PUBti NOTICE FACT SHEET And NPDES WASTEWATER DISCHARGE PERMIT EVALUATION

Department of Environmental Quality Western Region - Salem Office 750 Front Street NE, Suite 120, Salem, OR 97301-1039 Telephone: (503) 378-8240

PERMITTEE: City of Yamhill Yamhill, OR 97148 File Number: 99314 SOURCE LOCATION; 450 South Maple SOURCE CONTACT: Jim Dagget Telephone Number: (503)662-4344 PERMIT WRITER: Julie M. Berndt Telephone Number: (541)686-7838

PROPOSED ACTION: Renewal of a National Pollutant Discharge Elimination System (NPDES) wastewater discharge permit SOURCE CATEGORY: Minor Domestic

TREATMENT SYSTEM CLASS: Level I

COLLECTION SYSTEM CLASS: Level I

PERMIT APPLICATION DATE: October 9,2001

PERMIT APPLICATION NUMBER: 987307

BACKGROUND Introduction City of Yamhill operates a wastewater treatment facility located in Yamhill, . Wastewater is treated and discharged to North in accordance with National Pollutant Discharge Elimination System (NPDES) Permit number 101473. The Permit for the facility was issued on April 9,1997 and expired on February 28,2002.

The Department received a renewal application on October 9,2001, 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.

Facility Description The facility is located west of State Highway 47 just south of the City of Yamhill, Oregon (see Attachment #1). The City has operated wastewater treatment facilities since 1964, In 1997, the City completed a major upgrade to the facility and expanded the treatment capability to meet an increase in the City's population. The previous activated sludge plant and summer irrigation pond were demolished. At the time of the upgrade, summer irrigation and winter discharge to Yamhill Creek were discontinued, however the existing outfall was retained for emergency overflows from a new pump station, A new outfall was constructed to the . The current permit City of Yamhill Evaluation Report Page 2 identifies the location as River Mile 14. However, the Department's GIS tool identifies the discharge location as River Mile 12.9. The renewal permit will include a river mile of 12.9. The City currently discharges only during the winter discharge season (November - April).

Because of the new outfall location, the City was required to apply for a new NPDES permit at the time of the upgrade in 1997. Because of the increase in raw sewage influent flow and treatment capacity, the City applied for and received a mass load limit increase in Biochemical Oxygen Demand (BOD) Total Suspended Solids (TSS) loadings to the river.

The method of sewage treatment is a four-cell facultative lagoon. Raw wastewater is conveyed to the four cell facultative lagoon system via a duplex submersible pump station and 1300 foot force main. The lagoon system consists of a series of 4 lagoons with adjustable floating inlet piping for lagoons 2, 3, and 4 to enable the operator to minimize algae transfer. All four lagoons are lined with 60-mil polyethylene plastic (HDPE).

Gas chlorination using city water for solution is used for disinfection. A mechanical flash mixer is used at the point of chlorine injection to assure viral kill. Chlorination follows lagoon number three, using a 48-inch diameter conduit-type contact chamber. The contact chamber outlet is the compliance point for disinfection. Exposure to sunlight in the number four lagoon, which provides approximately 70 days hydraulic detention, provides adequate time for depletion of residual chlorine to meet the effluent limit contained in the permit.

The effluent pump station is the discharge compliance point for the other permit limits except for disinfection. An effluent flow meter and staff gauge is used to monitor total effluent discharge and to calculate water balances.

A 3000 foot effluent force main conveys the effluent to the North Yamhill River via a two port submerged diffuser. A vacuum release valve at the pump station allows the entire line to drain dry during the summer, thus avoiding possible septic discharges and toxicity concerns.

Influent samples collected are flow-proportionedb y the influent meter, Grab samples taken during November through April, are representative of the effluent from lagoon four with respect to pH, temperature, chlorine residual, bacteria, BOD, and TSS.

Outfalls Treated wastewater is discharged during the winter months to the North Yamhill River at river mile 12.9. The two port diffuser outfall was constructed and put into use in 1997 during the plant upgrade. The proposed allowable mixing zone is defined as that portion of the North Yamhill River contained within a radius of eighty (80) feet from the point of discharge. The Zone of Immediate Dilution (ZID) shall be defined as that portion of the allowable mixing zone that is within a radius of eight (8) feet from the point of discharge (see Attachment # 1).

