BRUNSWICK COUNTY — Brunswick County is close to securing the National Pollutant Discharge Elimination System (NPDES) permit it needs to operate its planned upgrade and expansion of the Northwest Water Treatment Plant.
The county is planning an $89.5 million low-pressure reverse osmosis upgrade and a $39 million expansion which inevitably includes a discharge outfall that will release effluent into the Cape Fear River.
When the upgrade and expansion are both complete, the Northwest Water Treatment Plant with a current ability of 24 million gallons a day (mgd) will nearly double capacity; at most, the plant will be capable of treat 36 mgd of reverse-osmosis-treated water and 45 mgd of conventionally-treated water.
In February, the county anticipated completing its necessary water expansion efforts by September 2022, leaving three more high-demand summers. But by late July, that timeline appears to have sped up significantly, with the county sharing an expected expansion date of December 2021, when the reverse osmosis upgrade is also projected to be complete.
At most, the water treatment plant will be permitted to release 5 million gallons a day (mgd) of reverse osmosis (RO) discharge into the Cape Fear River. The RO discharge will travel from the plant to its planned outfall location through a planned 4-mile, 16-inch pipeline that will cross under Mt. Misery Road to reach the river.
The Northwest Water Treatment Plant is currently permitted to discharge effluent through an existing outfall into Hood Creek, a smaller tributary of the Cape Fear River, located outside the City of Northwest. After expansion upgrades, the plant will be permitted to discharge an estimated 3.9 mgd from its Hood Creek outfall under conventional treatment methods.
Unlike Granular Activated Carbon, Cape Fear Public Utility Authority’s answer to emerging contaminants, low-pressure reverse osmosis will release industrial compounds back into the Cape Fear River. Brunswick County’s Northwest Water Treatment plant sources raw water from the Lower Cape Fear Water and Sewer Authority, which has an intake pump station in Riegelwood.
Outfall 001, the Hood Creek discharge location, will not be permitted with limits for: turbidity, aluminum, fluouride, nitrogen, phosphorus, or total hardness. Compliance with copper limits, with a monthly average of 8.12 parts per billion (ppb) and a daily maximum of 10.74 ppb, is delayed until April 1, 2022.
A DEQ spokesperson explained this compliance is delayed to offer the county a compliance schedule, as the limit was implemented during the last permit renewal, finalized in February 2018. “It is the division’s standard practice to implement compliance schedules when new limits are set for existing total metal parameters in a water treatment plant permit,” the spokesperson said.
DEQ will require the county to conduct Whole Effluent Toxicity Tests (WET), a testing method that exposes certain aquatic organisms (in this case, ceriodaphnia dubia, or simply, a water flea) to wastewater to test their ability to survive. At Outfall 001, the county will conduct WET testing four times a year until September 2021 on a monitoring basis only. Starting Oct. 1, 2021, DEQ will introduce a pass/fail WET limit with organisms showing reproductive success in an effluent concentration of 90%.
At the new discharge location into the Cape Fear River, Outfall 002, limits are not required for the following parameters that will be monitored on a varying basis: dissolved oxygen, salinity, conductivity, total dissolved solids, turbidity, arsenic, copper, zinc, ammonia nitrogen, lead, dichloroacetic acid, total nitrogen, total phosphorus, or total hardness.
The draft permit does include limits at Outfall 002 for pH, total chlorine, total chloride, fluoride, and perchlorate (a naturally-occurring and manufactured contaminant found in herbicides).
During pilot testing, the county’s consultant, CDM Smith, reported RO discharge would exceed state water standards or protective values for four parameters out of 280 tested, including manganese, aluminum, chloride, and dichloracetic acid. CDM Smith told the DEQ it could address this issue by further diluting the effluent.
The county must conduct four annual pass/fail WET tests on water fleas at Outfall 002 with an effluent concentration of 33%.
If WET test results indicate aquatic toxicity, DEQ may opt to re-open the permit.
Asked to explain why limits for several parameters were not included, a DEQ spokesperson said the draft permit is still subject to change. “Part of the public notice process is determining if additional limits or monitoring will be added to the final permit based on the public feedback received,” the spokesperson said.
For emerging compounds without established Maximum Contaminant Levels, DEQ will require the county to conduct semi-annual monitoring for 28 per- and polyfluoroalkyl substances (PFAS) related compounds.
Two years after discharge at Outfall 002 begins, DEQ will begin requiring monitoring for 41 additional parameters, including other emerging contaminants, like 1,4-Dioxane (view all parameters in the draft permit below).
Hood Creek at Outfall 001 is considered Class C (water protected for secondary recreation) Swamp Waters; the Cape Fear River at Outfall 002 is classified the same, plus has a Primary Nursery Area (PNA), where early aquatic development takes place.
Public comment, hearing
The draft NPDES permit is open for public comment until Dec. 5. The Department of Environmental Quality (DEQ) is hosting a public hearing on the permit Dec. 5 at Brunswick County Commissioner Chambers.
- Email comments to email@example.com
- Include the subject line, “Northwest Water Treatment Plant”
- Mail comments to: Wastewater Permitting, Attn: Brianna Young, 1617 Mail Service Center, Raleigh, NC, 27699-1617
DEQ’s public hearing will take place Thursday, Dec. 5 at 6 p.m at Brunswick County Commissioners’ Chambers in Bolivia. Speaker signup begins at 5:30 p.m.
Read the draft NPDES permit below:
Send tips and comments to Johanna Ferebee at firstname.lastname@example.org