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