Treatment Plant Capacity (Design and Current Flows/Loads) The proposed permit allows for discharges to the North Yamhill River from November through April each year. For this facility, the average design wet weather flow, or the effluent flow that the mass load limits are based on is 0.25 million gallons/day (MGD). City of Yamhill Evaluation Report Page 3

The Department reviewed Discharge Monitoring Report (DMR) data for the past two years (See Attachment #2). The actual dry weather influent flow to the facility (May 1 - October 31) was 0.062 MGD. The current actual average wet weather flow to the lagoons (November 1 through April 30) was 0.114 MGD. The current actual average effluent flow from the lagoons in winter is 0.346. The peak daily flow over the past two years is 0.67 MGD. See the section on Inflow and Infiltration for a further discussion of winter flows.

Biosolids Management and Utilization Waste sludge accumulates in the treatment lagoon. A Biosolids Management Plan (BMP) must be submitted 6 months prior to removing any biosolids from the lagoon. No beneficial land application will be allowed under this permit until a BMP is submitted by the permittee and is approved by the Department. The Biosolids Management Plan will ensure compliance with the federal biosolids regulations (40 CFR Part 503). It is anticipated that biosolids will be land applied at agronomic rates after approval of the application sites and the biosolids management plan by the Department.

Inflow and Infiltration (M) Based on an evaluation of summer and winter period flows and the peak flow, Inflow and Infiltration (I/I) 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 sub-basins or those in the worst condition.

In addition, the permittee was granted a mass load increase based on average wet weather design flow (AWWDF) during the last permit cycle. As required by rule, the permittee is required in Schedule C of this permit to submit to the Department for review and approval a proposed program and time schedule for identifying and reducing inflow within 180 days of permit issuance. Within 60 days of receiving written Department comments, the permittee shall submit a final approvable program and time schedule.

Pretreatment The permittee does not have a formal pretreatment program, nor is one required for this source.

Pollutants Discharged The current permit allows City of Yamhill to discharge treated effluent from the wastewater treatment plant from November 1 - April 30. The current permit sets limits on the following pollutants: Five- day Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS), and Fecal Coliform (FC) bacteria. The discharge is also replated for chlorine residual, pH and pollutant removal efficiency. The proposed permit will regulate the same pollutants.

Receiving Streams/Impact

Applicable water quality standards for the North Yamhill River are found in OAR 340-41-445. Included in Table 6 as beneficial uses for the Willamette Basin are: • Public domestic water supply, • Private domestic water supply, City of Yamhill Evaluation Report Page 4

• Industrial water supply, • Irrigation, • Livestock watering, • Anadromous fishpassage , • Salmonid fish rearing, • Salmonid fish spawning, • Resident fish and aquatic life, • Wildlife and hunting, • Fishing, • Boating, • Water contact recreation, and • Aesthetic quality • Hydro Power

The Oregon 2002 List of Water Quality Limited Water Bodies (303(d) List), lists the North Yamhill River as Water Quality Limited for the following parameters:

Record Waterbody Sub- River List Listing Parameter Season ID Name Basin Mile Date Status 0to 5962 North YarrM, YAMHILL Temperature Summer 1998 303(d) List River 201 North Yamhill Oto YAMHILL Fecal Coliform Winter/Spring/Fall 1998 303(d) List 6081 River 20.1 North Yamhill Oto YAMHILL Fecal Coliform Summer 1998 303(d) List 6876 River 20.1

7136 Nprth Yamhill YAMH|L|_ 20.1 to Temperature Summer 1998 303(d) List River 32.4 8530 North Yamhill YAMH|L|_ Oto Dissdved October 1-May 2QQ2 3QmLlBt

During the period of discharge, the North Yamhill River is water quality limited for dissolved oxygen and bacteria as follows:

Field Details [Basin Name Willamette Sub Basin Name Yamhill Waterbody Name Yamhill River, North LLID 1231445452259 Waterbody Boundaries Mouth to Turner Creek Parameter Bacteria Criteria Water Contact Recreation (fecal coliform-96 Std) Season Fall-Winter-Spring Listing Status 303(d) List Basis for Consideration DEQ Data; d1 in 305(b) Report (DEQ, 1994); NPS Assessment - segment 368: for Listing severe, data (DEQ, 1988) Supporting Data DEQ Data (2 Sites: 402605, 402606; RM 1.5, 4.5): 30% (6 of 20), 40% (21 of 53) FWS values respectively exceeded fecal coliform standard (400) with maximum values of 2400, 2400 between WY 1986 -1995.

