June 27, 1997

Ms. Mollie Netherland
CH2M HILL
777 108th Avenue, N.E.
Bellevue, Washington 98004-5118

Dear Ms. Netherland:

This is in response to your inquiry to the Occupational Safety and Health Administration (OSHA) requesting clarification of the scope of OSHA's Hazardous Waste Operations and Emergency Response (HAZWOPER) Standard (29 CFR 1910.120). Please accept my apology for the long delay in finalizing this reply.

You stated in your inquiry that CH2M HILL employs a "worst-case exposure modeling" method to determine the worst-case airborne exposure levels of hazardous substances present on a specific work site. Your inquiry provided a brief description and sample applications of this modeling method and inquired whether OSHA would consider the results derived from this modeling method, coupled with the use of personal protective equipment (PPE) to protect employees against dermal hazards, as sufficient demonstration that no exposure or no reasonable possibility of exposure existed on a worksite and that, therefore, the HAZWOPER standard did not apply.

OSHA's position is that employee exposure to a hazardous substance should consider exposure by all routes of entry (inhalation, ingestion, and skin absorption) without regard to the use of PPE. Employees are considered "exposed" when they encounter any amount of hazardous substance(s) in the workplace environment that would cause harm to the employees.

Employers must comply with all the provisions of 29 CFR 1910.120(c) during the site characterization and analysis for evaluation of the site in regard to employee exposure or potential exposure during site operations. This evaluation includes the identification and evaluation of the safety and health hazards present on-site that may pose inhalation, ingestion or skin absorption hazards; hazards that are immediately dangerous to life or health; or other conditions that may cause death or serious harm. If the results of this evaluation indicates control procedures are not and will not be potentially necessary to protect employees from the identified safety and health hazards during site operations, then employees will not be considered to be exposed to the safety and health hazards. Those site operations with employees who are not exposed to or who could not be exposed to safety and health hazards are not within the scope of the applicability of the HAZWOPER standard and, therefore, the provisions of the requirements of 29 CFR 1910.120 are not applicable. The employer is, however, required to comply with all other applicable OSHA standards such as 29 CFR 1910 and 1926.

As indicated in your letter, the determination that no possibility for employee exposure to health and safety hazards must be documented. This documentation must be maintained on site and available for review by regulatory officials. In addition, the employer is required to maintain a vigilance for any change in exposure status of employees to safety and health hazards during site operations and to initiate protective measures if it is indicated that employees are or potentially could be exposed to these hazards on site.

As stated above, the HAZWOPER standard covers hazardous waste operations only where employees are exposed to or potentially exposed to safety or health hazards during the operation due to the release of hazardous substances in the worksite. Safety hazards from hazardous substances could include fire, explosion, corrosive action, etc. from flammables, explosives, corrosive materials, etc. associated with the site. Health hazards from hazardous substances could include cancer or organ function impairment from toxic, carcinogenic, or infectious materials associated with the site. Safety hazards from sources not specifically associated with the hazardous substances on the worksite such as trenching, moving machinery, slips, trips, and falls do not require coverage of the worksite under the HAZWOPER standard.

We hope this response provides the clarification you need. If you have further questions, please feel free to contact the [Office of Health Enforcement at (202) 693-2190].

Sincerely,



Stephen J. Mallinger, Acting Director
Office of Health Compliance Assistance

[Corrected 10/20/06]



June 5, 1995

Maryann Garrahan
Francis Perkins Building
United States Department of Labor (DOL)
Occupational Safety and Health Administration (OSHA)
200 Constitution Avenue NW, Room N-3467
Washington D.C. 20210

Subject: Scope Interpretation of 29 CFR 1910.120

Dear Ms. Garrahan:

Introduction

As I mentioned in my telephone message of May 26, 1995, I need an interpretation of the scope of the Hazardous Waste and Emergency Response regulation, 29 CFR 1910. 120. In paragraph (a) of this regulation, it is stated that:

This section covers the following operations, unless the employer can demonstrate that the operation does not involve employee exposure or the reasonable possibility for employee exposure to safety or health hazards...

Does OSHA accept worst-case exposure modeling as a method to demonstrate no exposure or no reasonable possibility for exposure? Presented below is the general approach that CH2M HILL would like to use in demonstrating no reasonable possibility for exposure using worst-case exposure models. Following the general description, there is a example using a specific project site.

Approach to Demonstrating No Exposure

To demonstrating that there is no exposure and no reasonable possibility for exposure, the possible routes of exposure must be identified and then each route of exposure must be eliminated. The three routes of exposure that exist on most hazardous waste sites are:

• Ingestion-A minor route of exposure that can be controlled through the use of good work practices, establishing appropriate decontamination facilities, and prohibiting hand-to-mouth contact activities onsite.
   
