Surf, Sea Breezes, & Sewers

From the surfers hitting the waves before daybreak to the bonfires that last into the morning hours, Surf City, USA thrives on its oceanfront beauty to attract visitors and support its local businesses. Given the sensitive receptors and the dependency of local business on the natural beauty to attract visitors the understanding and management of the sewer odors became a key issue in the assessment and long term rehabilitation of a major trunk sewer by the oceanfront.Since the early 1980's Orange County Sanitation District.s Coast Trunk Sewer has serviced Southern California's surfing and beach-life mecca, Huntington Beach. Constructed to support Orange County.s exponential growth, the sewer is operated well below its design capacity as some of the expected development in the area never materialized. While sewer has never developed a problem with capacity, in a Catch-22 the sewer has been affected by issues of low flows, sediment, sediment accumulation, corrosion, and odor emissions.At the onset of the sewer condition assessment effort and initial odor assessment was conducted. Grab and continuous sampling of the wastewater and odor was done at locations along the 5 mile stretch that runs through downtown Huntington Beach and along the beaches as it heads south to the District.s wastewater treatment plant. The odor assessment and control was part of a greater assessment and rehabilitation plan that involved manned entry and CCTV inspection to determine the condition of the sewer and the development of a sewer cleaning and rehabilitation plan to extend the useable life of the trunk sewer.The odor control plan included an initial report detailing the approach of the field work that was required to measure odor potential. The District's Public Relations Department was actively involved with the City of Huntington Beach and State of California to notify the public before any field work was conducted. Additionally working with the District develop an effective plan to maintain excellent community relations while effectively and efficiently mitigating exposure to the community, which was a key to the success of the project.Prior to the assessment work it was expected, under normal sewer conditions, the highest levels of corrosion would have been found in the same locations as the worst odors, identified by the highest levels of H2S and sulfide in the wastewater. Strangely enough, the results demonstrated the worst odor, based on H2S and sulfide in the wastewater, were not aligned with the locations of most severe corrosion damage that were observed during manned sewer inspection. We will explain what factors contributed to making this sewer differ from the expected norm.The second feature of the study was the development of an odor control plan to be used during any entry into the manhole. The proposed odor control plan to be used during the inspection and rehabilitation consisted of a simple tiered approach that consisted of the following: location of the manhole (residential, downtown, beach, etc.); concentration of H2S; wind direction; proximity to receptor; timing of work; duration of work. We found that the simple approach seemed to work the best when approaching the work. We will explain how we followed the KISS principle in the development and implementation of a simple and feasible odor control plan.