Simultaneously Dredging Private Docks and a Federal Channel in an Urban Waterway...it Takes Villages

Abstract: San Rafael Creek is a San Francisco Bay tributary located just north of the Golden Gate Bridge. In 1919, Congress authorized the U.S. Army Corps of Engineers (USACE) to dredge and regularly maintain a navigable channel extending two miles upstream from the mouth of the Creek to two miles past the mouth to the deeper portion of the Bay. Dredging the Creek to maintain navigability and access to the Bay was conducted as an add-on to the USACE Work Plan every four to seven years for several decades. However, after the congressional moratorium on budget earmarks, funding the Creek maintenance dredging became a significant challenge. This challenge also impacted the 100+ residential and commercial docks who relied on the cost saving benefit of dredging in tandem with the federal channel project. The last time the Creek was fully dredged prior to 2023 was 2002, and siltation was preventing navigation in many areas below high tide.

The federally maintained portion of the Creek upstream from its mouth is populated by a diverse community of private residences and commercial businesses servicing the boating community. The south side of the Creek, known as the Canal District, is the most densely populated neighborhood in Marin County consisting of apartment buildings, light industry, commercial boatyards, and a large boat harbor. In contrast, the north side of the Creek is populated by affluent single-family residences along with a yacht harbor and docks servicing a shopping district. Beginning in 2016, representatives from many of the diverse Creekside communities and the City of San Rafael banded together in partnership with the USACE to more effectively lobby Congress for maintenance dredging funds. After four years of persistence, the USACE was granted funding to fully dredge the Creek, including the funds necessary for more costly ocean disposal of sediments exhibiting elevated contaminant concentrations too high for in-Bay disposal approval.

Obtaining funds for the federal portion of the Creek was only the first challenge to overcome. The City had to obtain new permits from five agencies in time to coordinate with the USACE dredging schedule. Simultaneous to this effort, the City needed to develop a strategy to solicit payment from 100+ dock-owners within a small timeframe dictated by the USACE’s environmental work window. Sediment contaminants were also a challenge. Sediments in the urbanized upstream portion of the Creek have historically contained elevated contaminant concentrations. New testing of Creek sediments showed that contaminants in the upstream sediments were still too high for in-Bay disposal but not at levels high enough to prohibit disposal at the ocean disposal site. However, it was also determined that the post-dredge sediment surface would have contaminants at unallowable concentrations. Working with the regulators, the USACE and the City developed a plan for placing a one-foot cap over the impacted area using “clean” sediments from the downstream project area. Close collaboration between the USACE, the City, the contractor, and the Creek community at large enabled the resolution of all logistical challenges allowing for completion of the entire project.

How does this project / topic contribute to the advancement of the industry and profession?: This project exemplifies how local partners to the U.S. Army Corps of Engineers can optimize the advantage of dredging private or municipal facilities in conjunction with dredging in a federal navigation channel even when multiple logistical and environmental challenges arise.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: In a new approach negotiated with the regulators and undertaken for maintenance dredging work in San Francisco Bay, the local sponsor (City of San Rafael) and the Corps of Engineers were allowed to place a clean sediment cap over a portion of the navigation footprint where elevated contaminants were observed in the post-dredge sediment surface. The City agreed to direct their contractor to use clean sediment from the non-federal portion of the waterway to cap the area of concern, most of which lied inside the federal channel.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: There were significant environmental and logistical challenges, which together made coordination among all stakeholders the greatest challenge. Clear and frequent communication between the City, the Army Corps, the private dock owners, the regulators, and the contractor was the key to successfully completing the project. Application of sound science and effective reporting and communication of resulting data were also important to resolving the contaminant issues in the San Rafael Creek navigation channel. Development of a strategic funding plan for the City and the dock-owners also played a role in making the project successful.

Who is the target audience for this paper?: Owners and managers of private, municipal (including ports) and federal waterways in need of maintenance dredging.