Vacuum sewer system is on to-do list after hanging fire for six years

The city is not only under pressure to fix the wastewater treatment plant due to an administrative order from the U.S. Environmental Protection Agency (see:https://sierracountycitizen.org/whitehead-has-a-plan-to-fix-citys-sewer-woes/  ) , it must also fix its vacuum sewer system before it pollutes the Rio Grande. 

It’s been a problem for years. 

Six years ago the City of T or C borrowed $473,000 from New Mexico Environment Department’s Clean Water State Revolving Fund, and at some unknown time, but made known during the recent budget process, $100,000 of that loan was “forgiven.” 

The city borrowed the money to fix its vacuum sewer system, which runs parallel to the Rio Grande, starting around Arrowhead Road. where the river turns north-northeast, and then the vacuum system takes a left turn away from the river and follows Mims Drive, also known as Rodeo Arena Drive, and branches into side streets. 

All that has been done since the system was installed, according to a January 2025 preliminary engineering report by the city’s on-call engineering firm, Wilson & Company, was to put in a new control panel in 2020 that “is compatible with the city’s SCADA system,” (Supervisory Control and Data Acquisition). In a recent phone call with the Citizen, City Manager Gary Whitehead said Wilson & Co. was paid $30,000 to do the vacuum system report. Please find the Wilson & Co. preliminary engineering report on the vacuum sewer system at the end of this article.

The recent budget that was adopted mid-July, says the city has about $440,000 left from the 2019 loan. 

The engineering report states the system was installed in 1995 and then expanded in 1997–yet it is 24 years old. Its collection pipes run for three miles, consisting of “ 4-inch PVC pipe and older cast iron pipe.” It serves 162 “residents” [I suspect “residences” is what they meant] and 5 commercial properties. 

The report repeatedly points out that the city has no records on maintenance, repairs, replacements and inspections, and therefore assumes none to little were done.  

Here’s a succinct description of how vacuum sewers work from Google’s AI Overview:

Valve pits are underground enclosures in a vacuum sewer system that house the interface valve and controller where wastewater gravity-flows from a home into the pit’s collection sump, triggering the valve to open and propel the sewage into the vacuum main using the vacuum created by the system’s vacuum pumps. These pits are sealed to maintain vacuum, are strategically located to account for topography, and often feature sensors or monitoring systems for leak detection and operational efficiency. [1, 2, 3, 4]

How a Vacuum Sewer System with Valve Pits Works

• Wastewater Collection: Wastewater flows by gravity from a house’s internal plumbing to the valve pit’s collection sump. [2]

• Valve Activation: As the sump fills, a sensor detects the rising liquid level, activating the controller within the pit. [2, 5]

• Valve Opening: The controller then opens the interface valve, allowing the liquid and a controlled amount of air to be drawn into the vacuum main. [1, 5]

• Conveyance to Station: The vacuum pumps at the central vacuum station pull the wastewater and air through the vacuum mains. [1, 2]

• Collection and Treatment: The mixture enters a collection tank at the station before being pumped to a treatment plant. [2]

Key Components of a Valve Pit

• Sump: The collection area where wastewater from the gravity line accumulates. [2]

• Interface Valve: A normally closed valve that opens to release the collected sewage into the vacuum main. [1, 2]

• Controller: An electronic unit that monitors the liquid level and controls the timing and operation of the interface valve. [5, 6]

• Vacuum and Air Terminals: Openings in the pit that facilitate the connection to the vacuum main and allow air to enter the system for operation. [1, 3]

• Sealed Lid: A traffic-rated, sealed, and hinged lid provides access for maintenance while preventing air infiltration and water entry. [3, 7]

Benefits and Considerations

• Environmentally Friendly: The sealed system prevents groundwater infiltration and protects the environment from leaks, as any leak would introduce air, triggering an alert. [4]

• Flexible Installation: Vacuum sewer systems are ideal for areas with difficult terrain, high water tables, or unstable soils where gravity systems are impractical. [2, 8]

• Monitoring: Many modern systems use sensors and wireless monitoring to detect leaks, monitor performance, and help operators identify and respond to problems quickly. [6, 9]
• Maintenance Access: The sealed design and accessible nature of valve pits allow for easier maintenance compared to conventional systems. [10, 11]

AI responses may include mistakes.

There are 81 valve pits in the system, 15 of which were constructed in 1997 during the “Mims Drive expansion.” There are 25 pits in the “southern portion” that are in “fair condition.” There are 56 pits in the northern portion that “need rehabilitation.” 

Although the collection lines are OK, the system “experiences frequent backups from water-logging leading to several issues including a large loss of pressure at the [northern]end of the system line.” 

“The pits were not designed well,” Whitehead told the Citizen. “They fill up with rain water. The Hagen Street line leaks and loses vacuum pressure.” 

The result is “overflow and backup of raw sewage that can possibly spread dangerous bacteria, parasites and viruses. With proximity to the Rio Grande, the aged sewer lines have the potential of leaching into the groundwater and making its way to the river. This area lies within the flood zone,” the engineering report warns. 

The engineering report gives two alternatives–replace the whole system for about $2.3 million, which includes engineering fees, or rehabilitate it for a little over $900,000. 

The city is going with the rehabilitation option. If the city follows the engineers’ suggestions, to alleviate the waterlogging issues, the city will do the following: 

–new vacuum pump

–new sewage pump

–add an electric air admission control system that will add pressure “during timed intervals,” which will propel the sewage along the vacuum main

Other repairs in the $900,000 estimate include: 

–replace all equipment in the vacuum system’s main building on Riverside

–rehabilitate 56 valve pits on the north side by replacing rubber pipe connections (cracked leaking), installing valve pit extension collars to reduce rain runoff 

–add an odor control drum to the system that has no odor control

In the last five months of Whitehead’s tenure, during budget and ICIP (Infrastructure Capital Improvement Plan) sessions, Whitehead has said that this vacuum system will be replaced with the traditional system the city has throughout the rest of the city. 

Arnie Castaneda, the water and wastewater director for two years, who left last January, also said the vacuum system should be replaced with a traditional system. He said the type of vacuum system that was installed is one that is used by boat yards to pump out a boat’s holding tanks. He said the company doesn’t make the parts any more, but they are of a proprietary design, and therefore replacement parts must be purchased at their dictated price. 

The Wilson engineering report confirms that “all equipment will be purchased from the manufacturer.” 

Whitehead told the city commissioners, at the August 27 meeting, that the vacuum system and the wastewater treatment plant fixes are meant to “stabilize” the sewer system for “five to seven years.” A major engineering report on the whole sewer system is currently in the works by Wilson & Company, which will determine how much else needs to be done to the system, how it should be phased, and how much it will likely cost.