-AAA 

DEQ 

State of Oregon 

Department of 

Environmental 

Quality 

National Pollutant Discharge Elimination System 

PERMIT EVALUATION AND FACT SHEET 

Oregon Department of Environmental Quality 

Northwest Region 

2020 SW 4th Avenue Suite 400 

Portland OR 97201 

(503) 229-5263 

Permittee: 

Existing Permit 

Information: 

Source Contact: 

Source Location: 

LLID: 

Receiving Stream: 

Proposed Action: 

Source Category 

Permit Writer: 

CityofWilsonville 

29799 Town Center Loop East 

Wilsonville, OR 97070 

File Number: 97952 

Permit Number: 101888 

Expiration Date: 12/31/2009 

EPA Reference Number: OR-002276-4 

Delora Kerber, 503-570-1542 

Public Works Director 

9275 SWTauchman Road 

Wilsonville, Oregon 

1227618456580-38.6 D 

Willamette River 

Permit Renewal 

Application Number: 971449 

Date Received: June 30,2009 amended June 28,2010 

NPDES Major - Domestic 

Lyle Christensen 

Natural Resource Specialist 
Table of Contents 

1.0 Introduction 3 

2.0 Facility description 3 

2.1 General 3 

2.2 Wastewater Treatment ...4 

2.3 Changes in Operation 5 

2.4 Groundwater Issues 5 

2.5 Storm Water 6 

2.6 Outfalls 6 

2.7 Industrial Pretreatment- majors only 6 

2.8 Biosolids 6 

2.9 Inflow and Infiltration (I/I) 7 

3.0 Permit History , 8 

3.1 Compliance history 8 

4.0 Receiving Water 8 

4.1 Receiving Stream Water Quality 9 

4.2 Mixing Zone Analysis 9 

4.3 Environmental Mapping ...• 11 

5.0 Permit limitations 11 

5.1 Existing Permit Limits 11 

5.2 Technology-Based Effluent Limits 12 

5.3 Water Quality-Based Effluent Limits 13 

5.5 Whole Effluent Toxicity 16 

5.6 Antidegradation 17 

6.0 Permit Draft Discussion 17 

6.1 Face Page 17 

6.2 Schedule A- Waste Discharge Limitations 17 

6.3 Schedule B- Minimum Monitoring and Reporting Requirements 17 

6.4 Schedule C- Compliance Schedules and Conditions 17 

6.5 Schedule D - Special Conditions 17 

6.6 Schedule E - Pretreatment 18 

6.7 Schedule F- NPDES General Conditions 18 

6.8 Permit Processing/Public Comment/Appeal Process 19 

Appendix A-Monitoring summary 20 

Appendix B-Anti-degradation worksheet 21 

Appendix C- Reasonable Potential Analysis Worksheets 23 
1.0 INTRODUCTION 

The existing National Pollutant Discharge Elimination System (NPDES) Permit expired on December 31, 2009. 

The Department received renewal application number 971449 from City of Wilsonville on June 30, 2009 and 

amendments to the application were received on June 28, 2010. As this renewal application was submitted to the 

Department in a timely manner prior to the expiration date of the permit, the permit shall not be deemed to expire 

until final action has been taken on the renewal application to issue the new permit as per OAR 340-045-0040. 

This permit evaluation report describes the basis and methodology used in developing the permit. The permit is 

divided into several sections: 

Schedule A - Waste discharge limitations 

Schedule B - Minimum monitoring and report requirements 

Schedule D - Special conditions 

Schedule E - Pretreatment 

Schedule F - General conditions 

The proposed permit contains the following substantive changes from the 2005 permit: 

In Schedule A, the limitations associated with excess thermal load were added to reflect the findings from the 

Willamette Basin Temperature TMDL that indicate that this facility has a defined waste load allocation. Another 

change in this schedule is that because emergency overflow points are no longer listed on the cover page of the 

permit, the limitations for emergency overflows have been removed. Overflows are now covered in Schedule F of 

the permit exclusively. 

In Schedule B, some additional sampling is now listed to reflect data requirements for evaluating this permit at its 

next renewal. These are not new requirements, but are listed for clarity within the sampling table. Though effluent 

temperature monitoring is still required, in addition, the calculation of heat load is necessary to determine 

compliance with the assigned allocation. The monitoring of emergency overflows has also been deleted as these 

events must now be reported in accordance with Schedule F of the permit. 

Schedule D includes some updated requirements regarding whole effluent toxicity (WET) testing. 

Schedule E has been updated to reflect current pretreatment program requirements. 

Schedule F contains substantial revisions to the NPDES General Conditions that were completed in 2009. In 

particular it is important to note substantial broadening of the reporting requirements in regard to spills and 

unplanned discharges from within the collection system. 

The Federal Water Pollution Control Act of 1972 and subsequent amendments require a NPDES permit for the 

discharge of wastewater to surface waters. Furthermore, Oregon Revised Statutes (ORS 468B.050) also require a 

discharger be granted a permit for the discharge of wastewater to surface waters. This proposed permit action by 

the Department complies with both federal and state requirements. 

2.0 FACILITY DESCRIPTION 

2.1 General 

The Wilsonville Wastewater Treatment Plant (WTP) is located at 9275 SW Tauchman Road within the City of 

Wilsonville in Clackamas County along the Willamette River (see photo next page). The treatment facility was 

constructed originally at this site in the 1970s. Major plant and process upgrades occurred in 1981 and 1998. The 
1981 improvements were the installation of rotating biological contactors which were then replaced with a more 

conventional activated sludge process in 1998. Minor improvements were made to the headworks in 1993 and 

2007. Odor control features were added originally in 1993 and were expanded in 2004. The permit application 

indicates that additional planned upgrades will be starting in 2011 with completion anticipated in about 2014. The 

facility treats primarily domestic wastewater and discharges the treated wastewater directly to the Willamette River 

at about river mile 38.6. In the permit application, City of Wilsonville reports a population of just over 17000 

residents. An evaluation of population equivalent loading to the treatment plant over the past three years indicates a 

population equivalent loading that is greater than resident population reported. * 

Population Equivalents Based on Influent BOD 

Load 

35000 

30000 

25000 

20000 

15000 

10000 

5000 

0 

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*Population equivalents = [influent flow (mgd) X influent BOD (mg/1) X 8.34] divided by 0.25 lbs/person/day 

2.2 Wastewater Treatment 

The treatment facility relies on an activated sludge process to treat wastewater to meet pollutant discharge standards 

for discharge to the Willamette River just upstream of the Boone Bridge lnterstate-5 crossing. Currently the plant 

4 
relies on a plug flow configuration utilizing anoxic selectors to achieve secondary treatment. During dry weather 

months traveling bridge sand filters are used to achieve better than secondary limits required. An odor control 

tower and a biofilter have been used in attempts to mitigate plant odors. Anticipated growth within the community 

and increasing loading to the plant have necessitated the initiation of plant expansion which is anticipated to occur 

by 2014. 

4^_* » 

2.3 Changes in Operation 

Since the permit's last renewal in 2005, there have been no significant changes to treatment at this facility. In 2007, 

headworks screening improvements were completed. Presently City of Wilsonville is going through a designbuild-operate process to initiate a number of plant site improvements in the next few years. The facility 

improvements are intended to keep the facility compliant with all permit limitations. A change noted in the renewal 

application occurred with biosolids processing where they have started using a centrifuge to dewater solids 

allowing them to be transported at lower cost to eastern Oregon during wet winter months. 

2.4 Groundwater Issues 

No groundwater concerns have been identified in association with this facility. All treatment occurs in water-tight 

basins and any storage of digested biosolids occurs in water tight storage basins totaling 412,000 gallons. 
2.5 Storm Water 

Plant site storm water is allowed to percolate into the ground within the plant site or flows off via overland flow. 

Building sumps and drains within the plant are routed through the treatment system via the influent pump station. 

Because there are no designed storm water discharge points for this plant site, a storm water discharge permit is not 

required. 

