FACT SHEET And NPDES WASTEWATER DISCHARGE PERMIT EVALUATION

Transcription

1 FACT SHEET And NPDES WASTEWATER DISCHARGE PERMIT EVALUATION Department of Environmental Quality Northwest Region - Portland Office 2020 SW 4th Ave., Suite 400, Portland, OR Telephone: (503) PERMITTEE: City of Portland, Tryon Creek Wastewater Treatment Plant 195 Foothills Road Lake Oswego, OR FILE NUMBER: SOURCE LOCATION: 195 Foothills Road, Lake Oswego, Clackamas County SOURCE CONTACT: Dan Clark Telephone Number: PERMIT WRITER: Lyle Christensen Telephone Number: PROPOSED ACTION: Renewal of a National Pollutant Discharge Elimination System (NPDES) wastewater discharge permit SOURCE CATEGORY: Major Domestic TREATMENT SYSTEM CLASS: Level IV COLLECTION SYSTEM CLASS: Level IV PERMIT APPLICATION DATE: March 4, 2003 PERMIT APPLICATION NUMBER: BACKGROUND Introduction City of Portland, Bureau of Environmental Services operates the Tryon Creek Wastewater Treatment Plant located in Lake Oswego, Clackamas County, Oregon. Wastewater is treated and discharged to Willamette River in accordance with National Pollutant Discharge Elimination System (NPDES) Permit number The Permit for the facility was issued on September 18, 1998 and expired on August 31, The Department received a partial renewal application on March 4, 2003 with additional information submitted May 13, 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.

2 Page 2 Facility Description The Tryon Creek Sewage Treatment Plant is operated by the City of Portland's Bureau of Environmental Services and serves approximately 70,000 persons living in the area of Southwest City of Portland and City of Lake Oswego. The wastewater treatment facility at this site was originally placed into operation in The treatment system was largely modified in Though no facility expansion has occurred since 1976, the facility has had a number of changes in the last several years. Most recently in the aeration basins were modified from complete mix using mechanical mixers to diffused air system with plug-flow selector system for operational flexibility. li f" { c fr Tryon Creek WTP </ \ " ;T llldtm 2 U«M'f J W. lit mm*/ 44 />.Di^josdl / V s M^ekV '! ".:'... \,:::.:>.,\A: The major treatment process used is activated sludge. The engineer who designed the facility determined the average design dry weather flow. It is the estimated maximum flow during May 1 to October 31 (expressed as a daily average flow), at which the design engineer expects the treatment facility can still consistently meet all effluent limits. The dry weather flows do not include the high levels of infiltration and inflow that are associated with the winter in Oregon. Therefore, the design dry weather flows are used mostly to estimate how much treatment capacity there is for organic loads. For this facility, the average design dry weather flow is 8.3 million gallons/day (MGD). The current actual dry weather flow for May 1 to October 31, for the past two years, is 6.9 MGD. Based on the current flows, this facility is at about 84% of organic treatment capacity. Based on the current flows compared to the design flows and the lack of recurring effluent violations, no expansion of the facility is needed at this time.

