NPDES WASTEWATER DISCHARGE PERMIT EVALUATION

Transcription

1 NPDES WASTEWATER DISCHARGE PERMIT EVALUATION Department of Environmental Quality Eastern Region - Pendleton Office 700 SE Emigrant, Suite 330, Pendleton, OR Telephone: (541) PERMITTEE: City of La Grande 800 X Avenue La Grande, File Number: SOURCE LOCATION: Four miles south of La Grande SOURCE CONTACT: GlenHogue Telephone Number: PERMIT WRITER: AI Murrey Telephone Number: PROPOSED ACTION: Renewal of a National Pollutant Discharge Elimination System (NPDES) wastewater discharge permit SOURCE CATEGORY: Major Domestic TREATMENT SYSTEM CLASS: Level III COLLECTION SYSTEM CLASS: Level III PERMIT APPLICATION DATE: August 1, 2002 PERMIT APPLICATION NUMBER: BACKGROUND Introduction The City of La Grande operates a wastewater treatment facility located in La Grande, Oregon that serves La Grande and Island City. Septage is also received at the City facility. Wastewater is treated and discharged to the Grande Ronde River in accordance with National Pollutant Discharge Elimination System (NPDES) Permit number The Permit for the facility was issued on 02/20/98 and expired on 01/31/03. The Department received a renewal application on August 1, A renewal permit is necessary to discharge to state waters pursuant to provisions of Oregon Revised Statutes (ORS) 468B.050 and the Federal Clean Water Act. The Department proposes to renew the permit. The treatment facility irrigates reclaimed water and discharges treated effluent to constructed wetlands and to the Grande Ronde River at river mile The Grande Ronde River has been designated by the Department as a water quality limited stream for aquatic growth, dissolved oxygen, fecal coliform, habitat and flow modification, nutrients, ph, sediment and temperature. In 2002, the City completed modifications to its facility including construction of 52-acres of constructed wetlands that provides for six days detention and chlorination prior to discharge to Oregon Department of Fish & Wildlife constructed wetlands. The treatment facility receives primarily domestic wastewater from residential and commercial sources. There are no categorical users that contribute to the wastewater flow to the facility at this time.

2 Page 2 Waste discharge limitations for discharge to the ODFW wetlands and mass loads for wet weather discharge that were incorporated by permit modification into the existing permit have been included in the renewed permit. In response to the TMDL established for the Grande Ronde River, the permit does not allow discharge to the Grande Ronde River from August 1 through September 30. The permit also restricts discharges to the Grande Ronde River during June and July based on river flows and during October based on river ph. Facility Description The wastewater treatment facility was originally placed into operation in about As indicated above, the last major modifications to the facility were completed in The City developed a sanitary sewer system during the period 1940 through 1963 that included treatment with a trickling filter system. In 1963 the City of La Grande completed a two cell, 97 acre lagoon system. The lagoon system was upgraded in 1980 with funding from the United States Environmental Protection Agency (USEPA). The upgrade included the addition of an aeration lagoon cell and tertiary solids removal. The average dry weather design flow for the treatment facility is 2.7 MGD while the peak design flow is 5.1 MGD. During the months of discharge in 2002, the average daily effluent flow from the wastewater treatment plant from outfall 001 was about 1.38 MGD. It has been determined that the hydraulic capacity ofthe facility is adequate. The City also discharged a substantial amount of effluent to the newly constructed wetlands in The City's wastewater treatment system headworks consists of two influent pump stations. The original pump station was installed in 1963 and the second pump station was added in The pump stations are equipped with a total of four pumps that have a total capacity of 11.8 MGD. Additionally, the pump stations are equipped with an auxiliary generator for back up power. Influent flow is measured at the headworks by an 18" Parshall flume. Wastewater is pumped from the pump stations into a 3.5 acre aeration cell located along the west dike ofthe north lagoon cell (equipped with mechanical aerators). The north lagoon cell is approximately 62 acres in size. From the north lagoon cell wastewater then flows to the 35 acre south lagoon cell (equipped with wind powered mixers). The south lagoon cell was constructed with the ability to discharge effluent at three different elevations. The intent of this installation was to allow withdrawal of wastewater with the optimum ph and minimize the amount of suspended solids or algae in the effluent. Effluent from the south lagoon cell goes to two settling cells and then either to the plant for tertiary treatment to effect additional suspended solids removal, or to the constructed wetlands. The tertiary treatment system removes suspended solids from the effluent through alum and/or polymer coagulation, and dissolved air flotation clarifiers. It then flows through a recently gutted, dual media type rapid sand filter. Effluent for discharge to the River is measured by two weirs located at the flocculation basin. The dual media type rapid sand filter is not used in the treatment process due to design deficiencies that make operation difficult. The hardware and media were removed from the sand filter. The existing basin can be utilized for chlorine contact and/or de-chlorination. The primary use of the basin at this time is as a wetwell for the effluent pump to outfall 002. Effluent from the wastewater treatment facility discharges to the Grande Ronde River through an 18-inch diameter, 5-mile long pipe line. The City also pumps treated wastewater to the Ladd Marsh Wildlife Area and to City-owned wetlands with effluent discharge to constructed wetlands which are owned by the Oregon Department of Fish and Wildlife. The treated wastewater is used for irrigation of crops for wildlife and development of constructed wetlands. Effluent discharge to the constructed wetlands is measured by two rectangular weirs, six-feet long, that are located at the chlorine contact basin. There is an emergency raw wastewater overflow to Gekeler Slough which is located at the head works prior to the pump stations. This overflow is identified in the proposed permit as outfall 003. There is also a possible discharge