2.6 Outfalls 

The current permit identifies ten separate outfalls. The treatment plant discharge point (Outfall 001) was 

constructed as a single port diffuser. The existing permit includes an identified water reuse outfall and eight 

emergency outfalls associated with pump stations within the collection system. The Department has determined 

that it will no longer list identified sewer system overflow (SSO) points as the monitoring and reporting of SSOs is 

now explicitly covered within Schedule F of the proposed permit. 

2.7 Industrial Pretreatment 

The current permit for this facility requires City of Wilsonville to manage a pretreatment program. The permit 

application identifies a number of significant industrial users that are connected to the Wilsonville sewage system 

necessitating an industrial pretreatment program. Pretreatment program related requirements were originally 

incorporated into the permit with program approval on June 25, 1996. The most recent local limits evaluation was 

approved by the Department in 2004. A revised local limits evaluation dated June 30,2009, was included with the 

permit renewal application packet. Pretreatment annual reports have been submiitted each year for this facility. 

2.8 Biosolids 

The renewal application packet for this facility included a copy of a biosolids management plan dated June 30, 

2009. Waste activated sludge is thickened and then digested in two aerobic digesters with a combined capacity of 

512,000 gallons. The digested sludge is then transferred to aerated storage basins with a combined capacity of 

412,000 gallons. The biosolids taken from storage can be either loaded directly to tanker trucks for field 

application nearby or dewatered using a centrifuge for transport to distant land application sites. 

Annual reports provide details of biosolids applications. In 2009 City of Wilsonville indicated that they sent all 

321 dry tons of biosolids produced to their land application sites. The 2009 annual report identified 16 sites by 

name that received biosolids application. Primarily they are grass hay/pasture sites, though some of the biosolids 

(157 dry tons) were applied on wheat and camaiina. Pathogen reduction and vector attraction reduction to meet 

Class B biosolids requirements are generally met through the volatile solids reduction afforded by the aerobic 

digester process. An annual average of the monitoring results for metals content in the final product to be land 

applied are noted below. All metals concentrations appear to be well below EPA pollutant concentration limits. 

Parameter 

Arsenic 

Cadmium 

Chromium 

Copper 

Lead 

Mercury 

Molybdenum 

Nickel 

Selenium 

Zinc 

Concentration (me/kef) 

1.9 

1.8 

17.7 

300 

16.1 

0.82 

13.2 

30.1 

5.6 

645 

EPA Pollutant Concentration Limits fme/ke) 

41 

39 

— 

1500 

300 

17 

— 

420 

100 

2800 
2.9 Inflow and Infiltration (I/I) 

Wastewater treatment systems are required to have an ongoing program in place that is used to control and limit the 

volume of I/I entering the treatment facility. Inflow is generally more easily removed as it is often found to be 

surface waters flowing into the collection system from roof and street drainage, while infiltration is often more 

wide spread and related to leaky and/or degraded sewer lines that require replacement or rehabilitation. City of 

Wilsonville's application indicate that they average just under 500,000 gallons per day of inflow/infiltraion to the 

daily plant flows. Flow monitoring records show the seasonal variation in flow for this facility. 

City of Wilsonville has provided annual I/I reports that summarize details regarding ongoing maintenance activities 

within the collection system. The most recent report for 2009 was submitted in March 2010. The report indicates 

that the City has approximately 380,000 lineal feet of sanitary sewer line in their system. Of this about 11,000 

lineal feet are identified as priority lines for annual cleaning and on the the remainder of the collection system it has 

been targeted so that 20 % be cleaned each year. In 2009 they indicated that all the priority lines had been cleaned 

but only about 50% (about 37000 lin feet) of the additional target was achieved. The report also indicates that each 

of the eight city lift stations are cleaned each year. 
3.0 PERMIT HISTORY 

The wastewater discharge from City of Wilsonville was first permitted in the early 1970's for a new 0.5 mgd design 

flow treatment plant at this location. The first National Pollutant Discharge Elimination System (NPDES) permit 

was issued in 1974. The permit was renewed in 1978 and then modified in 1982 when the facility was expanded to 

a 2.25 mgd design flow facility. Additional renewals occurred in 1983, 1988,1993,2000 and 2005. 

3.1 Compliance history 

The compliance history for this facility since its last permit renewal was reviewed in the file record. Four warning 

letters were issued by the Department since the 2005 renewal for permit violations related to reporting and 

monitoring in accordance with the permit and effluent limit violations. The first event was addressed in a Warning 

Letter (WL-WQ-NWR-05-0110) dated October 12,2005, related to exceeding the effluent limits for total 

suspended solids in August 2005. This was a Class III violation of the permit which is considered to be minor in 

nature and no further follow-up was warranted. The next Warning Letter (WL-NWR-WQ-08-0029) was dated 

April 7,2008, and addressed another minor Class III violation of effluent limits for suspended solids in February 

2008. On November 30, 2009, a warning letter (WL-WQ-NWR-09-0122) was issued to City of Wilsonville for 

failure to report the minimum number of samples for pH during the week of September 27 through October 3. The 

permit requires a minimum of three samples each week and yet only two samples were reported during this week. 

Though the failure to report required sampling is considered a serious violation (Class I) by the Department, this 

event was considered an oversight and no further action was necessary at this time. Had additional reporting 

violations occurred the Department would have included this event in any follow-up action. On March 30, 2010, 

City of Wilsonville self reported noncompliance via email and provided additional information with their March 

2010 discharge monitoring report. A Warning Letter with Opportunity to Correct (WL-WQ-NWR-2010-0062) 

dated April 19, 2010, was issued as a result of this violation. A determination was made based on explanations 

provided by the City that the violations occurred due to a plant "upset" precipitated by equipment failure that could 

not have been anticipated. No further action was taken in response to this set of violations. 

Compliance assurance site visits were conducted by the Department on October 25,2005, August 15, 2006, August 

21, 2007, and November 20,2008. No compliance issues were noted during these site visits. 

4.0 RECEIVING WATER 

The Wilsonville STP discharges to the Willamette River. The water quality standards for all water bodies (Oregon 

Administrative Rules Chapter 340, Division 41) and specifically the Willamette Basin (OAR 340-41-0340) were 

developed to protect the beneficial uses for the basin. The designated beneficial uses are as follows: 

• public and private domestic water supply, 

© industrial water supply, 

• irrigation, 

® livestock watering, 

» anadromous fish passage, 

• salmonid spawning and rearing, 

• resident fish and aquatic life, 

« wildlife and hunting, 

® fishing, 

» boating, 

• water contact recreation, 

® aesthetic quality, and 

® hydro power 
4.1 Receiving Stream Water Quality 

The Willamette River Basin drains an 11,500 square mile area of Oregon that includes the largest metropolitan 

portions of Oregon. Water quality standards violations in this reach of the Willamette River were reviewed for this 

facilitiy's discharge. Total Maximum Daily Loads (TMDLs) for temperature, mercury and bacteria were approved 

by EPA in September 2006. The reach of the river that City of Wilsonville discharges into is also noted in the 303d 

(impaired water quality) listings in the most recent integrated assessment of water quality for the following 

additional parameters: Aldrin, DDT, DDE, Dieldrin, PCB, iron and biological criteria. 

Data gathering efforts for temperature was used as part of the TMDL development process. The TMDL process 

established a waste load allocation for temperature which is proposed to be added to the permit. Further discussion 

of Temperature may be found below in Section 4.2 (Mixing Zone Analysis) and Section 5.3 (Water Quality-Based 

Effluent Limitations). 

Through the TMDL process it was estimated that all the domestic facilities discharging wastewater to the 

Willamette River contributed less than 3% of the total mercury load observed. The TMDL required that further 

evaluation be completed to determine if specific wasteload allocations for mercury are appropriate for point sources 

and what those should be. Mercury monitoring will also be continued under the next permit and that information 

will be used to do the reasonable potential analysis for that toxic. 

The TMDL provided wasteload allocations for bacteria that set the permitted effluent limits at the water quality 

standard. Bacteria limitations in the proposed permit continue to require that the facility meet the same end of pipe 

limitations. 