3 Page 3 The current actual average wet weather flow (November 1 through April 30), for the past two years, is 9.7 MGD. The peak day flow over the past two years is 27.5 MGD. See the section on Inflow and Infiltration for a further discussion of winter flows and hydraulic capacity issues. Schematics of the facility providing a site plan, hydraulic profile and process flows were included with the application submission. Biosolids Management and Utilization Two-stage anaerobically digested primary, thickened primary and thickened waste activated solids are produced at this facility. These solids are regularly pumped out and transported to the City of Portland's Columbia Boulevard plant where they are integrated with raw solids from that facility for further treatment and beneficial use as biosolids. In 2002, the permittee produced just over 2,000 dry tons of solids at this facility. In addition, in 2003, the permittee produced just over 1,230 dry tons of solids at this facility. In total, the final 2002 as well as the final 2003 biosolids production from City of Portland (Tryon Creek and Columbia Boulevard combined) was almost 13,000 dry tons each year. A Biosolids Land Application Plan was submitted on November 21, 2003, as part of the permit renewal application. City of Portland is responsible for ensuring compliance with the federal biosolids regulations (40 CFR Part 503) and the permit for the Columbia Boulevard facility is the governing authority. The permit for the Tryon Creek facility will require monthly reporting of the transportation of residual solids and biosolids to Columbia Boulevard STP and the submittal of an annual summary for this activity. Inflow and Infiltration (I/I) The last permit renewal included wet weather mass limits for this facility and the permit requires by condition that City of Portland have in place an ongoing program directed at identifying and reducing inflow to the collection system. The final inflow identification and reduction plan for the Tryon Creek collection system was submitted October 8, Average flows do not appear to have changed noticeably over the last few years. The permittee indicated on the renewal application that for 2002 the estimated contribution of I/I was 195 million gallons. Facility flow records reviewed in 1998 indicated that average reported daily flow from 1993 to 1998 was 9.8 MGD during the November through April months and 6.6 MGD during the May through October months. These numbers are reasonably consistent with the 9.7 MGD and 6.9 MGD flows observed during the same respective wet weather/dry weather periods the past two years. The influent flows are graphically represented below. The Tryon Creek WTP has portions of the collection system that contribute to the plant operated by City of Lake Oswego. I/I controls and corrections are the responsibility of both City of Portland and City of Lake Oswego. As an ongoing program the permit requires annual reports on the activities conducted to control I/I. The file record shows annual reports provided for each year this permit has been in place. The most recent report was dated July 26, The reports summarize the annual maintenance and repair activities throughout the Portland and Lake Oswego collection systems.

4 Page 4 Tryon Creek Monthly Average Influent Flow g c^ <* <<V <& * c<v <<V cv 5 rv> ^ ( ^ ( ^ ^ ^ ^ ^ ^ ^ C i - O^ O N Q N QT O^ O^ 3" O" $" 6" O" <V O 3 O J O 3 O 3 O 3 «* «* Q" «* <T #///// #^V A V>W ^///// ^>V A V>V A ' ^VV^VVV 1 ' ^V Month Inflow and Infiltration does not appear to be an extreme problem for the Permittee. The Department recommends a long-term program that will completely replace the collections system based on life expectancy (usually 60 to 80 years). The replacement program should be directed at the oldest subbasins or those in the worst condition. Pretreatment The City of Portland implements an industrial pretreatment program approved by the Department. Federal and state pretreatment requirements were included in the NPDES permit for this facility when the previous permit was issued. The Tryon Creek WTP has no categorical industries discharging to the system and is only a small part of the larger program that the permittee manages in the rest of the City of Portland area. Therefore the permit for Tryon Creek will no longer include the pretreatment Schedule F nor separate pretreatment metals monitoring. The permit will (in Schedule, Condition 5) reinforce the priority pollutant monitoring as required under the NPDES application (EPA Form 2A). Pollutants Discharged The current permit allows City of Portland, Tryon Creek Wastewater Treatment Plant to discharge treated effluent from the wastewater treatment plant year round. The current permit sets limits on the following pollutants: five-day biochemical oxygen demand (BOD 5 ), total suspended solids (TSS), chlorine, and Escherichia coli (E. coli) bacteria. The discharge is also regulated for ph and BOD 5 and TSS removal efficiency. The proposed permit will regulate the same pollutants.

