DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL

Division of Air and Waste Management

Site Investigation and Restoration Branch

Policy Concerning the Default Background Concentration of Arsenic and Revision to the Remediation Standards Guidance

February 2007

Prepared By: Christina Wirtz

DNREC Division of Air and Waste Management

391 Lukens Drive, New Castle, DE 19720

E-Mail: Christina.Wirtz@state.de.us

Phone: (302) 395-2515

Summary

The Department of Natural Resources and Environmental Control (DNREC) staff, after working with other state agency staff and reviewing extensive comments, have established 11 parts per million (ppm) as a default background standard for Delaware. This follows a significant public participation process to solicit and obtain public input before finalizing the arsenic default background standard. The Policy Concerning the Default Background Concentration of Arsenic and Revision to the Remediation Standards Guidance (Default Background Arsenic Policy), dated February 2007, has been prepared in response to Governor Ruth Ann Minner's June 9, 2005 directive to DNREC Secretary John A. Hughes to "review…and propose appropriate standards and policies" for arsenic in soil, focusing on ensuring the health and safety of Delawareans, and to solicit public input on the draft arsenic standard prior to adoption.

The DNREC Division of Air and Waste Management staff has prepared "Arsenic Risk Management Plan" and "The Response to Comments" documents, in collaboration with the Division of Water Resources (DWR), the Division of Public Health (DPH), and the Department of Agriculture (DDA) as part of DNREC's response to Governor Minner's directive.

The basis for establishing a default background level of 11 ppm is the need to reduce public exposure to arsenic as low as possible while taking into account naturally occurring Arsenic. For carcinogens like arsenic, Delaware law mandates that standards be set at levels associated with an incremental lifetime cancer risk increase of one in one hundred thousand (1/100,000 or 1 x 10-5) or, in cases where background concentrations exceed the concentration associated with the risk level, at the background concentration. These cleanup standards are established by regulation.

The Default Background Arsenic Policy and other associated arsenic documents may be inspected at the Department's offices located below:

DNREC

R & R Building - DAWM

89 Kings Highway

Dover, DE 19901

Division of Air and Waste Management

Contact: Tracy Sargent (302) 739-9400

DNREC - New Castle Office

391 Lukens Drive

New Castle, DE 19720

Front Lobby

Contact: Receptionist (302) 395-2600

DNREC - Grantham Lane Office

715 Grantham Lane

New Castle, DE 19720

Front Lobby

Contact: Receptionist (302) 323-4542

The Default Background Arsenic Policy and related arsenic documents may also be viewed at the Division of Air and Waste Management's arsenic website at: http://www.dnrec.state.de.us/dnrec2000/Divisions/AWM/SIRB/Arsenic/. For additional information, or appointments to review the Default Background Arsenic Policy, please contact Christina Wirtz, at DNREC's Field Office located at 391 Lukens Drive, New Castle, DE 19720, or e-mail to Christina.Wirtz@state.de.us.

Policy and Procedures

Subject: Policy concerning the default background concentration of arsenic and revision to the

Remediation Standards Guidance

Issued: February 2007

The Department of Natural Resources and Environmental Control-Division of Air and Waste Management adopts this policy to modify the Remediation Standards Guidance under the Delaware Hazardous Substance Cleanup Act 1999 (RSG) with respect to the default background concentration of arsenic.

Purpose

The purpose of this policy is to align the state’s default background concentrations, to be used in some cases as a cleanup standard for contaminated soil, based on the results of technical review and analysis conducted by DNREC since 2005, in coordination with other Delaware state agencies and other state, federal and international scientific analysis. In June 2005, Gov. Minner directed DNREC to “review…and propose appropriate standards and policies” for arsenic in soil. In June 2005, DNREC released the Proposed Arsenic Risk Management Plan which included technical background information on arsenic and summarized policy options. That document also established an interim default background concentration for arsenic in soil of 11 milligrams per kilogram (mg/kg). DNREC then conducted public meetings on the proposal and collected numerous written and verbal comments. This policy is the outcome of that public review process.

