Demolition & Removal of Water Infrastructure

The U.S. Department of Interior (DOI), National Park Service (NPS), Point Reyes National Seashore (PORE), initiated a plan for the demolition of an in-water infrastructure of abandoned oyster racks from Drakes Estero (in the Phillip Burton Wilderness), Point Reyes National Seashore. As part of the process, HECO was issued a scoping trip task order to meet with park staff and visit Drakes Estero on December 10th, 2014, to provide the Park with engineering expertise related to the oyster rack demolition in support of the Park’s collaboration with the permitting agencies. HECO submitted the final version of Scoping Trip Letter Report in January 2015 that included recommended A/E activities for the Title I Preliminary Engineering Report (PER). The Title I Preliminary Engineering task order was awarded in January 2015 and the pull-out field investigations were carried out in early February 2015. The Title I PER was prepared for inclusion with the compliance permit request the NPS submitted to the California Coastal Commission in early March 2015.

The resulting project removed and disposed of abandoned infrastructure and aqua cultural debris from Drakes Estero. There were 95 oyster racks that comprised approximately 7.07 acres of area. Approximately 2,230 vertical bent structures made of 2″x4″ and 2″x6″ lumber were sunk about 5 feet into the bed of the Estero. The material removed was between 200,000 and 250,000 total board feet of lumber. Overall the project removed more than 5 miles of racks and 500 tons of aquaculture and marine debris. Approximately 30% of the area beneath the oyster racks had moderate to heavy accumulation of oyster shell and debris. Within that area, there were locations totaling 1 acre of debris, including plastic tubes, oyster strings, wire and mesh bags full of oysters were removed. The area of heaviest shell accumulation under the racks was treated in-place to improve habitat for eel grass. Mechanically mixing shell down into the soil allowed more area for fine sediment and eelgrass growing habitat. In addition, the project removed oyster mats, escaped manila clam, anchors lines and buoys from some sand bar areas formerly used as growing beds. Approximately 15 sections of 12-foot wide plastic mat, covering approximately 16,900 SF was removed. The project removed escaped manila clam from isolated areas on the sand bars. The work also involved the removal of all remaining anchors, lines and buoys from other sandbars within the Estero.

Services Provided by HECO Engineers:

• Project Management
• Project Design
• Environmental Engineering
• Survey
• Title I Scoping
• Demolition Services