FINAL PHASE I REPORT STATEWIDE METHYL TERTIARY BUTYL ETHER RISK ANALYSIS FOR THE STATE OF NEW HAMPSHIRE Prepared for: NEW HAMPSHIRE DEPARTMENT OF ENVIRONMENTAL SERVICES 29 Hazen Drive P.O. Box 95 Concord, New Hampshire 03302-0095 Prepared by: WESTON SOLUTIONS, INC. One Wall Street Manchester, New Hampshire 03101-1501 August 2006 W.O. No.20111.010.001.7000 TABLE OF CONTENTS Section Page EXECUTIVE SUMMARY .................................................................................................... ES-1 1. INTRODUCTION.......................................................................................................... 1-1 2. LITERATURE AND DATA REVIEW ....................................................................... 2-1 2.1 HISTORY OF MtBE IN NEW HAMPSHIRE.................................................... 2-1 2.2 PREVIOUS STATEWIDE STUDY OF NEW HAMPSHIRE PUBLIC WATER SUPPLY WELLS AND DOCUMENTED RELEASES..................................... 2-2 2.3 NEW ENGLAND INTERSTATE WATER POLLUTION CONTROL COMMISSION SURVEY RESULTS FOR NEW HAMPSHIRE...................... 2-4 2.4 STATE OF MAINE STUDY............................................................................... 2-5 2.5 U.S. GEOLOGICAL SURVEY STUDY OF MtBE AND COMMUNITY WATER SUPPLY WELLS ................................................................................. 2-6 2.6 UNIVERSITY OF CONNECTICUT AND U.S. GEOLOGICAL SURVEY STUDIES OF MtBE IN DIESEL, HEATING OIL, AND WASTE OIL............ 2-8 2.7 U.S. GEOLOGICAL SURVEY STUDY OF MtBE IN STORMWATER ......... 2-8 2.8 UNIVERSITY OF NEW HAMPSHIRE STUDY OF MtBE IN PAUGUS BAY .................................................................................................... 2-8 2.9 U.S. GEOLOGICAL SURVEY STUDY OF VOLATILE ORGANIC COMPOUNDS OCCURRENCE IN GROUNDWATER AND SURFACE WATER ............................................................................................ 2-9 2.10 UNIVERSITY OF CALIFORNIA AT DAVIS STUDY OF MtBE IN SURFACE WATER FROM WATERCRAFT.................................................... 2-9 2.11 U.S. GEOLOGICAL SURVEY STUDY OF MtBE AND GASOLINE OCCURRENCE IN GROUNDWATER ........................................................... 2-10 2.12 CALIFORNIA U.S. ENVIRONMENTAL PROTECTION AGENCY STUDY OF FUEL HYDROCARBONS AND OXYGENATES IN GROUNDWATER .... 2-11 2.13 MOREAU SUMMARY OF TYPES OF UNDERGROUND STORAGE TANKS RELEASES........................................................................................................ 2-11 2.14 U.S. GEOLOGICAL SURVEY STUDY OF ATMOSPHERIC DEPOSITION POTENTIAL FOR MtBE.................................................................................. 2-12 2.15 U.S. ENVIRONMENTAL PROTECTION AGENCY AND NATIONAL WATER WELL ASSOCIATION AQUIFER VULNERABILITY MAPPING.......................................................................................................... 2-12 2.16 U.S. GEOLOGICAL SURVEY LITERATURE REVIEW OF MtBE SOURCES IN DRINKING WATER ................................................................................... 2-12 G:\PROJECTS\20111010\001\TASK 7000\FINAL PHASE I REPORT\FINAL PHASE I REPORT.DOC 11 AUGUST 2006 ii TABLE OF CONTENTS (Continued) Section Page 2.17 U.S. GEOLOGICAL SURVEY STUDY OF MtBE IN PRIVATE AND PUBLIC WELLS IN ROCKINGHAM COUNTY, NEW HAMPSHIRE ........ 2-12 2.18 U.S. GEOLOGICAL SURVEY STUDY OF MtBE OCCURRENCE IN THE NORTHEAST AND MID-ATLANTIC U.S..................................................... 2-13 2.19 U.S. GEOLOGICAL SURVEY REPORT ON MONITORED NATURAL ATTENUATION OF MtBE .............................................................................. 2-13 3. IDENTIFICATION OF POTENTIAL RISK FACTORS ......................................... 3-1 4. CONSTRUCTION OF STATEWIDE DATABASE .................................................. 4-1 4.1 DATA SOURCES............................................................................................... 4-1 4.2 ANALYTICAL DATA........................................................................................ 4-2 4.2.1 Completeness of the Water Supply Engineering Bureau Analytical Database............................................................................................. 4-2 4.2.2 Blended Samples................................................................................ 4-6 4.2.3 Public Water Supply Water Treatment.............................................. 4-7 4.3 GEOGRAPHIC INFORMATION SYSTEM DATABASE DEVELOPMENT . 4-7 4.4 SPATIAL QUERIES........................................................................................... 4-8 4.5 ACCESS DATABASE QUERIES.................................................................... 4-10 4.6 BREAKDOWN OF PUBLIC WATER SUPPLY CHARACTERISTICS DATA ................................................................................................................ 