3 Page 3 point to Gekeler Slough located in the south west corner of the south lagoon cell. This discharge point was the permitted outfall from 1963 to 1980 and is currently closed off. This discharge point has rarely been used. It was used in 1986 to prevent failure ofthe lagoons during a flood. Biosolids Management and Utilization Biosolids (waste sludge) accumulates in the treatment lagoon. Biosolids (predominately algae) are also generated in the tertiary treatment process and are transferred to four dewatering ponds. Each pond is two acres in size and two feet deep. Decant facilities help drain excess water, but the main mechanism for drying is evaporation. During upgrading ofthe treatment facilities in 2001 and 2002, biosolids were removed from the lagoons and land applied to local farmlands. A plan for management ofthe biosolids was approved by the Department on August 23, Subsequently, DEQ approved several sites for land application. The City may need to land apply additional biosolids at new land application sites over the next year or two in accordance with their Department approved plan. An updated Biosolids Management Plan must be submitted 6 months prior to removing any additional biosolids from the lagoon. The Biosolids Management Plan will ensure compliance with the federal biosolids regulations (40 CFR Part 503). Rags and grit collected from the collection and treatment system are disposed at the local sanitary landfill. The permittee conducted chemical testing of biosolids that were land applied in 2001 and 2002 which includes analysis of metals. The latest monitoring data taken from the City's annual biosolids reports are found as follows. Monitoring data from the 2001 Annual Biosolids Report, the averages ofthe 4 drying beds are shown below: Total Solids Volatile Solids dry wt ifimiitif! Total Kjeldahl Nitrate- Ammonia- Phosphorus Potassium % IBrfS Arsenic Cadmium Chromium Copper Lead 9 < Mercury Molybdenum Nickel Selenium Zinc 0.3 <2 6 <2 104

4 Page 4 The averages of 3 samples from the secondary lagoon are shown below: Total Solids Volatile Solids dry wt Total Kjeldahl Nitrate- Ammonia- Phosphorus Potassium % Arsenic Cadmium Chromium Copper Lead Mercury Molybdenum Nickel Selenium Zinc Aluminum 0.6 <2 7 < Monitoring data from the 2002 Annual Biosolids Report, the averages ofthe 2 drying beds used that year are shown below: Total Solids Volatile Solids dry wt liwniir Total Kjeldahl Nitrate- Ammonia- Phosphorus Potassium % Arsenic Cadmium Chromium Copper Lead 5.6 < Mercury Molybdenum Nickel Selenium Zinc Aluminum 0.20 < < The averages of 6 samples from the primary lagoon are shown below: Total Solids Volatile Solids dry wt Total Kjeldahl Nitrate- Ammonia- Phosphorus Potassium % Arsenic Cadmium Chromium Copper Lead 3.4 < <22 Mercury Molybdenum Nickel Selenium Zinc Aluminum 0.10 < <

5 Page 5 The combined and weighted averages (75% from lagoons and 25% from drying beds) ofthe above 8 samples in 2002 are shown below: Total Solids Volatile Solids dry wt Total Kjeldahl Nitrate- Ammonia- Phosphorus Potassium % Arsenic Cadmium Chromium Copper Lead 3.9 < Mercury Molybdenum Nickel Selenium Zinc Aluminum 0.12 < < Inflow and Infiltration (Ul) I/I does not appear to be a major problem for the permittee at this time. To control I/I, the Department recommends a long-term program that will completely replace collections systems based on life expectancy (usually 60 to 80 years). The replacement program should be directed at the oldest sub-basins or those in the worst condition. An I/I program will continue to be required with annual reporting to the Department. Pretreatment The permittee does not have a formal pretreatment program, nor is one required at this time. An industrial waste survey update was last submitted to the Department on December 31, The proposed permit includes a requirement to update the industrial waste survey. If the Department determines that a pretreatment program is required based on the updated survey results, the permit may be reopened and modified to incorporate a compliance schedule to require development of a pretreatment program Pollutants Discharged The current permit allows City of La Grande to discharge treated effluent from the wastewater treatment plant in November through May and conditionally in June, July, and October. The current permit sets limits on the following pollutants: Five-day Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS), E.coli bacteria, Total Residual Chlorine, and Total Ammonia. The discharge is also regulated for ph, flow, and pollutant removal efficiency. The proposed permit will regulate the same pollutants. Outfalls Treated wastewater is discharged to the Grande Ronde River through Outfall 001. During the growing season, reclaimed water may be irrigated on nearby farmland. This discharge is identified as Outfall 002. Outfall 003 is for emergency overflows only. The emergency raw wastewater overflow is located at the head works prior to the pump stations. Treated wastewater may also be discharged to the Ladd Marsh Wildlife Area and to the City's constructed wetlands which discharges to the Oregon Department of Fish and Wildlife constructed wetlands through Outfall 004. Outfall 005 is designated for the deposition of biosolids in the lagoon.

