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resourceful. naturally. BARR <br />engineering and environmental consultants <br />Technical Memorandum <br />To: Lanya Ross, Anneka LaBelle, Ali Elhassan <br />From: Evan Christianson, Ray Wuolo <br />Subject: Metro Pumping Optimization 3 <br />Date: April 2, 2015 <br />Project: 23/62-1087.01 <br />1.0 Introduction <br />This technical memorandum describes the optimization of pumping in the seven -county metropolitan <br />area. The goal of the optimization was to maximize total pumping from existing permitted wells while <br />meeting constraints on baseflow, hydraulic head, flow direction, and flux to/from surface water features as <br />specified by the Metropolitan Council. The optimization uses the steady-state version of the Twin Cities <br />Metropolitan Area Groundwater Flow Model, Version 3.0 (Metro Model 3; Metropolitan Council, 2014) <br />Optimizations described in technical memorandums dated August 15, 2014 and October 13, 2014 <br />(Barr, 2014a and Barr, 2014b), herein referred to as Optimization 1 and Optimization 2, are similar and <br />complimentary to the optimization described in this technical memorandum, herein referred to as <br />Optimization 3. <br />2.0 Optimization Software, GWM-VI <br />The Groundwater Management (GWM) Process for MODFLOW, developed by the USGS (Ahlfeld et al., <br />2000), was used for the optimization. The version used was GWM-VI (Banta and Ahlfeld, 2013) which <br />allows for parallel processing. No changes were made to the source code of GWM-VI for implementation <br />of this project. All optimization algorithms described in Banta and Ahlfeld (2013) and Ahlfeld et al. (2005) <br />are implemented with no change. However, several pre- and post -processing steps were used to <br />overcome hardwired limitations on the type of constraints available with the standard GWM-VI <br />implementation and are discussed in Section 2.3. Optimizations utilizing GWM-VI require two main inputs: <br />decision variables and constraints; each is discussed below. <br />2.1 Decision variables <br />Decision variables are quantifiable controls that are to be determined by the GWM-VI optimization <br />algorithms (Ahlfeld et al., 2000). Decision variables for both Optimizations 1, 2, and 3 were identical and <br />were provided to us by Metropolitan Council. They include existing permitted wells in the seven -county <br />metropolitan area open to any aquifer, except the Mt. Simon Hinckley aquifer, and with use codes from <br />Barr Engineering Co. 4700 West 77th Street, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com <br />