5 Page 5 Outfalls Treated wastewater is discharged to Willamette River. The discharge is through a multiport diffuser that is located about 250 feet offshore in 50+ feet of water at river mile A modeling effort followed by a field dye study concluded that the average dilutions during low flow conditions were 89 to 1 at the edge of the zone of initial dilution (20 feet) and 187 to 1 at the edge of the regulatory mixing zone (200 feet). Receiving Streams/Impact The designated beneficial uses of the receiving stream are: public and private domestic water supply, industrial water supply, irrigation, livestock watering, anadromous fish passage, spawning and rearing, salmonid passage, spawning and rearing, resident fish and aquatic life, wildlife and hunting, fishing, boating, water contact recreation, aesthetic quality, hydro power and commercial navigation and transportation. DEQ is required by the Federal Clean Water Act, Section 303(d) to identify all water bodies in Oregon that do not meet water quality standards. Once identified, the stream segments are placed on the DEQ's "303(d) list". This listing means that the standards that protect the most sensitive beneficial uses of the water are not being met and the Department is required to establish a plan with goals and pollution control targets for improving water quality. The "303(d) list" provides a way to identify and prioritize water quality problems. The list also serves as a guide for developing and implementing watershed pollution reduction plans (TMDLs) to achieve water quality standards and protect beneficial uses. From river mile 0 to river mile 24.8, the Willamette River is listed for the following parameters Parameter Criteria/Standard Season Temperature Fish Rearing 17.8 C (64 F) Summer Fecal Coliform Geometric Mean of 200, no more than 10% Winter/Spring/Fall >400 organisms per 100 ml Toxics Fish Tissue-DDT and DDT Metabolite (DDE) Year around Fish Tissue-PCB Fish Tissue -Aldrin Fish Tissue -Dieldrin Fish Tissue -Mercury Iron -Table 20 Water and Fish Ingestion Manganese-Table 20 Water and Fish Ingestion Pentachlorophenol-Table 20 Polynuclear Aromatic Hydrocarbons- Table 20 Year around Year around Year around Year around Year around Year around N/A Biological Criteria Skeletal deformities in squawfish N/A Year around

6 Page 6 A TMDL for the Willamette River for Temperature will be available for public comment in July of Further Temperature discussion was completed later in this evaluation report. A TMDL is also under development for bacteria in the Willamette River. A proposed permit limit for bacteria has been set and is an end of pipe limit for e. coli bacteria at the basin standard. Toxics such as Aldrin, Dieldrin, PCB, DDE, DDT, Pentachlorophenol and Polynuclear Aromatic Hydrocarbons are not known to be introduced to this domestic wastewater treatment facility through production or manufacturing processes. Expanded effluent testing data included with the permit application indicates that concentrations of these type materials are at non-detection levels. A Priority Pollutant scan will be required prior to the next permit renewal. Skeletal deformities in fish are a separate study. This source has not been evaluated for its contribution to skeletal deformities in squawfish. A recent study entitled Environmental Stresses and Fish Deformities in the Willamette River Project Status Report (December 2003)conducted by Departments of Environmental and Molecular Toxicology, Microbiology, and Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, indicates that parasites are major contributors to high prevalence of skeletal deformities in fish from Newberg Pool of the Willamette River. Mercury was evaluated as part of the reasonable potential analysis discussed below. There is no reasonable potential for mercury to cause or contribute to a violation of the water quality standard. Manganese and Iron are not included on the priority pollutant list of pollutants anticipated to be in wastewater and thus were not included in the expanded effluent testing data submitted. Reasonable Potential Analysis A reasonable potential analysis was conducted using effluent testing data included in the renewal application. When determining whether a discharge has the potential to exceed water quality standards, the Department accounts for the variability of the effluent. A multiplier is used to account for effluent variability in accordance with the methods outlined in EPA's Technical Support Document for Water Quality Based Toxics Control (March 1991). To determine whether the discharge has a reasonable potential to exceed water quality standards for these pollutants, a spreadsheet that simulates the approach in EPA's Technical Support Document for Water Quality Based Toxics was used. Maximum probable effluent concentrations (based on the multiplier), water quality criteria, and mixing zone dilution data are used to determine whether the discharge has a reasonable potential to exceed water quality standards. The City of Portland has been collecting high resolution metals data in the lower portion of the Willamette River. Because the City of Portland data is developed using state-of-the-art analytical techniques and is of high quality, the Department has used this data in the water quality analysis. The in-stream data was collected from at the Waverly County Club (RM 17.9). The results of the reasonable potential analysis are attached. The results indicate that the discharge does not have a reasonable potential to exceed water quality standards. Thus, water quality based effluent limits are not proposed for these pollutants at outfall 001. Temperature This segment of the Willamette River serves as a migration corridor for salmonids. OAR (4)(d) states that the 7-day average maximum temperature of a stream identified as a migration corridor may not exceed 20 C (68 F). As noted, this segment of the Willamette River does not meet water quality standards for temperature during the summer months. For streams that do not meet water quality standards, OAR (12) states the following: "Prior to completion of a temperature TMDL or other cumulative effects analysis, no single NPDES point source that discharges into temperature water quality limited water may cause the

