Document Qkb1eRGQzOrmopGQ7m76xRypL
EPA Inspection Report - Page 1 of 24
Region 6 - Enforcement & Compliance Assurance Division
INSPECTION REPORT
Inspection Date(s): Media Program: Regulatory Program(s)
03/12/2020 Water CWA - NPDES
Company Name: Facility Name: Facility Physical Location:
(city, state, zip code) Mailing address:
(city, state, zip code) County/Parish: Facility Phone Number Facility Contact:
Doa Ana County Utilities
Doa Ana County South Central Wastewater Treatment Plant
East Sloan Road and Montes Road
La Mesa, NM 88044
845 North Motel Boulevard
Las Cruces, NM 88007
Doa Ana
575-525-6194
Chuck McMann
Assistant County Manager
chuckm@donaanacounty.org
FRS Number: Identification/Permit Number: Media Identifier Number: NAICS: SIC:
110017841549 NM0030490
221320 4952
Personnel participating in inspection:
Amy Andrews, P.E.
USEPA/6-ECDWM
Rick Duffy
USEPA/OECA
Jessica Gray
ERG
Mireya Carnero
Doa Ana County Utilities
Jesus "Chuy" Reyes
Doa Ana County Utilities
Sonya Lazos
Doa Ana County Utilities
Environmental Engineer Supervisory Environmental Specialist Specialist Assistant Manager - Operations Wastewater Operator Wastewater Operator
EPA Lead Inspector Signature/Date
Supervisor Signature/Date
AMY ANDREWS
Amy Andrews
Digitally signed by AMY ANDREWS DN: c=US, o=U.S. Government, ou=Environmental Protection Agency, cn=AMY ANDREWS, 0.9.2342.19200300.100.1.1=68001003655888
Date: 2020.05.07 14:22:02 -06'00' Date
CAROL PETERS-WAGNON
Carol Peters
Digitally signed by CAROL PETERS-WAGNON DN: c=US, o=U.S. Government, ou=Environmental Protection Agency, cn=CAROL PETERS-WAGNON, 0.9.2342.19200300.100.1.1=68001003652679 Date: 2020.05.07 16:26:14 -05'00'
Date
6ENFORM-020-R8.2 (02/12/2020)
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Section I - INTRODUCTION
Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
PURPOSE OF THE INSPECTION
Environmental Protection Agency (EPA) Region 6 inspector, Amy Andrews, arrived at the Doa Ana County, South Central Wastewater Treatment Plant (WWTP) at 8:45 AM on March 12, 2020 for an unannounced inspection. Rick Duffy (EPA) and Jessica Gray (ERG) accompanied me for the purpose of testing software for a tablet-based inspection computer program. We met with Jesus "Chuy" Reyes and Mireya Carnero for the Opening Conference. I presented my credentials to Ms. Carnero and informed her that this was an EPA inspection to determine compliance with the facility's National Pollutant Discharge Elimination System (NPDES) permit and the Clean Water Act (CWA). The inspection was conducted under the authority of the NPDES permit program, in accordance with the Federal CWA. This report is based on information supplied by Doa Ana County Utility representatives (the permittee), observations made by the EPA inspector, and records and reports maintained by the permittee and the EPA.
FACILITY DESCRIPTION
The South Central WWTP is classified as a major industrial discharger under the CWA, Section 402, of the NPDES permit program and is authorized to discharge up to 1.05 million gallons per day (MGD) based on design flow, with an actual average discharge around 0.4 MGD. Discharge is to receiving waters of the Rio Grande River in waterbody segment 20.6.4.101 (NMAC, State of New Mexico Standards for Interstate and Intrastate Surface Waters) of the Rio Grande Basin. This segment includes the designated uses of irrigation, marginal warmwater aquatic life, livestock watering, wildlife habitat and primary contact.
Raw domestic sewage, collected from 28 lift stations and 16-inch force main, enters the plant's lift station and is then pumped to the entrance head works. At the entrance works, raw sewage flows through a 5 horsepower JWC Environmental shredder and then through a JWC Auger Monster. Rags are separated and dropped down a chute and into a container. A manual bar screen is available for a bypass during maintenance. Influent then flows through a US Filter Link-Belt C&9 Grit Collector. Flow is routed through a grit chamber and passes to an equalization basin.
