## Fact Sheet for NPDES Permit WA0 029181

West Point Wastewater Treatment Plant (WWTP)

and Combined Sewer Overflow (CSO) System



### December 19, 2014

Purpose of this f act s heet

This fact sheet explains and documents the decisions the Department of Ecology (Ecology) made in drafting th e proposed National Pollutant Discharge Elimination System (NPDES) permit for King County’s West Point WWTP, CSO treatment plants, and associated CS O outfalls.

This fact sheet complies with Section 173

- 220

- 060 of the Washington Administrative Code (WAC), which requires Ecology to prepare a draft permit and accompanying fact sheet for public evaluation before issuing an NPDES permit

. Ecology makes the draft permit and fact sheet available for public review and comment at least thirty (30) days before issuing the final permit

. Copies of the fact sheet and draft permit for King County’s West Point WWTP and CSO system , NPDES permit WA002918 1 , we re availab le for public review and comment from October 30, 2014 until November 29, 2014

. For more details on preparing and filing comments about the se documents , please see Appendix A

- Public

Involvement Information

. King County (County) reviewed the draft permit and fact sheet for factual accuracy

. Based on this review, Ecology provided additional clarification and corrected any errors or omissions regarding the facility’s location, history, or wastewater discharges prior to publishing this draft

fact sheet for public notice

. Significant comments from King County and Ecology’s responses

are listed in Appendix I

– Response to Comments

. After the public comment period closes, Ecology will summarize substantive comments and provide responses to them

. Ecology will in clude the summary and responses to comments in this

fact sheet as Appendix I

- Response to Comments , and publish it when issuing the final NPDES permit

. Ecology will not revise the rest of the fact sheet, but the full document will become part of the legal history contained in the facility’s permit file.

Summary

The proposed permit provides coverage for King County’s West Point WWTP, four CSO treatment facilities (Alki, Carkeek, Elliott West, and Henderson/MLK), and 38 CSO outfalls.

The West Point WWTP tr eats domestic, commercial, and industrial wastewater and CSO stormwater from the greater Seattle area using a high rate oxygenated activated sludge biological treatment process with chlorine disinfection before discharging the treated effluent to central

P uget Sound. For West Point WWTP, the proposed permit contains the same effluent limits for

CBOD 5 

### , total suspended solids, fecal coliform, pH, and total residual chlorine as the permit

issued in 2009.

This permit proposes a few changes for the four CSO treatment plants. For all four facilities, compliance with settleable solids standards will be assessed annually instead of on an annual and

per

- event basis as in the previous permit. This is consistent w ith the legal basis in regulation (WAC 173

- 245). For the Alki and Carkeek CSO treatment facilities the proposed permit includes the same limits and monitoring requirements as the previous permit. For Elliott West and Henderson/MLK facilities, the following changes are being proposed:Fact Sheet for NPDES Permit WA 0029181 Page 2 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Elliott West CSO treatment plant

- Due to a change in mixing dilution, the limits for total residual chlorine increased slightly from a maximum daily average of 104 to 109 μg/L. Fecal coliform limits became more stringent as t hey changed from a monthly limit of 154 (with

non

- discharge days calculated in the monthly geomean as ‘1’) to a guidance

- based monthly limit

of 400 counts/100 mL. Also, the proposed permit includes additional monitoring for dissolved

oxygen, copper and cya nide , and requires a study to evaluate options for reducing copper and

settleable solids concentrations.

Henderson/MLK CSO treatment plant

– For this facility effluent limits remain the same. Copper monitoring is required for each event and PCB monitoring is required using EPA method 1668 with a method detection limit of 0.0001 ug/L.Fact Sheet for NPDES Permit WA 0029181 Page 3 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Table of Contents

I. Introduction

................................ ................................ ................................ ............................ 7

II. Background Information

................................ ................................ ................................ ...... 8

A. Facility description

................................ ................................ ................................ ......... 10 History

................................ ................................ ................................ ................................ ......... 10 Background

................................ ................................ ................................ ................................ . 10 Collection system status

................................ ................................ ................................ .............. 13 Treatment processes

................................ ................................ ................................ .................... 16

Solid wastes/Residual solids

................................ ................................ ................................ ....... 19 Discharge outfalls

................................ ................................ ................................ ........................ 20



### B. Description of the receiving water

................................ ................................ ................. 26

C. Wastewater influent characterization

................................ ................................ ............. 29

D. Wastewater effluent characterization

................................ ................................ ............. 30

E. Sediment characterization

................................ ................................ .............................. 36

F. Summary of compliance with previous permit issued

................................ .................... 46

G. State environmental policy act (SEPA) compliance

................................ ....................... 50

III. Proposed Permit Limits

................................ ................................ ................................ ...... 51

A. Design criteria

................................ ................................ ................................ ................ 51

B. Technology

- based effluent limits

................................ ................................ .................... 53

C. Surface water quality

- based effluent limits

................................ ................................ .... 56 Numerical criteria for the protection of aquatic life and recreation

................................ ............ 56 Numerical criteria for the protection of human health

................................ ................................ 56

Narrative criteria

................................ ................................ ................................ ......................... 57 Antidegradation

................................ ................................ ................................ ........................... 57

Combined Sewer Overflows

................................ ................................ ................................ ....... 58 Mixing zones

................................ ................................ ................................ ............................... 58



### D. Designated uses and surface water quality criteria

................................ ....................... 66 Puget Sound Discharges:

................................ ................................ ................................ ............. 66

Duwamish River Discharge (Henderson/MLK):

................................ ................................ ......... 67



### E. Water quality and sediment impairments

................................ ................................ ....... 68

F. Evaluation of surface water quality

- based effluent limits for numeric criteria

............. 69 Estuarine Mixing Zones (West Point WWTP, Alki, Carkeek, and Elliott West)

........................ 69 Freshwater Mixing Zone (Henderson/MLK)

................................ ................................ .............. 70

Dilution Factors

................................ ................................ ................................ ........................... 70



### G. Human health

................................ ................................ ................................ ................. 79

H. Sediment quality

................................ ................................ ................................ ............. 79

I. Whole effluent toxicity

................................ ................................ ................................ .... 80

J. Gro undwater quality limits

................................ ................................ ............................. 81

K. Comparison of effluent limits with the previous permit

................................ ................. 81

IV. Monitoring Requirements

................................ ................................ ................................ ... 83

A. Wastewater monitoring

................................ ................................ ................................ .. 83

B. Lab a ccreditation

................................ ................................ ................................ ............ 83

V. Other Permit Conditions

................................ ................................ ................................ ..... 84

A. Reporting and record keeping

................................ ................................ ........................ 84

B. Prevention of facility overloading

................................ ................................ .................. 84

C. Operation and maintenance

................................ ................................ ........................... 85Fact Sheet for NPDES Permit WA 0029181 Page 4 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### D. Pretreatment

................................ ................................ ................................ ................... 85 Duty to enforce discharge prohibitions

................................ ................................ ....................... 85



### E. Solid wastes

................................ ................................ ................................ .................... 86

F. Spill plan

................................ ................................ ................................ ......................... 86

G. Combined sewer overflows

................................ ................................ ............................. 86 CSO Reduction Plan/Long

- Term Control Plan and CSO Reduction Plan Amendments

............ 87

Nine Minimum Controls

................................ ................................ ................................ ............. 87 CSO Monitoring

................................ ................................ ................................ .......................... 88 Annual CSO Report

................................ ................................ ................................ .................... 88

Post

- Construction Monitoring Program

................................ ................................ ...................... 88



### H. Outfall evaluation

................................ ................................ ................................ ........... 88

I. Elliott West CSO treatment plant

– copper reduction assessment

................................ . 88

J. Elliott West CSO treatment plant

– settleable solids removal assessment

..................... 89

K. General conditions

................................ ................................ ................................ ......... 89