6 Page 6 Receiving Streams/Impact In accordance with OAR , the designated beneficial uses ofthe Grande Ronde River are: public and private domestic water supply, industrial water supply, irrigation, livestock watering, anadromous fish passage, salmonid passage, spawning and rearing, resident fish and aquatic life, wildlife and hunting, fishing, boating, water contact recreation, and aesthetic quality. Temperature The applicable temperature standard for the receiving stream is a maximum of 64 F, based on a seven-day average of maximum daily temperature readings. The standard was set to protect salmonid rearing. Stream temperatures are generally rising throughout the State of Oregon and many streams violate the applicable temperature standard in the summer. Point source dischargers are required to help stop and reverse the warming trend by addressing thermal discharges, in addition to chemical and biological discharges. The receiving stream is water quality limited for temperature at the point of discharge. That is, the receiving stream has violated the temperature standard for the basin. To address the temperature and other water quality limited pollutants, Total Daily Maximum Loads (TMDLs) and waste load allocations (WLAs) for the Grande Ronde River were adopted by the Oregon Environmental Quality Commission (EQC) on October 3, To meet the temperature TMDL, limits were placed on allowable discharge periods so that no discharge is allowed in August and September, and conditional discharge is allowed in June, July, and October. Under the terms of a Mutual Agreement and Order, the City of La Grande completed construction of improvements to the facility to meet the restrictive discharge limitations, and to fulfill the temperature TMDL requirements and Department-approved temperature management plan. The proposed permit maintains these permit discharge restrictions. In order to prevent further warming, most discharge permits identify the maximum allowable thermal discharge. However, since the City of La Grande is no longer discharging during the critical summer period of August- September, no thermal load limit is required. ph The proposed permit for La Grande will maintain limitations for waste load allocations that will address the contributions ofthe effluent from the La Grande sewage treatment plant to water quality problems. One cause of the problems of aquatic growth, dissolved oxygen, nutrients, and ph is excessive nutrients contained in the effluent from the La Grande sewage treatment plant. These nutrients provide for the growth of periphyton which, in turn, causes large diurnal swings in both ph and dissolved oxygen. Periphyton can exist on very low nutrient levels and can only be controlled if orthophosphorus and dissolved inorganic nitrogen in-stream levels can be reduced to below 5 ug/1 and 40 ug/1, respectively. Treatment of sewage to reduce orthophosphorus levels below a concentration of 40 ug/1 is likely not achievable. The best practical and most economical way to achieve nutrient reduction is to not discharge during the critical periods. To control the growth and impact of periphyton on water quality as a result of La Grande's treated sewage, the Department prohibits discharge of effluent in the current and proposed permit when conditions for periphyton growth exist. As established in the current permit, the Department proposes to allow discharge in October only after the ph of the Grande Ronde River above the point of discharge is less than 9.0 SU (as measured between 2 and 3 PM) for 7 consecutive days. The Department continues to believe that this criterion should be a good indicator that periphyton activity has ceased for the remainder of the year. Toxicity

7 Page 7 Effluent from the City's wastewater treatment facility contains chlorine and ammonia. Chlorine is used as a disinfectant and ammonia is naturally occurring in domestic wastewater. Both of these parameters are known to have toxic impact to aquatic life at specific levels. OAR l-0725(2)(p) states that: (A) (B) Toxic substances shall not be introduced above natural background levels in the waters of the state in amounts, concentrations, or combinations which may be harmful, may chemically change to harmful forms in the environment, or may accumulate in sediments or bioaccumulate in aquatic life or wildlife to levels that adversely affect public health, safety, or welfare, aquatic life, wildlife, or other designated beneficial uses. Levels of toxic substances shall not exceed the criteria listed in OAR , Table 20. These were based on criteria established by EPA and published in Quality Criteria for Water (1986), unless otherwise noted. OAR (4) states, however, that the Department may allow a designated portion of a receiving water to serve as a zone of dilution for wastewaters and receiving waters to mix thoroughly and this zone will be defined as a mixing zone. The Department may suspend all or part of the water quality standards, or set less restrictive standards, in the defined mixing zone, provided that the following conditions are met: (A) (B) The water within the mixing zone shall be free of materials in concentrations that will cause acute toxicity to aquatic life as measured by a Department approved bioassay method. Acute toxicity is lethality to aquatic life as measured by a significant difference in lethal concentration between the control and 100 percent effluent in an acute bioassay test. Lethality in 100 percent effluent may be allowed due to ammonia and chlorine only when it is demonstrated on a case-by-case basis that immediate dilution of the effluent within the mixing zone reduces toxicity below lethal concentrations. The Department may on a case-bycase basis establish a zone of immediate dilution, if appropriate, for other parameters. The water outside the boundary ofthe mixing zone shall be free of materials in concentrations that will cause chronic (sublethal) toxicity. Chronic toxicity is measured as the concentration that causes long-term sublethal effects, such as significantly impaired growth or reproduction in aquatic organisms, during a testing period based on the test species life cycle. Procedures and end points will be specified by the Department in wastewater discharge permits. Furthermore, 40 CFR (d) states that, in addition to the conditions established under (a), each NPDES permit shall include any requirements in addition to or more stringent than promulgated effluent limitations guidelines or standards under sections 301, 304, 306, 307, 318 and 405 ofthe Clean Water Act (CWA) necessary to achieve water quality standards established under section 303 ofthe CWA, including state narrative criteria for water quality. Section (d) of also states that limitations must control all pollutants or pollutant parameters (either conventional, non-conventional, or toxic pollutants) which the Director determines are or may be discharged at a level which will cause, have the reasonable potential to cause, or contribute to an excursion above any state water quality standard, including state narrative criteria for water quality. Section (d) also states that when the permitting authority determines that a discharge causes, has the reasonable potential to cause, or contributes to an in-stream excursion above the allowable ambient concentration of a state numeric criteria within a state water quality standard for an individual pollutant, the permit must contain effluent limits for that pollutant.