Field Dotdilb Waterbody Name North Yamhill River Sub Basin Name YAMHILL LLID 1231445452259 City of Yamhill Evaluation Report Page 5

River Mile 0 to 20.1 Parameter Dissolved Oxygen Criteria Spawning: 11 mg/L or 95% saturation Season October 1 - May 31 Listing Status 303(d) List Supporting Data LASAR 10929 RM 4.3: 40% (25/63 samples) < 11 mg/L and 95 % saturation. Sample Matrix Description Water Column Beneficial Uses salmonid fish spawning

The North Yamhill River either meets criteria for other parameters or there is not enough information available to rationalize a listing. The Department is not aware of any water quality violations that may be attributable to this source. The Department expects to complete the Yamhill Total Maximum Daily Load (TMDL) by 2007 that will determine the corrective actions necessary to bring this water body back into compliance. The TMDL may assign pollutant Waste Load Allocations (WLA) to this point source discharge. This permit will be renewed in 2008 and the requirements and/or waste load allocations (WLA) of the Yamhill River TMDL will be incorporated into the permit at that time.

Anti-Degradation Review An Antidegradation Review was completed with a recommendation to proceed with this permit. action. A copy of the review sheet is attached (see Attachment #3).

Analysis of Water Quality Limited Parameters - Dissolved Oxygen The receiving stream is water quality limited for Dissolved Oxygen (DO) during the time of discharge. The current DO standard for the North Yamhill River is 11 mg/L or 95% saturation based on salmonid spawning criteria. According to the Oregon Department of Fish and Wildlife (ODFW) biologist and fish distribution maps, the area of the discharge is downstream of the spawning areas designated for Coho and Winter Steelhead. However, because they are listed T&E species, and because the stream DO level may be close to the listed criteria of 11 mg/l, this permit includes monitoring of the effluent for temperature for any future evaluations that must be completed.

During the facilities planning for the new treatment facility and the development of the current permit in 1997, the City and DEQ engineers evaluated the effects of the discharge from the new treatment facility on DO levels in the North Yamhill River. A Streeter-Phelps Model was used to predict the depression of instream DO levels (sag) at various conditions including low flow conditions during the permitted discharge period. All of the model runs demonstrated that the estimated maximum DO sag created by the WWTP discharge is less than 0.1 mg/l. It is important to note that all of the model runs used higher pollutant loading than are in the permit for the mass loading discharge limitations.

The models indicated that the proposed discharge would not have a significant impact on the North Yamhill River. The maximum DO deficit was 92 percent of saturation and would occur 21.6 miles downstream from the discharge point in the . The North Yamhill River joins the much larger South Yamhill River about 13 miles downstream from the proposed facility's outfall location which is not listed for DO.

Schedule B of the permit requires effleunt monitoring of dissolved oxygen. This data can be used to evaluate impacts on the stream. The construction of the new treatment plant by the City has eliminated violations of the permit and water quality standards. The treatment efficiency has City of Yamhill Evaluation Report Page 6 increased, and the pollutant loading to the river has decreased and has met the intent of the antidegradation policy by maintaining and protecting the existing water quality in the North Yamhill River. The Department therefore concludes that the discharge will not significantly contribute to the DO water quality standard violation. However, if the Yamhill TMDL establishes Waste Load Allocations (WLA) more stringent than current permit limits, the WLA will be incorporated into the permit to be issued in 2008.

Analysis of Water Quality Limited Parameters - Bacteria The North Yamhill River is water quality limited for fecal coliform bacteria year round. Discharges of disinfected wastewater that are in compliance with the permit should not significantly contribute to the instream bacterial standards violation. However, if the Yamhill TMDL establishes Waste Load Allocations (WLA) more stringent than current permit limits, the WLA will be incorporated into the permit to be issued in 2008.

Threatened and Endangered (T&E) Species There are Coho Salmon and Winter Steelhead present at certain times when discharge is permitted. Winter Steelhead are listed in the Oregon Department of Fish and Wildlife Fish Distribution inventory for rearing and migration. Coho Salmon are listed as present for migration only. These species are listed as threatened or endangered (T&E) under the Federal Endangered Species Act.