VI. Permit Issuance Procedures

................................ ................................ ................................ 89

A. Permit modifications

................................ ................................ ................................ ...... 89

B. Propo sed permit issuance

................................ ................................ ............................... 89

VII. References for Text and Appendices

................................ ................................ .................. 89

Appendix A

— Public Involvement Information

................................ ................................ ..... 92

Appendix B

— Your Right to Appeal

................................ ................................ ....................... 93

Appendix C

— Glossary

................................ ................................ ................................ ............. 94

Appendix D

— Receiving Water Data

................................ ................................ .................... 101

Appendix E

— Facility Data

................................ ................................ ................................ .... 102

Appendix F

— Technical Calculations

................................ ................................ ................... 127

Appendix G

— Significant Industrial Users

................................ ................................ ........... 163

Appendix H

— Process Flow Diagrams

................................ ................................ .................. 164

Appendix I

— Response to Comments

................................ ................................ ................... 168Fact Sheet for NPDES Permit WA 0029181 Page 5 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## List of Tables

Table 1

. General Facility Information

................................ ................................ ............................. 8
Table 2. Summary of West Poi nt WWTP’s Flow, BOD, and TSS Projections

............................ 11
Table 3. Future CSO Projects

................................ ................................ ................................ ........ 15

Table 4. Combined Sewer Overflow Outfalls (38)

................................ ................................ ........ 24
Table 5. West Point Ambient Background Data 1



### ................................ ................................ ......... 26
Table 6. Alki Ambient Background Data 1



### ................................ ................................ .................... 27
Table 7. Carkeek Ambient Background Data 1



### ................................ ................................ .............. 27
Table 8. Elliott West Ambient Background Data

................................ ................................ .......... 28
Table 9. Henderson/MLK Ambient Background Data 1



### ................................ ................................ 29

Table 10. Influent Characterization

- West Point WWTP

................................ ............................. 29

Table 11. Influent Characterization

- Alki

................................ ................................ ..................... 29

Table 12. Influent Characterization

- Carkeek

................................ ................................ ............... 30

Table 13. Influent Characterization

- Elliott West

................................ ................................ ......... 30

Table 14. Influent Characterization

- Henderson/MLK

................................ ................................ . 30

Table 15. Effluent Characterization

– West Point WWTP

................................ ............................ 31

Table 16. Effluent Characterization

– Alki CSO TP

................................ ................................ ..... 32

Table 17. Effluent Characterization

– Carkeek CSO TP

................................ ............................... 33

Table 18. Effluent Characterization

– Elliott West CSO TP

................................ ......................... 34

Table 19. Effluent Characterization

– Henderson/MLK CSO TP

................................ ................. 35

Table 20. West Point WWTP

– Sediment Test Results

................................ ................................ . 36
Table 21. Elliott West CSO treatment plant outfall

– sediment remediation activity 7



### .................. 39

Table 22. Henderson/MLK CS O treatment plant outfall

– sediment remediation activity

........... 40

Table 23. Untreated CSO outfalls

– sediment remediation activity

................................ .............. 42
Table 24. Sediment testing priorities for CSO outfalls & sampling results from 2011 & 2013

.... 43

Table 25. CSO outfalls scheduled to be controlled during this permit term.

................................ . 45

Table 26. Alki CSO Treatment Plant

– Permit Violations

................................ ............................. 46

Table 27. Carkeek CSO Treatment Plant

– Permit Violations

................................ ...................... 47

Table 28. Elliott West CSO Treatment Plant

– Permit Violations and Permit Triggers

............... 48

Table 29. Henderson/MLK CSO Treatment Plant

– Permit Violations and Permit Triggers

....... 50
Table 30. West Point WWTP Design Criteria

................................ ................................ ............... 51

Table 31. Alki CSO Treatment Plant

– Design Criteria

................................ ................................ 52

Table 32. Carkeek CSO Treatment Plant

– Design Criteria

................................ .......................... 53

Table 33. EWCSO Treatment Plant

– Design Criteria

................................ ................................ .. 53

Table 34. Henderson/MLK CSO Treatment Plant

– De sign Criteria

................................ ............ 53
Table 35 Technology

- based Limits (West Point WWTP)

................................ ............................ 54
Table 36 Technology

- based Mass Limits

................................ ................................ ..................... 54
Table 37. Technology & Guidance

- based Limits for CSO Treatment Plants

............................... 55

Table 38. Metal Translators Used in Reasonable Poten tial Analyses

................................ ........... 57

Table 39. West Point WWTP

- Critical Conditions Used to Model the Discharge.

...................... 60Fact Sheet for NPDES Permit WA 0029181 Page 6 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Table 40. CSO discharge flows used in dilution calculations

................................ ....................... 60
Table 41. Alki CSO TP: Critical Conditions Used to Model the Discharge.

................................ 61
Table 42. Carkeek CSO TP: Critical Conditions Used to Model the Discharge.

.......................... 61

Table 43. Elliott West CSO TP: Critical Conditions Used to Model the Discharge.

.................... 61

Table 44. Henderson/MLK CSO TP: Critical Conditions Used t o Model the Discharge.

............ 62
Table 45. Marine Aquatic Life Uses and Criteria

- West Point WWTP, Alki, and Carkeek

........ 67
Table 46. Marine Aquatic Life Uses and Associated Criteria

- Elliott West

................................ . 67

Table 47. Recreational Uses

- West Point WWTP, Alki, Carkeek, and Elliott West

.................... 67
Table 48. Receiving Water Criteria Comparison for Henderson/MLK

................................ ......... 68
Table 49. Comparison of Dilution Factors

................................ ................................ .................... 71
Table 50. Comparison of Previous and Proposed Effluent L imits

- West Point WWTP

.............. 81
Table 51. Comparison of Previous and Proposed Effluent Limits

- Alki CSO TP

....................... 81
Table 52. Comparison of Previous and Proposed Effluent Limits

- Carkeek CSO TP

................. 82
Table 53. Comparison of Previous and Proposed Effluent Limits

- Elliott West CSO TP

........... 82
Table 54. Comparison of Previous and Proposed Effluent Limits

– Henderson/MLK TP

........... 82

Table 55. Lab Accredited Parameters

................................ ................................ ............................ 84



## List of Figures

Figure 1. Facility Location.

................................ ................................ ................................ .............. 9
Figure 2. West Point WWTP outfall location.

................................ ................................ ............... 21
Figure 3. Alki CSO treatment plant outfall location.

................................ ................................ ..... 22
Figure 4. Carkeek CSO treatment plant outfall location.

................................ ............................... 22
Figure 5. Elliott West CSO treatment plant outfall l ocation.

................................ ......................... 23
Figure 6. Henderson/MLK CSO treatment plant outfall location.

................................ ................. 24
Figure 7. Sediment sampling locations for West Pt WWTP outfall.

................................ ............. 37
Figure 8. Fecal Coliform data for Elliott West CSO TP.