8 Page 8 The basis for toxic pollutant limits for chlorine and ammonia are contained in the two following sections. Chlorine According to EPA's 1986 Quality Criteria for Water (commonly known as the Gold Book) and 041, Table 20, chlorine concentrations of 11 ug/1 and 19 ug/1 can result in chronic and acute chlorine toxicity, respectively, in fresh waters. Compliance with acute standards is required at the edge ofthe Zone of Immediate Dilution (ZID). An end-of-pipe limit of 0.06 mg/l as a daily maximum and 0.02 mg/l as a monthly average based on the acute criteria was established in the current permit and is proposed for the permit renewal. Ammonia Ammonia toxicity criteria have been exceeded in the Grande Ronde River during the summer months. To address toxicity due to ammonia nitrogen, establishing limits are more complex because there is an increase in variables. The toxicity of ammonia depends not only on its concentration, but also the ph and temperature. The following discharge limitations were computed and established in the current permit: For a river ph less than 9.0 and greater than 7.75, the daily maximum concentration limit is 1.8 mg/l and the monthly average concentration limit is 0.8 mg/l. For a river ph less than 7.75, the daily maximum concentration limit is 19.7 mg/l and the monthly average concentration limit is 9.8 mg/l. The limits established for ammonia in the current permit are maintained in the proposed permit. Reclaimed Water Utilization of treated effluent for agricultural purposes is regulated under OAR Pursuant to the rules, the permittee must comply with the Department-approved Reclaimed Water Use Plan. The facility irrigates using disinfected Level I effluent on grass located on nearby farmland. Groundwater Upon the request ofthe Department, the City developed and submitted a groundwater monitoring plan entitled "Groundwater Monitoring Plan for the City of La Grande Constructed Wetlands at the Ladd Marsh Wildlife Area, 2001, George Chadwick Consulting" to the Department for approval. The Plan was required due to the proposed discharge to Oregon Department of Fish and Wildlife constructed wetlands. The City will be required to monitor parameters at a frequency designated in the approved Plan. No additional groundwater characterization or actions are required at this time. Stormwater General NPDES permits for stormwater are required for facilities with a design flow of greater than 1 MGD if stormwater is collected and discharged from the plant site. This facility does not discharge stormwater, therefore no stormwater permit is necessary.

9 Page 9 Permit History The existing permit expired on January 31, The Department received an application from the City on August 1, 2002, for a permit renewal. The Department of Environmental Quality (Department or DEQ) received a letter from the City of La Grande dated May 19, 2000, requesting modifications to the City's National Pollutant Discharge Elimination System (NPDES) Permit. The City requested modifications related to: (1) Polishing of secondary effluent with constructed wetlands; (2) A new discharge point from City-constructed wetlands into constructed wetlands owned and operated by the Oregon Department of Fish and Wildlife (ODFW); (3) A wet load increase related to the recently DEQ approved average wet weather design flow of 3.62 MGD; and (4) Modification of secondary treatment limits to treatment equivalent to secondary standards. A permit modification was issued on September 12, 2000, that responded to the City's request. An antidegradation review was completed with a recommendation to proceed with this permit action. The proposed activity will not result in a lowering of water quality in the Water Quality Limited Water. In fact, the stream quality should be measurably improved with the implementation of improvements to the facility in Compliance History On October 3, 1997, the Environmental Quality Commission (EQC) adopted a rule for portions ofthe Grande Ronde River establishing nutrient concentration limits. The EQC rule prohibits wastewater discharges to the Grande Ronde River if a discharge will cause specific concentrations to be exceeded instream. The rule required the City of La Grande to upgrade their wastewater treatment facilities by December 31, Mutual Agreement and Order (MAO) No. WQ/MW-ER was negotiated by DEQ and the City in February, 1998 to allow continued discharge of La Grande's effluent until the scheduled improvements to meet the nutrient rules and Total Maximum Daily Load (TMDL) were completed. Interim effluent limitations and a compliance schedule for completion of the wastewater facilities upgrade were specified in the MAO. The Wastewater Facility Plan for the City of La Grande was received by DEQ on October 2, 1998 and approved on February 16, The Plan proposed to construct two, new 30-acre non-aerated treatment lagoons and to expand the City's existing wastewater reclaimed water irrigation system to provide complete removal of effluent discharge to the Grande Ronde River from June 1 through October 31. The City's engineering consultant, Anderson Perry & Associates (A/P), requested a change in secondary discharge standards for BOD and TSS for the City of La Grande wastewater treatment facilities on November 8, The Department denied the request on November 22, 1999, since the existing facilities fail to consistently provide significant biological treatment as defined in 40 CFR, Part 133, Section However, since the modified facilities were designed to provide significant biological treatment (consistently achieve a 30-day average of at least 65% removal of BOD 5 ), the Department approved alternative secondary, treatment standards of 45 mg/l monthly average and 65 mg/l weekly average for BOD 5 and TSS in the effluent as requested by the City. In November, 1999, the City considered submitting a formal request for mass load increases to DEQ. After further deliberations including time delays, uncertainty in obtaining EQC approval, and realizing that mass load increases associated with approved design average wet weather flow could be approved by DEQ without a variance process, the City decided to not pursue mass load increases through the exception process. The City of La Grande sent a letter dated December 8, 1999, informing the Department that the Federal Aviation Administration and ODFW had determined that siting the new lagoons within 10,000 feet ofthe airport would be detrimental to air traffic and wildlife. Therefore, the City and A/P decided to explore other treatment and disposal alternatives. A/P, on behalf of the City of La Grande, sent a letter dated December 23, 1999, to DEQ indicating

