Frank W. Clark, P.E., P.G. Clay Snider, P.G. W&M Environmental - - PowerPoint PPT Presentation

Frank W. Clark, P.E., P.G. Clay Snider, P.G. W&M Environmental Group, LLC

Meet the Experts

Frank Clark, P.E., P.G. Technical Director Clay Snider, P.G. Remediation Division Manager

Oh, No….We Found Groundwater Contamination

 Site investigations for real estate transactions or

industrial closures often identify groundwater contamination.

 The most frequent COCs in

urban areas are volatile

• rganic compounds, petroleum

hydrocarbons, and heavy metals

 Groundwater cleanup is almost always the most

challenging aspect of site remediation

Cliff Notes on Historic Approaches to Groundwater Cleanup

 Pre-1970’s – non-existent  1970’s-1980’s – US EPA,

RCRA and Superfund

 1980’s-1990’s – advent

• f Environmental Site

Assessments; States develop cleanup rules

Leaking Underground Storage Tanks

Over 540,000 Leaking USTs in USA

Groundwater Cleanup Approaches

 Pump & Treat Systems

In-Situ Approaches

Cliff Notes on Historic Approaches to Groundwater Cleanup

 1990’s – Underground storage tank

market explodes; risk-based corrective action concepts are developed

 2000’s – Failure of traditional

remediation approaches recognized; RBCA techniques refined We haven’t done a good job cleaning up contaminated groundwater!!!

The Groundwater Cleanup Conundrum

 Presumed that all groundwater should be fit for

potable purposes

 Groundwater issues drive most remediation  Poor job of “engineering” groundwater

remediation

 The costs and time associated with groundwater

cleanup are too burdensome on most properties

 Other methods have their limitations

Risk-Based Cleanup Options in Texas

 Demonstration of low yield aquifer (no “beneficial

use”)

 Monitored natural attenuation – let Mother

Nature take care of it

 Plume Management Zones (PMZs) – show

plume stability and no harmful effects beyond the plume boundary

Municipal Setting Designations - The Concept

• Historic industrial activities

were prevalent in many large urban areas

• Most urban areas have

municipal water supplies

• Potable water often

derived from deep aquifers

• r surface water reservoirs
• Urban groundwater

impacts often do not threaten potable water So……restrict groundwater so it cannot be used for potable purposes

Urban / Municipal Setting Designations

 Concept first developed in Ohio in 1990’s  Introduced in Texas Legislature-2003  Stated purpose was to “provide a less expensive and

faster alternative to rules governing the cleanup of contaminated groundwater”

 Results in a deed-recorded restriction on the use of

groundwater from beneath the Site for potable purposes.

The MSD Process - Screening

 Public water available to properties within ½-

mile?

 Wells within ½ mile radius?  Support likely from local government ?  Support likely from cities within ½ mile?  Support likely from RPUs within 5 miles?  Exceed MSD-adjusted cleanup standards on the

property?

MSD Application Process – Local Governments

 Formal application process and fees  Very specific technical submittals (chemicals

types, source areas, plume stability, regulatory status, etc.)

 Deeds, registered surveys, affidavits  Public meeting scheduled  City Council hearing for approval

MSD Process – Water Well Notices

 Notice required to all well owners within 5 miles  Three attempts at notice

must be documented

 Most urban wells are abandoned

• r unknown to current owner

 Can involve 100-200 notices in DFW MetroPlex  Can involve 800-1,200 notices in Houston

MSD Process – TCEQ Approval

All the hard work is done……

 After approval of local government, separate

application submitted to TCEQ

 TCEQ reviews carefully to ensure administrative

aspects of the rule are met

 TCEQ issues an MSD Certificate that certifies

the MSD

Benefits of an MSD

• Relaxed Water Cleanup Standards

Chemical of Concern Occurrence Groundwater Ingestion PCL (mg/L) w/o MSD Air Inhalation PCL (mg/L) w/MSD Increase in Cleanup Target Benzene Component in gasoline 0.005 180 36,000x Trichloroethylene (TCE) Degreasing chemical 0.005 162 32,400x Tetrachloroethene (PCE) Dry cleaning solvent 0.005 327 65,400x Lead Leaded gas, urban pollution 0.015 DNA

• Arsenic

Pesticides 0.010 DNA

Benefits of MSDs – Reduced Delineation

 Assessment levels for TCEQ investigations

become the MSD-adjusted levels

 Little delineation and “plume chasing” required

Benefits of an MSD

• Relaxed Soil Cleanup

Chemical of Concern Occurrence Groundwater Protective PCL (mg/kg) w/o MSD Human Health PCL (mg/kg) w/MSD Increase in Cleanup Target Benzene Component in gasoline 0.026 66 2,538x Trichloroethylene (TCE) Degreasing chemical 0.034 152 4,470x Tetrachloroethene (PCE) Dry cleaning solvent 0.050 98 1,960x Lead Leaded gas, urban pollution

3*

500 167x Arsenic Pesticides

5*

24 4.8x

MSDs in North Central Texas

 Most cities rely principally on surface water

reservoirs

 Potable wells generally >1,000 feet deep  Contamination typically perched (10-30 feet

deep) in unconsolidated deposits

 Austin Chalk, Eagle Ford Shale and Taylor Marl

prevent vertical migration to underlying aquifers.

Geology in DFW MetroPlex

Case Study- Urban Brownfield Site

 Urban shopping center since 1960’s  Dry cleaner occupied one suite for 20+ years  Contamination found in Brownfields Site

Assessment

 PCE, TCE and DCE present  Chlorinated solvent plume migrated off-Site

Urban Shopping Center PCE Plume

MSD Benefits to Client

 Non-profit agency (CDC) could not afford expensive

monitoring or cleanup

 MSD process was supported by the City  Cleanup criteria adjusted, resulting in no response

actions

Chemical of Concern Max Detected in Water (mg/L) Groundwater PCL w/o MSD (mg/L) Groundwater PCL with MSD (mg/L) PCE 0.767 0.005 327 TCE 0.077 0.005 162 Cis-1,2-DCE 0.327 0.070 16,000

Summary of MSD Benefits

 Reduced cleanup values for contaminated

groundwater

 Eliminates most plume delineation  Reduced groundwater monitoring  Reduced soil cleanup values  A predictable closure strategy

(time and $)

MSD Challenges

 Involves local government and public

participation

 Third parties (e.g. RPUs) need to provide written

support

 MSDs do not include off-Site properties  If potable wells within ½ mile, response actions?  Does not address vapor intrusion issues

Contact Us

Frank Clark, PE, PG Technical Director W&M Environmental Group fclark@wh-m.com 972/509-9611 Clay Snider, PG Division Manager W&M Environmental Group csnider@wh-m.com 972/349-1731