................................ ............................... 49
Figure 9. Residual chlorine data for Elliott West CSO TP

... .......................................... 49
Figure 10. West Point’s WWTP’s Mixing Zone

................................ ................................ ........... 64
Figure 11. Alki’s Mixing Zone

................................ ................................ ................................ ...... 64

Fi gure 12. Carkeek’s Mixing Zone Zone

................................ ................................ ....................... 65
Figure 13. Elliott West Mixing Zone

................................ ................................ ............................. 65
Figure 14. Henderson/MLK Mixing Zones

................................ ................................ ................... 66Fact Sheet for NPDES Permit WA 0029181 Page 7 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## I. Introduction

The F ed eral Clean Water Act (FCWA, 1972, and later amendments in 1977, 1981, and 1987) established water quality goals for the navigable (surface) waters of the United States

. One mechanism for achieving the goals of the Clean Water Act is the National Pollutant Discharge Elimination System (NPDE S ), administered by the federal Environmental Protection Agency (EPA)

. The EPA authorized the s tate of Washington to manage the NPDES permit program in

our state

. Our state legislature accepted the delegation and assigned the power and duty for conducting NPDES permitting and enforcement to Ecology

. The L egislature defined Ecology's authority and obligations for the wastewater discharge permit program in 90.48 RCW (Revised Code of Washington)

. The following regulations app ly to domestic wastewater NPDES permits:

 

### Procedures Ecology follows for issuing NPDES permits ( c hapter 173

- 220 WAC)

 

### Technical criteria for discharges from municipal wastewater treatment facilities (c hapter

173

- 221 WAC)

 

### Water quality criteria for surface wa ters ( c hapter 173

- 201A WAC)

 

### Water quality criteria for groundwater s ( c hapter 173

- 200 WAC)

 

### Whole effluent toxicity testing and limits (chapter 173

- 205 WAC)

 

### Sediment management standards ( c hapter 173

- 204 WAC)

 

### Submission of plans and reports for construction of wastewater facilities ( chapter 173

- 240 WAC)

The following additional regulations apply to communities operating collection systems with

Combined Sewer Overflows (CSOs) :

 

### Submission of plans and reports for construction and operation of CSO reduction facilities (chapter 173

- 245 WAC)

 

### US EPA CSO control policy (59 FR 18688)
These rules require any treatment facility owner/operator to obtain an NPDES permit before discharging wastewater to state waters

. They also help define the basis for limit s on each discharge and for requirements imposed by the permit

. Under the NPDES permit program and in response to a complete and accepted permit application

, Ecology must prepare a draft permit and accompanying fact sheet, and make them

available for publ ic review before final issuance

. Ecology must also publish an announcement (public notice) telling people where they can read the draft permit, and where to send their comments, during a period of thirty days (WAC 173

- 220

- 050, s ee Appendix A

- Public

Involve ment Information for more detail about the public notice and c omment procedures)

. Aft er the public comment p eriod ends , Ecology may make changes to the draft NPDES permit in

response to comments

. Ecology will summarize the responses to comments and any cha nges to the permit in Appendix I

.Fact Sheet for NPDES Permit WA 0029181 Page 8 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## II. Background Information

Table 1

. General Facility Information

Facility Information

Applicant King County Wastewater Treatment Division (WTD)

, Department of Natural Resources and Parks ( DNRP )

Facility Name s and Address es West Point Wastewater Treatment Plant (WWTP) : 1400 Discovery Park Blvd, Seattle, WA 98199
Alki Storage and CSO Treatment Plant : 3380 Beach Drive SW, Seattle, WA 98116

- 2616
Carkeek Storage and CSO Treatment Plant : 1201 NW Carkeek Park Road, Seattle, WA 98177

- 4640
Denny/Elliott West Storage and CSO Treatment Plant : 545 Elliott Avenue West

, Seattle, WA 98119

Henderson /MLK Storage and CSO Treatment Plant : 9829 42 nd Avenue South

, Seattle, WA 98118

Responsible Official Chris tie True Director, King County DNRP 201 S. Jackson Street, Seattle, WA 98104

Type of Treatment West Point WWTP: Secondary (High

- rate oxygenated activated sludge)

Alki, Carkeek, Denny/Elliott West, and Henderson/MLK CSO Treatment

Plants: Primary with Disinfection

Facility Location
(NAD83/WGS84 reference datum) West Point WWTP: Puget Sound Lat: 47.661465 ̊, Long:

- 122.430693 ̊

Alki CSO Treatment Plant: Puget Sound

Lat: 47.574605 ̊, Long:

- 122.417348 ̊

Carkeek CSO Treatment Plant: Puget Sound

Lat: 47.710869 ̊, Long:

- 122.370723 ̊

Elliott West CSO Storage & Treatment Facility: Elliott Bay Lat: 47.624603 ̊, Long:

- 122.366339 ̊

Henderson/MLK CSO Storage & Treatment Facility: Duwamish River Lat: 47.514003 ̊, Long:

- 122.280776 ̊

Discha rge Waterbody Name and L ocation
(NAD83/WGS84 reference datum) West Point WWTP: Puget Sound

Lat: 47. 661111  ̊, Long:

- 12 2

. 446389  ̊

Alki CSO Treatment Plant: Puget Sound Lat: 47.57025 ̊, Long:

- 12 2

. 4225  ̊

Carkeek CSO Treatment Plant: Puget Sound Lat: 47.71264 ̊, Long:

- 12 2

. 38789  ̊

Elliott West CSO Storage & Treatment Facility: Elliott Bay Lat: 47.61755 ̊, Long:

- 12 2

. 36186  ̊

Henderson/MLK CSO Storage & Treatment Facility: Duwamish River Lat: 47.51194 ̊, Long:

- 12 2

. 29736  ̊

Permit Status

Issuance Date of Previous Permit June 22, 2009

Application for Permit Renewal Submittal Date June 27, 2013

Date of Ecology Acceptance of Application September 13, 2013

Inspection Status

Date of Last Sampling Inspec tion December 17

- 18, 2007

Date of Last Non

- sampling Inspection Date June 2 , 20 14Fact Sheet for NPDES Permit WA 0029181 Page 9 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 1

. Facility LocationFact Sheet for NPDES Permit WA 0029181 Page 10 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### A. Fa cility d escription

History

Metro (Municipality of Metropolitan Seattle) constructed the West Point W astewater Treatment Plant (WWTP) in 1965 as a primary treatment plant

. In 1972, the amended Federal Water Pollution Control Act (PL 92

- 500) established the National Pollutant Discharge Elimination System (NPDES) and pretreatment programs

. Federal law provided that all sewage treatment plants were to meet secondary treatment requirements by July 1

, 1977

. During the period 1976

- 1977, Metro, the agency having ownership of the plant at the time, prepared a draft facility plan and Environmental Impact Statement (EIS) and submitted a request for feder al funding through EPA Grant No C0530816

- 01 to meet s econdary treatment requirements at West Point

. In 1979, Metro applied to the USEPA for a Clean Water Act Section 301(h) Waiver from secondary treatment at West Point, Richmond Beach,

and Carkeek

. Metro also planned to apply for a waiver for the Alki treatm ent plant

. Metro withdrew from the 301(h) waiver process on September 7, 1984, which resolved this process

. On September 24, 1984, Ecology issued Metro an Adminis trative Order, Docket No. DE

84

- 577

. The Order directed Metro to proceed with planning for sec ondary treatment at West Point and set a schedule for attaining secondary treatment no later than February 1, 1991

. In November 1987, Ecology amended the Order by Consent Decree No. 87

- 2

- 05395

- 4 changing, among other things, the final compliance date to De cember 31, 1995

. On January 1, 1994, King County assumed control of Metro's assets and obligations under the existing NPDES permits issued by the Ecology.

On December 8, 1995, Ecology certified that the West Point WWTP achieved the secondary

treatment lev el.

Background

West Point WWTP



### King County’s Wastewater Treatment Division (WTD) owns and operates the West Point WWTP and associated regional facilities

. Figure 1 shows the location of the West Point WWTP along with the four CSO treatment plants and 38 CS O outfalls that are also regulated by the proposed permit. The West Point WWTP is part of King County’s regional system that collects and treats wastewater from homes, businesses, and industries surrounding the Lake Washington area

. King County’s other sec ondary wastewater treatment plan ts include South Plant (Renton), Brigh twater (outside of Woodinville), Vashon, and Carnation.

