Locating Domestic Water Supply Wells: National, Regional and Local Scale

Transcription

1 Locating Domestic Water Supply Wells: National, Regional and Local Scale Fran Kremer, Jim Weaver USEPA, Office of Research and Development Greg Pashia, David Anderson USEPA, Region 6 Jeffrey Lyons, Leonard Sabatino Eight Northern Indian Pueblo Council Office of Research and Development National Risk Management Research Laboratory

2 Use of GIS, and Vulnerability Analysis to Assess Impacts to Water Supply Wells from Contaminants Ground Water Quality and Quantity GIS Supply Wells and Contaminant Sources Modeling/ Vulnerability 1

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5 Density of people drinking shallow ground water multiplied by the density of service stations - estimate of the probability, normalized surface area, worst 30% (Vulnerability Index 1) 4 Earle, R., J. T. Wilson, F. Kremer, J.Weaver, and D. Burden. GIS Analysis to Assess where Shallow Ground Water Supplies in the US are Vulnerable to Contamination by Releases of Motor Fuel from Underground Storage Tanks EPA/600/R-11/108. December 2011

6 Understanding the Spatial Implications of Contaminants Impacting Ground Water Supplies Base Scenario with 2 pumping wells and 4 sources 5 Contaminant source 3 rd well is vulnerable to all sources, one original well no longer vulnerable Jim Weaver, USEPA, ORD

7 Objectives Develop nationwide estimate of areas likely to depend on private domestic wells Pilot in Oklahoma Test in local areas Determine the spatial relationship between these areas and hazardous release sites (leaking underground storage tanks, RCRA corrective action, CERCLA)

8 Private Domestic Wells (PDWs) Unregulated by Safe Drinking Water Act Some state regulations: New Jersey and Oregon require limited water quality testing at property transfer Nebraska requires registration of wells (with exemption of domestic wells prior to 1993) Several states require permits for drilling (Arizona, New Mexico, Colorado, Utah, etc)

9 Local PDW Data With few exceptions, state knowledge largely relies on reported well logs Data collection and availability varies among states What year did reporting begin? How consistent is reporting? Are data compiled and available?

10 Inference from 1990 census: 177,000 housing units on private wells Reported Domestic Well Logs: 17,500

11 Nationwide Picture of PDW usage National picture of private domestic well usage is limited USGS county-level estimates of self-supplied water Based on varying levels and types of information Census Bureau Historic data on water supply source ( ) U.S. Long Form Census from 1960 to 1990 asked source of water: public supply versus private well or other Oklahoma Example: 177,000 housing units on private wells versus 17,500 reported private domestic wells reported

12 U.S. Census U.S. Long Form Census from 1960 to 1990 asked source of water: public supply versus private well or other Oklahoma Example: 177,000 housing units on private wells versus 17,500 reported private domestic wells reported 11

13 12 (Upper bound: 1/10 ac lots and 640 ac/mi 2 If 6400 wells/mi 2 then 2470 wells/km 2 )

14 A National look at 1990 Well Use 13 Total water users: 102,263,270 Private Well Users: 15,131,584 (14.8%)

15 14 A Closer Look

16 Updating 1990 Census Estimates Two Methods: Wells Added (uses known wells constructed since 1990) Housing Unit Change: Uses Housing units combined with 1990 rate of well use to predict current well use

17 Changes in Boundaries Block Groups and Census Tracts change every Census year. # of Oklahoma Block Groups 1990: 3, : 2, : 2,965 # of Oklahoma Census Tracts 1990: : : 1,046 Zonal Statistics break rasterized data down to 250m cells and project their statistics onto updated boundaries.

18 2010 Estimates Net Housing unit method roughly equal to wells-added method

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20 Oklahoma City Tulsa 19

21 Oklahoma Aquifers (OWRB)

22 Public Water System Extent (OWRB)

23 Edmond Water system not built to full boundaries Subdivisions on individual private wells In circle above 77 homes counted, 55 wells reported Houses built after 2005 Census bureau classifies undeveloped land as rural Local densities higher than block group estimates

24 Nicoma Park Nicoma Park No public water system; 2/3 on public sewer Small number of wells reported to OWRB Most Buildings predate 1984 well reporting requirement 551 buildings in one square mile vs. estimate of 409 wells/sq mile 23

25 Enid 24 Enid terrace aquifer as public supply High density of private wells domestic water landscaping

26 August 2012 city ordinance banned use of sprinkler systems, if supplied from city water. Private wells were not included. 25

27 UST sites to Private Domestic Wells Data Oklahoma Corporation Commission list of active tank sites (~3000) 67,363 Well logs reported to Oklahoma Water Resources Board (to 2010) Model Estimate Wells-added method private well density estimate for 2010

28 Method Determine number of wells within each of the 2805 census block groups Well logs reported to OWRB + trial wells randomly generated according to WA 2010 estimated density Determine distance to each domestic well in the block group that contains the UST site Check neighboring block groups, then neighbors of neighbors, until no wells within selected trial distances of 50, 100, 250, 1000, 2500, 5000, 5280 Repeat 1000 times to generate probability distribution of the number of tanks within the trial distances

29 1) block group neighbors Calculation Strategy: only look in close proximity to block group containing UST 2) block group neighbors of neighbors 3) Block group neighbors of neighbors of neighbors

30 Well Set-Back Distances From Oklahoma 785:35 10 feet from closed sanitary sewer line 25 feet from aerobic sprinkler spray 50 feet from sprinkler head 300 feet from waste lagoon for feedlot or confined animal feeding operation 50 feet from other pollution sources 20 ft surface seal if 50 to 75 down gradient or level 75 feet if well is level with pollution source 100 feet if well is down gradient from pollution source