Domestic wastewater treatment plants are not considered to be sources of these legacy toxics like Aldrin, DDT, 

DDE, Dieldrin and PCB. 

Iron is listed as exceeding the drinking water standard because iron can be aesthetically unappealing in drinking 

water. Iron at low levels imparts a taste to the water. For these reasons, drinking water should not contain >300 

ug/L of iron. No effluent data was available to evaluate iron. Iron is not expected to be contributed by this source 

at levels above background. 

Though the listing for biological criteria remains in place, the reason for the listing, skeletal deformities in fish had 

been evaluated in a separate study. This source has not been evaluated for its contribution to skeletal deformities in 

squawfish. A 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, Corvaliis, Oregon, indicates that parasites are major 

contributors to high prevalence of skeletal deformities in fish from Newberg Pool of the Willamette River. 

4.2 Mixing Zone Analysis 

Federal regulations (40 CFR 131.13) allow for the use of mixing zones, also known as "allocated impact zones". 

These are small areas around a discharge where water quality standards may be suspended. Application of mixing 

zones must ensure acute toxicity to drifting organisms is prevented and the integrity of the waterbody as a whole is 

not impaired. EPA does not have specific regulations pertaining to mixing zones. Each state may adopt its own 

mixing zone regulations that are subject to review and approval by EPA. In States that lack approved mixing zone 

regulations, ambient water quality standards must be met at the end of the pipe. OAR 340-041-0053(1) provides 

that the Department may suspend all or part of the water quality standards in a designated portion of the receiving 

water to serve as a zone of dilution for wastes and receiving waters to mix thoroughly. 

The Department has developed mixing zone regulations and policy based in part on the acute and chronic aquatic 

life criteria. Based on EPA guidance and the Department's mixing zone regulations, two mixing zones may be 

developed for each discharge that reflect acute and chronic effects: 1) The acute mixing zone, also known as the 
"zone of initial dilution" (ZID), and 2) the chronic mixing zone, usually referred to as "the mixing zone". Acute 

criteria are suspended within the ZID but it is designed to prevent lethality to organisms passing through the ZID. 

Chronic criteria are suspended within the mixing zone and it is designed to protect the integrity of the entire water 

body as a whole. The allowable size of the mixing zone should be based upon the relative size of the discharge to 

the receiving stream, the beneficial uses of the receiving stream, location of other discharges nearby, location of 

drinking water intakes, and other considerations. More specific guidance is available from EPA regarding criteria 

used in appropriately sizing a ZID. Primarily the ZID must be designed to prevent lethality to drifting organisms. 

The City of Wilsonville's present permit designates the current mixing zone as "that portion of the Willamette 

River from the point of discharge to 150 feet downstream of the outfall. The zone of immediate dilution (ZID) 

shall be defined as that portion of the allowable mixing zone that is within fifteen (15) feet of the point of 

discharge." The outfall is a single 24 inch port diffuser that terminates in the river about 40 feet from the north 

river bank. The discharge plume spreads downstream and was evaluated for dilution at both the mixing zone and 

ZID boundaries. The June 2002 "Mixing Zone Study Report for the City of Wilsonville's WWTP" determined that 

the discharge had minimum dilutions of 3:1 at the ZID and 23:1 at the mixing zone boundary. 

The Department's mixing zone rules provide that water quality standards include temperature thermal plume 

limitations in accordance with OAR 340-04 l-0053(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 the Wilsonville STP are discussed below: 

« OAR 340-041-0053(d)(A): Impairment of an active salmonid spawning area where spawning redds are 

located or likely to be located. 

WilsonviUe STP discharge: There is no identified salmonid spawning near the outfall location in this 

segment of the Willamette River. This segment of the Willamette River does serve as a migration corridor 

for salmonids but the stream has been channelized so that the area is often referred to as the "Newberg 

Pool". The mixing zone study report indicates that salmonids do not spawn in the mainstem river areas 

like this. 

• OAR 340-041-0053(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. 

Wilsonville STP discharge: Based on temperature data submitted with the mixing zone study, the 

maximum effluent temperature at outfall 001 is around 25 °C. Thus, the discharge is not expected to 

cause an acute impairment or instantaneous lethality. 

• OAR 340-04 l-0053(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. 

Wilsonville STP discharge: The reported temperature of this effluent has seldom exceeded 25°C and the 

discharge is not going cause thermal shock as the plume at the edge of the mixing zone encompasses 

less than 5% of the stream cross section. At this location the stream is 700 feet wide with an average 

depth of about 25 feet. 5% of this cross section area would be about 800 square feet. The temperature 

plume above 25°C would need to be greater than 800 square feet. The vertical and horizontal plume 

from the outfall would be estimated at about 300 square feet when it reaches the mixing zone boundary 

which would be less than 2% of the cross section. 

• OAR 340-041-0053(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. 

Wilsonville STP discharge: Based on information provided in the outfall mixing zone field monitoring 

and modeling study, the Willamette River at the location of the outfall plume in the mixing zone 

10 
represents about a 300 square feet cross section out of a total river cross section of over 17500 square 

feet. As such migration blockage is prevented since this plume represents less than 2% of the cross 

section. 

Thus, the analysis indicates that the discharge from the Wilsonville STP meets the temperature thermal plume 

limitations in OAR340-041-0053(d). 

4.3 Environmental Mapping 

Environmental mapping was not completed as part of the mixing zone study completed in 2002. However at this 

locale, the Willamette River outfall is in a location of the river that has been described as "generally slow moving" 

and is popular for recreational use by both fisherman and other watercraft activities. As mentioned before this 

segment of the river is a migratory passage for fish. There are many private boat docks upstream and downstream 

from the discharge location. The outfall is about 40 feet from shore in about 15 feet of water at low water depth 

and should not conflict with these uses. Most of the river bank in this area has large lot sizes and is substantially 

already developed, so access to this outfall is limited. A marina and boat ramp exists on the far shore just upstream 

and across from the outfall area. Public parks are located just upstream (Boones Ferry Park) and slightly more than 

Vi mile downstream (Memorial Park) from the outfall location. Both parks have river frontage for public access 

and Memorial Park has a boat dock. The nearest drinking water intake is located about V_ mile upstream from the 

City of Wilsonville STP. 

5.0 PERMIT LIMITATIONS 

Two categories of effluent limitations exist for NPDES permits: 1) Technology based effluent limits, and 2) Water 

quality based effluent limits. Technology based effluent limits are developed by applying the secondary treatment 

standards as found in 40 CFR Part 133. Technology based effluent limits were established to require a minimum 

level of treatment for municipal sources using available technology. Water quality based effluent limits are 

designed to be protective of the beneficial uses of the receiving water and are independent of the available 

treatment technology. In addition, when performing a permit renewal, there are existing permit limits. These may 

be technology-based limits, water quality-based limits, or limits based on best professional judgment. When 

renewing a permit, the most stringent of technology based or water quality based limits apply. 

5.1 Existing Permit Limits 

Treated Effluent Outfall 001 

(1) May 1-October 31: 

Parameter 

CBOD5 

TSS 

(2) November 1 

Average Effluent 

Concentrations 

Monthly Weekly 

lOmg/L 15mg/L 

lOmg/L 15mg/L 

- April 30: 

Parameter 

BOD5 

TSS 

Average Effluent 

Concentrations 

Monthly Weekly 

30mg/L 45 mg/L 

30 mg/L 45 mg/L 

Monthly* 

Average 

lb/day 

190 

190 

Monthly* 

Average 

Ib/day 

560 

560 

Weekly* 

Average 

lb/day 

280 

280 

Weekly* 

Average 

lb/day 

840 

840 

Daily* 

Maximum 

lbs 

380 

380 

Daily* 

Maximum 

lbs 

1100 

1100 

11 
* Though the existing average dry weather design flow(design year 2015) to the facility equals 2.7 MGD, the mass 

load limits are based on the previous permit. 