This policy provides the revised technical guidance to DNREC’s staff for conducting cleanups and establishing acceptable risk levels under the Regulations Governing Hazardous Substance Cleanup [Section 9.4 Soil Cleanup Levels]. These HSCA regulations provide the overall requirements for ensuring protection of public health and the environment. In the case of arsenic, however, the technical guidance is particularly important because it is among a number of naturally-occurring mineral for which average background soil concentrations exceed the soil concentrations associated with the acceptable cumulative lifetime incremental risk established in HSCA regulations of 10E-5 (one-in-one hundred thousand).

The revised default background concentration of 11 mg/kg for arsenic in soil necessitates a revision to approved statistical tests for demonstrating attainment with cleanup goals or background concentrations described in the RSG Section 6.2.

Policy

1. The RSG Attachment 3 “Delaware Default Background Remediation Standards” shall be revised. The new default background remediation standard for arsenic in soil shall be 11 mg/kg.

2. The same attachment contains a column heading, Typical Delaware Soil Concentration, with the note that “The range of soil background values from representative sites in Delaware are provided for information only and are not default background standards. This information can be used to evaluate whether the development of site-specific background standards is appropriate or useful.” Based on the review of state-wide background studies during the Arsenic Management Plan process, the listing for arsenic is updated to 11 mg/kg.

3. The “75/10/2 Rule” described in Section 6.2 of the RSG is no longer valid for screening arsenic in soil against the default background concentration. It remains acceptable for other inorganic chemicals.

This policy will be distributed to relevant DNREC staff and approved HSCA consultants and will appear on the DNREC-SIRB web page. The changes will appear in any new revision of the Remediation Standards Guidance.

DNREC will review the Default Background Remediation Standards including the information for arsenic at regular intervals not exceeding five years.

Approved by: ________________________________ Date: ________________

James D. Werner, Director

Division of Air and Waste Management

Original signed by Jim Werner on 2/2/07

SFJ:vdc

SFJ06024

AD003 I A 3

DELAWARE DEFAULT BACKGROUND REMEDIATION STANDARDS

(REVISION TO ATTCHMENT 3, REMEDIATION STANDARDS GUIDANCE)

Revised February 2007

* - USERS ARE ENCOURAGED TO DEVELOP SITE-SPECIFIC BACKGROUND STANDARDS

TO ADDRESS SITE-SPECIFIC CONSIDERATIONS WHERE THE DEFAULT STANDARD MAY NOT BE

APPLICABLE OR APPROPRIATE

* - NOTE THAT ALL OF THE DEFAULT VALUES ARE EXPECTED TO BE UPDATED

IN THE FUTURE TO BE MORE STATISTICALLY REPRESENTATIVE OF DELAWARE CONDITIONS

(a) Ground-water values are a combination of ground-water URS and surface water URS, whichever are more stringent.

(b) Soil values are upper value of the concentration range detected in background samples collected statewide. Note that these soil values are expected to be updated to be more statistically representative of Delaware conditions in the future.

(c) Surface water values are a combination of ground-water URS and surface water URS, whichever are more stringent (dissolved data).

(d) Sediment values are a combination of the default background soil criteria and sediment URS, whichever are more stringent.

(e) Value presented is the most stringent soil URS value because the upper value of the concentration range (as described in item (b)) exceeds the unrestricted soil URS or the environment URS.

(f) Value presented is the surface water URS

(g) Value presented is the sediment URS

(h) The range of soil background values from representative sites in Delaware are provided for information only and are not default background standards. This information can be used to evaluate if the development of site-specific background standards is appropriate or useful.

(i) Value is the 95% UCL of the mean of a state-wide background data set

- All soil and sediment values are dry weight basis

- All ground-water values are either total (water supply source) or dissolved (monitoring well) concentrations, depending on the application.