King County provides wholesale wastewater treatment services to 17 cities, 16 local sewer utilities, and one Indian tribe. The county's WTD serves about 1.4 million people within a

420

- square

- mile service area, which includes most urban areas of King County and parts of south Snohomish County and northeast Pierce County

. The local agencies own and operate

in dependent collection systems, which include pipelines and pump stations to collect and convey wastewater flows in their service area to King County's regional system for treatment and disposal

. The local agencies have long

- term agreements with King County for this

service

. King County owns and operates the regional treatment plants, pipelines, pump stations, and other related facilities

. The following is a list of the municipalities, sewer districts, and water districts that contribute wastewater to this fa cility: Bothell, Brier, Lake Forest Park, Redmond, Seattle, Woodway, Alderwood Water District, Highlands Sewer District, North Shore Utilities, NE Sammamish Sewer & Water District, Valley View,Fact Sheet for NPDES Permit WA 0029181 Page 11 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Ronald Wastewater District, Sammamish Plateau Sewer & Water D istrict, Skyway Water & Sewer District, and Olympic Water & Sewer District.

In addition to the domestic and commercial wastewater, nearly all of Seattle’s industrial areas discharge to the West Point WWTP

. 48 significant industrial users discharge industrial flows to the West Point system

. Based on King County’s permit application, West Point receive s an estimated daily flow of 9.6 MGD from significant industrial sources

.
Table 2 presents a summary of the flow, BOD, and TSS projections, as described in the County’s NPDES permit application and waste load assessment analysis

. The population projections take into account planned changes in apportionment of fl ows between the West Point, South Plant , and Brightwater WWTPs

.

Table 2 . Summary of West Point WWTP’s Flow, BOD, and TSS Projections

Year Res. Population

+ Employment Percent

Increase Average Annual

Flow (MGD) * Influent BOD Loading (lb/day) Influent TSS

Loading (lb/day)

2014 1,251,888 95 140,000 157,900

2015 1,274,230 1.78% 96 142,500 160,400

2016 1,296,572 1.75% 97 145,000 162,800

2017 1,318,913 1.72% 98 147,500 165,300

2018 1,341,255 1.69% 99 150,000 167,800

2019 1,363,597 1.67% 100 152,500 169,800

Design 1,251,888 215 254,000 274,000

* Annual flow projections are based on average rainfall.



### The West Point WWTP is located on the Puget Sound at the western tip of Discovery Park between Shilshole Bay and Elliott Bay

. King County owns approximately 80 acres of land at

the West Point site ; t wenty of these acres are considered subtidal

. The current facilities

occupy approximately 25 acres of land

. The West Point WWTP serves mostly a combined sewer system area and therefore thi s NPDES permit contains additional permit requirements related specifically to combined sewer systems

. Currently, the West Point WWTP provide s secondary treatment for flows up to 300 MGD and provides primary treatment and disinfection for flows exceeding 3 00 MGD

. The plants hydraulic capacity is 440 MGD

. The West Point WWTP is rated as a Class IV treatment plant, according to regulation.

In addition to the West Point WWTP, t he proposed permit authorizes discharg es from four CSO storage and treatment facilit ies (Alki , Carkeek, E lliott West, and Henderson/MLK) and

38 individual CSO outfalls.

Alki CSO Treatment Plant



### Metro constructed the Alki treatment plant in 1958 as a primary treatment plant to serve the Alki Basin, an area of 4,095 acres

. It is located in West Seattle at the intersection of Beach

Drive and Benton Place on 2.8 acres

. The service area is largely residential with a projected saturation population of 43,700

. Commercial activity is concentrated along portions of

California Avenue and SW Alaska S treet

. Metro overhauled the facility’s mechanical and electrical systems in 1987 and added architectural enclosure s. In 1998, the County remodeled the facility to operate as a near

- fully automated CSO treatment plant , and added flow transfer

components suc h as the West Seattle Pump Station and the West Seattle Tunn el. In 1999,Fact Sheet for NPDES Permit WA 0029181 Page 12 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Ecology incorporated the Alki CSO treatment plant into the West Point WWTP NPDES

Permit

. Hydraulic capacity at Alki CSO treatment plant is 45to 65 MGD, depending on tide level. During dry

- weather operation, the County sends all flows to the West Point WWTP for secondary treatment. During wet

- weather operation, the Alki CSO treatment plant provides primary treatment

, chlorine disinfection , and dechlorination to flows that exceed d ownstream collection system capacity. Downstream capacity is limited to 18.9 MGD of flow and 7.1 MG of storage in the Alki/West Seattle tunnel. To protect the Alki plant, the County discharges excess flows a t the 63 rd 

### Avenue Pump Station outfall, a permitt ed CSO location

. According to the County’s 2013 wasteload analysis report, the Alki basin is considered substantially built out. The county expects i ncreased flows due to expected densification in the basin to be offset by a reduction in per capita water use due to conservation efforts

. The County expects n o net changes in base or average flows in the next 5 years.

The two pump stations upstream of the 63 rd 

### Pump Station (Murray & Barton) are undergoing

construction upgrade s

. These projects will increase th e storage upstream of the 63 rd 

### Pump Station, helping to reduce untreated combined sewer overflows

. These projects will also tend

to increase the volume treated at Alki

. The County will review o perational strategies at the

63 rd 

### PS, the inlet regulator gate, and the West Seattle Pump Station/Tunnel as these projects

move forward.

Carkeek CSO Treatment Plant



### Metro constructed the Carkeek treatment plant in 1962 as a primary treatment plant to serve

the Carkeek Basin

. It is located at 1201 NW Carkeek Park Road

. In 1994, the County constructed a pumping station and converted the plant to a CSO treatment facility

. The facility began operation as a CSO treatment facility on November 1, 1994, under its then

existing NPDES Carkeek permit

. The current West Point permit contains permit limits for the Carkeek CSO treatment plant.

During dry

- weather opera tion the facility operates as a pump station only and King County’s

West Section off

- site crew services the facility three times a week

. Durin g wet

- weather events, operators staff the plant during start up and shut down , as well as provide preventative maintenance and operational checks.

According to the County’s 2013 wasteload analysis report, the Carkeek basin is considered substantially built out. The county expects increased flows due to expected densification in the basin to be offset by a reduction in per capita water use due to conservation efforts

. The County expects no net changes in base or average flows in the next 5 years.

Elliot West CSO Treatment Facilities



### Ecology modified t he West Point NPDES Permit in 2005 to include the Elliott West CSO storage and treat ment facility

. The County constructed t he Elliott West CSO treatment plant

as part of the Denny Way/Lake Union CSO Control proje ct

. The Denny Way/Lake Uni on CSO Control project consists of several CSO facilities that store and treat CSOs from the County’s Dexter and Denny Regulators, and the City of Seattle ’s CSOs around Lake Union

. King County completed construction of the project in May 2005

. The project co nsisted of four major elements: the East Portal, which captures flow from a number of sewer lines in the South Lake Union area; the 14

- foot

- diameter Mercer Street Storage and Treatment Tunnel; and the Elliott West CSO treatment facility located on Elliott Bay; and the transition

and dec hlorination facilities adjacent to the Denny Way regulator station

. Two new CSOFact Sheet for NPDES Permit WA 0029181 Page 13 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### outfalls were built in Elliott Bay

— one outfall to replace the outfall structure at the Denny Way Regulator and another outfall for the Elliott West CSO treatment facility

. The Mercer Tunnel provides storage for up to 7.2 MG and primary clarification for all flows entering the

tunnel

. The County designed the Elliott West treatment facility to provide final treatment (screening, disinfection, and dechlorination) to settled flows t hat exceed the capacity of the tunnel. After storm events, the tunnel and wet well are emptied by pumping these stored

flows to West Point WWTP.

King County considers the Elliott West basin as already substantially developed. They expect

to see continued significant redevelopment in the South Lake Union area over the next 5

years

. Based on their 2013 wasteload analysis, t he County estimates base flows and average

wet weather flows will increase b y about 5 to 7% over the next 5 years due to densification in the basin; these values are partially offset by a reduction in per capita water use due to water

conservation efforts.

