#08 - Irrigation Alternatives for Oak Land Middle School

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Nathan Fuerst, City Administrator, City of Lake Elmo Oak-Land Middle School 2 of 6 Site Data The athletic fields that are currently irrigated by the School District are located on the northern side of the school property and within the existing athletic track. The total area of these athletic fields is about 297,000 square feet or 6.8 acres (see attached aerial photograph of the Oak-Land Middle School site). Current water use for irrigation of the athletic fields is about 15,980 gallons (2,136 cf) per day (based upon well data averaging monthly use quantities). The well was constructed in 1966 and has experienced more frequent repairs and maintenance over the past 10 years. The current well is 315 feet deep and the well is permitted through the Department of Natural Resources (DNR) for use of up to 4.3 million gallons per year. Irrigation Using Well Water The first alternative reviewed is using well water to irrigate the athletic fields. The current location of the existing well conflicts with the proposed improvements at the site that are a part of the current building addition and renovation project. This and in consideration of the current age and condition of the well, a new well would be required at the site. The DNR has indicated that typically a new well to replace an existing well would be permitted as long as the water use did not exceed that of the existing well. However, the DNR indicated this could not be assured in this situation with the regional water issues. A Preliminary Well Construction Assessment Application would be required by the DNR to evaluate the impacts of the well. Assuming a new well of similar size, depth, and capacity was allowed for irrigation of the athletic fields, well contractors have provided costs of $160,000 to install a new well. In addition to the well costs, associated costs for related electrical for power to the new location and modifications to the existing irrigation system would add additional costs of about $45,000, making the overall cost for this approach to be about $205,000 (not including maintenance and operation costs). However, as indicated previously the School District’s desire was to not use well water due to potential future health risks. The Minnesota Department of Health (MNDH) when contacted also mentioned concerns about potential health risks related to PFAS – Polyfluoroalkyl substances. This contamination is a concern in the east metro area based upon the MNDH (see attached PFAS Contamination Map). Review of Metropolitan Council PFAS maps indicates areas close to the Oak-Land Middle School that have PFAS contamination. Irrigation Using Water Re-Use with Underground Storage Tanks Another alternative reviewed is re-using water stored within new underground storage tanks for irrigation of the athletic fields. Permitting of re-use systems falls under several jurisdictions such as the MNDH, Minnesota Pollution Control Agency (MPCA), DNR, Minnesota Plumbing Code, and the Cities where the systems are located. This permitting could complicate the process and design considerations of the systems. However, the MPCA and the City of Lake Elmo do have guidelines for water re-use and for purposes of this review, we followed those general guidelines. The basic components of the water re-use system consist of the water source (storage tank), a pump or pumps to convey water through the system to the irrigation system, and filtering and treatment of the water before re-use in the irrigation system (see City of Lake Elmo Standard Drawing C-02). MPCA and City guidelines recommend filtering sediments and particulates from the water and treating the water with UV light and chlorination to address health and safety concerns.