This temporary bridge allowed Vallecitos Water District crews to repair a manhole without affected sensitive habitat. Photo: Vallecitos Water District rehab manhole

Vallecitos Water District Crews Rehab Manhole, Protecting Environment  

Vallecitos Water District crews sprang into action to repair and rehabilitate a manhole in danger of failing, successfully preventing a spill, which could have resulted in significant environmental damage.

Located just off Palomar Airport Road in a shared 30-foot easement with the Buena Sanitation District in Carlsbad, the manhole is part of a 30-inch outfall providing a main sewage drain for the City of San Marcos. The line feeds directly into the Encina Wastewater Treatment plant a half-mile from the project site.

Originally constructed in the 1980s, turbulence generated by a hard right-turn along the sewer easement creates hydrogen sulfide gases. These gases corrode concrete and weakened the manhole over the years. Flooding also occurs in the area and allows rainfall to infiltrate the manhole.

Preventing harm to sensitive habitat areas

Vallecitos Water District staff became concerned the structure could fail. The result would be a major sewage spill affecting the nearby Encinas Creek Habitat Conservation Area, ultimately spilling into the Pacific Ocean a mile downstream. The Habitat Conservation Area is owned by the Center for Natural Lands Management, which supports its management through an endowment.

The Encinas Creek HCA is also part of the City of Carlsbad’s habitat management preserve. It includes riparian habitat and is known to be home to state and federally protected species. The Center for Natural Lands Management works to protect the property from trespassing, nonnative invasive plant and animal species, and other issues.

The District determined emergency repairs were required. Although the Vallecitos Water District has proper easement rights to access, operate, and maintain the pipeline, the agency must avoid any impact to the existing habitat while repairing the manhole. This required some creativity by the work crews.

Creative thinking provides access for repairs

A look at the newly repaired manhole. Photo: Vallecitos Water District

A look at the newly repaired manhole. Photo: Vallecitos Water District

The District kept all construction activities within its existing easement to avoid any impacts to existing riparian vegetation. Crews constructed a temporary bridge over an existing stream obstructing access to the manhole. The bridge installation was designed to be temporary, and not affect the existing stream with footings or other supports. Constructing the bridge for access turned out to be the most complex part of the repair project.

District crews working with a contractor team took advantage of the lower sewage flow during the early morning hours, starting work at 3 a.m. to get as low into the waterline as possible. Repairs like this take advantage of the low flows to keep critically important sewer systems in operation.

Instead of replacing the manhole, the District used a polymer concrete replacement product to build a new manhole within the old manhole. As a result, no excavation was needed. Unlike regular concrete, the new material is corrosion-proof and should provide District customers in San Marcos with many years of reliable service while protecting the environment.

Vactor Truck-Leucadia Wastewater District-

Water Agencies Team Up to Reduce Potable Water Use

The Olivenhain Municipal Water District and Leucadia Wastewater District are reducing potable water use by switching to recycled water to flush sewer lines in their service areas.

With the recent installation of new equipment by both agencies, recycled water is now available to Leucadia for sewer line maintenance in the Village Park neighborhood in Encinitas and in the La Costa neighborhood in Carlsbad.

Regular flushing is important for gravity-fed sewer line maintenance. The process involves filling a specialized sewer cleaning vehicle, known as a vactor truck, with water and injecting the water into a sewer main. Flushing the pipes in proper working condition extends their lifetime by removing materials such as grease and roots, which can cause clogs and sewage overflows. Once flushed, a pipeline can be inspected and its condition assessed.

Recycled water, not potable water, now used to flush sewer lines

Prior to this project, Leucadia did not have access to recycled water in Olivenhain’s service area, instead filling vactor trucks with potable water. Leucadia identified the opportunity to reduce potable water use and save its ratepayers money, and approached Olivenhain about creating points at which the wastewater district could fill trucks with recycled water. Five locations throughout Encinitas and Carlsbad were selected.

“It’s a pleasure to partner with neighboring agencies for the common good,” said Olivenhain Municipal Water District Board President Ed Sprague stated. “Simple changes such as these add up and help ensure a reliable water supply for future generations.”

Regional partnership conserves drinking water

“Leucadia is excited to continue its regional partnership with the Olivenhain Municipal Water District,” said David Kulchin, Leucadia’s board president. “Using recycled water to clean sewer pipelines not only saves precious potable water supplies but continues our efforts to utilize renewable resources to the maximum extent possible.”

In addition to sewer line flushing, municipal street sweeping vehicles that were previously using potable water will be able to access recycled water thanks to the new connections. In accordance with state regulations governing recycled water use, the vactor trucks and street sweeping vehicles will have separate filling systems for potable and recycled water.

Approximately 14% of Olivenhain’s overall water demand is met with recycled water. Olivenhain produces up to two million gallons per day of recycled water at its 4S Ranch Water Reclamation Facility and supplements additional demand with recycled water purchased from Rancho Santa Fe Community Services District, City of San Diego, Vallecitos Water District, and San Elijo Joint Powers Authority.