(3) 

Other parameters (year-round) 

E. coli Bacteria 

pH 

BOD5 and TSS Removal Efficiency 

Limitations 

Shall not exceed 126 organisms per 100 mL monthly geometric 

mean. No single sample shall exceed 406 organisms per 100 

mL. 

Shall be within the range of 6.0 - 9.0 

Shall not be less than 85% monthly average for BOD5 and 85% 

monthly for TSS. 

5.2 Technology-Based Effluent Limits 

Secondary treatment requires at minimum the following standards be met for biochemical oxygen demand (BOD5), 

carbonaceous biochemical oxygen demand (CBOD5), total suspended solids (TSS) and pH: 

• BOD5 shall not exceed a 30-day average of 30 mg/I and a 7-day average of 45 mg/1 and the 30-day average 

percent removal shall not be less than 85 percent. 

• CBOD5 may be used as an alternative for BOD5 provided it is does not exceed a 30-day average of 25 mg/1 

and a 7-day average of 40 mg/1 and the 30-day average per-cent removal shall not be less than 85 percent. 

• TSS shall not exceed a 30-day average of 30 mg/1 and a 7-day average of 45 mg/1 and the 30-day average 

percent removal shall not be less than 85 percent. 

• pH shall be maintained within the limits of 6.0 to 9.0. 

The City of Wilsonville STP limitations for BOD5, CBOD5, TSS and pH are at least as stringent as the federal 

requirements in that the following must be met: 

• From May through October (typically dry weather w/lower stream flow) CBOD5 shall not exceed a 

monthly average of 10 mg/1 and a weekly average of 15 mg/1 and the monthly average percent removal 

shall not be less than 85 percent. From November through June (typically wet weather w/higher stream 

flow) BOD5 shall equal the federal requirements. 

• From May through October TSS shall not exceed a monthly average of 10 mg/I and a weekly average of 15 

mg_ and the monthly average percent removal shall not be less than 85 percent. From November through 

June TSS is equal to the federal requirement. 

• pH shall be maintained within the limits of 6.0 to 9.0. 

In addition DEQ requires that mass load limitations for BOD5,CBOD5 and TSS must be met when discharging to 

surface waters. These loads are required to be reported in pounds per day and include a monthly average, weekly 

average and daily mass limitation. For this facility these limit were established based on a dry weather design flow 

of 2.25 mgd that was established in 1982. Weekly limits are 1.5 times the monthly mass and the daily limit is twice 

the monthly mass. Limits are calculated as follows: 

12 
High stream flow BOD5 -

Average Monthly Limit = (2.25 mgd) (30 mg/1) (8.34 lbs/gal) -560 lbs/day 

Average Weekly Limit = (1.5)(560 lbs) - 840 lbs/day 

Daily Limit= (2.0)(560 lbs)= 1100 lbs 

High stream flow TSSAverage Monthly Limit = (2.25 mgd) (30 mg/I) (8.34 lbs/gal) =560 lbs/day 

Average Weekly Limit = (1.5)560 lbs = 840 lbs/day 

Daily Limit= (2.0)560 lbs= 1100 lbs 

Low stream flow CBOD5 and TSSAverage Monthly Limit - (2.25 mgd) (10 mg/1) (8.34 lbs/gal) =190 lbs/day 

Average Weekly Limit - (1.5)190 lbs (Average Monthly Limit) = 280 lbs/day 

Daily Limit- (2.0)190 lbs= 380 lbs 

5.3 Water Quality-Based Effluent Limits 

Reasonable Potential Analysis 

The Department performs an analysis to determine if there is a reasonable potential to cause or contribute to 

violations of instream water quality criteria. The Department has adopted EPA's recommended methodology for 

performing a reasonable potential analysis (RPA). This methodology was developed primarily for acute and 

chronic criteria but can be adapted to other criteria based on different frequencies and durations. This RPA takes 

into account effluent variability, available dilution (if applicable), and receiving stream water quality. The RPA for 

specific parameters are discussed below. 

In accordance with DEQ's "Internal Management Directive for Reasonable Potential Analysis for Toxic Pollutants" 

(September 2005), domestic sources like City of Wilsonville with a diy weather design flow greater than 1.0 mgd 

must be characterized for chlorine and ammonia as well as other potentially toxic parameters identified in their 

renewal application. The RPA spreadsheet using data from the most recent permit cycle indicates that there is no 

reasonable potential for toxic pollutants to cause or contribute to an excursion above State water quality standards. 

No evaluation for was made for chlorine because this facility disinfects with UV light and the permit explicitly 

prohibits the use of chlorine or chlorine compounds where they may affect the effluent. 

The RPA spreadsheets are attached (Appendix C). 

pH 

The pH is a measure of how acidic or basic a solution is. At a pH of 7.0 s.u. the solution is considered neutral. The 

purpose of an in-stream water quality pH standard is generally the protection of aquatic life since most aquatic 

organisms can only tolerate a fairly narrow range around 7.0 s.u. 

The Willamette Basin Water Quality Standard for pH is found in OAR 340-041 -0345(1 )(a). The allowed range is 6.5 

to 8.5 s.u. The proposed permit limits pH to the range 6.0 to 9.0 s.u. This limit is based on Federal secondary treatment 

standards for wastewater treatment facilities (40 CFR Part 133.102), and is applied to the majority of domestic NPDES 

permittees in the state. Within the permittee's mixing zone, the water quality standard for pH does not have to be met. 

The Department evaluated pH using a spreadsheet that derives the pH at the mixing zone boundary. 

13 
Calculation of pH of a mixture of two flows. 

Based on the procedure in EPA's DESCON program (EPA, 1988. Technical 

Guidance on Supplementary Stream Design Conditions for Steady State 

Modeling. USEPA Office of Water, Washington D.C.) 

INPUT ; 

1. DILUTION FACTOR AT MZ BOUNDARY - (Qe+Qr)/Qe 

2. UPSTREAM/BACKGROUND CHARACTERISTICS 

Temperature (deg C); 

PH: 

Alkalinity (mgCaC03/L): 

3. EFFLUENT CHARACTERISTICS 

Temperature (deq C): 

pH: 

Alkalinity (mqCaC03/L); 

4. APPLICABLE PH CRITERIA 

OUTPUT 

1. IONIZATION CONSTANTS 

Upstream/Background pKa: 

Effluent pKa: 

2. IONIZATION FRACTIONS 

Upstream/Background Ionization Fraction: 

Effluent Ionization Fraction; 

3. TOTAL INORGANIC CARBON 

Upstream/Background Total Inorqanic Carbon (mq CaC03/L): 

Effluent Total Inorqanic Carbon (mq CaC03/L): 

4. CONDITIONS AT MIXING ZONE BOUNDARY 

Temperature (deg C): 

Alkalinity (mq CaC03/L); 

Total Inorqanic Carbon (mq CaC03/L): 

pKa: 

pH at Mixing Zone Boundary: 

Is there Reasonable Potential? 

RPA for pH 

Lower 

PH 

Criteria 

23 

22.2 

7.4 

24.4 

24.0 

6.0 

190.0 

6.5 

6.37 

6.36 

0.92 

0.31 

26.66 

621.19 

22.28 

31.60 

52.51 

6.37 

6.5 

No 

Upper 

PH 

Criteria 

23 

22.2 

7.6 

24.4 

24.0 

9.0 

190.0 

8.5 

6.37 

6.36 

0.94 

1.00 

25.83 

190.43 

22.28 

31.60 

32.98 

6.37 

7.7 

No 

Mixing with ambient water within the mixing zone will ensure that the pH at the edge of the mixing zone meets the 

ambient criteria. Therefore, the Department considers the proposed permit limits to be protective of the water quality 

standard. 

14 
Bacteria 

The proposed permit limits are based on the E. colt standard contained in OAR 340-041-0009(5). 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. If a single sample exceeds 406 E. coli per 100 mL, then the permittee may take five consecutive resamples. 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 proposed limits are taken directly from the Oregon bacteria rule which is found in OAR 340-041-0009. This 

rule establishes numeric in-stream water quality standards (OAR 340-041-0009(1)) and establishes effluent 

limitations and the methodology for establishing a violation (OAR 340-041-0009(5)). 