Temperature Elevated instream temperatures are detrimental to cold water fish. OAR 340-04 l-0445(2)(b) sets the standard for temperature in the Basin. This standard restricts surface water temperature increases resulting from anthropogenic activities under certain environmental conditions

At the point of discharge, the receiving stream is not water quality limited for temperature during the discharge period. However, there is narrative temperature criterion contained in the Department's temperature standard applicable when T&E species are present and when the DO in the river may be close to the existing criteria. The narrative criterion listed in OAR 340-04 l-445(2)(b) states in part that...."no measurable increase in temperature (0.25 degrees F) is allowed outside of the assigned mixing zone above the ambient stream temperature when T&E species are present...."

Department guidance states that the following mass balance equation for temperature should be used for conducting an analysis to determine if the discharge creates a measurable temperature increase at the edge of the mixing zone;

Tmz = [(TE + DTs)]/(D+l) Where: D is the calculated or measured dilution at the edge of the mixing zone; Ts is the applicable temperature criteria; TE is the effluent temperature in °F; and Tinz is the temperature of the stream at the edge of the regulatory mixing zone in °F

This equation assumes that temperature is a conservative parameter. This assumption should be acceptable for most analysis since only near-field analysis is being conducted. In this area, mixing with the stream accounts for most of the reduction in effluent temperature. City of Yamhill Evaluation Report Page 7

Temperature data collected by the City of Yamhill shows a maximum November effluent temperature of 51 °F. Some data exists for temperature for the North Yamhill River and 45 °F will be used as a conservative estimate for this evaluation based on this data. Dilution data was gathered during analysis for planning completed during the recent plant upgrade. Through the use of the Environmental Protection Agency's expert computer model CORMLX 3, KPFF consulting engineers on behalf of the permittee, predicted a 33:1 dilution factor at the edge of the Mixing Zone and a 15:1 dilution factor at the Zone of Immediate dilution (ZID) during critical low flow conditions. Using these value, the evaluation is as follows:

Tim=[(TE + DTs)]/(D+ 1) = [51+33*45]/(33 + 1] = 45.176 Tmz= [1536] /34 = 45.176 Tmz = 45.176

The Department considers 0.25°F measurable. Therefore, using conservative temperature estimates, this discharge would not cause a measurable increase above the criteria at the edge of the mixing zone.

Because of the presence of T&E species and the stream being close to the DO standard, the permit will contain monitoring for effluent and stream temperature and flow, Elevated temperatures decrease the capacity of water to hold dissolved oxygen. In addition, in order to prevent further warming, the permit contains a condition in Schedule D that prohibits any increase in thermal load without prior approval from the Department.

Ammonia Toxicity During the facilities planning for the new facility, the City and DEQ engineers evaluated ammonia toxicity at the edge of the mixing zone and the zone of immediate dilution (ZID). The evaluation indicated that there is no expectation that ammonia toxicity would be a problem. However, it was recommended that data be collected and evaluated when the new plant was operational (see Attachment #4). The permit contains a requirement to monitor for ammonia monthly for one full year at which time monitoring can be discontinued unless otherwise notified in writing by the Department. The Department will use the data to evaluate whether there are violations or a reasonable potential of violations of the ammonia standard.

Groundwater A Priority Screening Criteria for Groundwater Review worksheet was completed during the permit evaluation and development (See Attachment #4).

All four lagoon cells are lined with 60-mil polyethylene plastic (HDPE). The current permit contains a compliance condition that required the permittee to conduct a leak test on each lagoon and submit to the Department the results of the leak test. The results of the leak test demonstrated that any leakage is within the acceptable limits set by the Department.

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. City of Yamhill Evaluation Report PageS Stormwater Stormwater is not addressed in this permit. General NPDES permits for stormwater are not required for facilities with a design flow of less than 1 MGD,

Compliance History This facility was last inspected April 23,2003 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. Based on this review, the following violations have been documented at this facility during the term of the current permit.

