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Reviewing UAW and RGPCD Numbers
In the Main - A technical assistance newsletter for Public Water Suppliers
September 2008 By Richard Friend
MassDEP has reviewed the Unaccounted for Water (UAW) and Residential Gallons per Capita Day (RGPCD) performance standard values submitted by water suppliers in their 2007 Annual Statistical Reports (ASR). The performance standards are included in Water Management Act registrations and permits. The values were reviewed for mathematical errors and for consistency with the procedures outlined in the ASR Instructions.
MassDEP adjusted the 2007 UAW values upward by an average of 2.7%. This is an improvement over the 2006 UAW adjustments, which averaged 3.0%. Of the 249 UAW values reviewed, 17 were adjusted downward between 1% and 8%, 101 were left unchanged, 88 were adjusted between 1% and 5% upward, 24 were adjusted between 6% and 10% up, and 19 were adjusted upward between 11% and 33%. Due to insufficient information, 25 UAW values could not be evaluated.
Reasons for the UAW adjustments varied, but the most common reason was lack of documentation of Confidently Estimated Municipal Use (CEMU) volumes for hydrant flushing, fire fighting, etc. In general, documentation of CEMU volumes greatly improved over the 2006 ASRs. Another common adjustment was made if water suppliers claimed common leakage as water main break volumes, especially when leaks occurred for uncertain and/or lengthy periods of time. Other reasons for adjusting UAW values included errors in transposing data from other sections of the ASR and mathematical errors.
MassDEP also reviewed RGPCD values included in the 2007 ASRs. Of the 250 values reviewed, 24 were adjusted downward between 1 and 34 gpd, 170 were left unchanged, 37 were adjusted upward between 1 and 5 gpd, 11 were adjusted upward between 6 and 19 gpd, and 8 were adjusted upward between 22 and 65 gpd. The average of the adjustments was 1.4 gpd upward. RGPCD values for 21 PWSs could not be evaluated due to insufficient information.
Reasons for adjusting the RGPCD values included errors in math, errors in transposing data, using total metered volume (instead of residential metered volume), and using the wrong average household size for estimating population in partially served communities.
At the end of April 2008, MassDEP sent a letter to each water supplier stating their reported and MassDEP-adjusted values for UAW and RGPCD. The letter included the reasons for any adjustments to the values. In response, approximately 50 suppliers provided additional information in support of their UAW and/or RGPCD values, mostly documentation of their CEMU volumes.
MassDEP will use the adjusted UAW and RGPCD values in the coming years to assess compliance with performance standards included in Water Management Act registrations and permits. The trends over time of the performance standards for each supplier will be considered when assessing compliance, so that if a PWS has high values this year, but is taking action that is expected to reduce the values in coming years, then MassDEP will consider the downward trend as progress toward compliance.
The 2007 adjusted UAW and RGPCD values for all public water suppliers are posted on MassDEP's website at http://www.mass.gov/dep/water/resources/rgpcd06.htm. If you have any questions regarding the UAW or RGPCD values, please call Richard Friend in the Boston office 617-654-6522 or email him at richard.friend@state.ma.us.
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