10 Page 10 that the City was evaluating the use of ODFW wetlands as a wastewater disposal alternative and requesting guidance from the Department. The Department responded by letter dated February 17, 2000, providing the requested guidance to the City and A/P. On February 29, 2000, A/P submitted a letter to DEQ providing an analysis supporting a design average wet weather flow for the existing treatment facilities of 3.62 MGD that was approved by the Department on March 30, Oregon Administrative Rules (OAR) l-0120(9)(a)(B) authorizes the Department to base mass loads on the approved design average, wet weather flow and the applicable monthly concentration effluent limit. Mass loads assigned as described in paragraph (B) cited above are not subject to OAR (3), the provision for granting exceptions to the presently allowed discharge loads. In other words, the Department may increase the mass loads for wet weather flow periods without going through an exception process. The mass loads are determined by multiplying the approved wet weather flow expressed in MGD times the applicable monthly concentration effluent limit expressed in mg/l times 8.34 pounds per gallons. In this case, the applicable concentration effluent limit is 45 mg/l for BOD5 and TSS that is based on the Department approved alternative secondary treatment standards. The calculation of mass loads for dry weather periods specified in OAR l-0120-(9)(a)(a) authorizes the Department to base mass loads on the approved design average, dry weather flow and the applicable monthly concentration effluent limit. However, the Department may not increase mass loads for dry weather periods without going through an exception process. Therefore, the mass loads are determined by multiplying the approved dry weather flow expressed in MGD times the applicable monthly concentration effluent limit expressed in mg/l times 8.34 pounds per gallons. In this case, the applicable concentration limit is 20 or 30 mg/l, the assigned effluent limits in the existing NPDES Permit corresponding to dry and wet weather flow periods designated in the Permit. A/P provided a letter to DEQ on March 15, 2000, that proposed a more detailed plan for effluent disposal using a City-constructed wetland as a component of the modified treatment system and treated wastewater discharge to the ODFW wetlands. The letter included design criteria and requested a DEQ response on the acceptability of this disposal alternative. The Department responded by letter dated March 30, 2000, by providing acceptable design criteria for the wetlands alternative. The City of La Grande decided to implement the wetlands alternative and requested changes in the Permit to reflect this wastewater treatment and disposal option. On April 30, 2002, the Department issued a Notice of Noncompliance (NON) for submittal of late discharge monitoring reports (DMRs). The NON was withdrawn on May 2, 2002, as the Department had incorrectly cited late submission of DMRs. On July 8, 2002, the Department issued a NON for an uncontrolled wastewater discharge to Gekeler Slough from a discharge point not authorized by the permit. The City adequately addressed the violation identified in the NON. Compliance inspections ofthe wastewater treatment facility were performed on May 6, 1998, February 22, 1999, March 29, 2000, March 14, 2001, and June 25, The City was in compliance with the terms and conditions of the NPDES permit at the time ofthe inspections. PERMIT DISCUSSION Face Page The permittee is authorized to construct, install, modify, or operate a wastewater collection, treatment, control and disposal system and to discharge treated effluent to the Grande Ronde River within limits set by the proposed permit. In addition, the permittee is authorized to irrigate with reclaimed water, discharge wastewater through an emergency overflow, and discharge treated effluent to wetlands within limits established by the proposed permit. The permittee is also authorized to discharge biosolids to the lagoon. All other discharges are prohibited.

11 Page 11 Schedule A - Waste Discharge limitations Schedule A establishes limitations on the permittee's discharge. BOD and TSS limits are technology-based. Bacteria, ph, flow, chlorine and ammonia limits are based on water quality criteria and/or the Grande Ronde River TMDL. BOD and TSS concentration and mass limits Based on the Grande Ronde Basin minimum design criteria, wastewater treatment resulting in a monthly average effluent concentration of 20 mg/l for BOD 5 and TSS must be provided for June, July, and October. From November 1 - December 31, a minimum of secondary treatment or equivalent control is required. Secondary treatment for this facility is defined as monthly average concentration limit of 30 mg/l for BOD 5 and TSS. Since the Department has approved alternative treatment standards, from November through May, the monthly average effluent concentration limits for BOD5 and TSS are 45 mg/l. The Department is proposing concentration limits at least as stringent as the basin minimum design criteria. The proposed monthly average summer BOD 5 concentration limit is 20 mg/l with a weekly average limit of 30 mg/l. The proposed monthly average summer TSS concentration limit is 20 mg/l with a weekly average limit of 30 mg/l. The proposed monthly average winter BOD 5 concentration limit is 45 mg/l with a weekly average limit of 65 mg/l. The proposed monthly average winter TSS concentration limit is 45 mg/l with a weekly average limit of 65 mg/l. The summer mass limits for biochemical oxygen demand (BOD 5 ) and suspended solids (TSS) are based on the design average dry weather flow (ADWF) of 2.7 MGD and the monthly average BOD 5 and TSS concentration limits of 20 mg/l and 20 mg/l, respectively. The winter mass load limits for the facility are based on the design AWWF of 3.62 MGD and the monthly average BOD 5 or TSS concentration limits of 45 mg/l and 45 mg/l, respectively. On any day that the daily flow exceeds 5.4 MGD, the daily mass load limits shall not apply. The limits are in accordance with OAR l-0120(9)(a). By basing the winter mass limits on AWWF, the permittee is required to remove all inflow sources from the collection system. The proposed permit includes a Schedule C condition requiring submittal of a program and time schedule for identifying and removing inflow. BODs and TSS The limits are: (1) June: BOD 5 TSS Average ; Effluent Concet ltrations Monthly Weekly 20 mg/l 30 mg/l 20 mg/l 30 mg/l Monthly Average lb/day Weekly Average lb/day Daily Maximum Lbs

