Tamarack Negotiation with Boulder/Centennial

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September 18, 2008 To: SPWRAP From: Steve Sims Re: Tamarack negotiations with Boulder/Centennial I asked Ronni if there was any change in the Boulder/Centennial position due to the entry of the recent Logan decree that used a 120 feet per day standard (Streambed Leakance expressed as (Ksb3/M4)) and she said na I asked Ronni if she would accept the top range that her experts' opinion (2.6 feet per day) as a compromise to settle the case and she stated that she would consider that proposal. The question for SPWRAP is whether they want to hold fast on the 20 foot per day standard of whether they would e willing to settle for less? Ronni's experts' opinion on the proper leakance factor ranges from 0.011 per day to 2.6 and this is based on the Dinsdale well pumping test done by DOW in conjunction with the other opposers. This is not the same as the Dinsdale decree which used the 20 foot per day number in their MODFLOW model. I have attached a table that shows the way different consultants looked at the same data (see Dinsdale APT.pdf, which Mary refers to below as Table 1). Mary Halstead explained the difference in data analysis as follows: Inspection of Table 1 indicates that the parameters derived from the Stieb test were moderately consistent. However the Dinsdale APT results varied significantly depending upon the party doing the analysis. Site conditions for the Dinsdale APT were much more complex than at the Stieb APT, thus requiring more complexity and detail in the analysis. These complex site-specific conditions at the Dinsdale site are detailed below: •The higher stream flow rate, lower pumping rate, and larger distance between the pumping well and the river at the Dinsdale site, resulted in correspondingly smaller changes in stream flow that could not be accurately measured. •The Dinsdale pumping well is partially penetrating. Thereby, it was more difficult to identify river or streambed impacts from the drawdown curves for the two monitor wells next to the pump. •The stream stage elevations significantly declined during the testing period due to a large drop in river flow rate. The stream flow rate at the beginning of pumping was approximately 150 cubic feet per second (cfs) which dropped to approximately 50 cfs by the end of the test. This necessitated adjusting monitor well drawdowns thereby imparting additional speculation on data interpretation. Due to this complexity of analysis and increased speculation involved with the Dinsdale test, CDOW recommends that the Hydrosphere recommended streambed parameters derived from the Stieb test be used to calculate stream depletions for the wells at the TRSWA Recharge Project.