7 Page 7 temperature of the waterbody to increase more than 0.3 degrees Celsius (0.5 degrees Fahrenheit) above the applicable criteria after mixing with either twenty-five (25) percent of the stream flow or the temperature mixing zone, whichever is more restrictive." Since a temperature TMDL has not been completed for the Willamette River, the above provision from OAR (12) applies. A mass balance analysis was conducted to determine whether the discharge would cause a temperature increase greater than 0.3 C. The calculation is as follows: T e =[(T mz *Q inz )-(Q s *T s )]/Q e Where: T e is the temperature in the effluent; Tmz is the temperature at the edge of the mixing zone (20.3 C); Q mz is the dilution at the edge of the mixing zone (187); Q s is the portion of the Willamette River available for mixing (186); T s in the water quality standard for the Willamette River (20 C); and Q e is the effluent dilution factor when compared to the stream (1). The mass balance analysis based on the available dilution within the mixing zone indicates that the allowable discharge temperature for the Tryon Creek facility would be 76.1 C. Tryon Creek has been collecting effluent temperature data for the past three years. This data shows that the maximum 7-day average of the daily maximum effluent temperature was 21.5 C and the maximum summer effluent temperature was 22 C. Thus, the discharge is not expected to increase temperature at the edge of the mixing zone by more than 0.3 C. Based on the above analysis, there appears to be no reasonable potential that this facility will cause or contribute to the temperature issues in the Willamette River. Thermal Plume Criteria Recent revisions to the Department's water quality standards include temperature thermal plume limitations in OAR (d). This section of the rules contains criteria to prevent potential adverse impacts that may result from thermal plumes. Note that the temperature thermal plume limitations that the Department has adopted are similar to the recommendations in the April 2003 EPA Region X Temperature guidance. The criteria as they apply to Tryon Creek STP are discussed below: OAR (d) (A): Impairment of an active salmonid spawning area where spawning redds are located or likely to be located. Tryon Creek STP discharge: There is no salmonid spawning in this segment of the Willamette River. This segment of the Willamette River serves as a migration corridor for salmonids. OAR (d)(B): Acute impairment or instantaneous lethality is prevented or minimized by limiting potential fish exposure to temperatures of 32 C or more to less than 2 seconds. Tryon Creek STP discharge: Based on temperature data collected over the past three years, the maximum effluent temperature at outfall 001 is 22 C. Thus, the discharge is not expected to cause an acute impairment or instantaneous lethality. OAR (d)(C): Thermal shock caused by a sudden increase in water temperature is prevented or minimized by limiting potential fish exposure to temperatures of 25 C or more to less than 5% of the cross-section of 100% of the 7Q10 flow of the waterbody.

8 Page 8 Tryon Creek discharge: Based on temperature data gathered over the past three years, temperature of this effluent has not exceeded 22 C. Thus the discharge is not going to be a cause for thermal shock. OAR (d)(D): Unless ambient temperature is 21 C or greater, migration blockage is prevented or minimized by limiting potential fish exposure to temperatures of 21 C or more to less than 25% of the cross-section of 100% of the 7Q10 flow of the waterbody. Tryon Creek STP discharge: As discussed above, the discharge is not expected to increase temperature at the edge of the mixing zone by more than 0.3 C. Modeling shows that the expected dilution within a few feet of the discharge diffuser would reduce temperatures within the mixing zone below 21 C. According to the model results, effluent mixing to below 21 C would occur within a half meter of the diffuser ports and the diffuser takes up a width of less than 100 ft of the total stream. At this location the stream is well over 1000 feet wide. So the thermal plume will not exceed 25% of the cross section at any time. Thus, the analysis indicates that the discharge from the Tryon Creek STP facility meets the temperature thermal plume limitations in OAR (d). Groundwater Based on the Department's current information, this facility has a low potential for adversely impacting groundwater quality. Therefore, Schedule D of the proposed permit states that no groundwater evaluations will be required during this permit cycle. The permit also includes a condition in Schedule A that prohibits any adverse impact on groundwater quality. Stormwater General NPDES permits for stormwater are required for facilities with a design flow of greater than 1 MGD if stormwater is collected and discharge from the plant site. This facility does not discharge stormwater as storm water flows are captured and treated through the facility or allowed to soak into the ground. Therefore, no storm water permit is necessary. Permit History The discharge from this facility has been permitted at this site since the mid 1960's when the Oregon State Sanitary Authority, Oregon DEQ's predecessor issued the initial "waste discharge permit". The first National Pollutant Discharge Elimination System (NPDES) permit was issued in Since that time, this permit has been renewed about every 5 years (1977, 1981, 1987, 1992, &1998). Compliance History This facility was last inspected June 15, 2004 and was found to be operating in compliance. The monitoring reports for this facility were reviewed for the period since the current permit was issued, including any actions taken relating to effluent violations. The permit compliance conditions were reviewed and all inspection reports for the same period were reviewed. In February 1999 at Notice of Noncompliance (NON-NWR-WQ ) was issued for effluent bacteria limit violations. In April 1999 NON-NWR-WQ was issued in response to the