There are two trains of Sequencing Batch Reactor (SBR) basins at the facility. One SBR basin is operated for domestic waste and the second train is operated for septage. The facility will discontinue processing septage in the near future as the domestic flow will increase with new housing developments added to the collection system. Floating solids and scum are collected manually. The reactor basins are designed to operate in a diffused aeration, clarification, and clear liquid decant sequence. Six, four-hour cycles are run per day in the aeration unit used to treat wastewater. After a programmed time interval, the aeration is stopped to allow for settling of the microorganisms and other solids from the treated wastewater. The solids settle to the bottom of the reactor and are either retained with in the reactor (RAS) or wasted (WAS) to a sludge holding tank (aerobic digester unit). The aerobic digester unit is
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Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
adjacent to the north of SBR #1 (north). One SBR activation basin was being used to treat septage brought to the facility by contract septage haulers. After treatment in this unit, the solids portion of the septage is sent to the digester in preparation for mixing with the digested activated sludge and sent on to the belt filter press. The decant liquids are mixed with the influent to the domestic side of the treatment basins. The treated domestic and mixed septage liquids are and sent through the UV disinfection and effluent flow meter before being discharged to the river. The unit has two independent banks of UV bulbs which are on at the same time unless they are cleaning them. Effluent flow is measured by an 18" Parshall flume and a Milltronics ultrasonic level transducer.
Sludge is wasted six times per day. Waste Activated Sludge (WAS) is pumped to the aerobic digester for dewatering and thickening. The digester is located in a long open channel just north of the two activation basins. Thickened sludge is pumped to a filter press where a polymer is added to the sludge to enhance processing. Flow from the plant wash down and decant from the belt press are returned to the plant lift station and recirculated. Processed sludge is hauled to the Corralitos Landfill in roll-off dumpsters.
Section II - OBSERVATIONS
There are plans to add around 270 new sewer connections from surrounding communities by July 2020, which will push the limits of capacity for the one SBR basin currently being used for domestic waste. This will require the facility to use both SBR basins for domestic waste and terminate acceptance of septage at the facility. The original plan was to terminate acceptance of septage on April 20, 2020, however that date was expected to be pushed back by two months to June 2020.
Facility personnel state that the South Central WWTP has received approximately $3.1 million in funding from NMED for plant improvements to include a new headworks (grit removal system and automatic bar screen), two new sludge drying beds, a third (new) blower, and the engineering and whatever construction may be necessary to meet the DO limits that will go into effect August 1, 2022 (in accordance with the schedule of compliance in permit NM0030490).
The facility has had reoccurring issues with the UV disinfection system, which has resulted in exceedances of E. coli in multiple months. The UV bulb intensity panel is not functional, so bulbs are cleaned every Tuesday with Limeaway during periods that the SBR is not decanting. Because of the issues with the UV system, the facility has started chlorinating the decant at the splitter box in the SBR basin and dechlorinating the effluent after the UV system. Effluent samples are collected for total residual chlorine (TRC) after the dechlorination and before the effluent flow meter (Parshall Flume).
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Section III - AREAS OF CONCERN
Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
Requirement 1
NPDES Permit NM0030490, Part I: Section A.1. Final Effluent Limits for Flow:
POLLUTANT
30-DAY DAILY
7-DAY
MEASUREMENT SAMPLE TYPE
AVG
MAX
AVG
FREQUENCY
Flow
Report
Report
Report
Continuous
Totalizing Meter
MGD
MGD
MGD
Concern 1A
It is not clear how the flow values are being calculated, but the reported values do not correlate to the
totalized values recorded for December 2019 (see Appendix 1):
Flow
30-DAY DAILY
7-DAY
AVG
MAX
AVG
Reported
0.361
0.400
0.368
Calculated from 0.375
0.438*
0.511
totalized values
*
Totalized flow rates are not always recorded on weekend days so it is impossible to positively
determine the daily max.
Concern 1B
All loading values (BOD5, TSS, and E. coli) must be calculated from the actual totalized flow in MGD for
the date of sample collection.
Requirement 2 NPDES Permit NM0030490, Part I: Section A.1. Final Effluent Limits - Biochemical Oxygen Demand, 5day (BOD5) and Total Suspended Solids (TSS) - Sample Type, 6-hr composite NPDES Permit NM0030490, Part III: F.22.e. 6-hour composite sample consists of six effluent portions collected no closer together than one hour (with the first portion collected no earlier than 10:00 am) and composited according to flow. Concern 2 Facility personnel report that composite samples were not being composited according to flow and the first portion is collected around 8:00 AM.
Requirement 3
NPDES Permit NM0030490, Part I: Section A.1. Final Effluent Limits for E. coli:
POLLUTANT
30-DAY 30-DAY
DAILY
MEASUREMENT SAMPLE TYPE
AVG
AVG
MAX
FREQUENCY
E. Coli Bacteria 5.01 billion 126 (*1)
410 (*3) Once/Week
Grab
(*3)(*4)
*3
Colony forming units (cfu) per 100 ml or Most Probable Number (MPN) per 100 ml. The 30-day
average for E. coli bacteria is the geometric mean of the values for all effluent samples collected during a
calendar month
*4
Billion (1.0 x 109) cfu/day. The loading limit shall be calculated as follows: [Flow in MGD x cfu/100
mL in effluent x 3.79 x 107]/1.0 x 109
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Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
Concern 3 On December 5, 2019, an E. coli sample was collected and analyzed according to the m-Coliblue-24 method, and the results came back as Too Numerous to Count (TNTC). The following day facility personnel replaced some of the UV bulbs, cleaned the effluent channel, and resampled for E. coli. That sample result was reported to be 6.06 cfu/100 ml. The TNTC value was not reported on the DMRs for the month of December 2019; the daily max value reported was 32.79 cfu/100 ml. No excursions were reported for the month. Facility personnel stated that they didn't know how to report TNTC on the DMRs. See Appendix 2 for E. coli bench sheets.
