WWTP Digester Gallery Enclosure for Town of Friday Harbor, WA: 2009 - When the Town's Wastewater Treatment Plant Improvements Project was completed in 2004, the piping gallery adjacent the new aerobic digester was, by design, open to the weather. The designers had believed, based on the comparatively mild climate, that heat trace and insulation would be sufficient protection against freezing weather. This proved in error. After construction there were several hard winter freezes lasting several days causing burst piping, broken valves and heavy damage to the progressive cavity sludge pump located in the vault.

Wayne Haefele & Associates, Inc. was asked to design a cover for the pit. After discussions with the Town Administrator and the WWTP manager we decided to create a shed roofed structure that would be attractive to look at and harmonize with the nearby buildings.

The enclosure is constructed entirely of treated lumber to resist rot, since the interior of the pipe gallery is constantly damp and humid. The structure is insulated with finished interior ceiling and screened ventilation at eves and peak to hold heat and prevent condensation. For interior ventilation and natural lighting, two manually opening domed skylights were included in the design. The exterior is finished with metal roof and siding matching that used on two existing pole barn structures at the site while the colors used were chosen to blend with several other nearby flat roofed, giant brick buildings, thus tying together the two disparate styles.