4-10 5. DETAILED STUDIES OF SELECTED PUBLIC WATER SUPPLY WELLS..... 5-1 5.1 DESCRIPTION OF INVESTIGATION METHODS ......................................... 5-1 5.1.1 Detailed Study Objectives.................................................................. 5-1 5.1.2 Selection of Public Water Supply Sources for Detailed Studies ....... 5-2 5.1.3 Detailed Study Scope of Work .......................................................... 5-5 5.1.4 Assessment of Wellhead Protection Area/Source Water Protection Area Delineation .............................................................................. 5-10 5.2 DETAILED STUDY RESULTS ....................................................................... 5-13 5.2.1 Caveats Regarding the Detailed Study Results................................ 5-13 5.2.2 Public Water Supply Well/Surface Water Source Properties.......... 5-20 5.2.3 Nearby Potential Point Sources ....................................................... 5-22 5.2.4 Nearby Potential Non-Point Sources ............................................... 5-28 5.2.5 Other Potential Risk Factors ............................................................ 5-31 5.2.6 Public Water Supply Assessment Survey Ranking Totals .............. 5-34 5.2.7 Detailed Study Opinions Regarding Risk Factors ........................... 5-35 5.2.8 Additional Observations Regarding Risk Factors............................ 5-35 G:\PROJECTS\20111010\001\TASK 7000\FINAL PHASE I REPORT\FINAL PHASE I REPORT.DOC 11 AUGUST 2006 iii TABLE OF CONTENTS (Continued) Section Page 5.2.9 Observations Regarding Data.......................................................... 5-36 5.3 CONCLUSIONS FROM DETAILED STUDIES............................................. 5-36 6. FOCUSED EVALUATION OF SURFACE WATER SOURCES............................ 6-1 6.1 DESCRIPTION OF INVESTIGATION METHODS ......................................... 6-1 6.2 RESULTS OF FOCUSED EVALUATIONS OF SURFACE WATER SOURCES............................................................................................................ 6-4 6.3 CONCLUSIONS OF FOCUSED EVALUATIONS OF SURFACE WATER SOURCES............................................................................................................ 6-6 7. FOCUSED EVALUATION OF REMEDIATION SITES......................................... 7-1 7.1 DESCRIPTION OF INVESTIGATION METHODS ......................................... 7-1 7.2 RESULTS OF FOCUSED REMEDIATION SITE EVALUATIONS ............... 7-3 7.2.1 Great North Woods One Stop, Inc..................................................... 7-4 7.2.2 Stratham Village Market.................................................................... 7-5 7.2.3 Marlborough Sunoco......................................................................... 7-6 7.2.4 Mt. Washington Trading Post............................................................ 7-6 7.2.5 Plum Potter Auto Yard.......................................................................7-8 7.2.6 7-Eleven Store No. 32500.................................................................. 7-9 7.3 CONCLUSIONS OF FOCUSED EVALUATIONS OF REMEDIATION SITES................................................................................................................. 7-10 8. STATISTICAL ANALYSIS OF STATEWIDE DATA ............................................. 8-1 8.1 DATA PROVIDED TO UNIVERSITY OF NEW HAMPSHIRE FOR STATISTICAL ANALYSIS ............................................................................... 8-1 8.2 PATHWAY ANALYSES.................................................................................. 8-16 8.3 TREND ANALYSIS......................................................................................... 8-24 8.3.1 Statewide Annual Mean MtBE Concentrations............................... 8-25 8.3.2 Kendall’s Trend Test........................................................................ 8-25 8.3.3 Annual Status of Individual Wells................................................... 8-26 8.3.4 Seasonal Trends............................................................................... 8-26 8.4 PREDICTIVE MODELING.............................................................................. 8-28 8.5 PRELIMINARY DATA PREPARATION FOR PREDICTIVE MODELING ...................................................................................................... 8-28 8.6 VARIABLE SELECTION ROUTINES............................................................ 8-29 8.6.1 Classification and Regression Trees ................................................ 8-29 8.6.2 Stepwise Logistic and Stepwise Linear Regression......................... 8-33 G:\PROJECTS\20111010\001\TASK