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ALAN rl il. Ii :1t TECHNICAL MEMORANDUM <br /> A�'OCIAi1 '. IN( <br /> him& <br /> ENVIRONMENTAL <br /> ENGINEERS AND SCIENTISTS <br /> August 2017 Metersense Water Interval Data <br /> City of San Marcos <br /> Project No.: 0600-018-01 <br /> Date: December 18,2017 <br /> Prepared For: Laurie Moyer, P.E. <br /> Prepared By: Stephen J. Coonan, P.E. (TX No.65516) <br /> INTRODUCTION <br /> The City of San Marcos provides water and wastewater service to customers within its service area. The <br /> City is experiencing continued strong growth, requiring that the City construct improvements to the water <br /> and wastewater system to meet the growing demand. The City has a policy of collecting Impact Fees <br /> from new developments to offset a portion of the cost of providing service to the new customers. <br /> Historically, the Impact Fee was assessed based on the number of Service Unit Equivalents (SUE) <br /> assumed based on the size of the water meter installed with the new development. The City previously <br /> retained Alan Plummer Associates, Inc. (APAI)to conduct an evaluation of this policy. <br /> As demonstrated in the attached Memorandum, the result of that analysis showed that the use of the <br /> water meter size was under estimating the impact that new developments had on the water system. The <br /> under estimation was the result of two factors: first, the capacities of water meters have increased for a <br /> given size over the years resulting in more flow and more SUEs being served; second, the comparison of <br /> the capacity of a larger meter to the capacity of a single-family meter did not appropriately consider the <br /> differences in the probability of peak demands actually occurring. As an example, a new development <br /> with a six-inch meter and a peak flow of 500 gallons per minute (gpm) would be determined to have 50 <br /> SUEs. However, the likelihood that 50 single-family residences would ever have a combined demand of <br /> 500 gpm is very low. <br /> The previous analysis completed by APAI indicated that when considering the likelihood of coincidental <br /> peak demands, the average single family residential customer has a demand of 0.4 gpm. Based on this <br /> analysis, it was recommended that the City redefine the calculation of the number of SUEs by dividing the <br /> peak calculated demand by 0.4 gpm. <br /> Texas Registered Engineering Firm F-13 1 of 4 <br /> m:iproiscts'I) OCIJ I%3 )Ilimpact tees -capacII san mar^os 2017 sue determination docx <br />