12 Page 12 (2) July and October: BOD 5 TSS Average Effluent Concentrations Monthly Weekly 20 mg/l 30 mg/l 20 mg/l 30 mg/l Monthly Average lb/day Weekly Average lb/day Daily Maximum Lbs (3) Novembe r 1 - December 31: BOD5 TSS Average Effluent Concentrations Monthly Weekly 45 mg/l 65 mg/l 45 mg/l 65 mg/l Monthly Average lb/day Weekly Average lb/day Daily Maximum Lbs (4) January 1 -May 31: BOD5 TSS Average ; Effluent Concet ltrations Monthly Weekly 45 mg/l 65 mg/l 45 mg/l 65 mg/l Monthly Average lb/day Weekly Average lb/day Daily Maximum Lbs Calculations: (1) June TSS and BOD, (a) (b) (c) 3.62 MGD x 8.34 #/gal x 20 mg/l monthly avg. = 600 lbs/day 600 lbs/day monthly avg. x 1.5 = 900 lbs/day weekly avg. 600 lbs/day monthly avg. x 2.0 = 1200 lbs/day daily max. (2) July and October TSS and BOD 5 (a) (b) (c) 2.7 MGD x 8.34 #/gal x 20 mg/l monthly avg. = 450 lbs/day 450 lbs/day monthly avg. x 1.5 = 680 lbs/day weekly avg. 450 lbs/day monthly avg. x 2.0 = 900 lbs/day daily max. (3) November and December TSS and BOD5 (a) (b) (c) 2.7 MGD x 8.34 #/gal x 30 mg/l monthly avg. = 680 lbs/day 680 lbs/day monthly avg. x 1.5 = 1020 lbs/day weekly avg. 680 lbs/day monthly avg. x 2.0 = 1360 lbs/day daily max. (4) January through May TSS and BOD5 (a) (b) (c) 3.62 MGD x 8.34 #/gal x 45 mg/l monthly avg. = 1360 lbs/day 1360 lbs/day monthly avg. x 1.5 = 2040 lbs/day weekly avg lbs/day monthly avg. x 2.0 = 2720 lbs/day daily max.

13 Page 13 No changes from the current permit (with permit modifications incorporated) are proposed. With the recently completed modifications to the facility, the City should be able to comply with the permit limits. BOD and TSS Percent Removal Efficiency A minimum level of percent removal for BOD5 and TSS for municipal dischargers is required by the Code of Federal Regulations (CFR) secondary treatment standards (40 CFR, Part 133). However, the permittee can qualify for a lower percentage removal of BOD5 and TSS if certain conditions can be demonstrated pursuant to 40 CFR (d). A determination was made in previous permitting that the City qualifies for lower removal efficiencies of 65 percent (%). Therefore, the Department proposes maintaining a 65 % removal efficiency limit for both BOD5 and TSS. These limits will not affect effluent quality, or cause any additional impacts on the Grande Ronde River. ph The Grande Ronde Basin Water Quality Standard for ph is found in OAR l-0725(2)(d). The allowed range is 6.5 to 9.0. The proposed permit limits ph to the range 6.0 to 9.0 as is required in the current permit. This limit is based on Federal wastewater treatment guidelines for sewage treatment facilities, and is applied to the majority of NPDES permittees in the state. Within the permittee's mixing zone, the water quality standard for ph does not have to be met. It is the Department's belief that mixing with ambient water within the mixing zone will ensure that the ph at the edge of the mixing zone meets the standard, and the Department considers the proposed permit limits to be protective ofthe water quality standard. Bacteria The proposed permit limits are based on an E. coli standard, OAR l-0725(2)(e), approved in January The proposed limits are a monthly geometric mean of 126 E. coli per 100 ml, with no single sample exceeding 406 E. coli per 100 ml. The bacteria standard allows that if a single sample exceeds 406 E. coli per 100 ml, then the permittee may take five consecutive re-samples. If the log mean ofthe five re-samples is less than or equal to 126, a violation is not triggered. The re-sampling must be taken at four hour intervals beginning within fifty-eight (58) hours after the original sample was taken. In addition, the proposed permit limits for E. coli bacteria specified above are also required for reclaimed water and effluent discharged to constructed wetlands. The proposed effluent limits are achievable through proper operation and maintenance. Chlorine Residual Disinfection of the effluent with chlorine is the process the permittee uses to comply with the waste discharge limitations for bacteria. Chlorine is a known toxic substance and as such is subject to limitation under Oregon Administrative Rules. The rule (OAR l-0725(2)(p)) states in part that toxic substances shall not be discharged to waters of the state at levels that adversely affect public health, aquatic life or other designated beneficial uses. In addition, levels of toxic substances shall not exceed the criteria listed in Table 20 which were based on criteria established by the EPA and published in Quality Criteria for Water (1986), unless otherwise noted. However, OAR (4) states that the Department may allow a designated portion of a receiving water to serve as a zone of dilution for wastewaters and receiving waters to mix thoroughly and this zone will be defined as a mixing zone. The Department may suspend all or part ofthe water quality standards, or set less restrictive standards, in the defined mixing zone, provided the water within the mixing zone is free of materials in concentrations that will cause acute toxicity to aquatic life as measured by the acute bioassay method and outside the boundary ofthe mixing zone is free of materials in concentrations that will cause chronic toxicity.

