Hookston Station AreaBaseline Risk Assessment
Community MeetingJune 20, 2005
Cal/EPA -SF Bay Regional Water Quality Control Board
1
Introductions
• Water Board• Department of Health Services, Environmental
Health Inv. Branch (DHS/EHIB) • Union Pacific Railroad• Mr. Dan Helix• Contra Costa County Redevelopment Agency• Environmental Resources Management (ERM)*• Center for Toxicology & Environmental Health
(CTEH)** consultants to responsible parties
2
• Open Forum• Introduction (Water Board)• Status of Hookston Station Area
Project (Water Board)• Baseline Risk Assessment (CTEH)• Next Steps (Water Board)
Meeting Agenda
3
Chronology
• Investigations conducted 1989 and 1996
• Water Board notified of potential release in 2001
• Water Board order (SCR) adopted April 2003
• Water Board staff requiring investigation of other potential contaminant sources
4
Primary Chemicals of Concern
• Tetrachloroethylene (PCE)
• Trichloroethylene (TCE)
• Dichloroethylene (DCE)
5
Hookston Station
I-680
Walnut Creek channel
6
Documents Available
• RI – Remedial Investigation
• QMR – Quarterly Monitoring Reports
• Soil Vapor Sampling – in QMRs
• Environmental Risk Assessment
• Off-Site Investigation Reports
7
Review Reports
• Pleasant Hill Library – paper copy
• Geotracker – electronic copy www.geotracker.waterboards.ca.gov
• Choose ‘Case Finder’• Case #07S0156• Choose ‘Report’ then ‘Site Documents’
8
Progress Since Last Meeting
• 35 monitoring wells installed
• Private well surveys resulted in abandonment of 5 out 12 wells reported
• Initial round of indoor air sampling completed– 17 homes tested
• Additional soil gas sampling performed
9
Intrusioninto
buildings
Soil
Crawl Space
Groundwater
Vapor Intrusion Basics
Vapors
Plume
Indoor air circulatio
n
10
Indoor Air Sampling
• 17 homes sampled Jan-April 2004 (winter season)
• 6 homes contained TCE in indoor-air above Water Board screening level of 1.2 ug/m3 (range from 2 to 5 ug/m3 )
• Summer season sampling to begin July or August 2005
11
Next Steps
• Finalize Baseline Risk Assessment
• Submit Feasibility Study (FS / RAP)
• Public review and comment
• Issue final enforcement order to approve FS / RAP and set cleanup standards
• Implement approved FS / RAP including additional sampling / monitoring