• Dermal—Depending on the types of contaminants, this route of exposure can be significant; however, it is typically easily controlled through the use of personal protective equipment (PPE). Personnel using PPE would have to trained and medically monitored in accordance with OSHA regulations on PPE.
   
• Inhalation—This is typically a significant potential route of exposure on most hazardous waste sites. In conjunction with an external industrial hygienist, CH2M HILL has developed worst-case exposure models to predict the severity of the route of exposure.
   

Worst-Case Model

CH2M HILL uses three worst-case exposure models to predict the severity of inhalation hazards on hazardous waste sites. At sites with minimal contamination CH2M HILL would also like to use these models to demonstrate that there is no reasonable possibility for exposure to safety or health hazards which means that the scope of 29 CFR 1910.120 would not apply. A brief discussion of each model is presented below and more detailed information on each model is presented in the referenced attachments.

• Groundwater to Air (for Volatile Compounds)—This model predicts an equilibrium air concentration for dilute concentrations of volatile compounds in groundwater. (See Attachment 1.) This model incorporates a conservative assumption that the system is closed and unventilated. If the air concentration under these conditions is below the permissible exposure limit (PEL), it is not chemically possible for breathing zone concentrations to exceed the PEL. If dermal hazards are controlled through the use of PPE, would OSHA accept this approach as a demonstration of no exposure and no reasonable possibility for exposure and therefore allow the conclusion that 29 CFR 1910.120 does not apply?
   
• Soil to Air (for Volatile Compounds)—This model predicts an air concentration for given concentrations of volatiles in soil. The basis of this model is partitioning properties of the compounds. (See Attachment 2.) This model incorporates a conservative assumption that the system is closed and unventilated. If the air concentration under these conditions is below the permissible exposure limit (PEL), it is not chemically possible for breathing zone concentrations to exceed the PEL. If dermal hazards are controlled through the use of PPE, would OSHA accept this approach as a demonstration of no exposure and reasonable possibility for exposure and therefore allow the conclusion that 29 CFR 1910.120 does not apply?
   
• Soil to Air (for Nonvolatile Compounds)—This model predicts an air concentration for given concentration of nonvolatile compounds in soil. This model calculates the amount of airborne dust necessary for the contaminants' PELs to be exceeded. (See Attachment 3.) CH2M HILL would use visual dust as an action level for stopping work. If the worst-case calculations indicate that dust levels must exceed visual dust in order for the PELs to be exceeded and dermal hazards are controlled through the use of PPE, would OSHA accept this approach as a demonstration of no exposure and reasonable possibility for exposure and therefore allow the conclusion that 29 CFR 1910.120 does not apply?
   

Project Site Application of Worst-Case Model

A CH2M HILL client has a site that is Resource Conservation Recovery Act (RCRA) listed site because of an inactive surface impoundment. The majority of the contaminated soil in the surface impoundment has already been excavated, stabilized, and disposed of offsite but the groundwater below the surface impoundment is contaminated with nickel. During the initial investigation, soil samples were collected and found to contain the maximum concentrations listed below.

• Chromium: 1,400 mg/kg
• Lead: 200 mg/kg
• Nickel: 900 mg/kg
• Zinc: 390 mg/kg

Additional work at the site will include removing the remaining contaminated soil, removing uncontaminated stormwater in the excavated area, stabilizing the walls of the excavated area by adding bentonite (or similar material), backfilling and compacting the excavated area, implementing erosion control measures, and capping the surface impoundment area. Only the first activity may involve potential exposure to contaminated media.

When the soil to air model for nonvolatile compounds is applied to this site, the airborne dust level needed to exceed the contaminants' PELs is 32 mg/m³. This model assumes that the maximum concentrations for the four chemicals listed above were detected in a single soil sample. This assumption is not valid, but is used because it makes the model more conservative and therefore more protective. If dermal exposures are controlled and there is no visual airborne dust, would OSHA accept that there is not a reasonable possibility for exposure to safety or health hazards and conclude that 29 CFR 1910.120 does not apply? It is assumed that if OSHA accepts this approach, that other OSHA regulations such as Hazard Communication and the PPE regulations would still be applicable.

Summary

CH2M HILL is requesting the OSHA provide a written interpretation of whether the three worst case models summarized above are an acceptable method to demonstrate that there is no reasonable possibility for exposure and whether we can conclude that 29 CFR 1910.120 does not apply when these models predict that PELs will not exceeded and dermal exposures can be controlled through the use of PPE. In addition, we are requesting an interpretation for the project site described above. Since work on the project site is scheduled to begin within a few weeks, a prompt response would be appreciated.

If you have any questions or need clarification on the information presented in this letter, please do not hesitate to contact me at (206) 453-5005 extension 5342.

Sincerely,



CH2M HILL
Mollie Netherland
Corporate Health and Safety Manager