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Home My WebLink AboutNC0041696_Other_20230928 DocuSign Envelope ID:OBFAFD2C-9056-4ECD-BD9D-839AlACCC5BB t,,STATE ROY COOPER Governor 2r ELIZABETH S.BISER Secretary RICHARD E.ROGERS,JR. NORTH CAROLINA Director Environmental Quality September 28, 2023 Mr. Greg Padgett, Water Resources Director Town of Valdese PO Box 339 Valdese,North Carolina 28690 Subject: Modified Letter of Understanding Full-Scale Peracetic Acid Pilot Study Lake Rhodhiss WWTP Burke County NCO041696 Dear Mr. Padgett: The Division of Water Resources (Division) issued a Letter of Understanding(LOU)to the Town of Valdese (Town) on July 17, 2023 for an ongoing full-scale pilot study utilizing Peracetic Acid (PAA) as a disinfectant at the Lake Rhodhiss WWTP (NC0041696). The Town's ongoing pilot study at Lake Rhodhiss WWTP (NC0041696) utilizes VigorOx's WWT II Peracetic Acid 15.9% for the study in hopes to replace the existing primary disinfectant, chlorine gas and sodium dioxide gas. The timeline for the study, as determined in the July 17, 2023 LOU, is from May 22, 2023 to a time in which the Division has either approved or denied the use of PAA as a permanent means of disinfection at the Lake Rhodhiss WWTP. The EPA 2012 Recreational Water Quality Criteria for Bacterial Indicators of Fecal Contamination recommends states set bacteriological water quality standards for primary recreation freshwaters using either the Escherichia coli or Enterococcus pathogenic indicators. North Carolina's current recreational surface water quality standards for Class B (primary recreation) waters use the fecal coliform bacteria group pathogenic indicator. In addition to the ongoing pilot study, the Division sent a letter to the Town on March 8, 2023 requesting participation in a E. coli Study being conducted across the state. This study was being conducted to evaluate the financial impacts of switching to an E. coli standard for all Class B freshwaters. The data will inform the Regulatory Fiscal Note a required part of the rulemaking package. The study covered the 2023 Swim Season, April through August, and requires instream and effluent monitoring and reporting of fecal coliform, E. coli, turbidity, temperature, DO, conductivity and pH. Additionally, instream sampling events are to be accompanied by a concurrent precipitation recording. Upon review of the data provided by the Town as part of the 2023 Swim Season E. coli study, an increase in effluent E. coli was observed after commencement of the PAA pilot study. As such, the Division has modified the terms of the LOU to include monitoring and reporting requirements for effluent E. coli. The Town submitted a modification request to the Division on July 17, 2023 for NPDES permit NCO041696 to incorporate requirements related to use of PAA. The Division is requiring that Pl E Q:> North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611 919.707.9000 DocuSign Envelope ID:OBFAFD2C-9056-4ECD-BD9D-839A1ACCC5BB additional E. coli data be provided to aid in determination of capability of the proposed PAA disinfection to achieve E. coli removal goals. The Division is providing Town of Valdese the following Modified Understanding to Conduct: A full-scale pilot study which feeds PAA 15.9% from a tote into the contact chambers via a pump skid that will sit next to the chlorine contact chamber. A dose of 2.0 mg/L (as PAA) will be used during the first week of trial. Weekly adjustment of the PAA dose will be made as needed, based on the observed microbial indicator counts from the previous week. During the trial period, the Site personnel and Sterling Water Technologies/Coyne Chemical staff will review testing data weekly and make necessary adjustment for dosing. This Modified Letter of Understanding is subject to the following conditions: 1. The project shall not cause or contribute to any violation of water quality standards in Lake Rhodhiss (Catawba River),which is classified WS-IV, B, CA waters in the Catawba River Basin. The NPDES permit terms and conditions shall be complied with during the pilot study at the facility. 2. The facility shall keep chlorine gas and sodium dioxide gas onsite during the duration of the full-scale pilot study as a backup and notify the Division if returns to gaseous chlorine for disinfection for any reason. 3. Monitoring and Reporting. a. No later than 2 days prior to initiating the pilot study and 2 days following the completion of the pilot study, the Town of Valdese shall notify the Asheville Regional Office and the NPDES Municipal Permitting Unit. b. Collect daily effluent water samples at the current effluent sampling point and monitor parameters including Total Fecal Coliform, E. coli, PAA residual, BOD, TSS,pH, temperature and DO. c. Report the monitoring results mentioned in Condition 3.b weekly to the Division by email to michael.montebellogdeq.nc.gov. Final summary reports for the PAA pilot study shall be made in writing and sent to: NCDEQ/DWR NPDES Municipal Permitting Unit Attn: Michael Montebello 1617 Mail Service Center Raleigh,NC 27699-1617 and by email to: michael.montebellogdeq.nc.gov Pl E Q:> North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611 919.707.9000 DocuSign Envelope ID:OBFAFD2C-9056-4ECD-BD9D-839A1ACCC5BB d. The Town shall report to the Asheville Regional Office any noncompliance that potentially threatens public health or the environment. Any information shall be provided orally within 24 hours from the time the Town becomes aware of the circumstances. A written report shall also be provided within five days of the time the Town becomes aware of the circumstances. Occurrences outside normal business hours may also be reported to the Division's Emergency Response personnel at(800) 858-0368 or(919) 733-3300. 4. The Town shall make available upon the Division's request any monitoring results or other information necessary to ensure compliance with this letter of approval. The Division may modify this Letter of Understanding upon the written request of the Town. The Division also reserves the right to modify or withdraw this Letter of Understanding if the project does not conform to the above conditions or results in unacceptable impacts to water quality. In such case,the Division shall notify the Town in writing of its findings and identify actions required of the Town. This Letter of Understanding applies only to conducting the full-scale PAA pilot study from May 22, 2023 to a time in which the Division has either approved or denied the use of PAA as a permanent means of disinfection at the Lake Rhodhiss WWTP. If the Town elects to permanently utilize PAA to replace the existing gaseous chlorine for disinfection,the Division will consider the results of this study and the scope of work in order to determine whether the system will require other permits. If you have any questions concerning this letter,please contact Michael Montebello at(919) 707- 3624 or at michael.montebello&deq.nc._og_v. Sincerely, EDocuSigned byy:�Al•� 'e.'' khvlt" h C4645314316 44FE... for Michael Montebello, Branch Chief NPDES Municipal Permitting Unit Hardcopy: NPDES Files Ecopy: DWR/Asheville Regional Office Pl E Q:> North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611 919.707.9000