Henderson/MLK CSO Facilities



### Ecology modified the West Point NPDES Permit in 2005 to include the Henderson/MLK CSO storage and treatmen t facility

. The County implemented the Henderson/ Norfolk CSO control project to control the Henderson and Martin Luther King (MLK) CSOs into Lake Washington and Norfolk CSO s into the Duwamish River

. King County upgraded the

Henderson/MLK Pump Station and c onstructed a large storage and treatment tunnel between Henderson Street and Norfolk Street in the Rainier Valley

. The County designed the facilities

to provide final treatment (screening, disinfection, and dechlorination) to settled flows that

exceed the capacity of the storage and treatment tunnel

, and to discharge treated flows through the Norfolk CSO outfall in the Duwamish Waterway

. The County transfers b ase flows, settled solids, and s tored flows from the tunnel to the South Plant at Renton or to the West Point WWTP, depending on capacity in the Elliot Bay Interceptor, for secondary

treatment

. According to the County’s 2013 wasteload analysis report, the Henderson/MLK basin is considered substantially built out. The county expects increased flows due to expected densification in the basin to be offset by a reduction in per capita water use due to

conservation efforts

. The City of Seat tle is starting construction on their Henderson South CSO project that will increase conveyance and pumping capacity to the Henderson/MLK

basin , resulting in increased volumes and peak flows. The City and the County signed an agreement on the South Henders on Projects in January 2014 to address any impacts of these new flows. Increased volumes are expected from the City’ s CSO basins 44, 45, 46, 47b/171, and 47c. Peak flow volume increases are expected from basins 46, 47b/171, and 47c. It is

unknown at this t ime if flow changes are expected from basin 49 since that project is still under review. The County expects that the increased flows from the City will not result in violating the CSO control standard at the Henderson Pump station CSO outfall or the

Hender son /MLK CSO s torage and t reatment facility. The County and City will monitor changes with flow monitoring and modeling.

C ollection s

ystem s tatus

The King County wastewater service area is divided into the East and West Section s

. Wastewater from the East Se ction is conveyed to the South Treatment Plant; West Section

wastewater flows to the West Point WWTP

. The West Section service area includes areas north and west of Lake Washington and the City of Seattle

. Developments within the north Lake Washington area were constructed with separate sanitary and storm sewers

. Within theFact Sheet for NPDES Permit WA 0029181 Page 14 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### City of Seattle, approximately 42,000 acres or 75 percent of the total area is constructed with

combined sewers

. Sanitary and combined flows from Seattle are merged prior to arriving at

the West Point WWTP.

West Point WWTP receives wastewater from the west division collection system, a series of pump and regulator stations and related trunks and interceptors

. Sewage flows by gravity via two influent tunnels (Ft. Lawton 144” Diameter and t he Old Ft. Lawton Tunnel 84” Diameter) and enters the WWTP site at the influent control structure

. The County’s supervisory control and data acquisition ( SCADA) computer systems automatically monitor and control the flow through the west division collection system

. The control system minimizes surges, maximizes flow to the plant, and maximizes use of collection system storage to limit combined sewer overflows.

Combined Sewer Overflows



### King County has 38 combined sewer overflow outfalls which discha rge untreated sewage and stormwater during periods of heavy precipitation, within the city of Seattle. The collection system, as configured in 1983, discharged nearly 2.3 billion gallons per year of untreated sewage and stormwater from a total of 431 overf low events

. Since 1988, the

Metro/ County has completed a number of projects to reduce the volume and frequency of

CSOs

. Based on data from 200 6

- 20 12 , King County’s average annual untreated CSO volume has been approximately 811 million gallons per year.

Bet ween 1995 and 2005, King County constructed the Elliott West and Henderson/MLK projects, in addition to other CSO projects, to reduce CSO overflows. The County also implemented a real

- time, web

- based notification system that the public can use to assess

wh en CSOs are discharging

. The website can be found at:
http://www.kingcounty.gov/environment/wastewater/CSO/RealTime/SeattleOverview.aspx



### . The County’s 200 8 CSO Reduction Plan Update identified priority projects at locations near beach areas. Consequently, King County began construction on four CSO control projects

near beach areas in late 2013 . The se projects include CSO storage tanks in South Magnolia,

Nort h Beach, and at the Murray pump station, and neighborhood green stormwater

inf rastructure in the Barton neighborhood of West Seattle.

In 2012 , the King County Council adopted the 2012 CSO Long Term Control Plan

Amendment , and in 2013 the County entered a CSO consent decree with Ecology, EPA, and

the DOJ. Both the LTCP and CD include nine CSO control projects to reduce CSOs to no more than one untreated event per year on ave rage at each CSO location by 2030

. Table 3

outlines future CSO control p rojects as presented in the County’s 2012 CSO Long Term

Control Plan Amendment and 2013 consent decree.Fact Sheet for NPDES Permit WA 0029181 Page 15 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 3

. Future CSO Projects

Project Name Project Description Project Completion Water Body

Hanford #1 (DSN 031) 0.34 MG storage and new conveyance 2019 Duwamish River

Brandon Street / South Michigan Street (DSN 041/039) 66 MG peak

- flow CSO treatment facility and new conveyance 2022 Duwamish River

Chelan Avenue (DSN 036) 3.85 MG storage tank 2023 Duwamish River

3 rd Avenue W (DSN 008) Joint City

- County 7.23 MG storage tank

or County

- only 4.18 MG storage tank 2023 West Ship Canal

West Michigan Street / Terminal 115 (DSN 042/038) 0.32 MG storage pipe 2025 Duwamish River

University/Montlake
(DSN 015) Joint City

- County 5.23 MG storage tank

or County

- only 2.94 MG storage tank 2028 Lake Union/ East Ship Canal

Montlake (DSN 014) Joint City

- County 7.87 MG storage tank

or County

- only 6.6 MG storage tank 2028 West Ship Canal

Hanford #2/ Lander Street/ K ing
Street/ Kingdome (DSN 032/030/028/029) 151 MG peak

- flow CSO treatment facility 2030 Duwamish River

11 th Avenue NW Increased conveyance providing 3,200
feet of 84

- inch diameter pipe 2030 West Ship Canal



### Inflow and Infiltration



### King County created a Regional Infiltration and Inflow (I/I) Control Program in 1999 as part of the Regional Wastewater Services Plan (RWSP) to explore the feasibility of regional I/I

control

. The purpose of the program is to reduce the amount of peak wet weather flow entering the County's wastewater conveyance system when it is cost

- effective to do so

. Reduction of I/I in the system may prevent sanitary sewer overflows and decrease the costs

of conveying and treating extraneous flows.

In response to the RWSP I/I Control Program policies, County staff, working in a

consensus

- based approach with the local sewer agencies, conducted a comprehensive 6

- year, $41 million, I/I control study

. The study b egan in 2000 and culminated with the County

Executive ’ s recommendation for a regional I/I control program

. The following work was completed as part of this study:

 L evels of I/I for each local agency tributary to the regional system were defined through ext ensive flow monitoring and modeling program (2001

- 2002).

 10 pilot projects were s elected and constructed in 12 local agency jurisdictions to demonstrate the effectiveness of collection system rehabilitation projects and to test various technologies and gain cost information (2003

- 2004).

 F inal draft model standards, procedures, policies, and guidelines were developed (October 2004) for use by local agencies to reduce I/I in their systems.

 A thorough benefit

- cost analysis was conducted to determine the co st

- effectiveness of I/I reduction (November 2005).

 A long

- term regional I/I control plan was developed; appro ved by the King County Council in May 2006

.Fact Sheet for NPDES Permit WA 0029181 Page 16 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



###  King County worked with the local sewer agencies to conduct an I/I reduction feasibility analysis and selected three initial I/I reduction project areas (2007

- 2009).

