2020 NOV. 21 ISSUE: CORRALES SEWER CLOG CLEARED; SCHOOL’S HOOK-UP MAY BE SOLUTION

The sewer line along Corrales Road experienced a major blockage in early November when Los Lunas-based Southwest Sewer Service was called in to remediate. The blockage was cleared within a few hours, although the Corrales Public Works Department continued to flush the line for several more hours. Public Works Director Mike Chavez said he could not definitively identify the cause of the problem. “We noticed we had an issue when the pressure on the line increased. We isolated the area in question and applied vacuum on one end and pressure on the other until the blockage loosened up and we could remove it.

“We did have to rotate between the vacuum and pressure a couple of times. We did have to isolate the area so the main was put out of service in the area we were working on.

“We pumped out the tanks at the businesses and residences in said area as to not introduce liquids as we were working. At this point I would not speculate on the exact cause of the blockage, being an enclosed system under pressure, we couldn’t see what the blockage was.” Chavez said the cost of repair would not be known until calculations were made for pumping, staff time and contracted service. Under normal operation, the Village’s six-inch diameter wastewater line is pressurized by a pump at each septic tank connected to the system. If that effluent cannot discharge to the sewer, or encounters unusual difficulty in doing so, the pressure builds, setting off alarms. South of Meadowlark Lane, the wastewater line is eight-inches in diameter.

Hook ups by owners of residential and commercial properties have been slow, at one point leading the funding source, the N.M. Environment Department, to threaten legal acton against the Village. (See Corrales Comment Vol.XXXIII No.1, February 22, 2014 “Corrales Avoids Default on NMED Loan for Sewer Project.”) After decades of confusion, political turmoil and technical and bureaucratic delays, the Corrales sewer system went into operation in February 2014.

With no fanfare or ribbon-cutting, the controversial liquids-only, pressurized sewer system began sending waste water toward Albuquerque’s sewers around 2:15 p.m. that day, pumping from the Corrales Recreation Center’s septic tanks and those at the Village Office. Finally, after more than six years, the biggest hold-out to connecting to the municipal wastewater line, Albuquerque Public Schools, is set to do so in the weeks ahead. APS Director of Operations John Dufay told Corrales Comment November 16 that crews began work on the connection in late summer. He could not say exactlly when the tie-in might come.

Dufay said a variety of factors indicated the time had come to finally connect the school to the Village’s sewer line. “Due to COVID-19, we decided now is a good time to start doing it. Everything just fell into place to do it at this time.” He said the school’s innovative constructed wetlands at the east end of the property —which he designed and directed years ago— has continued to function well. The project will continue to be used, but as an outdoor classroom rather than the schools’s primary wastewater treatment method. The school’s “black water” will be routed to a large septic tank, sand filtration unit and pumping station before it goes to the sewer line along Corrales Road.

Dufay said some amount of “grey water” will still be delivered to the constructed wetlands for educational purposes. When school is fully in session, he expects about 15,000 to 18,000 gallons of wastewater per day will be sent to the municipal sewer. Back in 2014, a letter from the N.M. Environment Department (NMED) about the acceptability of the Village Council’s sewer ordinance arrived just before the council’s February 11 meeting.

Signed by then-NMED Secretary Ryan Flynn, the letter conceded that not all property owners adjacent to the sewer line in the commercial district needed to connect to it immediately. The argument had been advanced by Councillor John Alsobrook the previous year was accepted; that NMED should be satisfied if nearly all the wastewater volume from the business district was sent to the sewer, which he said would be accomplished if municipal facilities, the Catholic church and the elementary school connected.

Flynn’s letter noted, “You and [Village Attorney John] Appel previously conveyed that you anticipate several commercial and government facilties to connect to the system as soon as allowed. Further, these facilities constitute the majority of the anticipated flow rate for the system. “In an effort to assure a functional and healthy system and avoid costly litigation, the Department will re-evaluate the success of [Corrales] Ordinance 13-007 and withhold judgment of potential default of the terms of the loan agreement for two years.

“The department will recognize substantial compliance with the loan agreement’s mandatory connection ordinance requirement under the following circumstances: 50 percent of the anticipated flow rate for the entire Corrales Road High Density Area [the commercial district, Wagner Lane to Meadowlark] is connected by December 31, 2014; 70 percent of the anticipated flow rate for the entire Corrales Road High Density Area is connected by June 30, 2015; and 80 percent of the anticipated flow rate for the entire Corrales Road High Density area is connected by January 31, 2016.”

The NMED secretary asked for reports telling which properties in the commercial district would be hooked up to the sewer as of April 1 that year, as well as on January 15, 2015, July 15, 2015 and February 15, 2016. He also wanted to know how many “fixture units” were to be hooked up at each address by those dates. “This information will allow us both to determine when the milestones outlined above have been met.”

Flynn closed his letter by noting, “I hope the approach outlined above provides a beneficial path forward and meets our mutual goal of a fully functional and fiscally sustainable wastewater collection system.” But Corrales was nowhere near achieving the results that NMED demanded.

NMED’s Environmental Health Division director, Tom Blaine, and Construction Programs Bureau chief, Jim Chiasson, had argued the Village of Corrales was fundamentally in default of its loan and grant agreement that funded completion of the system the previous year. The agreement stated that use of the system must be mandatory.

But council members twice rejected such an ordinance that required property owners to connect to the sewer line immediately, citing financial hardship for long-time, modest income residents. As the impasse seemed to be leading to an NMED lawsuit against the Village, then-Mayor Gasteyer had several meetings with ranking NMED officials and their attorney, and finally a meeting in the governor’s office. The conflict essentially evaporated once a new mayor, Scott Kominiak, was sworn in.