Regarding the general condition 6 found in Section B of Schedule F in this permit which prohibits overflows from 

wastewater conveyance systems, the Environmental Quality Commission (EQC) recognizes that it is impossible to 

design and construct a conveyance system that will prevent overflows under all storm conditions. The applicant is 

not seeking permit coverage for overflows and the permit does not authorize such discharges. The State of Oregon 

has determined that all wastewater conveyance systems should be designed to transport storm events up to a 

specific size to the treatment facility. Therefore, in exercising its enforcement discretion regarding Sanitary Sewer 

Overflows, the Department will consider the following: 

(1) Whether the permittee has conveyance and treatment facilities adequate to prevent overflows except during 

a storm event greater than the one-in-five-year, 24-hour duration storm from November 1 through May 21 

and except during a storm event greater than the one-in-ten-year, 24-hour duration storm from May 22 

through October 31. In addition, DEQ will also consider using enforcement discretion for overflows that 

occur during a storm event less than the one-in-five-year, 24-hour duration storm from November 1 

through May 21 if the permittee had separate sanitary and storm sewers on January 10, 1996, had 

experienced sanitary sewer overflows due to inflow and infiltration problems, and has submitted an 

acceptable plan to the Department to address these sanitary sewer overflows by January 1, 2010; 

(2) Whether the permittee has provided the highest and best practicable treatment and/or control of wastes, 

activities, and flows and has properly operated the conveyance and treatment facilities; 

(3) Whether the permittee has minimized the potential environmental and public health impacts from the 

overflow; and 

(4) Whether the permittee has properly maintained the capacity of the conveyance system. 

DEQ will review the permittee's determination of the one-in-five-year, 24-hour duration winter storm and the onein-ten year, 24-hour duration summer storm as described above in the permit holder's facilities plan. In the event 

that a permit holder reports an overflow event associated with a storm event and DEQ does not have information 

from the permit holder sufficient to determine whether or not the storm event exceeds storm events as specified in 

OAR 340-041-0009(6) & (7), DEQ will perform the determination using the information contained in Figure 26 of 

the 1973 NOAA Atlas 2 entitled "Precipitation-Frequency Atlas of the Western United States, Volume X -

Oregon". This figure is entitled "Isopluvials of 5-yr 24-hr precipitation in tenths of an inch". The Atlas can be 

obtained on line at http://hdsc.nws.noaa.gov/iKisc/pfds/other/or_pfdsJitml. however the file is veiy large. A 

scanned version of Figure 26 is available at: http://www.wrcc.dri.edu/pcpnfreq/or5y24.gif. DEQ will compare the 

information in this figure with rainfall data available from the National Weather Service, or other source as 

necessary. 

Temperature 

Willamette Basin TMDL. The City of Wilsonville discharge is included under the "Individual waste load allocations 

for low streamflow conditions" for thermal contribution, per the Willamette Basin temperature TMDL (Page 4-69) as 

follows: 

15 
The Willamette Basin TMDL identified 30 separate individual waste load allocations (WLA) and City of 

Wilsonville STP received an explicit summer 7Q10 WLA of 39 million Kcal per day. The TMDL was structured 

such that potentially higher heat loads might be assigned provided the city can document ambient stream flow and 

temperature in the Willamette River to accommodate the higher excess thermal loads. 

Effluent temperature monitoring will be required in the permit and would be used for determination of compliance 

with the waste load allocation. Monitoring will be required only during June through September which includes the 

period considered critical for this salmon migration corridor within the Willamette River. 

5.5 Whole Effluent Toxicity 

In addition to analyzing the effluent for individual pollutants, the effluent is also tested to determine the aggregate 

effect the effluent has on aquatic organisms. These tests are known as whole effluent toxicity (WET) tests. 

Effluent samples are collected and aquatic organisms are subjected to various effluent concentrations in controlled 

laboratory experiments. EPA has developed WET test protocols using both freshwater and marine/estuarine test 

species. EPA recommends running tests using an invertebrate (crustacean), vertebrate (fish) and a plant (alga). 

Organisms used in WET tests are indicators or surrogates for the aquatic community to be protected, and a measure 

of the real biological impact from exposure to the toxic pollutants. To protect water quality, EPA recommends that 

WET tests be used in NPDES permits together with requirements based on chemical-specific water quality criteria. 

WET tests are used to determine the percentage of effluent that produces an adverse effect on a group of test 

organisms. The measured effect may be fertilization, growth, reproduction, or survival. EPA's methodology 

includes both an acute test and a chronic test. An acute WET test is considered to show toxicity if adverse affects 

occur at effluent concentrations less than that which is found at the edge of the zone of immediate dilution (ZID), 

A chronic WET test is considered to show toxicity if adverse affects occur at effluent concentration less than that 

which is known to occur at the edge of the mixing zone. 

Five WET tests were included as part of this renewal application. These tests represented annual sampling over the 

5 years prior to the expiration of the permit. No acute toxicity was noted in any of these tests for 100% effluent. In 

addition, no chronic toxicity was observed at worst case effluent concentrations expected to be found at the edge of 

the mixing zone (4.3%) which occurs with 23:1 dilution. The DEQ recommends that a point estimate (IC25) be 

used to assess the likelihood of chronic toxicity. The table that follows demonstrates the effluent concentrations 

that caused in a 25% reduction in a biological measurement (i.e. growth, reproduction) and the corresponding 

dilution in which chronic toxicity would be anticipated from the effluent. For example: In 2008, a significant 

reduction was estimated in reproduction for the crustacean water flea at an effluent concentration of 7.1%. The 

corresponding dilution (14:1) can be compared to the demonstrated dilution (23:1) which occurs at the mixing zone 

boundary. The mixing zone study demonstrated dilution is greater than the dilutions at which chronic toxicity was 

estimated and thus these adverse effects noted do not occur at concentrations less than the 4.3% worst case effluent 

concentration expected to be found at the mixing zone boundary. The WET results indicate the effluent is not 

causing either an adverse acute or chronic aggregate effect on the aquatic community. 

Sampling 

month/vear 

June/July 2009 

November 2008 

Sept/Oct 2007 

December 2006 

September 2005 

Ceriodaphnia dubia 

(Water Flea) 

Concentration 

>100% 

7.1% 

>100% 

32.4% 

>100% 

Dilution 

1:1 

14:1 

1:1 

3:1 

1:1 

Pimephales pomelas 

(Fathead Minnow) 

Concentration 

>100% 

>100% 

>100% 

>100% 

>100% 

Dilution 

1:1 

1:1 

1:1 

1:1 

1:1 

Raphidocelius subcapitata 

(Algae) 

Concentration 

59.9% 

24.0% 

>I00% 

80.4% 

>100% 

Dilution 

1.7:1 

4.2:1 

1:1 

1.2:1 

1:1 

16 
5.6 Antidegradation 

An Antidegradation Review was performed for this discharge. The permit is being renewed without any increase in 

discharge loadings. Permit renewals with the same discharge loadings as the previous permit are not considered to 

lower water quality from the existing condition. Based on the antidegradation review, the Department determined 

the proposed discharge complies with the Antidegradation Policy for Surface Waters found in OAR 340-041-0026 

(see Appendix B). 

6.0 PERMIT DRAFT DISCUSSION 

6.1 Face Page 

The face page provides information about the permittee, description of the wastewater, outfall locations, receiving 

stream information, permit approval authority, and a description of permitted activities. The permittee is authorized 

to construct, install, modify, or operate a wastewater collection, treatment, control and disposal system. The permit 

allows discharge to the Willamette River within limits set by Schedule A and the following schedules. All other 

discharges are prohibited. 

6.2 Schedule A, Waste Discharge Limitations 

The proposed permit contains the exact same limitations as the previous permit with the exception of excess 

thermal load. The current permit will reflect the TMDL conclusion that the DEQ should assign an excess thermal 

waste load allocation for this source. 

