1. Preliminary Findings* of the 12-State MTBE/VOC Drinking Water Retrospective A cooperative study by the USGS and the USEPA Stephen Grady U.S. Geological Survey East Hartford, Conn. (860) 291-6758 sgrady@usgs.gov Michael Osinski U.S. Environmental Protection Agency Washington, D.C. (202) 260-6252 OSINSKI.MICHAEL@epamail.epa.gov PROVISIONAL--Information included in this presentation is preliminary and subject to revision * additional analysis of data will be conducted through mid-1999 with a final interpretive report planned for release in December 1999

2. Design n 12 Northeast and Mid-Atlantic States n Only community water systems (CWSs) n Representative sample of 20% of all CWSs n Stratified-random selection by source of water, size of system, and State n Water-quality data for 1993-98 obtained from State Agencies PROVISIONAL--Information included in this presentation is preliminary and subject to revision

3. Major Points--for 10-States* MTBE detected in drinking water from: 7% of CWSs at concentrations > 1  g/L 2% of CWSs at concentrations > 5  g/L 1% of CWSs at concentrations > 20  g/L MTBE detected in drinking water from: 7% of CWSs at concentrations > 1  g/L 2% of CWSs at concentrations > 5  g/L 1% of CWSs at concentrations > 20  g/L MTBE projected to affect: ~600 CWSs at concentrations > 1  g/L ~180 CWSs at concentrations > 5  g/L ~ 80 CWSs at concentrations > 20  g/L MTBE projected to affect: ~600 CWSs at concentrations > 1  g/L ~180 CWSs at concentrations > 5  g/L ~ 80 CWSs at concentrations > 20  g/L PROVISIONAL--Information included in this presentation is preliminary and subject to revision * no MTBE data for drinking water in DE and PA

4. Major Points--continued n MTBE detected in 15% of CWSs in RFG/OXY* areas and 3% outside n BTEX detected in ~5% of CWSs, but not with MTBE n VOCs co-occur in ~half of samples with MTBE; mostly solvents & THMs PROVISIONAL--Information included in this presentation is preliminary and subject to revision * where oxygenate used is MTBE

5. PROVISIONAL--Information included in this presentation is preliminary and subject to revision

6. Projecting MTBE occurrence for all community water systems PROVISIONAL--Information included in this presentation is preliminary and subject to revision

7. MTBE detected* 5 times more often in drinking water from CWSs in RFG/OXY areas * at concentrations > 1  g/L Percent of CWSs

8. PROVISIONAL--Information included in this presentation is preliminary and subject to revision