 T he Skyway Water and Sewer District I/I reduction project (2010

- 201 4 ).

The County is currently a naly zing the effectiveness of the Skyway Initial I/I Reduction Project (“Demonstration Project” )

. The p roject set out to rehabilitate close to 350 side sewers on private property, aiming to reduce flows by at least 60%, or about 1 MGD, in a Skyway

Water and Sewer District basin

. This reduction predict ion was based conservatively on the

reduction a ch ieved in a similar, adjacent pilot project completed in 2003/4 , in which I/I peak flow was reduced by 88.5%. For the Skyway Project , a 60% f low reduction would eliminate

the need for the downstream 0 .27 MG Bryn Mawr Storage Project. Project results fell sh ort of the goal, with peak flows reduced by only 19% in the project basin. There are many complex reasons for this lower than expected flow reduction , most of which are contributed

to basin

- specific characteristics and conditions encountered during construction. One unique challenge was the discovery of a previously unrecognized flow diversion that sent flows from an adjacent basin into the project basin, diluting flow reduction results when flow mon itoring was conducted. Other challenges include the effects of sump pumps and foundation drains, groundwater entering unrehabilitated side sewers downslope in the basin, and a higher than anticipated number of sewers being left out of the project for repla cement due to field conditions. While the full reduction target was not met, it is still estimated that the sizing or timing of the storage project were beneficially affected by the Skyway project. Continued flow monitoring and modeling will determine the ultimate storage requirements, at which point the resulting benefit of the I/I reduction can be determined. For more information see the full report on the County’s I/I Program website

.

T reatment p rocesses

West Point WWTP



### The West Point WWTP is a 215

- million

- gallon per day (maximum month design flow) high rate oxygen activated sludge secondary plant

. Metro designed the plant to provide secondary treatment of flows up to 300 MGD

. The liquid treatment process includes screening, grit removal, primary clarification, biological treatment using high rate oxygenated activated sludge, secondary clarification, chlorine disinfection, and dechlorination

. The disinfected effluent discharges to Puget Sound through a multi

- port diffuser located about 3,600 feet offshore at a depth of about 240 feet below mean lower low water

. For flows above 300 MGD and up to 440 MGD, the treatment process consists of screening, de

- gritting, primary sedimentation in clarifiers, disinfection with sodium hypochlorite in a chlorine contact channel, and dechlorination

. As for solids treatment, the primary and waste activated solids

are blended in a tank and co

- thickened via gravity belt thickeners

. The thickened sludge is anaerobically digested, and dewatered by centrifuges

. The plant produces several products including biosolids used in agriculture and forestry, reclaimed water used for in

- plant processes and irrigation, and methane that fue ls the raw sewage pump engines and power generation system

. A schematic of the treatment proces s is p resented in Appendix H

. King County indicated i n their permit application that 29 non

- categorical significant

industrial users (SIUs) and 19 categorical SIUs contribute to the collection system . Th ese number s are down from five years ago when King County reported 33 non

- categorical SIUs and 31 categorical SIUs. See Appendix G for a listing of the significant users.Fact Sheet for NPDES Permit WA 0029181 Page 17 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### The West Point WWTP is rated as a Class IV plant

. The West Section employs personnel in operations, maintenance, facilities, process control, laboratory analysis, administration , and

off

- site operations and maintenance

. The section consists of approximately 156 FTEs with 10 to 15 vacancies at any given time

. Operations staff consists of about 70 employee s, where 21 employees have Group IV certifications, 21 have Group III certifications, 13 have Group II certifications, and 11 have Group I certifications

. Wet Weather Operation

- The proposed p ermit authorizes CSO

- related bypasses of the secondary treatme nt portion of the West Point WWTP when the instantaneous flows to the WWTP exceed 300 MGD as a result of precipitation. The wastewater that bypasses secondary treatment must receive floatables removal, primary clarification, and disinfection,

and must at a ll times meet the effluent limits listed in S1. See Section III.A of this fact sheet

for more information on wet weather authorization.

Alki CSO Treatment Plant



### The Alki CSO treatment plant operates only when flows in the Alki service area exceed 18.9

MGD or when the storage in the tunnel has been filled

. The County diverts the base flow to the West Seattle Pump Station, then directly to the West Poi nt WWTP for secondary

treatment

. The County diverts wet weather flows in excess of 18.9 MGD or 7.1 million gallons of storage (West Seattle Tunnel) to the Alki CSO treatment plant for treatment

. Treatment consists of disinfection using sodium hypochlorite, screening, and primary

sedimenta tion followed by dechlorination with sodium bisulfite

. Treated flows discharge to the Puget Sound through the existing outfall.

Flows in excess of the Alki CSO treatment plant capacity discharge through the 63rd Avenue pump station outfall, which is a perm itted CSO located upstream of the treatment plant

. King County is already meeting the Ecology standard of no more than one untreated overflow per year at this location.

Treatment plant solids and grit are conveyed to the Alki Trunk for transfer to the West Seattle Tunnel and further conveyance to West Point WWTP

. S creenings are collected

, stored on

- site, and disposed of as solid waste

.

Carkeek CSO Treatment Plant



### During dry weather and normal flows, the facility operates as a pump station only, pumping

wast ewater to the West Point WWTP. The Carkeek CSO treatment plant operates only during storm events when the combined sanitary/stormwater flow s exceed the Carkeek Pump

Station capacity (9.2 MGD), or when the downstream interceptor is full

. The plant stores

ex cess flows, solids

, and grit , and then automatically returns them to the pump station wet well when there is capacity available at the pump station, or at the end of the storm

. T he pump station the n pumps flow to the West Point WWTP.

If flows exceed the st orage capacity of the treatment tanks , treated flows discharge to Puget

Sound through a 4,200

- foot long outfall

. After the storm event, or when there is capacity available at the pump station , any wastewater in the plant is pumped to the West Point WWTP.

T he treatment process consists of bar screens, a grit chamber, primary sedimentation, disinfection with sodium hypochlorite, and dechlorination with sodium bisulfite. When pumping capacity is exceeded wastewater spills over the pump wet well weir into the v ault where hypochlorite is added to control odors and provide disinfection. From the vault wastewater flows into the grit tank that is equipped with aerators; settled grit is pumped to the solids storage tanks. From the grit tanks, the wastewater flows into two primary sedimentationFact Sheet for NPDES Permit WA 0029181 Page 18 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### tanks. Solids settled in the primary sedimentation tanks are also pumped to the solids storage

tanks

. When both sedimentation tanks are ful l, wastewater flows into the contact tank for

dechlorination , and from there over a weir to the outfall in Puget Sound.

Elliott West CSO Storage and Treatment Facility



### The Elliott West CSO storage and treatment facility and associated conveyance facilitie s work to reduce CSOs to south, east, and west Lake Union and to Elliott Bay at the Denny Way Regulator Station

. King County operates the facility in five modes depending on the magnitude of the rain event

. The operating modes are as follows 1 

### :

Standby Mode (Dry Weather Operation)

- Under dry weather conditions, the facility does not

divert flow

. Wastewater continues to flow through the Lake Union Tunnel and other conveyance

facilities to the Ellio tt Bay Interceptor (EBI) to be treated at the West Point WWTP

. The Mercer Tunnel is empty so that the storage capacity is maintained for storm event s

. Tunnel Storage Mode

- During storm conditions, when water levels rise to established level s in the Lake Union Tunnel Regulator, Central Trunk Diversion Structure, and /or Denny Way Diversion Structure, the County diverts flow from these structures to the Mercer Street

Tunnel for storage

. After the storm, or when ever the EBI has capacity , stored wastewater is pumped to West Point

. Wastewater that previously discharged into Elliott Bay or Lake Union

CSOs now is captured in the Mercer tunnel.

