Agenda - 03-23-2000 - 7 - Laserfiche WebLink

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3 MEMORANDUM TO: County Commissioners John Link, County Manager FROM: Paul Thames, PE, County Engine DATE: March 20, 2000 SUBJECT: Preliminary summary of the evaluation of relationship between water use and home size in the Efland area The BOCC, at the 19 October 1999 meeting and public hearing on revisions to the "Rules and Regulations for Operation of the System" for the Efland sewer system, adopted a revised fee structure for access and taps onto the system. The Board did, however, direct staff to conduct a study of water use in the Efland area to determine if there was a demonstrable correlation between water use and size of dwellings. The underlying concept was to ascertain (in a manner similar to a recent OWASA water and sewer availability fee study) if a sliding scale of availability fees determined by home size could be justified on the basis of varying degrees of service demand impact on the system. Accordingly, County Engineering Associate Abdoul Koura -Bodji has spent approximately 300 hours in the process of collecting, evaluating, manipulating and analyzing water use and property tax record data on current Orange - Alamance Water System customers. The data collection effort has been targeted at those customers living in the area that would become a part of a built -out Efland sewer system if that system were developed in accordance with the 1986 sewer master plan. The study area includes approximately 532 metered customers of Orange - Alamance (the area also contains an unknown number of homes served by on -site wells). However, the analysis of water use relative to home size eventually came to include only 458 customers. Forty-two customers were eliminated as non - residential users. An additional thirty-two customers were eliminated because the water use records were problematic (building may have been unoccupied, for example) or because the customer records could not be matched with the County's property and property tax data (size of building could not be determined). Of the 458 customers included in this analysis, 348 were in "stick - built" houses and fixed foundation double -wide mobile homes (both types of dwelling having property tax data that includes heated square footage). The remaining 110 customers were in single -wide mobile homes that were assumed to have a maximum size of 700 square feet. The average home size, excluding the single wide trailers, was found to be 1320 square feet with an average monthly water use of 4370 gallons. The average water use for the single -wide trailers — with the assumed average size of 700 square feet — was found to be 4150 gallons per month. Analysis of the data collected for the customer base described above does show a relatively consistent and direct correlation between the size of a home and the amount of water used if the water use of the single -wide mobile homes is not included in the analysis. The water demand for the single wide mobile homes, when compared to the square footage of the units, is such that it skews the analysis. When home sizes are separated into five ranges — less than 900 square feet, 901 to 1200 square feet,