Monday, November 28, 2022

A Brunswick County sewer plant is pushing its permitted capacity. What does that mean?

The DEQ notified Brunswick County's Northeast Wastewater Treatment Plant it violated the terms of its discharge permit by exceeding its monthly capacity -- operating at 110 percent -- in December. What are the real-world implications of a sewage plant operating at, near, or above its permitted capacity?

The Northeast Wastewater Treatment Plant, which discharges treated wastewater into the Cape Fear River visible from the I-140 Bypass, is consistently operating critically near its state-permitted capacity. (Port City Daily photo/Johanna Ferebee)
The Northeast Wastewater Treatment Plant, which discharges treated wastewater into the Cape Fear River visible from the I-140 Bypass, is consistently operating critically near its state-permitted capacity. (Port City Daily photo/Johanna Ferebee)

BRUNSWICK COUNTY — When a wastewater facility operates at full capacity, whether it’s for a limited or continuous time period, it puts the environment at risk. Brunswick County’s Northeast Wastewater Treatment Plant is doing just that.

The plant breached its permitted capacity limit in December 2018. In turn, the state issued the plant a violation notice and is assessing a forthcoming civil penalty.

Read part one of this piece here: DEQ issues violation notice after Brunswick sewer treatment plant goes over capacity

This month, according to the Department of Environmental Quality, the plant is operating at 92 percent of its permitted capacity — and it’s located in the fastest growing county in the state. A planned expansion isn’t expected to come online until August 2021. How did we get here? And, with over two years before the plant gets capacity relief, what are the potential consequences?

When sewer plants approach capacity

Many states have a planning mechanism in place to prevent plants from reaching full capacity. Once a wastewater plant consistently reaches a certain point – for instance, 80 percent of its average permitted hydraulic treatment capacity – regulative authorities step in, requiring expansion plans or other actions to reduce potential environmental harm.

According to the Water Environment Federation, an international trade group of water professionals, having a wastewater treatment capacity that’s too low can be a problem, too. Just under 80 percent, according to the federation, is a good place to be.

Under state statute, North Carolina facilities must submit engineering evaluation of future wastewater treatment and disposal needs, including expansion plans, before reaching 80 percent capacity. Before reaching 90 percent capacity, expansion permits must be submitted, alongside a construction schedule, and all permits must be obtained. If this isn’t done, or justifications explaining the situation aren’t submitted, the state may restrict the facility’s ability to accept new flow.

Initial plans to expand Brunswick County's Northeast Wastewater Treatment Plant include doubling the plant's ability to process wastewater, which was nearing 90 percent capacity in 2016. (Port City Daily/Courtesy Brunswick County)
Initial plans to expand Brunswick County’s Northeast Wastewater Treatment Plant include doubling the plant’s ability to process wastewater, which was nearing 90 percent capacity in 2016. (Port City Daily/Courtesy Brunswick County)

Increased pressure, increased risk

The reason why this rule exists — and why similar laws are in place elsewhere — is to ensure wastewater treatment systems have plans in place, like expanding in time to meet growth trends, to prevent environmental contamination issues. It’s the same reason why the Department of Environmental Quality (DEQ) places limits on NPDES permits in the first place: a facility is only designed to treat so much sewage at once. Untreated sewage, especially in large quantities, can be harmful to human health and the environment if improperly released.

“When that sewer stuff starts spewing out from the manholes or starts busting out from the pipes, it’s a serious contamination problem,” Dr. Larry Cahoon, a University of North Carolina at Wilmington biology professor, said.

Much of Cahoon’s research centers around wastewater and the environment. He spoke to Port City Daily about facility treatment plants in general and not specifically about the Northeast Wastewater Treatment Plant.

“Technically [wastwater treatment plants] are allowed to operate at up to 100 percent capacity,” Cahoon said. “But they don’t wait until its 100 percent — let’s put it that way.”

Unlike water systems, which can and sometimes do implement water shortage suggestions and requirements, wastewater systems don’t ask the public to change its behavior, according to the Water Environment Federation.

Cahoon agreed, “You can’t go to existing homeowners and say, you can’t flush your toilets. You just can’t do that. There’s really no mechanism to make individual homeowners and businesses ramp back on their sewer use. There’s no way. There’s no practical sense that you can do that.”

When a system is strained by consistently high capacity needs, Cahoon said it can lead to several problems. The older the system, the more likely its infrastructure is to be degrading, Cahoon said. With older systems, pipe leaks and bursts are more likely due to incoming pressure higher than the system was designed to handle. Also, going over capacity can reduce or significantly impair a facility’s ability to adequately treat the wastewater passing through it. This can lead to untreated, or incompletely-treated wastewater, Cahoon said, entering public surface waters.

Brunswick County’s problem

Brunswick County’s northern wastewater system accepts sewer flow from five communities: the Town of Navassa, the City of Northwest, Brunswick Regional Water and Sewer H2GO, the Town of Leland, and unincorporated Brunswick County residents. Both Leland and Navassa maintain their own wastewater collection systems, of which they rely completely on the Northeast Wastewater Treatment Plant to treat wastewater.

