Fort Wainwright Utilidor Upgrade

Fort Wainwright, Alaska
Doyon Utilities

Utilidor expansion and refurbishment is a specialty that RESPEC has been providing throughout Interior Alaska for the past several decades. In 1986, we designed a $28 million expansion of the utilidor system in the southeast industrial area of Fort Wainwright (FWA) to support the extension of water distribution, steam district heating, and sewer collection systems and serve the needs of the 6th Infantry Division. The utilidor upgrade rehabilitated more than 2 miles of existing utilidor and added 2 miles of new utilidor.

When Doyon Utilities took ownership of the FWA utilities in 2008, RESPEC provided a post-wide characterization study of the water, sewer, and steam district heating utilities. This study included a field condition assessment of 30 miles of utilidors and associated vaults.

The characterization study is used for identifying and ranking capital improvement projects. The recommendations for the utilidors in this project generally included the following:

• Replace steel-pipe sewer and water mains to increase the life of these utilities.
• Replace the insulation on steam and condensate pipes for steam district heating to reduce the ambient temperature in the utilidors and deliver warmer steam in outlying areas. (Where sewer and district heating pipe travel through the same utilidor, heat loss from steam and condensate piping heats the wastewater, which leads to hydrogen sulfide forming and corroding the sewer pipe.)

Since the 2008 utility study, RESPEC has designed six utilidor projects as the prime consultant by providing the civil, structural, mechanical, and electrical engineering services and performing land surveys. These projects have typically included completely removing and replacing steam, condensate, water, and sewer pipes. The work has also included installing connections to distribution mains (both within utilidor vaults and direct-buried underground); connections to building services within mechanical rooms; and all of the anchors, pipe guides, expansion joints, drip legs, valves, cleanouts, and other fittings, devices, and appurtenances that are necessary for a complete and operable system.

The post-2008 FWA utilidor work has required asbestos abatement. The original 1950s vaults and some of the later vaults are also being upgraded with hatch and entrance safety devices, lighting, and passive ventilation, and will be elevated to prevent surface-water inflow. The vaults have occasionally been completely replaced to provide clearance and maintenance access for upgraded pipe and fittings.

Current knowledge of the field conditions is important to our design process. On-site inspections are performed in confined spaces and areas of known or potential contamination with hazardous materials. We take the safety of our employees seriously. Our civil engineers, surveyors, and other staff who may need to enter utilidors receive annual asbestos awareness training, confined space training, and respiratory protection training along with fit testing so that they can safely perform these field inspections.