Coastal Treatment Plant Sludge Line Replacement Project


UPDATE: On June 8, 2016, the California Coastal Commission approved the Coastal Treatment Plant Sludge Line Replacement Project. For more information, please view the Coastal Commission Staff Report here.

SOCWA maintains two four-inch sludge lines that run through Aliso and Wood Canyons Wilderness Park, carrying treated sewage sludge from SOCWA’s Coastal Treatment Plant in Aliso Canyon to the Regional Treatment Plant in Laguna Niguel.

These sludge lines are more than 30 years old and have deteriorated to the point they need to be replaced quickly, or we risk future sewage spills in the environmentally sensitive Wilderness Park and Aliso Creek, which drains to the ocean. Two recent breaks, one in December 2010 and one in January 2011, are evidence that action is needed.

The SOCWA Board of Directors approved an environmental impact report in March, 2013, in which options for replacing the sludge line were analyzed, including proposed alignments on either side of the creek, an alternative that would transport the sludge using trucks and construction of a solids-handling facility at the Coastal Treatment Plant that would eliminate the need for the sludge pipelines. The solids-handling alternative was a direct result of our public outreach, and was among a number of alternatives proposed by members of the community that received significant study and consideration.

After carefully studying the alternatives, SOCWA staff recommended placing the new sludge pipeline on the east side of the creek. Doing so will allow for the region’s sewage to continue to be treated and disposed of in a safe and cost-effective way while minimizing negative impacts on the environment and to South County’s local quality of life.

sludge line map


SOCWA’s Coastal Treatment Plant – and the sludge lines through Aliso and Wood Canyons Wilderness Park – make it possible to safely treat and dispose of the sewage that is generated by thousands of homes and businesses in south Orange County. That’s approximately 3.5 million gallons of sewage each day — day in and day out, without interruption — that must be treated before it can be safely discharged without harming the ocean. This treatment results in a sludge byproduct that is sent via the sludge lines to our larger treatment facility in Laguna Niguel for processing.

The treatment and safe disposal of our region’s sewage is a critical, but often overlooked, activity that defends the coastal environment and protects public health.

The sludge lines must be replaced or we can expect more breaks and more sewage sludge spills. And that’s not acceptable because it is counter to SOCWA’s mission of protecting public health and the environment.


Final Environmental Impact Report

Addendum to Final EIR

Appendix A — Notice of Preparation (NOP) and NOP Comments

Appendix B — Air Pollutant and Greenhouse Emissions Estimates

Appendix C — Biological Resources Technical Report

Appendix D — Extended Phase I Archeological Investigations

Appendix E — Geotechnical Reports

Appendix F — Hazardous Materials Memorandum

Appendix G — Hydrology Memorandum

Appendix H — Paleontological Resource Assessment

CEQA Notice of Completion Form November 2012

Coastal Treatment Plant Export Sludge Force Main Preliminary Design Report September 2012

Coastal Treatment Plant Export Sludge Replacement Energy and Greenhouse Gas Projections September 2012

Coastal Treatment Plant On-Site Sludge Processing Analysis June 2012

Notice of Public Scoping Meeting

Cultural Assessment for the ACES Project (RWM Paleo, 2000)

Lower Aliso Creek Erosion Assessment – No Appendices – April 2012

Lower Aliso Creek Erosion Assessment – with Appendices – April 2012


SOCWA is committed to listening to our many project stakeholders and to incorporating their comments where possible as we seek a solution to this important issue. SOCWA held three public workshops during the EIR process and worked closely with project stakeholders to solicit input on various project alternatives. Several alternatives proposed by members of the public received significant study and consideration, including one that was analyzed in the environmental impact report.

We also want to make sure your questions are answered. Please click hereto ask a question, provide a comment or to be made aware as more information becomes available.



Why does SOCWA need to replace the pipelines?

The sludge lines are more than 30 years old and have failed twice since December 2010. In order to avoid sewage sludge spills in the sensitive Aliso and Wood Canyons Wilderness Park, a new method for transporting the Coastal Treatment Plant’s sludge to our facility in Laguna Niguel needs to be completed soon. Aliso Creek runs through the canyon as well, which means that future line breaks have the potential of quickly reaching the ocean and causing beach closures.

Is sewage sludge harmful to the environment?

Yes. It contains harmful bacteria, so public health agencies consider it much the same as they do untreated sewage. A break in one of the sludge lines could affect water quality in Aliso Creek and lead to beach closures, so SOCWA hopes to replace the aging Coastal Treatment Plant sludge lines as quickly as the environmental review process allows.

Why are these sludge pipelines so important for South Orange County?

South Orange County homes and businesses served by the Coastal Treatment Plant produce about 1.3 billion gallons of sewage every year, so you can see the benefit of having a reliable infrastructure system to meet this critical need. The continuous removal of sewage sludge from the Coastal Treatment Plant is critical to protecting the environment, because if it isn’t removed, ocean water quality can suffer.

Why not wait until the pipelines can be replaced in conjunction with other projects planned in Aliso Canyon?

We have worked for years to coordinate with various Aliso Creek restoration proposals, but none of these projects has advanced to the planning and funding stages. Now the risk of a serious sewage sludge spill has become so great we can no longer wait for these proposed projects. Two recent sludge line breaks, one in December 2010 and one in January 2011, are evidence that action is needed now on these aging and degraded pipelines.