6.3 Schedule B - Minimum Monitoring and Reporting Requirements 

Due to the types of treatment processes utilized to treat domestic wastewater, the DEQ developed recommended 

monitoring frequencies for parameters based on the size and type of treatment facility. Wastewater discharge 

permit monitoring frequencies of similar type facilities were reviewed (e.g., lagoons) for specific parameters in 

relation to the facility design flow. Similar monitoring frequencies for parameters allow for statewide consistency 

based on facility design flow and type. The monitoring and reporting requirements in this pennit are in accordance 

with the DEQ's monitoring matrix for an activated sludge facility with a design flow greater than 1 MGD but less 

than 5 MGD. Appendix A provides a monthly summary of data reported on the City of Wilsonville's discharge 

monitoring reports for the past three years 

Additional sampling requirements have been added to this permit to meet the effluent testing for the EPA Form 2A 

renewal application dated January 1999 and the monitoring requirements prescribed in the DEQ Internal 

Management Directive for the Reasonable Potential Analysis for Toxic Pollutants dated September 2005. 

6.4 Schedule C, Compliance Schedules and Conditions 

This permit includes no compliance schedules or conditions. 

6.5 Schedule D - Special Conditions 

This permit includes eight special conditions. 

The first two conditions are related to the bio-solids management practices that are to be followed and include a 

reopener condition should the standard bio-solids practices be changed so that they become more stringent than the 

proposed permit under the Clean Water Act. 

17 
The third condition details the requirements related to whole effluent toxicity (WET) testing or bioassay testing to 

look for the potential for toxic effects from this wastewater discharge. The condition specifies the organisms and 

protocols for both acute and chronic testing, how those tests should be evaluated, the quality assurance and 

reporting specifics and a reopener for the permit should it become appropriate based on the WET results. 

The next condition defines the operator certification requirements that must be adhered to in accordance with 

Oregon Administrative Rules, Chapter 340, Division 49. 

Two conditions are the same conditions that were found in Schedule C of the previous permit in regard to offering 

the City the opportunity to demonstrate a wet weather design flow for the facility. Potentially that engineering 

exercise could result in higher mass limits during wet weather, but the city would also have to provide to DEQ a 

proposed program and schedule for inflow identification and reduction to qualify for the wet weather mass 

allowance. 

The permit requires that notification be made to the Department for malfunctions at the treatment facility such that 

corrective actions can be coordinated if appropriate. 

The final special condition requires that the permittee have in place a contingency plan that lays out prevention 

measures and a response plan for spills or unplanned discharges. This condition is included to reinforce the new 

requirement within the permit's General Conditions (Schedule F, Section B.8) for an "Emergency Response and 

Public Notification Plan". Though not totally a new requirement, the Department believes that this plan is critical 

for the protection of public health as it relates to sewage overflows and unpermitted releases from within the 

collection system. 

6.6 Schedule E, Pretreatment Program Activities 

City of Wilsonville has had an approved industrial pretreatment program since 1996. The program requirements 

are laid out in this schedule of the permit. The Program was recognized in 1999 and again in 2005 with EPA's 

National Pretreatment Excellence Award. 

6.7 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. 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. Section C contains requirements for 

monitoring and reporting. This section includes conditions for representative sampling, flow measurement, 

monitoring procedures, penalties of tampering, reporting of monitoring results, additional monitoring by the 

permittee, averaging of measurements, retention of records, contents of records, and inspection and entry. Section 

D contains reporting requirements and includes conditions for reporting planned changes, anticipated 

noncompliance, permit transfers, progress on compliance schedules, noncompliance which may endanger public 

health or the environment, other noncompliances, and other information. Section D also contains signatory 

requirements and the consequences of falsifying reports. Section E contains the definitions used throughout the 

permit. 

These conditions can be changed or modified only on a statewide basis. The latest edition of the NPDES General 

Conditions is from 2009 and this edition is included as Schedule F of the draft permit. The summary of the 2009 

changes is as follows: 

18 
• There are additional citations to the federal Clean Water Act and CFR, including references to 

standards for sewage sludge use or disposal. 

• There is additional language regarding federal penalties. 

• Bypass language has been made consistent with the Code of Federal Regulations. 

• Overflow language has been modified. Formerly the language stated that overflows in response to 

the five or ten year event would not violate the permit. Now it states that overflows are prohibited. 

DEQ will continue to exercise enforcement discretion with respect to overflows consistent with the 

provisions of the Bacteria Rule (OAR 340-041-0009). 

• Reporting requirements regarding overflows have been made more explicit. 

• Requirements regarding emergency response and public notification plans have been made more 

explicit. 

• Language pertaining to duty to provide information has been made more explicit. 

• Confidentiality of information is addressed 

6.8 Permit Processing/Public Comment/Appeal Process 

The beginning and end date of the public comment period to receive written comments regarding this permit, and 

the contact name and telephone number are included in the public notice. The permittee is the only party having 

standing to file a permit appeal. If the permittee is dissatisfied with the conditions of the permit when issued, they 

may request a hearing before the EQC or its designated hearing officer, within 20 days of the final permit being 

mailed. The request for hearing must be sent to the Director of the Department. Any hearing held shall be 

conducted pursuant to regulations of the Department. 

