Remediating Existing Buildings

By Ken Kastman, PE

Old buildings can be loaded with charming details that can be preserved, retaining a unique touch, as they are reborn for new uses. Unfortunately, they may also contain environmental dangers that need to be addressed before they are redeveloped.

The American Society of Testing and Materials (ASTM) Standard D 1527-00 is the most widely used guide for identifying potential environmental concerns. Referred to as a Phase 1 Environmental Site Assessment (ESA), this standard identifies recognized environmental conditions (RECs) that could impact the property.

RECs identified in a Phase 1 ESA relate to impacts from spills or contaminated soils and groundwater. However, the Phase 1 ESA may not identify other environmental issues inside the structure that need to be addressed prior to reuse.

There are several potential conditions to look out for when redeveloping existing structures. (See our chart link to chart for these conditions, their risk drivers and common solutions.) The remediation techniques for most of these concerns are generally well understood and the remediation is straightforward, though sometimes expensive. Cleanup procedures are defined within various regulations and standards.

Vapor Intrusion Concerns

Vapor intrusion, however, is becoming a more significant concern in the redevelopment of contaminated properties or reuse of existing buildings. The environmental concern is caused when the soil or groundwater under a building is contaminated with volatile organic compounds (VOCs) that can seep upward into the building. Occupants of the building can be at risk from the inhalation of the VOCs.

Vapor intrusion concerns are becoming more widely identified and some state regulations are changing to respond to the increase of knowledge regarding the potential risks. The potential for vapor intrusion into buildings may trigger the re-evaluation of closed properties under various state voluntary cleanup programs (VCPs).

For example, the New York Department of Environment Conservation (DEC) has issued a draft policy relating to revisiting legacy sites (pre-2003) relative to vapor intrusion. According to Ken Kamlet of the Newman Development Group LLC, and a member of the New York chapter of the NBA, “The policy may have a potential chilling effect on brownfield development in New York if issues relating to roles, responsibilities and liabilities are not more clearly defined.” (Read the New York chapter of the NBA's comments on the proposed guidance.)

The status of federal vapor intrusion regulation is in flux. The Occupational Safety and Health Administration (OSHA) typically governs the regulation of indoor air. The U.S. EPA typically governs environmental risk. There is a controversy over who governs indoor air environmental risk.

OSHA standards are less stringent — this is because OSHA can direct that employers inform and train workers as a means of protecting the worker from undue risks. The U.S. EPA argues that visitors to a building or unsuspecting residents are not subject to direction or training and are at potentially greater risk. Therefore, the U.S. EPA suggests more stringent cleanup levels to protect these unsuspecting persons.

Managing Vapor Intrusion

Managing vapor intrusion issues in existing buildings is largely a “retrofitting” exercise. The process is fairly simple and is based on methods for managing naturally-occurring radon gas. Over 500,000 homes and buildings have been remediated or protected from radon inhalation risk.

The remediation concept is to reduce vapor levels to acceptable risk levels. This can be done by preventing vapor intrusion into the building or removing the vapors after entry.

Many buildings act like chimneys that draw air upward from the ground into, and subsequently outward from, the building. This chimney effect is caused by a variety of processes, such as the rising of warm air in the building (especially in colder climates), the active use of heating, ventilating and air conditioning (HVAC) systems or even processes as simple as the active venting of clothes dryers.

Choosing a design for the remediation of vapor intrusion issues should take into consideration:

For example, buildings may be placed directly on the soil (slab on grade), have a “crawl” space or have a basement. Recent investigations by the U.S. EPA have suggested that in buildings that have water sump systems to prevent flooded basements, these sumps are the primary intrusion pathway for contaminates, through a direct water interface to the building’s indoor air.

The design of a remediation system for each pathway is different. The most typical procedures for managing vapor intrusion include:

Sealing soil gas entry routes, including sumps: Paint-on or spray-on liquid sealing products can be applied from the inside to floors and slabs on grade.
Passive vapor barriers: Passive barriers such as plastic sheets are typically not used in existing buildings because they are placed under floor slabs.
Building depressurization systems: Systems using fans and blowers to remove vapors can be quite effective for buildings with crawl spaces or slab on grade construction where a porous stone base exists under the slab.
Passive and active absorption systems
Active soil depressurization: These can be effective when placed within the soil contamination plume area, but they require maintenance and regular operation. Active systems are typically more effective than passive systems.

Concerns relating to vapor intrusion and other environmental issues in existing buildings can be identified, costed and resolved. The property redevelopment “deal equation” should consider these concerns and costs like any other aspect of the transaction.

Ken Kastman, PE, is a senior principal engineer and vice president of URS Corporation, leading the company’s property redevelopment network from the Chicago office.