14 Page 14 Furthermore, 40 CFR (d) states that permit limitations must control all pollutants or pollutant parameters which are or may be discharged at a level which will cause, have the reasonable potential to cause, or contribute to an excursion above any state water quality standard, including state narrative criteria for water quality. The fresh water criteria for chlorine were used to calculate permit limitations. According to OAR , Table 20, chlorine concentrations of 11 micrograms per liter (ug/1) can result in chronic toxicity in fresh waters while 19 ug/1 can result in acute chlorine toxicity in fresh waters. Compliance with acute toxicity criteria is required at the edge ofthe Zone of Immediate Dilution (ZID) and compliance with chronic toxicity criteria is required at the edge ofthe mixing zone. The existing permit contains the following total chlorine residual limit: Shall not exceed a daily maximum concentration of 0.06 mg/l and a monthly average concentration of 0.02 mg/l. The previous permit's limit was derived by the Department after an evaluation ofthe dilution available within the mixing zone and ZID. The Department proposes to retain the existing residual chlorine limit. The permittee uses calcium thiosulfate to dechlorinate the effluent prior to discharge to reduce potential toxic effects on the receiving stream and meet permit limits. The permittee should be able to meet the limits on a consistent basis with the facilities available. Ammonia As required by the current permit, the Department is proposing the following effluent limitations for ammonia for the months of June, July, and October: Temperature * For a river ph greater than 7.75, the daily maximum concentration limit is 1.8 mg/l and the monthly average concentration limit is 0.8 mg/l. * For a river ph less than 7.75, the daily maximum concentration limit is 19.7 mg/l and the monthly average concentration limit is 9.8 mg/l. As mentioned previously, a thermal load limit for the effluent is not proposed. Also, since the City no longer discharges during the critical summer period, no temperature limit is proposed. Minimum Dilution Effluent from the City's wastewater treatment facility is required to meet a minimum dilution ratio when discharging to the Grande Ronde River. OAR (1) (c) requires that the effluent BOD 5 concentration in mg/l, divided by the dilution factor (ratio of receiving stream flow to effluent flow) shall not exceed one (1) unless otherwise authorized by the permit. As specified in the current permit, the Department has proposed a formula which substitutes actual BOD 5 monitoring results with the NPDES permit monthly average concentration limits. The dilution formula is manipulated as follows.

15 Page 15 or Effluent Flow x BODs < 1 River Flow Effluent Flow < River Flow (1) BOD 5 By substituting concentration limits the following limits are derived: For the Months of June, July, and October Mixing Zone and Zone of Immediate Dilution Effluent Flow < River Flow 20 OAR l-0725(4)(a) allows the Department to designate a portion ofthe receiving stream water to serve as a zone of dilution for wastewaters and receiving waters to mix. OAR l-0725(4)(b) allows the Department to suspend all or part of the water quality standards, or set less restrictive standards, in the defined mixing zone, provided that a number of conditions are met. The current permit for the treatment facility allows for a mixing zone in the Grande Ronde River that shall not extend beyond 500 feet downstream from point of discharge and a zone of initial dilution to be 10% ofthe size of the existing mixing zone. This mixing zone has been retained for the proposed permit The Department believes that the beneficial uses ofthe receiving stream will not be affected by the discharge and this mixing zone, and that the defined mixing zone meets the criteria in the rule. Reclaimed Water The utilization of treated effluent for agricultural purposes is regulated under OAR The facility produces disinfected Level I reclaimed water. Up to 325 acres of land are available for irrigation. The application of reclaimed water must be managed in accordance with the approved Reclaimed Water Use Plan. All reclaimed water shall be distributed on land, for dissipation by evapotranspiration and controlled seepage by following sound irrigation practices so as to prevent: a. Prolonged ponding of treated reclaimed water on the ground surface. b. Surface runoff or subsurface drainage through drainage tile. c. The creation of odors, fly and mosquito breeding or other nuisance conditions. d. The overloading of land with nutrients, organics, or other pollutant parameters. e. Impairment of existing or potential beneficial uses of groundwater. Specific crops, application rates and buffers have been approved by the Department within the Reclaimed Water Use Plan. Emergency Overflows The limitation does not allow a discharge from this outfall except as identified in OAR (13) and (14). These rules allow for discharge overflows during extreme storm events.

16 Page 16 Biosolids The discharge (Outfall 005) and accumulation of biosolids is permitted on an annual basis until such time that biosolids must be removed to maximize treatment efficiency and/or provide additional storage space. Biosolids land application and management must comply with Oregon biosolids rules and guidelines including OAR and other applicable statutes, rules and federal regulations. Land application activities are to be conducted in accordance with an approved biosolids management plan. Groundwater The wastewater treatment facility must be operated and maintained in accordance with OAR so that existing or potential uses of groundwater are not impaired. Schedule B - Minimum Monitoring and Reporting Requirements In 1988, the Department developed a monitoring matrix for commonly monitored parameters. Proposed monitoring frequencies for all parameters are based on this matrix and have not changed from the current permit. The proposed monitoring frequencies for all parameters correspond to those of facilities of similar size and complexity in the state. The permittee is required to have a laboratory Quality Assurance/Quality Control program. The Department recognizes that some tests do not accurately reflect the performance of a treatment facility due to quality assurance/quality control problems. These tests should not be considered when evaluating the compliance ofthe facility with the permit limitations. Thus, the Department is also proposing to include in the opening paragraph of Schedule B a statement recognizing that some test results may be inaccurate, invalid, do not adequately represent the facility's performance and should not be used in calculations required by the permit. Monitoring for E. coli bacteria must be performed in accordance with one of the methods approved by the Department. Total chlorine residual and chlorine used must be monitored daily. Daily flow monitoring of influent and effluent flow for Outfall 001 is required in this permit. In addition, calibration ofthe flow meters is required on a semi-annual basis. Monitoring of ph is required three times a week. Monitoring of BOD5 and TSS is required twice a week. Plant influent flow is measured at the headworks by an 18" Parshall flume. Outfall 001 effluent monitoring requirements include: total residual chlorine, quantity chlorine used, total ammonia as N, and E. coli bacteria. The City monitors the effluent flow discharged to the River by two weirs located at the flocculation basin. The flow of reclaimed water is measured by a magnetic flow meter prior to discharge to the land application sites. The City monitors the flow of treated water to the ODFW wetlands through two rectangular weirs, six-feet long, located at the chlorine contact basin. The proposed permit includes a requirement to monitor the treated effluent discharged to Outfalls 002 and 004 for certain nutrients. Monthly monitoring of Total Kjeldahl (TKN), nitrate plus nitrite nitrogen, and ammonia (004 only) is proposed when the discharge is occurring. The permittee will be required to meet a minimum of 65 % BOD 5 and TSS removal efficiency on a monthly average. Calculation and reporting ofthe monthly average removal efficiency for these parameters is being retained in the proposed permit.

