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

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 organic 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 of 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 or surface water reservoirs So……restrict groundwater so it cannot be used for • Urban groundwater impacts often do not potable purposes threaten potable water

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 or 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 Groundwater Increase Chemical of Occurrence Ingestion PCL Air Inhalation in Concern (mg/L) PCL (mg/L) Cleanup w/o MSD w/MSD Target Benzene Component in 0.005 180 36,000x gasoline Trichloroethylene Degreasing 0.005 162 32,400x (TCE) chemical Tetrachloroethene Dry cleaning 0.005 327 65,400x (PCE) solvent Lead Leaded gas, 0.015 DNA --- urban pollution 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 Groundwater Chemical of Occurrence Protective Human Health Increase Concern PCL PCL in (mg/kg) (mg/kg) Cleanup w/o MSD w/MSD Target Benzene Component in 0.026 66 2,538x gasoline Trichloroethylene Degreasing 0.034 152 4,470x (TCE) chemical Tetrachloroethene Dry cleaning 0.050 98 1,960x (PCE) solvent Lead Leaded gas, 500 167x 3* urban pollution Arsenic Pesticides 24 4.8x 5*

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 Max Detected Groundwater Groundwater Concern in Water PCL w/o MSD PCL with (mg/L) (mg/L) 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 Clay Snider, PG Technical Director Division Manager W&M Environmental Group W&M Environmental Group fclark@wh-m.com csnider@wh-m.com 972/509-9611 972/349-1731