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The Monterey Interceptor between Seaside Pump Station and Monterey Beach Resort is buried in the dunes, approximately 100 to 175 feet from the dune bluff. Between Monterey Beach Resort and Tide Avenue the pipeline is not under imminent threat of erosion damage (PWA and Griggs, 2004). However, the pipeline could be vulnerable during a large storm event towards the end of the 50-year planning horizon. From Tide Avenue to Monterey Pump Station, the pipeline is located in the dunes a minimum of 115 feet from the shoreline. Between Monterey Pump Station and Wharf II, the Monterey Interceptor was originally buried beneath the back beach, but due to erosion is now at mid-beach.Based on approximate future erosion rates of between 1.5 and 3.0 ft/year, the shoreline between Seaside Pump Station and Monterey Beach Resort would be expected to erode 75-150 feet over the next 50 years, and parts of the pipeline between these two locations may be compromised over the next 40 years. The erosion could uncover the pipe and/or manholes and make them vulnerable to damage. Hence, the Monterey Interceptor between Seaside Pump Station and Monterey Beach Resort is a facility at high risk of erosion (PWA and Griggs, 2004). Between Monterey Beach Resort and Monterey Pump Station, the future erosion rate is estimated at approximately 1.5 ft/year, and therefore the pipeline would be at low risk of chronic erosion over the next 50 years. However, given the accuracy of the base map (+/- 16 feet) used to define the position of the pipeline in the dunes here (PWA and Griggs, 2004), it is designated as a moderate risk facility with the potential for storm damage towards the end of the 50-year planning horizon. Between Monterey Pump Station and Wharf II the shoreline is estimated to erode at an average future rate of approximately 1.0 ft/year and the beach has been observed to scour during storms (Dingler and Reiss, 2002). Manhole covers are now sometimes exposed at low tide during the winter and are vulnerable to damage. At this location, the Monterey Interceptor pipeline is under imminent threat of erosion damage and is at high risk of erosion (PWA and Griggs, 2004).The Monterey Interceptor carries all of the raw (untreated) wastewater from the cities of Pacific Grove and Monterey. This flow is pumped through Monterey and Seaside Pump Stations to the MRWPCA Regional Treatment Plant. The pipeline is a vital facility that needs to remain fully operational indefinitely, and the consequences of erosion would be significant economic, environmental, and human health impacts. A breach to this facility would have adverse environmental impacts to the dunes and beaches, and water quality impacts within the MBNMS. The exposure of the pipeline would be a threat to marine resources if erosion caused a spill to occur. The Monterey Interceptor between Seaside Pump Station and Wharf II is therefore a high consequence facility. The shapefile showing the occurence of the pipline and the segments according to risk was prepared by PWA for the Southern Monterey Bay Coastal Regional Sediment Management Plan (AMBAG, 2008) |