot be controlled other than on or off. This re- sults in the interconnect only being useable to re-fill the City's towers ma- nually. The interconnect provides no ability to react to a fire event as it takes time both for a low pressure issue to be detected and for staff to be dispatched to manually turn the interconnect on. This operation takes about 20 minutes or more with staff in town on duty, and 40 minutes or more after hours. Additionally, because it is not automated, it takes up to four staff to visually monitor the system during operations. Staff needs to be posted at each water tower to report when the overflows begin along with staff monitoring the City's SCADA (City's Computerized Water System Controls). In 2006, based on growth and water supply demand, the City Council au- thorized construction of Well No. 10. Due to concerns about the Savage Fen the DNR required that Well No. 10 be built on the west side of Prior Lake. A bedrock valley runs along Spring and Prior Lakes providing a bar- rier to protect the Fen from water pumped on the west side of Prior Lake. The Savage Fen is a protected calcareous fen that's primary source of wa- ter is ground water derived from the Prairie du Chien-Jordan Aquifers. The Jordan Aquifer is the City of Prior Lake's primary water source. Prior to construction of Well No. 10, the City initiated test drilling to ensure adequate aquifer supply would be present. The City drilled several test holes and determined that the Jordan Aquifer did not exist over a large area on the west side of Prior Lake. Based on that information, construc- tion of Well No. 10 was canceled. In 2007 the DNR agreed that, due to wa- ter supply restrictions, an additional Jordan well could be constructed on the east side of Prior Lake if the City reduced the use of Well No. 5 during normal conditions. The City proposed to construct Well No. 10 near Fire Station No. 1 after completion of the Water Treatment Facility (WTF). Transmission piping was installed from the proposed location of Well 10, near Fire Station No. 1 to the WTF site as part of the CR 21 and Brooksville Hills Reconstruction Projects. By constructing the well after the WTF the City would realize about $600,000 in project savings as a well house and separate treatment equipment would not be required. In June 2010, the City Council approved the Capital Improvement Program with Well No. 10 construction scheduled for 2011. Current Circumstances Since approval of the CIP with Well No. 10 included, several factors have changed that might modify the City's plan to meet peak day and fire flow needs. In 2010 the City of Savage increased their use of Burnsville Sur- C:1Documents and Settingslcgreen\My DocumentslSharePoint DraftslWell 10 Agenda.doc 2 face Water Treatment Facility substantially increasing the amount of non- designated supply available. Savage's agreement with Burnsville allows them to take up to 700 MG per year. The City of Prior Lake and the SMSC staff agreed on a joint water system study that could provide for open con- nection of the SMSC's northern system to Prior Lake thereby increasing system capacity. This study is budgeted for early 2011. Both of these in- terconnect options provide viable alternatives that should be considered by the City Council prior to proceeding with Well No. 10. Conclusion The City's water system in its current state can provide domestic water to the community in most circumstances. However there are circumstances under which the City would struggle to provide sufficient flow to the com- munity in the event of an emergency, water break or well failure. Staff, therefore, recommends that a water supply options report be pre- pared that evaluates cost and water supply/fire protection viability for the following options: 1) Well No. 10 2) Automated Interconnect with City of Savage 3) Automated Interconnect/Joint Northern Water System w/ the SMSC Quite simply, this report will identify the most productive and frugal way to add peak pumping capacity to meet emergency needs into the foreseeable future. Once the report is accepted and reviewed by the City Council the best op- tion for the City can be implemented at the City Council's discretion. By completing the study and presenting it to the Council in February all options could still be completed in time for the 2011 peak water season. Pending the recommendations of the report, City staff recommends the City Council proceed with system capacity improvements in 2011 to address system supply and fire flow deficiencies. ISSUES: As noted in the history discussion above, the City currently has two major issues related to water supply and fire protection: 1) If a large fire were to occur on a peak water use day, the City may be unable to provide adequate fire pressure throughout the City. 2) If the City were to have one of our three large wells out of service, a high use water day, and a fire occur, the City may be unable to provide adequate supply or fire pressure throughout the City. In addition to the above events based on the City's current water produc- tion capabilities, if a large watermain break or any of the above scenarios were to occur, a brown water event will most likely occur. When the City's towers are drained, the sudden changes in water flow direction or surges in the system result in iron and manganese that accumulated in the system prior to the construction of the WTF breaking loose from pipes causing brown water events. Brown water events such as the one experienced due to a watermain break in 2009 cost the City upwards of $20,000 in addition to the private costs due to damage to appliances and personal property. C:1Documents and SettingslcgreenlMy DocumentslSharePoint DraftslWell 10 Agenda.tloc 3 Due to these issues the City staff believes the City should move to remedy this issue in 2011 either via installing an automated interconnect between Prior Lake and either Savage or the SMSC or by the construction of Well No. 10. FINANCIAL IM- The Water Supply Options Report will detail costs. Failure by the City to PACT: proceed with remedying the fire flow situation could increase the City's lia- bility in the event of a fire. The options being considered include interconnects and a well. The annual cost of these facilities depends on their use and the cost of water. An in- terconnect has a lower up front capital cost and minimal annual cost if it is o~ used as an emergency source. If the interconnect is to be used to provide a water supply equal to that of a new well, the costs will be dramat- ically higher. The annual cost to provide 100 MG (average annual water supply from a new well) from an interconnect with Savage is $268,000 an- nually based the rate supplied by Savage for this analysis. Over a well life of 50 years, that is $13,400,000. The annualized cost to the City of con- structing, operating and maintaining a well over a 50-year life is about $25,000 per year. The difference is due to the cost of water purchase ver- sus direct pumping. The purchase cost includes a portion of the selling entity's infrastructure and O & M costs. The report will detail the impacts on costs if a long term agreement with Savage were to be executed. The interconnect costs with the SMSC are unknown at this point because that proposal involves a joint system which could dramatically impact the costs. All costs of available options will be detailed in the Water Supply Options Report. ALTERNATIVES: 1. Direct staff to complete a Water Supply Options Report. 2. Deny the resolution and direct staff to provide specific information. 3. Take no action. RECOMMENDED Alternative No. 1 MOTION: Re ~e ed i' Frank oy a it Manager C:1Documents antl SettingslcgreentMy DocumentslSharePoint DraftslWell 10 Agenda.tloc 4