17 Page 17 Temperature monitoring ofthe effluent is required for discharge periods during June, July, and October. In addition, the permittee will be required to calculate the weekly average maximum temperature of the effluent and the weekly excess thermal load (ETL) discharged. The monitoring and calculation of ETL is for the purposes of ensuring antidegradation requirements are met. The maximum ETL is currently 74.8 kcal/day during the June, July, October period. Monitoring may be waived for certain months after two full years of monitoring are completed, provided the following condition is met: No single daily effluent temperature in that month for the past two years has exceeded the applicable stream temperature criteria. Because this facility is classed as a major discharger, the Department has required annual whole effluent toxicity (WET) or bioassay tests using three species in the proposed permit. One bioassay will be required annually for Bioassay tests are to be conducted in accordance with EPA test methods and procedural requirements as defined in Schedule D. The current permit required two bioassay tests in 2003 after completion of the improvements to the facility. The results of the bioassay tests required in 2003 will be submitted to the Department later this year. The permittee will be required to monitor the Grande Ronde River for ph, flow and temperature when discharging in June, July, and October. The permittee will be required to monitor the flow from the emergency overflow and estimate the volume and duration ofthe overflow during any discharges. The permittee will be required to measure biosolids accumulation in the lagoon cells annually, and measure cell depth and conduct a perimeter inspection weekly. For effluent discharge to the constructed wetlands, the permittee will be required to monitor flow on a daily basis. Average detention time is required on a weekly basis. Ammonia, TKN, and nitrite plus nitrate-nitrogen are required to be measured on a monthly basis. The quantity of chlorine used and total residual chlorine are required to be monitored on a daily basis. Monitoring of E. coli bacteria is required weekly. The proposed permit includes monitoring ofthe reclaimed water for flow, chlorine used and residual, ph, E. coli bacteria, and nutrients. The monitoring frequencies are in accordance with Department rules and guidance. An annual report describing the effectiveness ofthe reclaimed water system is required. The Department approved a Groundwater Monitoring Plan titled "Groundwater Monitoring Plan for the City of La Grande Constructed Wetlands at the Ladd Marsh Wildlife Area, January 2001, George Chadwick Consulting". The proposed permit requires sampling to be conducted for those parameters and frequencies specified in the Plan, the submittal of groundwater monitoring results semi-annually, and annual submittal of a data analysis report to the Department. The report needs to be submitted by May 1 st of each year and present data collected, and an evaluation ofthe results ofthe data collected. A condition is also provided that outlines resampling requirements if concentration limits are exceeded or there is a significant increase or decrease in values of a parameter monitored. Discharge monitoring reports must be submitted to the Department monthly by the 20th day ofthe following month. The monitoring reports need to identify the principal operators designated by the Permittee to supervise the treatment and collection systems. The reports must also include records concerning application of biosolids and all applicable equipment breakdowns and bypassing. Schedule B of the permit includes the requirement for the submittal of annual reports in addition to the groundwater reporting mentioned above. The conditions are standard language requirements concerning: Annual report on inflow and infiltration removal

18 Page 18 Annual report on the use of reclaimed water Industrial Users Survey Schedule C - Compliance Conditions Under Schedule C, the permittee is required to submit to the Department the expanded effluent testing data based on a total of 3 scans that was required for the permit renewal application process by Part D ofthe NPDES Form 2A Application Overview. The City submitted expanded effluent testing data for the application process based on one scan and indicated they plan to collect the remainder ofthe data after completion ofthe treatment plan upgrade. The expanded effluent data is required to be submitted to the Department within 6 months of permit issuance. Schedule C of the Permit includes a compliance condition requiring submittal a report identifying known raw sewage overflow points and providing a schedule to eliminate the overflows. Schedule C also requires the permittee to meet the compliance dates established in this schedule or notify the Department within 14 days following any lapsed compliance date. Schedule D - Special Conditions The proposed permit includes a number of special conditions. The requirements include: a contingency plan, management of biosolids in accordance with an approved plan, biosolids application site criteria, submittal of an updated biosolids plan, reclaimed water use, operator certification, corrective action notification, bioassays, and management and maintenance of groundwater monitoring wells. The permittee is required to have an adequate contingency plan for prevention and handling of spills and unplanned discharges in force at all times. The permittee is required to manage biosolids in accordance with an approved biosolids management plan upon Department approval of a plan. The permittee is required to submit an updated biosolids management plan in accordance with OAR , "Land Application of Domestic Wastewater Treatment Facility Biosolids, Biosolids Derived Products, and Domestic Septage", and 40 CFR 503. The updated plan will need to be submitted at least six (6) months prior to the anticipated disposal of biosolids. All new biosolids sites are required to meet site selection criteria set forth in OAR The permittee must have the facilities supervised by personnel certified by the Department in the operation of treatment and/or collection systems. Schedule D includes a condition requiring the permittee to comply with the rules concerning the use of reclaimed water and the Reclaimed Water Use Plan approved by the Department. A condition is included in Schedule D that requires the permittee to keep a cover crop on the irrigation site at all times unless otherwise approved by the Department in the Reclaimed Water Use Plan. Schedule D of this permit includes a condition specifying the necessary procedures for conducting whole effluent toxicity testing. It also includes a condition that requires the permittee to perform a priority pollutant scan at least once during the term of the proposed permit. Schedule D includes a condition requiring the development and implementation of a contingency plan for the prevention and handling of spills and unplanned discharges. There is a condition in Schedule D requiring proper operation and maintenance of groundwater monitoring wells. The condition also specifies procedures for abandoning old wells and installation of new wells.