02/28/2001 Env Bd Packet - Laserfiche WebLink

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Memorandum To: Jeff Smyser From: Marty Asleson Date: 02/21/01 Re: EAW Town Center #18 &19. Parsons refer to rate control and treatment of storm water. Are there any specific treatments the writer is referring to? It is believed that increased water volume discharges can also be an impact. Sodium Chloride applied to parking lots may be an impact. Certainly higher concentrations of sodium chloride can have stressing effects on an ecosystem that has already been stressed in the past. There are other deicers that have been used as a replacement to sodium chloride. Has this been investigated? Increased salt can lead to stratification of small lakes and hindering lake turnover. Mobile sodium and chloride ions can readily reach ground water and concentration levels can temporarily increase during low -flow spring - thaws. Annual phosphorous loads from a one acre parking lot is about 2 lbs. /acre /year as compared to .5 lbs. /acre /year for a natural meadow area. Annual nitrogen load is about 15.4 lbs. /acre /year, as compared to about 2lbs /acre /year for a natural meadow area. Phosphorus is the limiting element for plant growth in lake systems. Frequent sweeping can help remove the impacts of impervious to water quality. #26. Although the Herons did indeed relocate last year, it is an6ticipated that the birds may return to this very rare and historic nesting area. Flight patterns observed by Hawkins do not appear to be affected by the location of this project.