D.irc of Violation Type of Fnforcemcnt Action Dcsci iption of Violation March 10,1999 Notice of Permit Violation (NPV) Permit Compliance Violations November 16,1998 Notice of Noncompliance (NON) Permit Compliance Violations

The City was required in Schedule C to begin taking composite samples and had not done so by the compliance date listed in the permit. The City received an NPV following the NON because it was a Class 1 violation. It required the City to respond to the DEQ with a plan to correct the violation within 5 days. Following the NON cited above, the City had immediately purchased and began using a composite sampler. The above violation is considered to be minor and has been corrected. Therefore, the Department considers this facility to be in substantial compliance with the terms of the current permit.

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 North Yamhill within limits set by Schedule A and the following schedules. All other discharges are prohibited. The face page identifies the level of certification needed by the supervisory staff designated by the Permittee for the treatment and collection systems,

Schedule A - Waste Discharge limitations The waste discharge limitations are based on secondary treatment standards and the Willamette Basin water quality standards and minimum design criteria: BOD and TSS concentration and mass limits

Based on the Willamette Basin minimum design criteria, wastewater treatment resulting in a monthly average effluent concentration of 10 mg/L for BOD5 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. Federal secondary treatment standards (40 CFR 133.103(c)) allow states to give lagoons special consideration in setting concentration limit for TSS. Therefore, secondary treatment for this facility is defined as monthly average concentration limit of 30 mg/L for BOD5 and 50 mg/L for TSS.

The Department is proposing concentration limits at least as stringent as the basin minimum design criteria. The proposed monthly average BOD5 concentration limit is 30 mg/L with a weekly average limit of 45 mg/L. The proposed monthly average TSS concentration limit is 45 mg/L with a weekly City of Yamhill Evaluation Report Page 9 average limit of 68 mg/L based on the evaluations conducted during the last permit renewal following the completion of the new facility.

Monthly average mass load limits are based on the maximum month discharge flow of 0.25 MGD. This is based on wet weather flows. The weekly average and daily maximum are based on what the treatment plant can achieve at projected weekly and daily effluent flows. The projected weekly daily effluent flows were derived from the peak daily and peak weekly (projected for the 20 year design life) sewage influent flow rates for a 2 year storm event.

The Department evaluated the mass load limits listed above during the last permit cycle and the Department believes them to be acceptable. The Department made the findings and considered the issues listed in OAR 340-41-026(3), The same limits are proposed except that some mass load limits are rounded to two significant digits.

BODj and TSS

The limits are:

(1) May 1-October 31:

No discharge to state waters is permitted.

(2) November 1 - April 30: 1 Average Efllucnl Monthly Weekly Daily Concentrations Average Maximum Parameter 1 Monthly : Weekly Average lb/clay Lbs lb/day BOD5 30 mg/L 45 mg/L 62 120 140 TSS 45 mg/L 68 mg/L 94 180 210

Calculations:

BODs (a) 0.25 MGD x 8.34 lb/gal x 30 mg/l monthly avg. = 62 lbs/day (b) 0.31 MGD x 8.34 lb/gal x 45 mg/l weekly avg. = 116 lbs/day (c) 0.37 MGD x 8.34 lb/gal x 45 mg/l weekly avg. = 139 lbs/day daily maximum

TSS (a) 0.25 MGD x 8.34 lb/gal x 45 mg/l monthly avg. = 94 lbs/day (b) 0.31 MGD x 8.34 lb/gal x 68 mg/l weekly avg. = 176 lbs/day (c) 0.37 MGD x 8.34 lb/gal x 68 mg/l weekly avg. = 210 lbs/day daily maximum

Monthly average mass load limits are based on the maximum month discharge flow of 0.25 MGD. The weekly average and daily maximum are based on what the treatment plant can achieve at projected weekly and daily effluent flows. The projected weekly daily effluent flows were derived from the peak daily and peak weekly 20 year design sewage influent flow rates for a 2 year storm event.

The Department must make certain findings and consider certain issues in accordance OAR 340-41- 026(3) before allowing a mass load increase to a river. During the last permit renewal, the mass load City of Yamhill Evaluation Report Page 10 increase was granted based on the findings that were made. The Department proposes to keep the same limits in this renewal.

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,

A review of recent monitoring data (see Attachment #2) indicates the City should generally be able to comply with the permit limits.