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33 Well log and housing unit methods indicate areas of high private well density Net housing unit method gives approach to extend to whole US regardless of well-log data availability Expanding cities only gradually extend their water systems where aquifers provide alternative Pockets of private domestic well use persist for long periods Estimated 1845 tanks (of 3033) with PDW within 1 mile Contact: Jim Weaver weaver.jim@epa.gov

34 ASSESSING POTENTIAL IMPACTS OF UNDERGROUND STORAGE TANKS ON DRINKING WATER SOURCES Region 6 Greg Pashia David Anderson

35 REGION 6 TRIBAL UST FACILITY UNIVERSE 107 FACILITIES LISTED IN USTRAC DATABASE START OF EFFORT 11 FACILITIES WERE DESIGNATED SWP REQUIRING ANNUAL INSPECTION

36 NEW MEXICO PUBLIC WATER SOURCES INCLUDES BOTH PUBLIC SUPPLY WELLS AND SURFACE WATER INTAKES INCLUDES ACTIVE AND INACTIVE

37 NEW MEXICO PRIVATE WATER WELLS PLOT DOES NOT INCLUDE ALL REGISTERED WELLS AT THIS SCALE

38 TRIBAL WELLS NOT INCLUDED IN THE STATE REGISTRATION

39 1000 FOOT BUFFER PLOT MULTIPLE OVERLAPS

40 SOURCES WITHIN 1000 FEET OF TRIBAL UST FACILITIES

41 LIMITS OF DATABASE STAR PRIVATE WELLS FROM STATE DATABASE TRIANGLES WELLS IDENTIFIED BY INSPECTOR DURING TRIP TO SITE.

42 INACCURATE LOCATIONS OF WELLS LOCATION SYSTEM PLOTTED LOCATION ¼ OF ¼ OF ¼ OF A SECTION 10 ACRES ACTUAL LOCATION

43 SURFACE WATER EVALUATION STRE AM

44 POTENTIAL REGION 6 SWP FACILITIES WELL OR SURFACE WATER WITHIN 1000 FEET OF TANKS AT FACILITY ADDED TO USTRAC SWP FIELD 46 FACILITIES NOW 57 FACILITIES IN LIST

45 BEFORE GIS ANALYSIS 11 ANNUAL SWP INSPECTIONS YEAR INSPECTIONS ANNUAL WORKLOAD INSPECTIONS AFTER GIS ANALYSIS 57 ANNUAL SWP INSPECTION = YEAR INSPECTIONS ANNUAL WORKLOAD INSPECTIONS 67% INCREASE IN WORKLOAD

46 QUESTION BECOMES: CAN WE MODIFY THE INSPECTION FREQUENCY CRITERIA FOR THE SWP FACILITIES? HOW DO WE PRIORITIZE THE SWP FACILITIES?

47 PRIORITIZATION CRITERIA FACILITY INFORMATION NUMBER OF TANKS SIZE OF TANKS CONSTRUCTION OF TANKS AGE OF TANKS FACILITY HISTORY (LEAKS)

48 GROUNDWATER GROUNDWATER USE PUBLIC SUPPLY PRIVATE DOMESTIC IRRIGATION INDUSTRIAL AQUIFER CHARACTERISTICS DEPTH TO AQUIFER DEPTH OF WELLS GEOLOGY/HYDROLOGY SURFACE WATER SURFACE WATER USE DISTANCE TO INTAKES STREAM FLOW WETLANDS PRESENT/ABSENT

49 48 Jeffrey Lyons Leonard Sabatino Eight Northern Indian Pueblos Council

50 GAPS IN DATA TRIBALLY OWNED WELLS DATA GATHERING METHODS 1. ON SITE DATA GATHERING 2. UTILIZING TRIBAL UTILITY & GIS STAFF 3. CREATE A TRIBAL GIS WORKING GROUP 4. DATABASE MANAGEMENT 5. GIS/GOOGLE EARTH ANALYSIS 6. VERIFYING RECEPTORS IN THE FIELD AND GPS QA/QC

51 WHAT DO WE DO WITH THE DATA? CREATE AND MAINTAIN A SITE VULNERABILITY RANKING SYSTEM CONTINUE TO HAVE WORKING RELATIONSHIP WITH TRIBAL GIS & ENVIRONMENTAL STAFF CENTRAL GEOGRAPHIC DATA BASE (ENIPC- OETA) ENVIRONMENTAL ASSESSMENT AND/OR HYDROLOGICAL ASSESSMENT FOR NEW WELL LOCATION CREATE USER FRIENDLY ONLINE MAPPING TOOL FOR TRIBES TO ANALYZE AND CREATE MAPS FOR TRIBAL PROJECTS

52 BENEFITS OF A VULNERABILITY STUDY!! GREAT COMMUNICATION TOOL FOR TRIBAL GOVERNMENTS TO ANALYZE POTENTIAL RISK TO THEIR PEOPLE S DRINKING WATER SUPPLY START & CONTINUE SAMPLING OF MONITORING WELLS IDENTIFYING RECEPTORS THAT TRIBAL STAFF CAN CONTINUE TO ANALYZE WATER QUALITY TESTING NEAR VULNERABLE FACILITY SITES TRIBAL ENVIRONMENTAL AWARENESS & MOTIVATION TO PROTECT OUR PEOPLE!!