The majority of the communities have been rapidly developing over the last several years and, in part because of that, the Northeast Wastewater Treatment Plant has been inching closer to hitting capacity. During the month of October 2016, Northeast Wastewater Treatment Plant operated at nearly 90 percent of its capacity.

The following year, Brunswick County’s Board of Commissioners approved choosing an engineering firm in April 2017 to consider the plant’s expansion. As of January of this year, the county was still seeking to secure funding for the $39.1 million expansion. The county is expecting Navassa to contribute $8 million, but the town said it had no plans to help finance the project.

But, assuming the county reaches an agreement – with or without Navassa – to come up with the missing $8 million, there is still the issue of operating the current system, pushing its capacity limits, until the expansion is complete. In the county’s response to the notice of violation it received in January, it told the DEQ its permitting phase will wrap up this fall. The planned expansion, which will double the plant’s capacity, won’t be operational until August 2021.

State statute grants the DEQ discretion to allow facilities to continue adding new flow when they are over 80 and 90 percent capacity. A facility is exempt from state law — treating more sewage than it’s permitted to handle — provided two requirements are met: the government unit has funding secured for expansion, and the added waste won’t significantly degrade the water quality wherever the discharge ultimately takes place (in Brunswick’s case, the Cape Fear River).

It’s not clear Brunswick County meets these exemption criteria. When asked what the DEQ’s next steps are to respond to the county’s capacity issue, Christy Simmons, DEQ spokesperson, said, “the Wilmington Regional Office team is analyzing the permitted flow to the wastewater treatment plant and how that could be affected by extreme weather in the coming months.”

Prior issues

January’s notice isn’t the plant’s first run-in with the DEQ. In 2017, DEQ fined the plant twice.

The first fine was issued when the Northeast Wastewater Treatment Plant exceeded its permitted average limit of total suspended solids — undissolved particles — by 108 percent and 25 percent over two weeks in September 2017. That same month, it went over its permitted Biochemical Oxygen Demand (BOD) limit by 30 percent, a measurement that allows biological organisms the oxygen needed to break down organic material. DEQ fined the county $1,637 for the violations. 

In the county’s response to the violation, Donald Dixon, the county’s director or public utilities, said the reports were attributed to heavy rainfall.

“Under normal flow conditions a slight excursion can generally be handled, but with flows more than permitted capacity for 5 consecutive days we were unable to achieve the weekly parameters,” Dixon wrote in the November 2017 response.

DEQ also fined the county $617 for events earlier that year.

In January 2017, the plant exceeded its monthly and weekly average permitted limit of total suspended solids. “A review of historical data, unfortunately, indicates that during the winter months multiple adjustments to plant operations are required to keep the plant in compliance,” Dixon wrote in the county’s March 2017 violation response.

The DEQ issued two notices of violation to Brunswick County for issues at its Northeast Wastewater Treatment Plant in 2017. (Port City Daily/Courtesy DEQ)
The DEQ issued two notices of violation to Brunswick County for issues at its Northeast Wastewater Treatment Plant in 2017. (Port City Daily/Courtesy DEQ)

Leaks, I&I, contamination

Northeast Wastewater Treatment Plant, first operational in 2003, is young compared to other aging systems in the region. According to Cahoon, mid-20th-century plants used the material, like cast iron, that corrodes over time.

“A lot of these collection systems are old. They’re hard to maintain,” Cahoon said. “Testing for leaks is not easy to do. They’re underground.”

In his research, Cahoon looks for inflow and infiltration, a key indicator that reveals flaws in a wastewater collection system (inflow, meaning stormwater coming into sewer lines from manholes, and infiltration, meaning water getting in the system from the ground).

“Storm drains are not connected to sewer lines,” Cahoon said. “That is not allowed in this state.” 

These extraneous sources of water, once inside a wastewater system, can lead to sewer overflows, water quality issues, and system degradation, Cahoon’s research, published this year, shows. Heavy rainfall, temperature, and sea level rise, all drive statistically significant inflow and infiltration rates in 90 percent of central stormwater systems in coastal North Carolina, according to Cahoon’s findings.

“When they say inflow and infiltration, yeah, it’s stormwater in a sense. It’s diluting down the sewage that’s already in the pipes,” Cahoon said. “The sewage is pretty filthy stuff. It’s raw sewage – it’s absolutely not something to get loose.” 

So, how does the water get in there?

“Water getting in through the ground. Cracks and opening through the pipe system,” Cahoon said. 

According to the Water Environment Federation, utilities that consistently struggle with inflow and infiltration show more work can and should be done to address the system.

Though inflow and infiltration is present in most all wastewater systems, Cahoon sees increased or consistent findings of it as an indicator of a failing or poorly managed system. For instance, during storm events, systems frequently see high inflow and infiltration.

“Those are acts of God — the term act of God is a dodge — we know it’s going to rain,” Cahoon said. “But it’s a reflection that the system does have leaks in it.”

Author’s note: This is part one of a two-part series. Catch up on part one, DEQ issues violation notice after Brunswick sewer treatment plant goes over capacity.”


Send tips and comments to Johanna Ferebee at johanna@localvoicemedia.com

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