CSO Pumping and Treatment Mode

- When tunnel storage and the EBI reach capacity

, Elliott West treatment begins

. Flow is pumped from the downstream end of the Mercer

Tunnel into the floatable

- control channel

. The wastewater flows through mechanical screens to remove floatable materials, then into the effluent channel for injection with sodium hypochlorite for disinfection

. Prior to discharge into Elliott Bay, the treated was tewater is

treated with sodium bisulfite to neutralize residual chlorine. Throughout this pump and treatment mode, the County pumps solids from the base of tunnel to the EBI, reducing the discharge of solids to the Puget Sound.

Pumping and Treatment Extrem e Event Mode

– The County designed the CSO treatment plant with a capacity of 250 MGD, for the one

- event

- per

- year storm

. When flows exceed 250

MGD untreated wastewater discharge s from the Denny Way Regulator Station via the extended Denny Way CSO outfall

. Flows entering the Mercer Street Tunnel in exce ss of 250

MGD can overflow with no floatables control or disinfection

. Meanwhile , 250 MGD of

treated effluent continues to discharge th rough the Elliott West outfall.

Dewatering Mode (Tunnel Drawdown)

- Follow ing a CSO event, when capacity is available

in the EBI , wastewater stored in the tunnel is pumped to the EBI and conveyed to the West

Point WWTP for secondary treatment. Solids that settled in the tunnel during the event are

also flushed to West Point WWTP

.

Henderson/MLK CSO Treatment and Storage Facility



### King County’s East Section operates and maintains the Henderson /MLK CSO storage and

t reatment facility . The facility reduces CSO discharges to Lake Washington and the

Duwamish River. The Henderson/MLK tun nel is 14’8” in diameter and 3100 feet long and holds 3.5 million gallons of combined wastewater. The different operating modes for the facility depend on the rain event magnitude as follows:

1 King County and City of Seattle, Denny Way/Lake Union CSO Control Facilities Plan , July 1998.Fact Sheet for NPDES Permit WA 0029181 Page 19 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Inlet Regulator Operation

- The Henderson/MLK tunnel inlet regulator accepts flows from the Henderson pump station and the Empire Way Trunk. Under typical, non

- storm

- event flow conditions wastewater flows through the Henderson tunnel inlet regulator, to the Henderson Street Trunk on Martin Luther King Way, to the Henderson Diversion structure, and then on to South Plant for treatment. When the conveyance line reaches capacity, the MLK regulator gate closes, filling the regula tor station until combined sewage flows over a weir into the Henderson/MLK tunnel.

Storage Mode

- The tunnel stores combined sew age during peak flow events, and as long as the tunnel capacity is not exceeded, the combined sew age is returned to the collection system for additional treatment at a WWTP. Hypochlorite is injected automatically upon flow overtopping the tunnel ’ s inlet weir. The hypochlorite feed rate is controlled automatically based on the quantity of combined sew age entering the tunnel. After a filling event, when the trunk line returns to a specified level, the modulating drain val ve opens and slowly drains the

tunnel. The tunnel is drained such that the stored flows can be diverted at the Henderson Diversion Structure to either South Plant or West Point. After draining, the County has the ability to flush settled solids from the tu nnel into the Henderson Trunk to convey them to a

WWTP for treatment.

Treated CSO

- In the event that the tunnel reaches capacity and wastewater continues to flow into the tunnel, the combined sew age flows over the discharge weir and discharges by gravity through two bar screens, where it is dechlorinated, then flows to the Norfolk outfall (044) on the Duwamish River at river km 10.5. After the storm event, combined sewage remaining in the tunnel is drained into the Henderson Trunk and conveyed to a WWTP fo r treatment.

Solid wastes

/Residual s olids

West Point WWTP



### The treatment facilities remove solids during the treatment of the wastewater at the headworks (grit, screenings, debris, rags), and at the primary and secondary clarifiers , in addition to

incident al solids (rags and other debris) removed as part of the routine maintenance of the equipment

. The plant generates approximately 3,500 tons of grit annually

. Grit, rags, and screenings are drained and recycled or disposed of as solid waste

. The County inst alled new influent screens with 3/8 inch openings in 2014 . As a result of these new screens, the capture of screenings, rags, and debris is expected to increase.

Primary sludge and waste

- activated sludge are blended together and thickened by gravity belt

t hickeners

. The thickened sludge is then pumped to one

- of

- six anaerobic, mesophilic digesters

. From the digesters, the digested sludge is withdrawn and dewatered by one

- of

- four centrifuges

. Polymers are used in the gravity belt thickener s and centrifuges to aid sludge thickening/dewatering

. The digestion process produces nutrient

- rich, organic byproducts called biosolids.

According to the County’s 20 12 Biosolids Quality Report , biosolids contain water, sand, organic mat ter, microorganisms, trace metals, and other chemicals

. The report states, “ b ecause of their moisture content, humus

- like characteristics, essential nutrients for plants, and very low levels of pollutants, biosolids are beneficial and safe to use as a soil conditioner, fertilizer for

forest tre es and agricultural crops, and as an ingredient of composts for landscaping.”Fact Sheet for NPDES Permit WA 0029181 Page 20 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### King County Was tewater Treatment Division began recycling biosolids on land in 1973

. The program has grown to beneficially recycle more than 110,000 wet tons (or approximately 27,000 dry tons) annually in forestry, agriculture, soil reclamation and compost.

Biosolids are regulated under both state and federal regulations (WAC 173

- 308 and 40 CFR Part 503)

. King County routinely monitors its biosolids for physical, chemical, and m icrobial characteristics, to examine changes over time, and to determine appropriate application rates

for biosolids at reuse sites

. The County’s West Point biosolids continue to meet quality standards for metals, pathogen reduction (Class B), and vector a ttraction reduction, which means it is safe for all land application projects.

The 2012 data report indicates that King County’s biosolids quality is excellent when compared with all relevant criteria

. Concentrations of regulated metals in biosolids were

c onsistently below the most stringent state and federal standards for land application

. While not required by federal or state biosolids regulations, King County analyzes its biosolids for 135 trace organic compounds listed on the EPA Priority Pollutant Lis t (40 CFR 423, Appendix A) and the Hazardous Substances List (40 CFR 116.4 A & B)

. Less than

15 percent of these compounds were detected in biosolids during 2007

. The County detected twenty priority pollutants at very low concentrations in the West Point b iosolids

. These compounds included polynuclear aromatic hydrocarbons (PAHs), phthalates, polychlorinated biphenyls (PCBs), and solvents.

CSO Treatment Plant

s



### For the Alki and Carkeek CSO facilities, grit and primary sludge settle in the storage tanks

. Afte r the storm subsides, t he storage tank contents, solids and liquids, are pumped to the

West Point WWTP for treatment.

F or the Elliott West and Henderson/MLK facilities, solids settle in t he storage tunnels

. Following each storm event, s olids in the Mercer Tunnel are automatically flushed and pumped to the West Point WWTP and solids in the Henderson/MLK Tunnel are flushed and pumped to the South Plant or West Point WWTP for treatment.

Discharge outfall

s

West Point WWTP Outfall



### T he plant discharges treated effluent to the Puget Sound via an eight

- foot diameter, reinforced concrete pipe

. The diffuser section consists of 600 feet of pipeline with 200 ports that run on the north and south sides of the pipe

. The 4.5

- to 5.75

- inch diameter ports are

located about one foot above the spring line

. The diffuser terminates about 3,600 feet offshore at a depth of approximately 230 feet below mean lower low water.Fact Sheet for NPDES Permit WA 0029181 Page 21 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 2 . West Point WWTP outfall location



### A 2004 outfall inspection revealed that all external components of the outfall appear ed to be in good condition with no physical damage or lack of flow coming from the diffusers

. The inspectors found minimal m arine growth along the outfall alignment with slightly more

lo cated in the diffuser area.