9 Page 9 bypass of primary effluent at the primary effluent pump station. In December 2000 NON-NWR- WQ was issued for a sewage overflow at the Riverview Pump Station. In April 2001 a civil penalty was assessed for the pump station overflow. Since 2001 no other permit violations have been documented and no additional enforcement actions taken. Therefore, this facility is considered to be operating in compliance with the current permit. Antidegradation The Department's antidegradation policy in OAR requires that a review of discharges to surface waters be conducted to ensure that existing water quality is not lowered unless there are no reasonable alternatives available and the lowering of water quality is necessary for economic and social benefit. The NPDES permit for Tryon Creek STP is a permit renewal with no increase in discharge load. Permit renewals with no increase in discharge load are not considered to lower water quality from existing water quality. Thus, the Department finds that the discharge is not subject to an in-depth antidegradation review. (Antidegradation Policy Implementation Internal Management Directive for NPDES Permits and Section 401 Water Quality Certifications, ODEQ March 2001). PERMIT DISCUSSION Face Page The permittee is authorized to construct, install, modify, or operate a wastewater collection, treatment, control and disposal system. Permits discharge of treated effluent to the Willamette River and for reuse within limits set by Schedule A and the following schedules. All other discharges are prohibited. Schedule A - Waste Discharge Limitations BOD and TSS concentration and mass limits Based on the Willamette Basin minimum design criteria in Oregon Administrative Rules (OAR) (3), wastewater treatment resulting in a monthly average effluent concentration of 10 mg/l for BOD 5 and TSS must be provided from May 1 - October 31. From November 1 - April 30, 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 30 mg/l for TSS. The Department is proposing concentration limits that are the same as the previous permit, but less stringent than the basin minimum design criteria during the dry weather months. 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. In accordance with OAR l(4)(c), compliance with the minimum design criteria have been deferred for this facility until such time as the facility needs to expand or otherwise modify or replace the existing facilities. The proposed monthly average winter BOD 5 concentration limit is 30 mg/l with a weekly average limit of 45 mg/l. The proposed monthly average winter TSS concentration limit is 30 mg/l with a weekly average limit of 45 mg/l.

10 Page 10 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 8.3 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 12.3 MGD and the monthly average BOD 5 or TSS concentration limits of 30 mg/l and 30 mg/l, respectively. On any day that the daily flow exceeds 16.6 MGD (twice the design average dry weather flow), the daily mass load limits shall not apply per OAR l(10)(a)(c). All mass load limitations are rounded to two significant figures. By basing the winter mass limits on AWWF, the permittee is required to remove all inflow sources from the collection system. The permit includes a requirement to submit an annual report detailing the sewer collection system maintenance activities used for identifying and removing inflow. BODj and TSS The limits are: (1) May 1-October 31: Parameter BOD 5 TSS Average : Effluent Concei 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 (2) November 1 - April 30: Parameter BOD 5 TSS Average : Effluent Concei ltrations Monthly Weekly 30 mg/l 45 mg/l 30 mg/l 45 mg/l Monthly Average lb/day Weekly Average lb/day Daily Maximum Lbs Calculations: (1) Summer BOD 5 (a) (b) (c) 8.3 MGD x 8.34 #/gal x 20 mg/l monthly avg. = 1400 lbs/day 1400 lbs/day monthly avg. x 1.5 = 2100 lbs/day weekly avg lbs/day monthly avg. x 2.0 = 2800 lbs/day daily max. (2) Summer TSS (a) (b) 8.3 MGD x 8.34 #/gal x 20 mg/l monthly avg. = 1400 lbs/day 1400 lbs/day monthly avg. x 1.5 = 2100 lbs/day weekly avg.

