Agenda - Parks and Recreation Commission - 05/08/2003

Home

replanted to native trees, shrubs, ~asses and forbs and if appropriate, a temporary cover crop will be established. Item 13 Mitication Element. Because the RTC site is within a DB/SMA, special precautions are needed to protect groundwater resources. To make sure this occurs, any discharge of runoff into an area dedicated to infiltration will be pre-treated through such practices as particulate sealing, vegetative filtration, sk/mming, installation of compact, sub-grade treatment (ex. catch basin inserts, cyclonic separators, filters), and var/om types of pre-treatment soil filtering systems. These practices Mi1 be routinely maintained and. inspected to make sure these pre-treatment practices do not provide a pathway for contamination of groundwater. Areas that are potential ma/or sources, of contamination ("hot-spots") will be identified during construction and special precautions added. These areas would include any location where pollutant spills We more likely to occur (service stations, public works/police/fire fueling operations, significant chemical storage). Within WIq[PAs, the use of conventional under~ound storage tanks to store anything: other than water is restricted. If underground tanks are utilized in these areas they must be double-walled with interstitial sensors and a network of monitoring wells must be installed to assess potential ~oundwater contain/nation. In addition, an emergency response plan should be developed for the immediate remediation of any spills or leaky tank~. When assembling the issues that were to be addressed as part of this AUAt% it was noted by the Anoka Conservation District and by the DNR that there is a possible cormection between the increased demand for municipal ~oundwater and the observed lowering of wetlands in the vicinity of Municipal Wells..3, 4 and 5. Appendix F was prepared to assess the general magnitude of the problem and the solutions required to address the issue. It is now apparent that the wetlands in question experience natural drying during periods of relative low precipitation. The photographic history included as part of the Wetland Delineation report shows wetlands in the vicin/ty of the RTC site disappearing during the mid to late 1980's which is prior to the development of the municipal wells. I'his same phenomenon occurs again in the mid to late 1990's and pr/or to the installation of Wells 4 and 5. The evaluation also found, as stated earlier, that drawdown levels [n the - FIG unit are minimal and, therefore, could not be influencing the wetlands. To verify these f'mding, however, it is recommended that long term monitoring be performed. There is also some concern that increased pumping in the FIG aquifer could impact private wells that pump from this aquifer. Again, the residual drawdown levels in the' FIG average 5- to 1 O-feet during the peak summer pumping period (Appendix F) iud recover fully during the Fall, Winter and Spring. Therefore, the radius of' influence of the wells will be very- small meaning there could be no impacts to private wells developed in the same unit. Before additional wells are constructed, additional appropriations will be applied ~'~- through the" DNR. This will most likely require both short- and long-term testing and monitoring to verify the above findings. Through this process, the-City can insure that there continue to be no impacts on gToundwater and surface resources due to their appropriations from r. he FIG.