Agenda - Environmental Policy Board - 10/15/2018

Home

compares extremely well with the projected residential population at the RTC site of 10,378 persons (Table 13.6). Similarly, the total future projected water usage for 2020 is estimated to be 4.505 MGD which equates to an equivalent population of about 30,000 persons. In comparison, the information contained in Tables 13.1 and 13.2 estimates the 2020 population served by the community water system to be approximately 28,000 persons. The difference between the two of 2,000 equivalent persons is in line with the 2001 Comprehensive Plan and can be attributed to two factors. First, the number of new housing units to be built between 2000 and 2020 was estimated in the Plan to be 4,800 (3,346 single family and 1,434 multi -family units). Of this amount, we now know that the RTC site will contribute 2,400 housing units alone while using only a small percentage of the land available for development within the Urban Growth area. Secondly, the Plan did not consider the higher water usage per acre of developed land using the higher density development model inherent in the RTC design. The historic peaking factor for water usage is about 2.6. Based on the above, the peak daily flows for 2020 will be about 11.7 MGD. Potential impacts on the FIG or other resources during average and peak demand are discussed in Appendix F. In addition, storage and distribution designs for the RTC and future development should take into account the need to meet these demands. In short, growth projections and the assumed resulting water usage estimated in the 2001 Comprehensive Plan seem to be generally in line with the projections of this Item. The difference discussed above, which is based on design and growth information not available during the preparation of the Comprehensive Plan, results in an increase in future water usage of about 7% above that anticipated. Summ ry of Environmental Impact. To meet the projected future demands, the City will most likely increase appropriations from the Franconia -Ironton -Galesville (FIG) aquifer. At a minimum, two additional wells (#6 and #7) will be required to meet the RTC demand with the need for additional wells as growth continues. Appendix F indicates that at full 2020 build out, there will be a need for as many as 4 or 5 additional wells pumping at rates similar to the existing ones. Groundwater level data for the FIG that is collected continuously by the City shows that trending has been in an upward direction in the last two years meaning a recharge condition existed during this period (Appendix F). In addition, because the pumps operate intermittently, they allow the aquifer to recover on a daily basis with a maximum residual drawdown level averaging of 5- to 10-feet during peak summer demand. This would mean that the radius of influence for the wells is very, very small. Taken together, that water levels are rising in the FIG and that there is very little drawdown, water level fluctuations in the surficial drift material are not anticipated. In addition, it does not appear that the municipal wells would have any negative influence on private wells developed in the same unit. However, long term monitoring of the surficial aquifer's 13-7