BOD and TSS Percent Removal Efficiency A minimum level of percent removal for BODS and TSS for municipal dischargers is required by the Code of Federal Regulations (CFR) secondary treatment standards (40 CFR, Part 133). In accordance with the federally approved standards for Oregon under 40 CFR 133.105, certain types of treatment facilities (including trickling filters and facultative lagoons) are eligible for consideration of lower percent removal limits. The proposed permit requires a minimum monthly average BODS and TSS removal efficiency of 85 and 65 percent respectively.

An examination of the DMR data (see Attachment #2) indicates the permittee will have little difficulty meeting the limit with the current facilities. The Department proposes to keep the same limitations.

EH The Willamette Basin Water Quality Standard for pH is found in OAR 340-04 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 oh 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.

Bacteria The proposed permit limits are based on an E. coli standard approved in January 1996. 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 of the five re-samples is less than or equal to 126, a violation is not triggered. The rule states that the re- samples should be taken at four hour intervals beginning as soon as practicable (preferably within 28 hours) after the original sample was taken. The rule also allows for changing the resampling timeframe if it would pose an undue hardship on the treatment facility. After discussions with the permittee, the Department is proposing that the five re-samples be taken beginning no later than 48 hours after the original sample was taken. This is the same as in the current permit.

Total 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. According to OAR 340-041, Table 20, chlorine concentrations of 11 pg/L can result in chronic toxicity in fresh waters while 19 pg/L can result in acute chlorine toxicity in fresh waters. City of Yamhill Evaluation Report Page 11

Compliance with acute standards is required at the edge of the Zone of Immediate Dilution (ZID) and compliance with chronic standards is required at the edge of the mixing zone. The existing permit contains the following total chlorine residual limit:

Shall not exceed 0.29 daily maximum,

The previous permit's limit was derived through the use of the Environmental Protection Agency's expert computer model CORMIX 3. KPFF consulting engineers on behalf of the permittee, predicted a 33:1 dilution factor at the edge of the Mixing Zone and a 15:1 dilution factor at the Zone of Immediate dilution (ZID) during critical low flow conditions. The Department calculated proposed final NPDES permit limits for total residual chlorine based on actual dilution available within the mixing zone.

The Department's revised spreadsheet (see Attachment #5) calculated a slightly more stringent limit (0.28 mg/L) and determined that a monthly average limit (0.11 mg/L) should be included. Therefore, the Department proposes new total chlorine residual limits of:

Shall not exceed a monthly average concentration of 0.11 mg/L and a daily maximum concentration of 0.28 mg/L

The permittee uses storage in a fourth lagoon to dechlorinate the effluent prior to discharge to reduce potential toxic effects on the receiving stream and meet permit limits, In addition, the permittee uses a multiport diffuser to enhance dilution within the mixing zone to reduce potential toxic effects on the receiving stream and meet permit limits. The permittee has consistently met the chlorine residual limit with the facilities available during this permit cycle.

Temperature The evaluation contained in this report shows that there is no measurable increase above ambient stream temperatures during times when T&E species are present. The permit will contain monitoring of effluent temperature as is in the current permit,

Groundwater A groundwater prioritization worksheet was completed for this permit evaluation. The permittee conducted leak tests on the new lagoons after construction and results of the tests showed that any leakage is within the acceptable limits of the Department. Therefore, no groundwater monitor or characterization is required in this permit. Schedule A prohibits adverse impacts to groundwater.

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 City of Yamhill Evaluation Report Page 12 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.

Monthly ammonia monitoring must be conducted for one year. Data will be evaluated for compliance with the ammonia standard.

Total chlorine residual and chlorine used must be monitored daily and is a grab sample.

Monitoring of dissolved oxygen concentration of the effluent is required weekly.

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.

Discharge monitoring reports 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

Schedule C - Compliance Conditions The proposed permit includes 2 compliance conditions with compliance deadlines. The requirements include:

1) The permittee was granted a mass load increase based on average wet weather flow during the last permit cycle, As required by rule, the permittee is required to submit to the Department for review and approval a proposed program and time schedule for identifying and reducing inflow within 180 days of permit issuance. Within 60 days of receiving written Department comments, the permittee shall submit a final approvable program and time schedule.

2) The permittee will be required to submit a Biosolids Management Plan (BMP) to the Department for approval at least six months prior to the removal of biosolids from the lagoon.

