Embed Size (px)
Citation preview
EPA Update/
40 Ground Water Monitoring & Remediation 29, no. 3/ Summer 2009 NGWA.org
Journal compilation © 2009 National Ground Water AssociationNo claim to original US Government works.
Regulatory Performance of Community Water Systems Supplied by Ground Water under the Influence of Surface Waterby Charles Job
A category of community water systems (CWS) that has unique physi-cal and regulatory characteristics is water systems supplied by ground water under the direct influence of sur-face water (GUDI). While it is a small group of water systems, they serve nearly 10% of the publicly supplied population in the United States. Their regulatory performance as a group is not as good as other directly supplied water systems. However, if they pur-chase their GUDI water, they may have a somewhat better regulatory perfor-mance.
GUDI is defined as any water beneath the surface of the ground with significant occurrence of insects, other macroorganisms, algae, or large diam-eter pathogens such as Giardia lamblia or any water beneath the surface of the ground with significant and relatively rapid shifts in water characteristics such as turbidity, temperature, con-ductivity, or pH that closely correlates with climatological or surface water conditions (40 CFR 141.2).
The determination of GUDI is based on criteria set by states and mea-sured through water quality analysis or documentation from well construc-tion or field geological evaluation. These waters may result from ground water–surface water interaction that has received significant attention in the literature, but has characteristics more like surface waters that affect their quality. Thus, they are regulated
under the Safe Drinking Water Act as surface waters.
GUDI and GUP SystemsFrom the U.S. Environmental Pro-
tection Agency’s inventory of drink-ing water systems, GUDI systems comprise 0.9% of all CWS (defined as a system that serves at least 15 ser-vice connections used by year-round residents or regularly serves at least 25 service connections used by year-round residents). Additionally, water systems that purchase GUDI water from a GUDI system are GUDI “pur-chase” systems (GUP) that account for another 0.2% of CWS. Together these systems served 2,903,529 persons in 2008, or 9.9% of the population served by CWS. Table 1 provides details on the distribution of these water systems by size.
Regulatory PerformanceIn 2008, GUDI and GUP CWS ac-
counted for 3070 violations or 1.2% of all CWS violations. Sixty-six percent of these violations were for not con-ducting monitoring or not reporting monitoring results. Of the remaining violations, 325 were because of an exceedance of a maximum contami-nant level (MCL, the maximum con-centration of a contaminant allowed to be present in drinking water based on health determinations) or of a treatment technique (TT) not being properly ap-plied. The other violations were related
gwmr1250.indd 40gwmr1250.indd 40 7/25/09 6:48:51 PM7/25/09 6:48:51 PM
From wireless data collection in the field to data analysis and reporting in the office, Diver-NETZ*, fromSchlumberger Water Services, integrates superior field instrumentation with the industry’s latestcommunication and data management technologies.
� Connect wirelessly to your groundwater monitoring networks and dramatically improve data collection in the field - up to 70% more efficient than traditional field collection methods
� Achieve precise measurements of groundwater levels, temperature, and conductivity† with a completely expandable, industry-proven technology
� Enjoy a complete suite of dataloggers, transceivers, desktop, and handheld software� Transfer your valuable data to robust software for analysis and reporting
Our field to office products enable you to effectively manage your groundwater resources for the long-run.For more information, call us at 519-746-1798.
Technology integration without boundaries
©Schlumberger * Mark of Schlumberger † Available exclusively with CTD-Diver*
Groundwater Monitoring Networks
gwmr1250.indd 41gwmr1250.indd 41 7/25/09 6:48:53 PM7/25/09 6:48:53 PM
42 Ground Water Monitoring & Remediation 29, no. 3/ Summer 2009 NGWA.org
Table 2Violations in 2008 by System Size (Population Served) and
Violation Type
Water System Type System Size
Violation Type
MCL TT MR Other Total
CWS-GUDI Very small 38 143 1098 217 1496Small 14 60 357 66 497Medium 1 7 81 7 96Large 3 3 40 46Subtotal 56 213 1576 290 2135
CWS-GUP Very small 2 1 14 9 26Small 4 5 20 29Medium 1 1Large 4 4Subtotal 7 6 38 9 60
Total 63 219 1614 299 2195
Table 3Health-Based Violations at GUDI and GUP CWS in 2008
ViolationsSystems in Violation
Population in Violation
Total Systems
Total Population
Systems with Health-Based Violations (%)
Population Receiving Drinking Water from Systems with
Health-Based Violations (%)
All CWS 12,535 5786 23,346,498 51,988 292,300,076 11.1 8.0CWS-GUDI 269 132 278,332 481 2,663,600 27.4 10.4CWS-GUP 13 6 10,812 99 239,929 6.1 4.5Note:CWS-GW 7698 3995 7,007,260 37,912 84,645,089 10.5 8.3CWS-GWP 174 111 183,615 2389 3,393,958 4.6 5.4CWS-SW 3198 1003 12,699,950 4408 143,254,086 22.8 8.9CWS- SWP 1183 539 3,166,529 6683 57,937,031 8.1 5.5
to failure to provide public notification or consumer confidence reports.
For health-based violations (vio-lations of MCLs or treatment tech-nique requirements), 95% occurred at
Table 1Inventory of Water Systems
PWSType Category
Size Distribution of Water Systems (range of population served by water systems in size category)
Grand Total
Very Small (25–500)
Small (501–3300)
Medium (3301–10,000)
Large (10,001–100,000)
Very Large (100,001 or more)
All CWS Total Systems 29,160 13,858 4838 3728 404 51,988Total Population 4,857,104 19,868,795 28,134,557 106,310,834 133,128,786 292,300,076
CWS-GUDI Total Systems 235 164 46 30 6 481Total Population 44,785 235,551 267,156 768,674 1,347,434 2,663,600
CWS-GUP Total Systems 45 35 13 6 0 99Total Population 9445 53,266 80,355 96,863 0 239,929
systems serving 3300 or fewer per-sons. Table 2 provides further detail by violation type.
For health-based violations, GUDI CWS had a higher percentage of its
group with health-based violations in 2008 than the “average” CWS. GUP systems were below the average, as shown in Table 3. Notably, GUDI sys-tems had a significantly higher per-centage of systems with health-based violations than systems supplied by ground water (not under the direct influence of surface water) and mar-ginally higher than CWS receiving surface water supplies. Most health-based violations were due to not meet-ing requirements of the rules relating to surface water treatment, disinfection byproducts, total coliform, and lead and copper.
More information on these and other data are available from the Office of Ground Water and Drinking Water on its website athttp://www.epa.gov/safewater/databases/pivottables.html.
This article was prepared by Charles Job, Office of Ground Water and Drinking Water, Washington, DC 20460, based on information available from EPA’s website and is not a state-ment of EPA policy.
gwmr1250.indd 42gwmr1250.indd 42 7/25/09 6:49:00 PM7/25/09 6:49:00 PM
gwmr1250.indd 43gwmr1250.indd 43 7/25/09 6:49:01 PM7/25/09 6:49:01 PM
