commitment & integrity drive results risk based corrective action using site-specific risk...

COMMITMENT & INTEGRITY DRIVE RESULTS

Risk Based Corrective Action

Using site-specific risk assessment to achieve Regulatory Closure


Manage Risk at Sites

• Identify levels of exposure• Assess if level of exposure is acceptable:

– “Risk Characterization” • Change level of exposure if risk is

unacceptable:– Reduce concentration, reduce exposure,

eliminate exposure


What is Risk Assessment?

• A tool that supplies information about risks to human or ecological “receptors” due to exposure to identified hazards

• Use it to focus remediation on identified risks or to demonstrate NFA

• Relies on environmental media data, site use, fate and transport, and toxicological information


What is Risk Assessment?


The House is Only as Good as the Foundation it is Built On

• Nature and extent of contamination (vertical and horizontal) must be characterized

• Site boundaries must be defined• Data usability must be assessed and data

must be adequate• Current and future site activities and uses

must be understood


Steps in a Human Health Risk Assessment

• Hazard Identification

• Exposure Assessment

• Toxicity Assessment

• Risk Characterization

• Uncertainty Analysis


Evaluate Key Risk Questions

• WHO? Is Exposed? Workers, future residents (children, adults)

• WHAT? Are they exposed to and at what concentrations? What are potential toxic effects?

• WHEN? Does exposure occur? Current site conditions? In the future?

• WHERE? Does exposure occur (Exposure point)?

• HOW? Does exposure occur and how often?

Example: Facility Worker


…To Produce Quantified Results

Incremental cancer risk (e.g., 1/100,000, 1/1,000,000)

Non-cancer risk (Hazard Quotient, relative to 1)

SiteConcentration

Calculated Risk(4.3 x 10-4)CALCs


Risk-Based Decision Making

• Who: regulator, owner, client, consultant, buyer, neighbor

• What: risks from current and future land use

• When: now, near future, 30+ years


Risk-based Decision Making• Where: on-site, off-site

• Why: regulatory, liability, business profile

• How: balanced consideration and weighting of factors within your control and/or influence


Making Risk-Based Decisions

• Cost-benefit analysis

• Risk-benefit analysis


Risk Management Applications

Risk = f(Conc, Exposure, Toxicity)

Which element can managed, and how?


Case Study #1: Human Health Cleanup goals for a Beach Area for Lead

• Site is on Harbor area and includes numerous habitats and exposure points such as:

- Harbor sediment and surface water

- Beach area

- Bike path

- Upland area slated for residential development


Case Study 1 Cont.• Back calculated cleanup goals for a recreational receptor,

(on the beach, jumping off a bridge, swimming), construction worker, utility workers

• Lowest cleanup goal among three receptors was selected as remedial target

• Guided remediation by removing maximum location and calculated residual mean (EPC) until achieved target

• Mapped remedial areas based on this: Regulators reviewed this approach and approved it

Derivation of Risk-Based Concentration - Lead


Risk-Based Cleanup Level =

Concentration in media = X

Associated risk level Target risk level

3892 = X 2.8 1

X = 1390

Derivation of Risk-Based Concentration – Ratio Formula


Risk Management

• Site specific action levels and compliance points result in targeted remediation

• Be creative in application of various remedial approaches

• Consider partial closure strategies

• Time sequencing/prioritizing cleanup efforts


Case Study 2: EcologicalMonitored Natural Recovery for

Cadmium in Reservoir• Exceedance of AWQC for Cd but Comprehensive

Ecological Risk Characterization says No Significant Risk • SW concs > AWQC but all the other lines of evidence

said it is not a risk; considered this as part of Feasibility study

• Correlated SW and Sediment data, used a regression equation to target what sediment concentration in sediment would give an allowable SW value


Risk Management

• Although exceeded AWQC, ERC indicated NSR

• Risk for implementing “active” remediation outweighed benefits

• Future assessment of MNR processes reduce exposure and risk with minimal disruption


Case Study #3 - Risk Management Approaches for PCBs

• Can use risk-based approach to gain flexibility in sampling, soil management, response actions and disposal

• Consider use of exposure mitigation rather than remediation

• Can “mix and match” Self Implementing (SIP) and Risk-based Approaches


PCB Case Study for TSCA & State SuperfundSite

• Former record manufacturing facility that included vehicle maintenance

• Current use as offices (corporate headquarters)

• LNAPL with elevated PCB concentrations (>260 mg/L) identified


PCB Case Study Cont.

• Comprehensive characterization of soils outside of and below building footprint

• Sediments and groundwater also evaluated

• Soil concentrations up to 570 mg/kg

• No clear gradient from suspected sources (waste oil USTS) due to redevelopment


PCB Case Study Cont.

• Approach combined SIP and Risk-based closure

• Outside of Building:– Deed restriction for “low occupancy”– Used either 25 ppm or 100 ppm with clean soil cap

• Building Footprint:– Deed restriction for Commercial/Industrial use and

maintenance of slab– Used Risk Assessment to show residual concentrations

(up to 350 ppm) posed NSR


Overall Themes

• Must satisfy regulatory requirements

• Client goals and needs

• Flexibility and choices

• Risk balancing

• Creative conservatism

commitment & integrity drive results risk based corrective action using site-specific risk...

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