LAKE TAHOE, Calif./ Nev. – Tahoe’s clarity report card just came out, yet two sewage spills occurring within less than two weeks of each other have minds on murkier matters.

A private contractor working for Caltrans on Highway 28 near Gar Woods struck a North Tahoe Public Utility District’s main sewer export pipeline the morning of July 18. This sent an estimated 85,000 gallons of raw sewage into Carnelian Bay. The spill closed beaches and a myriad of health advisories ensued, warning of elevated water bacteria counts. All advisories finally lifted on July 31.

“It was not a case of infrastructure failure in any way,” NTPUD Public Information Officer Justin Broglio said, explaining it was 100% human caused and upgrades would not have helped in this situation. While upgrades would not have avoided the north lake spill, a corroded valve caused a spill just 11 days later and many miles south.

---

---

On July 28, the corroded valve broke and gave way to 5-10 gallons of sewage spilling into Tahoe’s neighbor, Fallen Leaf Lake. The much smaller Tahoe counterpart lies immediately south of Tahoe and across Highway 89, but connects to Lake Tahoe by Taylor Creek. While bacterial levels in Fallen Leaf Lake never reached levels requiring beach closures there, warning signs remained posted until bacterial counts dropped to baseline levels 36 hours later.

South Tahoe Public Utility District’s board of directors had approved a corrosion protection program just the month before, in June, which would assess the condition of the district’s corrosion monitoring systems and develop a plan for future corrosion control projects.

---

---

Their Fallen Leaf Lake system put itself first in line with its corroded valve caused spill. The district is replacing the same valve at other Fallen Leaf Lake pump stations to address and avoid any future issues.

STPUD Director of Public and Legislative Affairs, Shelly Thomsen, says work on that system is no easy task with over 200 connections requiring 14 pump stations to transport wastewater to Highway 89. “Due to the topography,” Thomsen says, “this infrastructure is located along the one-lane road, right on the shore of Fallen Leaf Lake, making access difficult.”

These recent spills brought back memories of past spills and discussions on prevention.

The Kings Beach spill of 2005 brought about some changes to permitting, and ignited partnerships between special districts. The spill, caused by a private contractor hitting a line while building a private pier, also started talks of relocating sewer lines away from the lake shore and surrounding areas. However, the cost back then of relocation, estimated at $92 million, was enough to raise eyebrows and discussions on whether tax payers could shoulder that.

It’s unclear what happened to the discussions on relocation, as NTPUDs Risk-Based Sewer System Management Plan adopted in October of 2013 an updated September 2016 has no mention of relocation.

Following the 2005 spill, news articles around the time say districts made plans to develop sewer project identification processes, determine sewer prioritization, support education and outreach on the topic.

Since the Kings Beach spill, the Lahontan Water Board and the Tahoe Regional Planning Agency have added language to their permit conditions, noting permittee’s obligation and responsibility to locate underground utilities before starting activity by contacting USA DIGS. The water board says it’s also state law.

In the recent July 18 north Tahoe spill, according to Caltrans, the project that led to the spill had a survey done. One possibility being investigated is whether the survey had mistaken the lines as gas lines, instead of sewage. However, John O’Connell with Caltrans says that possibility has not yet been confirmed.

Most of the lines around Tahoe are aging. According to NTPUDs Risk-Based Sewer System Management Plan, sewage export systems, including force mains, were place between 1968-1969. That’s around the time many sewage pipelines around the basin were installed with the passage of the Porter-Cologne Water Quality Control Act, which established regulatory measures to protect and maintain California’s water resources.

For Tahoe, the act essentially outlawed septic tanks and cesspools after 1972 and required all waste from buildings go through sewage systems and be transported outside the Lake Tahoe watershed.

When NTPUD’s force main lines were installed, there was no real way of inspecting them thereafter, so the district takes advantage of any opportunity to check on their internal condition during accidents and incidents. “When repairs were made, the force main was found to be in good condition,” their 2013plan reads, updated in 2016.

With most of the basin’s sewage pipelines approaching 60 years old, infrastructure upgrades are on basin districts’ minds. Incline Village General Improvement District is currently in the middle of multi-year project replacing a 20.5 mile long effluent export pipeline that runs along Highway 28.

This line is a part of the district’s wastewater collection, treatment, and export system that services Incline Village and Crystal Bay, Nev., and the Nevada State Parks (Sand Harbor, Spooner, and Memorial Point). Their Wastewater Resource Recovery Facility treats approximately 800,000 to 1.5 million gallons of sewage each day and the effluent export pipeline pumps the wastewater out of the Tahoe basin.

This is an example of the overhaul replacing the underground infrastructure looks like. The district is completing the project over the course of four years and was estimated at the start of the project to cost around $59 million. The hope is that it will all be worth it after the last pipeline has had multiple failures in recent years. Jeff Cowen, Public Information Officer for the Tahoe Regional Planning Agency, says the pipe going in is made of material rated to last a lot longer than the material crews are taking out.

This is just for the export pipeline, which takes sewage out of Tahoe.

STPUD’s Thomsen gives an idea of the intricacy of a sewer system in a town such as South Lake Tahoe, before it is exported out of the Basin over Luther Pass. “It is a complex system, with over 330 miles of pipe and 39 pump stations needed to convey sewage from the far reaches of our community to the wastewater treatment plant in the center of town.”

Their asset management program is responsible for maintaining and replacing the infrastructure to extend the life of the system. Maintaining a system that serves over 18,000 homes and businesses isn’t a walk in the park.

“One of the challenges,” Thomsen says, “with sewer pipes is that they are underground and the only way to assess their condition is by sending a TV camera through them.”

Their crews aim to video 10% of their gravity sewer mains each year to assess conditions, fix immediate concerns and prioritize future replacement or rehabilitation projects.

The Lahontan Water Board is investigating both spills.