Requirement 4 NPDES Permit NM0030490, Part III: C.2. Representative Sampling: Samples and measurements taken for the purpose of monitoring shall be representative of the monitored activity. Concern 4 UV bulbs are being cleaned, during periods when the SBR basins are not decanting, with Limeaway, and the runoff drains into the effluent channel just prior to the effluent Parshall Flume. This location is after the effluent sample point and sampling does not capture the runoff.
Requirement 5 NPDES Permit NM0030490, Part III: C.6. Flow Measurements: Appropriate flow measurement devices and methods consistent with accepted scientific practices shall be selected and used to ensure the accuracy and reliability of measurements of the volume of monitored discharges. The devices shall be installed, calibrated, and maintained to insure that the accuracy of the measurements is consistent with the accepted capability of that type of device. Devices selected shall be capable of measuring flows with a maximum deviation of less than 10% from true discharge rates throughout the range of expected discharge volumes. Concern 5 The Parshall Flume installation needs to be evaluated by a qualified engineer for excess turbulence.
Requirement 6 NPDES Permit NM0030490, Part III: C.5.a. Monitoring must be conducted according to test procedures approved under 40 CFR Part 136, unless other test procedures have been specified in this permit or approved by the Regional Administrator. Concern 6A In accordance with the test method for E. coli that the facility has chosen (m-Coliblue-24), at least three different appropriate dilutions should be selected for analysis such that at least one filter has between 20 and 60 colonies present after incubation. All samples analyzed during the month of December 2019 had only two dilutions used. During the month of December 2019, none of the filters had more than 20 colonies present except the TNTC filters, and all samples were run with two dilutions, making these tests invalid. The fact that the number of colonies found on each filter was not an order of magnitude difference between the different dilutions also brings the test validities into question. During the month of January 2020, all analyses run by Doa Ana County Utilities were run with two dilutions, and the sample from January 8, 2020, did not have more than 20 colonies on either filter.
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Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
Concern 6B In mid-January 2020, the facility began sending additional samples to Professional Water Testing LLC, in Las Cruces, NM to verify their own results. In accordance with the test method for E. coli that Professional Water Testing used (also m-Coliblue-24), Average coliform colonies in 100 mL = Sum of colonies in all samples sum of mL sample 100. Professional Water Testing is not using the colonies from filters with less than 20 colonies on them in the calculations, which is under-reporting the results.
Requirement 7 NPDES Permit NM0030490, Part III: C.5.c. An adequate analytical quality control program, including the analyses of sufficient standards, spikes, and duplicate samples to insure the accuracy of all required analytical results shall be maintained by the permittee or designated commercial laboratory. Concern 7 No evidence of having run positive and negative controls with the samples was provided on bench sheets.
Requirement 8 NPDES Permit NM0030490, Part III: D.5. Additional Monitoring by the Permittee: If the permittee monitors any pollutant more frequently than required by this permit, using test procedures approved under 40 CFR Part 136 or as specified in this permit, the results of this monitoring shall be included in the calculation and reporting of the data submitted in the Discharge Monitoring Report (DMR). Such increased monitoring frequency shall also be indicated on the DMR. Concern 8 E. coli sample results cannot be thrown out due to TNTC values and cannot be averaged on a daily basis. All values obtained from analysis, including duplicates and samples collected the following day, must be included in the DMR reporting (daily max) and calculations (30-day average) as individual results.
Requirement 9 NPDES Permit NM0030490, Part III: D 9. Where the permittee becomes aware that it failed to submit any relevant facts in a permit application, or submitted incorrect information in a permit application or in any report to the Director, it shall promptly submit such facts or information. Concern 9 The permittee must review at least the last two years of DMR reports for potential issues listed above and revise the DMRs as appropriate.
Section IV - FOLLOW UP
EPA Region 6 inspector, Amy Andrews, conducted a closing conference at the Doa Ana County South Central WWTP at 12:05 PM on March 12, 2020 for the inspection. During the closing conference, the Areas of Concern noted during the inspection (above) were discussed.
No additional information was received by EPA after exiting the Facility on March 12, 2020.
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Section V - LIST OF APPENDICES
Doa Ana County / South Central Wastewater Treatment Plant Inspection Date 03/12/2020
Appendix 1 - Flow totalizer log for December 2019 Appendix 2 - E. coli bench sheets for December 2019 and January 2020
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Appendix 1 Flow totalizer log for December 2019
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Appendix 2 E. coli bench sheets for December 2019 and January 2020
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