The final condition requires the permittee to meet the compliance dates established in this schedule or notify the Department within 14 days following any lapsed compliance date. City of Yamhill Evaluation Report Page 13

Schedule D - Special Conditions

The proposed permit includes five (5) special conditions. The requirements include: 1) The permittee is prohibited from increasing their thermal load without prior approval from the Department. 2) The permittee must have the facilities supervised by personnel certified by the Department in the operation of treatment and/or collection systems.

3) The permittee must manage all biosolids or septage in accordance with the current biosolids or septage management plan approved by the department The permit may be modified to incorporate any applicable standard for biosolids use or disposal promulgated under section 405(d) of the Clean Water Act.

4) The proposed permit includes a condition in Schedule D that prohibits any adverse impact on groundwater quality. No groundwater characterization is required in this permit unless impacts are discovered.

5) The permittee shall notify the appropriate DEQ Western Region Office in accordance with the response times noted in the General Conditions of this permit, of any malfunction so that corrective action can be coordinated between the permittee and the Department.

Schedule F, NPDES General Conditions All NPDES permits issued in the State of Oregon contain certain conditions that remain the same regardless of the type of discharge and the activity causing the discharge. These conditions are called General Conditions. These conditions can be changed or modified only on a statewide basis. The latest edition of the NPDES General Conditions is December 1,1995 and this edition is included as Schedule F of the draft permit. Section A contains standard conditions which include compliance with the permit, assessment of penalties, mitigation of noncompliance, permit renewal application, enforcement actions, toxic discharges, property rights and referenced rules and statutes. Section B contains requirements for operation and maintenance of the pollution control facilities. This section includes conditions for proper operation and maintenance, duty to halt or reduce activity in order to maintain compliance, bypass of treatment facilities, upset conditions, treatment of single operational events, overflows from wastewater conveyance systems and associated pump stations, public notification of effluent violation or overflow, and disposal of removed substances. ATTACHMENT #2 Facility ID#: 99314 Common I Citv of Yamhill Year: 2000-01 EFFLUENT VALUES/LIMITS

Influent Effluent pH BOD BOD lbs. BOD % TSS TSS (lbs) TSS % & coli C12 Flow Flow 6.0-9.0 (mSfl) 62/120/140 Removal fmg/n 94/180/210 Removal (#/100ml) Residual (MGD) (MGD> 30/45 45/68 126/406 Month .011/.28 8 January max: 0.592 0.552 7.2 28 mtw. 5 19 -Sk.-Tl.Js,-.. <2 0.10 min: 0.096 0.221 6.9 5 16 5 17 <2 0.04 ave: 0,212 0.392 7 6 22 96 5 18 l)7 <2 0.07 r February max: 0.316 0.532 8 14 44 3SS . .=>\K 7 22 •at£. <2 0.10 min; 0.082 0.226 7.1 10 18 5 17 <2 0.04 ave: 0.123 0.366 7.5 11 28 93 6 20 <>7 <2 0.07 0.554 7.6 11 : March max: 0.273 52 mmm 8 37 '-&&*• <2 0.11 min: 0.07 0.238 7.1 3 8 -|psSi| 5 12 <2 0.03 ave: 0.122 0.394 7.4 7 30 97 7 25 9fi <2 0.07 April max: 0.074 3.557 7.9 5 18 #H#fe 4 15 '•SSS'BSw^^" <2 0.11 min: 0 0.301 7.0 5 18 4 15 <2 0,05 ave: 0.064 0.607 7.5 5 18 98 4 15 98 <2 0.06 May max: 0.102 min: 0.052 ave: 0.069 June max: 0.133 min: 0.007 ave: 0.071 July max: 0.069 min: 0.047 ave: 0.059 August max: 0.093 min: 0.039 ave: 0.059 September max; 0.041 min: 0.061 ave: 0.06 October max: 0.112 min: 0.04 ave: 0.066 November max; 0.107 0.496 9.5 16 56 21 66 <2 0.07 min: 0.054 0.286 8.7 12 48 7 24 <2 0.03 ave: 0.07 0.4 9.1 14 52 97 14 45 95 <2 0.05 December max: 0.188 0.392 8.6 6 16 6 20 i^SslSSS <2 0.12 min: 0.057 0.112 7.3 6 5 6 6 <2 0.08 ave: 0,087 0.335 8 6 14 98| 6 17 99 <2 0.09 Average 7.75 10 27 97 15 16 97 <2 0.07 ADWF 0.000 AWWF 0.403 ATTACHMENT #3

ANTIDEGRADATION REVIEW SHEET FOR A PROPOSED INDIVIDUAL NPDES DISCHARGE

City of Yamhill Proposed NPDES Renewal

1. What is the name of Surface Water that receives the discharge? North Yamhill River near the City of Yamhill

Briefly describe the proposed activity: Renewal of NPDES permit for the City of Yamhill to treat and discharge municipal wastewater to the North Yamhill River at Mile 14.