11 Page 11 (c) 1400 lbs/day monthly avg. x 2.0 = 2800 lbs/day daily max. (3) Winter BOD 5 (a) (b) (c) 12.3 MGD x 8.34 #/gal x 30 mg/l monthly avg. = 3100 lbs/day 3100 lbs/day monthly avg. x 1.5 = 4600 lbs/day weekly avg lbs/day monthly avg. x 2.0 = 6100 lbs/day daily max. (4) Winter TSS (a) 12.3 MGD x 8.34 #/gal x 30 mg/l monthly avg. = 3100 lbs/day (b) 3100 lbs/day monthly avg. x 1.5 = 4600 lbs/day weekly avg. (c) 3100 lbs/day monthly avg. x 2.0 = 6100 lbs/day daily max. A review of recent monitoring data (see Attachment #A) indicates the City should generally be able to comply with the permit limits. No changes from the previous permit are proposed. BODj and TSS Percent Removal Efficiency A minimum level of percent removal for BOD 5 and TSS for municipal dischargers is required by the Code of Federal Regulations (CFR) secondary treatment standards (40 CFR, Part 133). An 85 percent removal efficiency limit is included in the proposed permit to comply with federal requirements. An examination of the DMR data indicates the permittee will have little difficulty meeting the limit with the current facilities. Since 2000, the average percent removal at Tryon Creek STP has been 96%) for BOD 5 and 97% for TSS. ph The Willamette Basin Water Quality Standard for ph is found in OAR l-0445(2)(d). The allowed range is 6.5 to 8.5. The proposed permit limits ph to the range 6.0 to 9.0. 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 of the water quality standard.

12 Page 12 Bacteria The proposed permit limits are based on an E. coli standard 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 new 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 of the five re-samples is less than or equal to 126, a violation is not triggered. The resampling must be taken at four hour intervals beginning within 28 hours after the original sample was taken. The bacteria limits for irrigation of level II reclaimed water are a 7-day median of 23 organisms/100 ml, with no two consecutive samples to exceed 240 total coliform per 100 ml. 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 (2)) 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 (1) 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 of the 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 of the mixing zone is free of materials in concentrations that will cause chronic toxicity. 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 ug/l can result in chronic toxicity in fresh waters while 19 ug/l can result in acute chlorine toxicity in fresh waters. Compliance with acute toxicity criteria is required at the edge of the Zone of Immediate Dilution (ZID) and compliance with chronic toxicity criteria is required at the edge of the mixing zone. The existing permit contains the following total chlorine residual limit: Shall not exceed a daily maximum of 1.7 mg/l and a monthly average of 0.7 mg/l.

13 Page 13 The proposed permit will retain the previous permit's limit which was derived by the Department after an evaluation of the dilution available within the mixing zone and ZID using computer model and a dye study for verification. Total chlorine residual and chlorine used must be monitored daily. Mixing Zone and Zone of Immediate Dilution The allowable mixing zone is that portion of the Willamette River extending two hundred (200) feet downstream from the outfall. The Zone of Immediate Dilution (ZID) shall be defined as that portion of the allowable mixing zone that is within twenty (20) feet of the point of discharge. Reclaimed Water The utilization of treated effluent for beneficial purposes is regulated under OAR This facility could produce Level II reclaimed water but has not done so as of yet. Prior to irrigation of the reclaimed water, the discharge must comply with total coliform limits based on protection of human health due to human pathogens. For Level II reclaimed water, the limits include a weekly median of 23 total coliform per 100 mis with no two consecutive samples to exceed 240 total coliform per 100 mis. The application of reclaimed water must be managed in accordance with an 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 will be approved by the Department within the Reclaimed Water Use Plan. The bacterial effluent limitations are achievable through proper operation and maintenance. Emergency Overflows No waste may be discharged from these outfalls unless it is due to a storm event as allowed under OAR (6) and (7). In the summer, raw sewage overflows are prohibited except during a storm event greater than the one-in-ten-year, 24-hour duration storm. In the winter, overflows are prohibited except during a storm event greater than the one-in-five-year, 24-hour duration storm.