19 
Appendix A- Wilsonville STP DMR Summary 

Month 

Aug-10 

Jul-10 

Jun-10 

May-10 

Apr-10 

Mar-10 

Feb-10 

Jan-10 

Dec-09 

Nov-09 

Oct-09 

Sep-09 

Aug-09 

Jul-09 

Jun-09 

May-09 

Apr-09 

Mar-09 

Feb-09 

Jan-09 

Dec-08 

Nov-08 

Oct-08 

Sep-08 

Aug-08 

Jul-08 

Jun-08 

May-08 

Apr-08 

Mar-08 

Feb-08 

Jan-08 

Dec-07 

Nov-07 

Oct-07 

Sep-07 

Aug-07 

Jul-07 

Jun-07 

May-07 

Apr-07 

Mar-07 

Feb-07 

Jan-07 

Influent 

BOD 

mg/L 

438 

552 

296 

470 

379 

389 

282 

346 

318 

335 

322 

339 

299 

370 

336 

310 

346 

292 

315 

279 

335 

313 

350 

363 

329 

407 

335 

353 

311 

323 

274 

234 

242 

324 

323 

346 

375 

333 

344 

341 

322 

266 

267 

273 

TSS 

mg/L 

416 

612 

284 

351 

261 

296 

224 

234 

257 

313 

309 

314 

333 

318 

305 

338 

331 

297 

296 

287 

321 

314 

318 

314 

335 

410 

313 

317 

282 

335 

277 

216 

228 

284 

295 

294 

301 

282 

288 

271 

267 

225 

234 

233 

PH 

max 

7.9 

9.1 

7.7 

9.5 

8 

7.7 

7.7 

7.7 

8 

7.8 

8 

7.8 

8 

7.6 

8.2 

7.7 

7.9 

8.2 

8.6 

7.9 

8.2 

7.9 

7.9 

8.2 

7.9 

8.6 

8.1 

8.5 

8.5 

8.2 

8.1 

7.7 

8.5 

8.4 

8.1 

8 

8 

8 

8.6 

8.2 

8.5 

8.8 

8 

8 

min 

7.3 

7.1 

7.3 

7.3 

7.1 

7 

7.2 

7.2 

7 

7.4 

7.2 

7.3 

7.2 

7.1 

7.3 

7.3 

7.2 

7.2 

7.3 

7.2 

7.4 

7.2 

6.6 

6.8 

7.2 

7.2 

7.3 

7.3 

7.3 

7.4 

7.2 

7.2 

7.1 

7.3 

7.2 

7.3 

7.2 

7.2 

7.4 

7.3 

7.4 

7.3 

7.3 

7.2 

Flow 

mgd 

1.592 

1.602 

1.978 

1.825 

2.052 

1.965 

1.974 

2.388 

1.963 

1.8 

1.603 

1.587 

1.582 

1.551 

1.621 

1.774 

1.707 

1.88 

1.725 

2.30,9 

1.853 

1.704 

1.631 

1.568 

1.575 

1.568 

1.658 

1.718 

1.894 

2.052 

2.262 

2.519 

2.434 

1.936 

1.862 

1.705 

1,725 

1.697 

1.74 

1.756 

1.858 

2.092 

2.117 

2.356 

Effluent 

BOD 

mg/L 

5 

7 

7 

7 

12 

36 

11 

11 

15 

10 

3 

4 

4 

5 

6 

7 

12 

9 

9 

8 

11 

10 

4 

4 

4 

5 

5 

9 

9 

10 

14 

9 

9 

9 

3 

4 

5 

5 

4 

3 

8 

9 

9 

10 

% 

rem 

99 

99 

98 

99 

97 

91 

96 

97 

95 

97 

99 

99 

99 

99 

98 

98 

96 

97 

97 

97 

97 

97 

99 

99 

99 

99 

98 

98 

97 

97 

95 

96 

96 

97 

99 

99 

99 

98 

99 

99 

97 

97 

96 

96 

CBOD 

mg/L 

4 

6 

5 

6 

2 

3 

3 

4 

5 

6 

8 

5 

5 

3 

3 

3 

4 

4 

5 

5 

2 

3 

4 

4 

4 

2 

6 

5 

TSS 

mg/L 

5 

6 

4 

5 

12 

31 

11 

9 

11 

9 

2 

4 

4 

4 

3 

4 

9 

11 

9 

9 

12 

8 

4 

2 

2 

3 

3 

4 

10 

12 

22 

12 

13 

8 

3 

3 

4 

3 

4 

2 

8 

^ 

12 

10 

% 

rem 

99 

99 

99 

98 

95 

89 

95 

96 

96 

97 

99 

99 

99 

99 

99 

99 

97 

96 

97 

97 

96 

97 

99 

99 

99 

99 

99 

99 

96 

96 

91 

94 

94 

97 

99 

99 

99 

99 

99 

99 

97 

96 

95 

96 

E.coli 

max 

69 

36 

14 

37 

76 

2419 

345 

70 

47 

308 

91 

121 

326 

144 

326 

144 

435 

69 

88 

35 

136 

276 

50 

136 

345 

165 

248 

186 

461 

579 

308 

187 

65 

60 

1203 

1733 

1733 

517 

17 

2419 

144 

10 

36 

219 

geo 

7 

9 

3 

5 

33 

47 

26 

18 

19 

14 

13 

24 

48 

21 

36 

1 

44 

26 

25 

11 

51 

53 

10 

30 

79 

53 

36 

17 

11 

13 

45 

35 

40 

21 

9 

13 

60 

39 

3 

8 

12 

5 

9 

61 

PH 

max 

7 

7 

6.9 

6.7 

6.9 

7.1 

6.9 

6.8 

6.9 

6.9 

6.8 

6.8 

7.6 

6.9 

6.9 

7.7 

7.1 

6.8 

7 

6.9 

6.9 

7.6 

6.8 

6.9 

6.8 

6.9 

6.8 

6,8 

6.9 

6.9 

6.9 

6.8 

6.8 

6.9 

7 

6.9 

7 

6.8 

6.9 

7 

7.3 

7.3 

7.2 

7 

Ammonia 

min 

6.7 

6.7 

6.5 

6.4 

6.4 

6.4 

6.3 

6.3 

6.2 

6.6 

6.4 

6.5 

6.6 

6.6 

6.5 

7.3 

6.7 

6.6 

6.7 

6.6 

6.6 

6.7 

6.6 

6.5 

6.6 

6.5 

6.6 

6.6 

6.5 

6.6 

6.5 

6.5 

6.5 

6.6 

6.5 

6.7 

6.7 

6.6 

6.6 

6.6 

6.6 

7 

6.8 

6.7 

max 

0.8 

4.2 

7.7 

6.7 

8.1 

9.9 

6.4 

0.8 

2 

0.4 

0.8 

9.2 

8.6 

6.9 

4.7 

2.1 

0.3 

4.7 

5.2 

5 

10.6 

8.9 

1.4 

0.1 

0.4 

1 

0.2 

1.6 

5 

2.1 

23.6 

ave 

0.3 

0.7 

3 

3.5 

6.7 

7.7 

4.5 

0.3 

0.3 

0.2 

0.3 

4.5 

5.3 

6 

4.7 

1.1 

0.2 

1.5 

1.8 

2 

6.5 

4.9 

1.4 

0.1 

0.1 

0.7 

0.1 

0.6 

1.5 

0.6 

13 

in 

temp 

72.4 

70.8 

65.4 

65.2 

62 

62.3 

61 

60.2 

61.8 

66.5 

69.6 

73.5 

73.6 

72.1 

68.7 

65.1 

63.4 

61.1 

61.8 

60.6 

62.4 

66.5 

69.9 

73 

73.7 

71.4 

66.4 

65.2 

61.4 

59.8 

59.4 

59.4 

61.9 

66.3 

69.4 

73.3 

73.7 

72.7 

69.8 

66.7 

63.8 

61.5 

60.5 

60.2 

eff 

temp 

74.4 

72.8 

67 

66 

62.4 

62.1 

61 

59.8 

61.5 

66.1 

70.4 

74.3 

75.4 

74.5 

70.6 

66 

63.7 

60.6 

60.9 

59.9 

62.5 

66.9 

70.6 

73.4 

74.5 

73 

68.3 

66.2 

62.2 

60.8 

59 

58.3 

60.8 

65.5 

69 

73.8 

75.2 

74.4 

71 

67.2 

63.4 

61.2 

59.6 

58.6 

b-solid 

gal(00C 

352 

357 

437 

399 

530 

651 

482 

426 

591 

329 

360 

268 

272 

204 

602 

375 

355 

256 

280 

747 

232 

192 

340 

360 

276 

405 

175 

220 

257 

334 

706 

479 

356 

284 

456 

316 

288 

320 

256 

324 

523 

590 

166 

464 
Appendix B: Antidegradation Review Sheet 

ANTIDEGRADATION REVIEW SHEET 

FOR A PROPOSED INDIVIDUAL NPDES DISCHARGE 

1. What is the name of Surface Water that receives the discharge? Willamette River 

Briefly describe the proposed activity: Discharge of treated municipal wastewater. 

Is this review for a (renewal) OR new (circle one) permit application? 

Go to Step 2. 

2. Is this surface water an Outstanding Resource Water or upstream from an Outstanding 

Resource Water? 

Yes. Go to Step 5. 

CNoD GO to Step 3. 

3. Is this surface water a High Quality Water? 

Yes. Go to Step 8. 

CjMo) Go to Step 4. 

4. Is this surface water a Water Quality Limited Water? 

Go to Step 14. 

Go to Step 2. Note: The surface water must fall into one of three (3) categories: 

Outstanding Resource Water (Step 2), High Quality Water (Step 3), or Water Quality 

Limited Water (Step 4). 

14. Will the proposed activity result in a Lowering of Water Quality in the Water Quality Limited 

Water? [see OAR 340-041-0004(3)-(5) for a description in rule of discharges that do not result in 

lowering of water quality or do not constitute a new and/or increased discharge or are otherwise 

exempt from antidegradation review; otherwise see "Is an Activity Likely to Lower Water Quality?" 

in Antidegradation Policy Implementation Infernal Management Directive for NPDES Permits and 

Section 401 Water Quality Certifications^ 

Yes. Go to Step 15. 

(Ht£) Proceed with Permit Application. Applicant should provide basis for conclusion. Go to 

Step 21. 

21 
21. 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. 

Action Approved 

Section: Northwest Region Water Quality Source Control Section 

Review Prepared By: Lyle Christensen 

Phone: 503-229-5295 

Date Prepared: September 2010 

22 
Appendix C - Reasonable Potential Analysis 

Facility Name: 

Dilution Values?(V/ti » v -i>A:. 

