CASE STUDY #2: previous owners make good on remediation costs
The Hensley Field Operations Center was the first building to begin construction under the Dallas Green Building Program. Located on 827 acres that had been used for more than 70 years as a military base, the LEED Gold-certified vehicle maintenance center is a renovated Navy operations building.
The city bought the land in 1932 and leased it to the military in 1941 for use as an air field. In 1990, the Dallas Naval Air Station was one of the installations identified for closure under the federal Base Realignment and Closure program. The Navy ended operations on the site in 1998; and in 2002, when its lease expired, turned the property back over to Dallas.
Knowing it would eventually take possession, in 1994 the city directed the Navy to assess the extent to which the land had been contaminated, a process called a Resource Conservation and Recovery Act Facility Investigation. The resulting 2001 report identified 139 solid waste management units and 450 environmental concerns including land filling, fuel management operations, improper waste/solvent disposal, oil/water separators, and underground storage tanks. Soil and groundwater samples included various heavy metals, petroleum hydrocarbons, chlorinated solvents, petroleum solvents, and polynuclear aromatic hydrocarbons.
The lease required the Navy to return a “clean” property. When negotiations over the definition of clean broke down, the city successfully sued. In 2003, soil remediation was completed. The deadline for groundwater remediation is 2017.
In 2006, the city contracted Terra-con Consultants Inc. to review reports documenting soil and groundwater remediation, long-term groundwater monitoring, and other correspondence generated by Navy contractors. The firm's role is to ensure the city's interests regarding remediation, redevelopment, and use are considered and met, and that the Navy complies with settlement agreement provisions. To that end, the firm's analysis was given to the Texas Commission on Environmental Quality and U.S. EPA in addition to the city.
PROJECT: Hensley Field Operations Center
OWNER: Dallas Sustainable Development and Construction Department, Real Estate Division
COST: $4 million
ARCHITECT: JMA Architecture Studios
REMEDIATION OVERSIGHT AND ENVIRONMENTAL CONSULTING: Terracon Consultants Inc.
With groundwater remediation still under way, the Navy is working toward receiving a Ready for Reuse designation from EPA. For this site, that requires evaluating the indoor air vapor intrusion pathway, which is the migration of volatile vapors from soil and/or ground-water that migrate through the soil column and building slab into the interior space of buildings.
In the meantime, the 80,000-square foot Hensley Field Operations Center is operating as a vehicle maintenance center. Though planned for LEED silver status, the renovation earned enough points to garner Gold status with features such as:Plumbing fixtures that have cut water consumption in half.High-efficiency light fixtures and daylighting strategies that have reduced electricity usage by 25%. Natural light provides more than half the daytime lighting in the building.A photovoltaic array that further offsets electricity usage.A rooftop cistern that collects rain used to irrigate plants inside the building.Native landscaping that eliminates the need for exterior irrigation.A geothermal well for cooling to reduce air-conditioning equipment sizes and overall electricity usage.An under-floor air distribution system with air vents in the floor for more efficient circulation.More than 85% of the waste generated during construction was recycled or reused.Almost 25% of the construction materials were made of recycled content.More than 80% of construction materials used onsite was manufactured locally, and more than 40% of those materials were extracted regionally.Construction materials also included paints, adhesives, and sealants made with low-volatile organic compounds.
In addition to renovating buildings for its own use, the city plans to lease buildings to other tenants and build new ones for both public and private use.
— Sallman (firstname.lastname@example.org) is a professional geoscientist and principal in the Dallas office of Terracon Consultants Inc.WEB EXTRA
Every year, consultants and vendors gather at the International City/ County Management Association and U.S. EPA's Brownfields Conference. This year's meeting was last month in Philadelphia. Visit www.brownfields2011.org/en/home to access sessions, videos, and podcasts from all previous conferences.