14 Page 14 Groundwater A condition has been included that reiterates that Groundwater Quality Protection Rules (OAR ) must not be violated by the operations associated with this facility. 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, in some cases, may have 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 of the 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 must be performed in accordance with one of the methods approved by the Department. Monitoring for total coliform must be performed when irrigating reclaimed water. Total chlorine residual must be monitored daily. Daily monitoring of influent and effluent flow is required in this permit. In addition, calibration of the flow meter is required on a regular basis. In order to characterize the treatment facility's contribution of nutrients to the receiving stream during low flow periods, the proposed permit includes a requirement to monitor the treated effluent for certain nutrients. Weekly monitoring of Total Kjeldahl Nitrogen, nitrate plus nitrite, ammonia and total phosphorus is proposed for the period from May 1 through October 31 each year. Temperature monitoring of the effluent is required. Because this facility has a pretreatment program, the Department required quarterly whole effluent toxicity (WET) or bioassay tests using two species in the permit. Bioassay tests were conducted in accordance with EPA test methods and procedural requirements as defined in Schedule D. Bioassays were conducted quarterly for one year (1999) early in the permit cycle and once in 2003 prior to renewal application submission. A review of the bioassay results indicates that the discharge does not exhibit acute or chronic toxicity at the dilutions that occur at the edge of the ZID and mixing zone, respectively. Because of the size of the discharge, the Department is proposing to continue requiring WET testing.

15 Page 15 The proposed permit includes monitoring of the reclaimed water for flow, ph, and total coliform. The monitoring frequencies are in accordance with Department rules and guidance. An annual report describing the effectiveness of the reclaimed water system is required. The estimated duration and volume of any overflow from the emergency outfalls must be recorded. Discharge monitoring reports (DMRs) must be submitted to the Department monthly by the 15th day of the 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. The conditions are standard language requirements concerning: Annual report on inflow and infiltration removal Annual report on transporting sludge to another facility Annual report on the use of reclaimed water Schedule C - Compliance Conditions The proposed permit includes two compliance conditions with compliance deadlines. The requirements include: 1.) That a Reclaimed Water Use Plan be submitted to the Department for approval at least 90 days prior to releasing any treated effluent for reuse. 2.) That the permittee meet the compliance dates established in this schedule or notify the Department within 14 days following any lapsed compliance date.

16 Page 16 Schedule D - Special Conditions The proposed permit includes seven special conditions. The conditions include: That the permittee must manage their biosolids in accordance with a current approved management plan. The permit would be reopened if more stringent standards for biosolids use or disposal are promulgated during this permit cycle. That the permittee must have the facilities supervised by personnel certified by the Department in the operation of treatment and/or collection systems. That specifies the necessary procedures for conducting whole effluent toxicity testing. That all facilities with average daily design flow greater than 1 MGD and/or with industrial pretreatment programs must include priority pollutant scan results in accordance with the application Form 2A for permit renewal. Schedule D of this permit includes a condition requiring such submittal and specifying the necessary procedures for conducting the priority pollutant scan. That the permittee must comply with the rules concerning the use of reclaimed water and the Reclaimed Water Use Plan must be approved by the Department. Finally, the permittee is required to notify the Department if a malfunction occurs at the facility that might cause a permit limit violation to occur. Schedule F - NPDES General Conditions Schedule F includes: permit standard conditions; requirements related to operation and maintenance of pollution controls; conditions for monitoring and recordkeeping related to this permit; reporting requirements; and permit related definitions.