_*vFtow__ft>n @ ZID mm 

lov/FbwD_tt)n©MZ(7O101 

LoW Ffaw DMfon & m (30O5I 

Hiati FbwDiAbn® __DflO101 

Hqhfbw DkMX> & MZfTOiO) 

Hqh Fb* DM_bn @ MZ (3005) 

Enter data' taifiw i f' no 'di S uHtra da 

Data toestimate dilution"-;?^;:: 

EfnueitFUvfrnod) = 

1010fCfSl = 

7O10fCFS) = 

30O5fO-l = 

%<Jijti_)natMZ = 

%d_tonatZID = 

Confrfence Level = 

Probabtv Basis = 

PARAMETER 

Low Ro w Sea son 

CHLORINE 

AMMONIA - Freshwater 

AMMONIA-Saltwater 

AMfiSONM - Proposed lhr/4dav* 

AWiONlA - Proposed3tkfsy* 

Hiah Flo w Season 

CHLORINE 

AMMONIA - Freshwater 

AMMONIA - Saltwater 

AfilMONlA - Proposed ihr/4dav* 

At-IMONIA - Proposed'30day* 

B______Hle STP 

V 

3 

23 

* 

3 

23 

* 

'•• eatu_ted 

* 

* 

* 

* 

* 

* 

tals'ava!fa'W_'~"v,-

; 

: Summer 

* 

* 

* 

* 

* 

* 

99% 

95% 

# o f 

Samples 

* 

206 

* 

* 

* 

* 

16 

* 

* 

t 

•-"•• Winter 

* 

* 

* 

* 

* 

* 

Hiahest 

Cone. 

mq/ l 

* 

15.5 

* 

* 

* 

t 

9.900 

* 

* 

* 

_ [ 

i 

! 

1 

Coef. of 

Variance 

* 

0.90 

* 

* 

* 

* 

0,90 

* 

t 

* 

Calculated 

Maximum 

Cone. 

mil 

* 

15.50 

* 

* 

* 

* 

20.79 

* 

* 

* 

Summer 'data..-.:.- '•; :•••}• ', 

• EH* = 

Temp * = 

Akaiftv = 

Sahionas Resent? (Y/N) 

SarnonH Eoawiira? (Y/N) 

Freshwater? fY/H) 

Satttvfpptl 

Winter data ;'•:•'.-; '•<••%-•; 

DH* = 

Temo * = 

Afc__v = 

Sahicn_; Present? CflU) 

Shionid Soawihq? (Y/M) 

Fresh Water ?Ci7N) 

Saiity foot) 

1 

BacKq round 

Cone. 

mtj/l 

* 

0,20 

t 

i 

* 

* 

0.20 

* 

* 

* 

Maximum 

Cone, at 

ZID 

nw/l 

* 

5.30 

* 

* 

n/a 

* 

7.06 

* 

* 

n/a 

^'Effluents; 

6.5 

25 

55 

n/a 

n/a 

n/a 

* 

7 

17 

55 

n/a 

n/a 

n/a 

* 

Maximum 

Cone, at 

MZ 

nw/i 

* 

0.87 

* 

* 

* 

* 

1.10 

* 

* 

* 

Stream 

7.4 

22 

24 

v 

n 

v 

* 

7.2 

15 

24 

v 

n 

V 

1 

Date: I 9/21/2010 

i 

Vf &/-Mixed v--. 

"•••:__>;.-i 

6.7 

23.0 

?';MZ*' 

7.2 

22.1 

16.5-91 

° C 

* 

7.1 

15.7 

* 

7.2 

15.1 

f 6.5-91 

°C 

* 1 * 1 

i 

WO CRITERIAAcute! 

(CMC) 

IW/I : 

0.019 

17.8 

n/a 

29.1 

n/a 

0.019 

18.6 

n/a 

22.2 

n/a 

Chronic 

(CCC) 

V'flWfl0.011 

1.05 

n/a 

8.30 

3.3 

0,011 

1.8 

n/a 

13.14 

5.3 

. 

REASONABLE 

POTENTIAL? 

ACUTE 

* 

NO 

* 

* 

n/a 

* 

HO 

* 

* 

n/a 

CHRONIC 

* 

NO 

* 

* 

• 

* 

NO 

* 

* 

* 

Facility Name: 

bilytiohfVal ues>?' (if/N);:• 

Diitbn @ ZID 

Dkitbn @ HZ 

Cityo 

A^;A 

3 

23 

If 'ho dtafem values enterWb'beSw':^'-

FacStv effluent Fbw 

7Q10 

IfilO 

% dkitbn at ZID 

% diutbn at MZ 

Fresh Water? (Y/N) 

PARAMETER 

ANTIMONY * 

ARSENIC V * (inorqanfc) 

ARSENIC I H fhoraanfcV 

CADMIUM + 

CHROMIUM II I + 

CHROMIUM VI 

COPPER + 

CYANIDE 

IRON * 

UEAD + 

MERCURY 

NICKEL + 

SELENIUM 

SILVER + 

THALLIUM * 

ZINC + 

* 

* 

* 

* 

* 

y 

# o f 

Samptes 

9 

51 

* 

51 

51 

51 

51 

45 

* 

51 

45 

51 

51 

51 

9 

51 

FWilsom 

catiilate_;:

! 

* 

* 

MGD 

CFS 

CFS 

% 

% 

Highest 

Cqnc. 

See 1KB 

MQ/I 

0.27 

0.60 

* 

0.50 

1.55 

1.55 

13.03 

31.00 

* 

0.90 

0.023 

58.50 

1,70 

1.20 

0.01 

105.10 

rille STI 

Coef. of 

Variance 

0.60 

0.26 

* 

0.99 

0.33 

0.33 

0,39 

1.03 

* 

0,40 

0,94 

1,66 

0.54 

0.98 

0.54 

0.22 

_> 

Cafcubted 

Max Effluent 

Cone. 

UO/f 

0.59 

0.66 

* 

0.65 

1.71 

1.71 

14.33 

40.30 

* 

0.99 

0.03 

81.90 

2.04 

1.56 

0.01 

115.61 

Hardness : 

Effluent 

Stream 

Mixe d ^ 

ZID 

MZ 

m_/LCaC03. 

69 

25 

40 

27 

Confidence Level 

Probability E 

Background 

Cone. 

Sne 1MD 

ua/l 

0.3 

0.4 

* 

0,060 

* 

1.00 

2.1 

0.10 

* 

0.41 

0.003 

0.52 

2.06 

0.01 

0.10 

3.32 

•asls 

Maxrnum 

Cone, at 

ZID 

UG/1 

0.40 

0.49 

* 

0.26 

* 

1.24 

6.18 

13.50 

* 

0.60 

0.01 

27.65 

2.05 

0.53 

0.07 

40.75 

(Hardn 

be> 2 

9 9 % 

9 5 % 

Maxftium 

Cone, at 

MZ 

ua/l 

0.31 

0.41 

* 

0.09 

* 

1.03 

2.63 

1.85 

* 

0.44 

0.00 

4.06 

2.06 

0.08 

0.10 

8.20 

Date: 

. 

s 

i 

i 

ess values should 

>and<4GQ mg/1 ) 

1 

WQ CRITERIA 

lHou r 

(CMC) 

ua/l 

9000 

850 

360 

1.38 

814 

16 

7.4 

22,0 

2000 

25 

2.40 

649 

260 

0.83 

1400 

53 

4 Da/ 

(CCC) 

pq/l 

1600 

48 

190 

0.40 

71 

11 

3.9 

5.2 

1000 

0.60 

0.012 

52 

35 

0.12 

40 

35 

09/22/2010 

i 

! 

i 

! 

REASONABLE 

POTENTIAL ? 

ACUTE 

NO 

NO 

— 

NO 

— 

NO 

NO 

NO 

--

NO 

NO 

NO 

NO 

NO 

NO 

NO 

CHRONIC 

NO 

NO 

-. 

NO 

--

NO 

NO 

NO 

--

NO 

NO 

NO 

NO 

NO 

NO 

NO 

23