The blockage last month may well re-open another debate: possible use of grinder pumps to process wastes from homes and businesses before they are sent to the sewer line. Back in 2013, an assessment was made that the sewer pipe in the ground from Corrales’ commercial district to an Albuquerque sewer station could function with grinder pumps as well as liquids-only septic tank effluent pumps —as long as Village officials were willing to flush the line weekly with water from the fire station.

Village Engineer Steve Grollman, then with The Larkin Group, gave the mayor and Village Council that general evaluation at a work-study session March 19, 2013.  His assessment matched that of original determinations by the Souder, Miller and Associates engineering firm which designed and supervised installation of the six-inch diameter sewer main, with the added operational advantage of pumping clean-out water into the line where it starts north of San Ysidro Catholic Church.

“This analysis indicates that it is most likely that there will be minimal difficulties in maintaining the system, subsequent to the ultimate flow of approximately 200,000 gallons per day envisioned in the design documents provided to us,” Grollman wrote in his preliminary report discussed at the 2013 work-study session.

But until enough homes and businesses were hooked up to supply sufficient volume and velocity, there’s a strong probability that solids will settle in the sewer main and begin to clog the system, Grollman cautioned. Mayor Phil Gasteyer said he expected the study would show that the infrastructure in the ground could handle sewage from grinder pumps as well as waste water effluent from septic tank effluent pumps.

The liquids-only system is referred to as a “septic tank effluent pressurized,” or STEP, system. “Though construction of either pressurized system could be costly at individual properties, over time the grinder option will be significantly simpler and cheaper for those connecting, since there is no longer need for a septic tank.”

But in councillors’ discussion following Grollman’s 2013 presentation, general consensus focused on starting the system up for STEP operations on a voluntary basis for property owners along Corrales Road to get as many sewer users as quickly as possible, perhaps even providing the STEP pumps free.

Once there is adequate flow into the sewer main, then allow property owners to apply to install grinder pumps, they reasoned. The sewer system designed by Souder Miller was for liquids-only pumps, so that sewage solids remained in septic tanks which would have to be pumped out perhaps every three years. Even so, at the time the Souder Miller design was approved and implemented, engineers anticipated that a limited number of grinder pumps, primarily needed by restaurants, could also be accommodated.

Mayor Gasteyer and others concluded grinder pumps discharging waste water and ground-up solids into the sewer main would be a better option. It would be cheaper in the long run, the mayor asserted; it would eliminate septic tanks altogether along with associated maintence costs, and would eliminate the need for homeowners’ cleaning septic pump filters.

The mayor said he was convinced that homeowners were unlikely to perform the STEP filter cleaning ritual as diligently as would be required, resulting in malfunctions that could require burdensome maintenance responses. With grinders, there is no effluent filter to clean, but… the ground-up solids going out to the sewer main are likely to settle in the bottom of the pipe and eventually clog the system, especially in the first year or so before all homes and businesses are hooked up.

That’s why Village Engineer Grollman recommended flushing the sewer main out with water weekly, at least until all potential users of the system were discharging into it. And that’s why the pending connection of Corrales Elementary to the Village’s sewer line could be just what’s needed to make the system work optimally.

Even so, as Gasteyer explained on March 15, 2013, “Introduction of grinder pumps will present some different maintenance issues, because flows must be maintained at certain velocities to avoid settling out of solids, particularly in the early months of operation as initial customers are joining the system.

“This could mean additional operation and maintenance costs for the Village utility system compared with a STEP-only system,” he cautioned. “Periodic ‘flushing’ may be needed from a hydrant at the north end of the line, near Old Church Road.” Grollman’s preliminary report for the 2013 work-study session gave details of what might be required. “The entire force main system should be flushed on a weekly schedule to remove solids that have settled in the lines,” he wrote, estimating that such flushing would take 400 to 450 gallons per minute with 60 to 75 pounds per square inch pressure for 90 minutes.

That calculates to at least 36,000 gallons of water each week to make the sewer work. Using less water at higher pressure would run the risk of bursting the sewer pipe, the engineer warned. In a quick estimate, then-Village Attorney John Appel said Corrales had sufficient water rights to flush the line weekly.

It would help to add more volume to such a grinder pump system by extending sewer service to higher density residential neighborhoods that need it, such as those along Priestly and Coroval Roads, the mayor pointed out. But as Grollman noted in his report seven years ago, “Paradoxically, some of the installed ‘neighborhood laterals’ for future expansion are smaller than would be designed for grinder pump use” which could also lead to sewage blockages.

Grollman estimated homeowners opting for a grinder pump system, rather than a liquids-only STEP system, would pay about $12,000. That breaks down to $7,000 for the grinder and pump, $2,000 for electrical service to the grinder, $2,000 for buried sewer pipe out to Corrales Road, $500 for a vault and valve and another $500 for “septic tank abandonment.”

Appel noted, “The advantage of using a grinder pump from the standpoint of both the Village and the property owner,” Appel said, “is that the use of a grinder pump allows you to eliminate the septic tank entirely. You don’t need to worry about that element, and the grinder pump allows all waste water, including semi-solids to be ground up in the grinder pump and put into the system to be discharged eventually to the Bernalillo County Water Utility Authority.

“The potential problem is that with those solids it can be difficult to ensure that the flow in the pressure system will be maintained. That’s presently being evaluated by the engineers at Larkin Group, so we don’t know the extent yet to which grinder pumps can be used.

“I would point out one of the potential disadvantages of the use of grinder pumps for some potential users, particularly domestic users, is that the grinder pump requires 220-volt power at the source [of the grinder pump installation] which is going to be the responsibility of the property owner.

“If your present system is not sufficient to handle that, a STEP pump which can use 115-volt power may be to the advantage of the individual property owner.”