Park Water Company is one of three subsidiaries of an investor owned/privately held water utility serving communities in California and Montana providing water for a population of over 200,000. Park Water Company's (PWC) service areas include the cities of Bellflower, Norwalk, Compton, Lynwood, parts of Artesia and Santa Fe Springs and adjacent un-incorporated areas of Los Angeles County.
PWC was mandated to comply with the Stage 2 Disinfectant and Disinfection Byproducts Rule and the Initial Distribution System Evaluation (IDSE) component set forth by the Environmental Protection Agency (EPA). PWC receives the majority of its water from Central Basin Municipal Water District using MWD turnouts. Because of this, under the Stage 2 DBP Rule, PWC had the choice to either do extensive bi-monthly sampling for one year from a new set of estimated sampling locations or use a hydraulic model to determine the water residence times, a surrogate for Trihalomethane levels in water and perform only one round of sampling which is called a System Specific Study (SSS). The new SSS sampling sites would only need one round of sampling and reporting. PWC has three separate systems, Compton East, Compton West and Bellflower-Norwalk, each having their own unique set of facilities and demands. PWC dilemma was to either do the extensive year long sampling and reporting costing the company over $50,000 in lab fees or to upgrade their existing steady-state H2ONET Models to perform extended period simulations (EPS) and produce the needed data in the Rule and a new set of SSS sampling sites. PWC's Engineer and GIS Coordinator, Aaron J. Gutierrez, suggested to PWC's V.P. of Water Quality, Mr. Gary Lynch and General Manager, Mrs. Jeanne-Marie Bruno how upgrading their existing hydraulic models would benefit the company as a whole not only in learning about the system in this study but also these newly upgraded EPS models could be used for contaminant tracing, master planning, and even pre-design and capital improvement. After a close investigation and comparison of cost vs. benefits for each scenario, it was concluded that upgrading the existing hydraulic models would benefit the PWC in the long run and provide the compliance sought from the EPA rule, thus providing the company with a useful tool for less money than the original cost to comply with the Rule.
Beginning in November 2006, one of the first items in upgrading the models was to make sure that all of the piping was up to date and had the necessary input data, as well as modeling all facilities correctly with the needed controls for the calibration day selected. Since MWD reported to PWC that the highest formation of TTHM in their water at PWC's turnouts was in April, PWC engineers concluded that the model would be calibrated for the minimum days in April for each system. Using Customer Information Billing data and SCADA production data, PWC engineers determined these minimum days for each system.
The second item needed to move this project to meet a deadline of April 1, 2007 was to convert the H2ONET models into InfoWater models. This proved to be very easy with the very efficient import tool available in InfoWater. Essentially with the press of one button the PWC H2ONET models were converted into InfoWater Models complete with controls and other necessary input data. PWC was well equipped to use InfoWater since all engineers had access to ArcView or ArcInfo to run the InfoWater modeling tools. The learning curve was minimal as well since all tools and buttons in the H2ONET environment are very similar to those in the InfoWater environment. Another big advantage in using InfoWater was the use of the Demand Allocator tool MWH Soft provides in its modeling suite. After several days of demand data-production adjustments, meter location placement and tabular and manual joining meter locations to billing data, the Demand Allocator tool allowed PWC engineers to do the Closet Pipe allocation which provides the most detailed demand allocation, for any model, in just minutes. The Demand Allocator tool not only improved the results of the models but also reduced the days needed to conduct an accurate demand allocation. Calibration proved to be less labor intensive as well since InfoWater uses ArcMap finding and querying elements needed to adjust for calibration where done quickly.
Since water residence times are used as a surrogate for TTHM levels and is one output data type used to determine the Stage 2 monitoring sites essential for this study, InfoWater and ArcMap worked wonderfully together to produce and illustrate this. Adding other existing data like water quality results for TTHM, HAA5, chlorine residuals and heterotrophic plate count (HPC) bacteria allowed PWC the Water Quality VP to determine the locations of the new Stage 2 SSS monitoring sites and illustrate this to those state regulators needing to approve the study.
The result was an overall calibration with an overall error of 5.5% for all flows and 6.2 % error for all pressures for points used in calibration and 3.8% error in the all important tank levels needed for this study. EPA uses tank levels as a measurement of accuracy when using hydraulic models to comply with the IDSE Stage 2 Disinfectant and Disinfection Byproducts Rule. PWC presented the entire processes to the California Department of Health Services engineers overseeing the study for the EPA and has submitted the necessary documentation, system modeling maps and results (see attached) to the EPA and the California Department of Health Services engineers who all have accepted the results. PWC has begun sampling using the new Stage 2 sampling sites and is getting ready to finish the sampling later this month.
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