2. Is this surface water an Outstanding Resource Water or upstream from an Outstanding Resource Water? No. Go to Step 3.

3. Is this surface water a High Quality Water? No. Go to Step 4.

4. Is this surface water a Water Quality Limited Water? Yes. Go to Step 13.

13. Will the proposed activity result in a Lowering of Water Quality in the Water Quality Limited Water? No. Proceed with Permit Application. Applicant should provide basis for conclusion. This conclusion is explained and supported by data in the Permit Evaluation Report and attachments accompanying the proposed NPDES Permit Renewal. There is no request for a mass load increase. The effluent limitations are the same as in the existing permit. Dissolved and temperature oxygen will be monitored to assess any potential lowering of water quality,

Go to Step 24.

24. On the basis of the Antidegradation Review, the following is recommended: X Proceed with Application to Interagency Coordination and Public Comment Phase. Deny Application; return to applicant and provide public notice.

Section; Western Region - WQ Review Prepared By: Julie M. Berndt Phone: (541) 686-7838 x 234 Date Prepared: July 16,2003 ATTACHMENT #4

GROUNDWATER PRIORITIZATION WORKSHEET City of Yamhill

WATER QUALITY PROGRAM NPDES AND WPCF PERMITTED FACILITIES PRIORITIZATION SCREENING CRITERIA FOR GROUNDWATER REVIEW

Permit Type (circle one): NPDES

Type of Facility: Facultative lagoon

Application Number: 987307 File Number: 99314

WorksheefCompletcd. by: Approved by:

Date:

Prioritization-Worksheet .and Preliminary Groundwater Assessment Steps Waived by Permit Applicant. Applicant will proceed directly to Hydrogeologic Characterization.

Approved by: Date: •

Page 1 WATER QUALITY PROGRAM NPDES AND WPCF PERMITTED FACILITIES PRIORITIZATION SCREENING CRITERIA FOR GROUNDWATER REVIEW

DOMESTIC WASTEWATER FACILITIES

EXISTING Wastewater and Sludge/Biosolids Impoundment Systems (confirm all statements given as true or false):

1, System (any or all of its individual impoundment components) does not leak excessively, (An "excessively" leaking lagoon system or cell may True be defined as one that has been designed for subsurface infiltration, rarely or never needs to discharge, dries up in the summer, or contains rooted vegetation,) 2. System is not located in a Groundwater Management Area where an identified contaminant of concern (ie. nitrates) may be associated with True domestic wastewater or sludge. 3. System is not located within 500 ft, of an existing public or private drinking water supply well, is not located within a designated Wellhead True Protection Area, and all land within 500 ft. of the system is zoned such that no drinking water wells are likely to be installed in the future. 4. There are no exceptional situations under which the impoundment system may require further groundwater review to determine the True likelihood of an adverse impact

DOMESTIC WASTEWATER FACILITIES (CONTINUED) NEW and EXISTING Wastewater and Sludge/Biosolids Land Application (confirm all statements given as true or false):

1. Application is in compliance with the "reuse" rules (or municipal sewage sludge application rules) and application rates are at or less than True agronomic rates. (Note: Nominal leaching fractions may be considered to be in compliance with the "reuse" rules in some areas of the state such as parts of eastern Oregon where climate conditions indicate the need.) 2. There are no exceptional situations under which the impoundment system may require further groundwater review to determine the True likelihood of an adverse impact.

If all answers for a given facility type are true, then no further information is needed. Non-numerical groundwater limits should be included in the permit.

If ME answers for a given facility type were false, then more information is needed. The permit applicant may proceed with a Preliminary Groundwater Assessment. If there is reason to believe the facility poses a high risk to groundwater quality, the applicant may be encouraged to skip the Preliminary Groundwater Assessment step and proceed directly with the Hydrogeologic Characterization.

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