King County inspected the West Point outfall and diffuser again on September 14, 2011

, and provided Ecology with a report with video. The inspectors observed that the outfall line was completely buried from a rock pile at 196 fe et of water to the shoreline. The inspectors found gaps in the pipeline around station 30 but they no ted that no effluent appeared to be discharging from these gaps. Overall they found the outfall pipe in good condition with heavy sea anemone growth along the deeper sections. No remedial actions were

recommended. The proposed permit requires another inspection during the permit term.

Alki CSO Treatment Plant Outfall



### The Alki CSO treatment plant discharges p rimary treated and disi nfected CSO effluent to the Puget Sound via a 42

- inch diameter pipe, which extends approximately 2,000 feet offshore and terminates at a depth of approximately 143 feet below mean lower low water

. The

diffuser is fitted with eight 1 2 inch diameter risers/ports, with rubber check val ves, spaced 20 feet apart in alternating direction s . The two end ports discharge at an angle of 135  with respect to the other risers/ports

. Engineers rated the outfall capacity at 45 MGD at mean higher high water and 65 MGD at mean lower low water

. Flows in excess of these values discharge via the 63rd Avenue Pump Station outfall, a permitted CSO location.Fact Sheet for NPDES Permit WA 0029181 Page 22 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 3 . Alki CSO treatment plant outfall location



### Carkeek CSO Treatment Plant Outfall



### The Carkeek CSO treatment plant discharges p rimary treated and disinfected CSO effluent to
the Puget Sound via a 33

- inch diameter 4,200

- foot outfall, which extends approximately 2,200 feet offshore and terminates at a depth of 195 feet below mean lower low water

. The

outfall consists of a 50 foot diffuser with 13 ports

.

Figure 4 . Carkeek CSO treatment plant outfall location



### Elliott West CSO Storage and Treatment Outfall



### The Elliott West CSO treatment plant discharges primary treated and disi nfected CSO effluent to Elliott Bay via a 96

- inch diameter outfall

, which extends 400 feet offshore and terminates at a depth of 60 feet below mean lower low water

. During large storm events when the Mercer tunnel and Elliott West facility capacities are exceeded, the Denny Regulator Station discharges untreated CSO water to Elliott Bay via the Denny CSO outfall. The 120

- inch Denny CSO outfall extends 100 feet offshore a nd terminates at a depth of 20 feet be low mean lower low water

.Fact Sheet for NPDES Permit WA 0029181 Page 23 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 5 . Elliott West CSO treatment plant outfall location



### Henderson/MLK CSO Treatment and Storage Outfall



### T he Henderson/MLK CSO facility discharges primary treated and disinfected CSO effluent

t o the Duwami sh River through the existing Norfolk outfall

. The Norfolk outfall is located on

the north bank of the Duwamish River at approximately river km 10.5

. The 84

- inch diameter outfall approaches the river bank at a 90

- degree angle to the river flow and is flush with the

bank

. The outfall terminates with a flap gate that is assumed to be completely open during discharge events. 2



### Combined Sewer Overflow Outfalls



### Table 4 lists King County’s 38 combined sewer overflows outfalls (not including the CSO treatment plant outfalls), which have the potential to discharge untreated sewage and

stormwa ter during precipi tation events

. Based on monitoring data in King County’s 2012 Annual CSO Report and King County’s 2012 Long Term Control Plan Amendment

, 16 of the

38 CSO outfalls meet the controlled performance standard of “greatest reasonable reduction”

as defined in cha pter WAC 173

- 245

- 020(22). Table 4 provides project status for the uncontrolled outfalls as described in King County’s 2012 Long Term Control Plan

Amendment

.

2 King County, Department of Natural Resources, Wastewater Treatment Division, Henderson/M.L. King CSO Control
Facilities Plan, February 2002. Chapter 22, pg. 2

.Fact Sheet for NPDES Permit WA 0029181 Page 24 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 6 . Henderson/MLK CSO treatment plant outfall location

Table 4 . Combined Sewer Overflow Outfalls (38)

Outfall

No. Outfall Name Receiving Water Control
Status Project Status

003 Ballard Siphon Regulator Lake Washington Ship Canal Uncontrolled Control project completed in

December 2013.

004 11 th Avenue NW ( East Ballard Overflow) Lake Washington Ship Canal Uncontrolled Overflow r eduction project underway

. 006 Magnolia South Overflow Elliott Bay/Puget
Sound Uncontrolled Control project underway

.

007 Canal Street Overflow Lake Washington Ship Canal Controlled

008 3 rd Avenue West Overflow Lake Washington Ship Canal Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

009 Dexter Avenue Regulator Lake Union Uncontrolled Control project completed. Full control being achieved by operational adjustments and upstream GSI

. 011 E

. Pine Street PS Emergency
Overflow Lake Washington Controlled

012 Belvoir PS Emergency Overflow Lake Washington (Union Bay) Controlled

013 Martin Luther King Way
Trunkline Overflow Lake Washington Controlled

014 Montlake Overflow Lake Washington Ship Canal Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

015 University Regulator Lake Wash Ship
Canal (Portage Bay) Uncontrolled Overflow reduction project completed in 1994. Control project in KC’s Recommended CSO Control Plan.

018 Matthews Park PS Emergency
Overflow Lake Washington Controlled

027a Denny Way Regulator Elliott Bay/Puget
Sound Uncontrolled Control project completed. Full control being achieve d by operational adjustment and facility
mods

.Fact Sheet for NPDES Permit WA 0029181 Page 25 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 4 . Combined Sewer Overflow Outfalls (38)

Outfall

No. Outfall Name Receiving Water Control
Status Project Status

028 King Street Regulator Elliott Bay/Puget
Sound Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

029 Kingdome ( Connecticut St Regulator) Elliott Bay/Puget
Sound Uncontrolled Installation of a storage pipeline in

1994. Partial separation in 1999

. Control project in KC’s
Recommended CSO Control Plan.

030 Lander Street Regulator Duwamish River

– East Waterway Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

031a ,b

,c Hanford #1 Regulator Duwamish River

– East Waterway Uncontrolled Overflow reduction project completed in 1992. Final control project included in KC’s
Recommended CSO Control Plan.

032 Hanford #2 Regulator Duwamish River

– East Waterway Uncontrolled Control project in KC’s
Recommended CSO Control Plan

. 033 Rainier Avenue PS Emergency
Overflow Lake Washington Controlled

034 E. Duwamish Siphon/Duwamish
PS Emergency Overflow Duwamish River Controlled

035 W

. Duwamish Siphon/Duwamish PS Emergency Overflow Duwamish River Controlled

036 Chelan Avenue Regulator Duwamish River

– West Waterway Uncontrolled Control project in KC’s
Recommended CSO Control Plan

. 037 Harbor Avenue Regulator Duwamish River

– West Waterway Uncontrolled Control project completed.
CSO site appears controlled

– Modeling confirmation underway

. 038 Terminal 115 Overflow Duwamish River Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

039 Michigan S. Regulato r Duwamish River Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

040 8 th Avenue South Regulator (West Marginal Way PS Emergency Overflow) Duwamish River Controlled

041 Brandon Street Regulator Duwamish River Uncontrolled Overflow reduction project completed in 2003. Final control project included in KC’s
Recommended CSO Control Plan.

042 Michigan W. Regulator Duwamish River Uncontrolled Control project in KC’s
Recommended CSO Control Plan.

043 East Marginal Way PS Emergency Overflow Duwamish River Controlled

044a Norfolk Street Regulator Duwamish River Controlled

045 Henderson Street Pump Station Emergency Overflow Lake Washington Controlled

048 North Beach PS Emergency
Overflow Puget Sound Uncontrolled Control project underway

049 30 th Avenue N.E. PS Emergency Overflow L. Wash

. Ship Canal (Union Bay) Controlled

053 53 rd St SW PS Emerg

. Overflow Puget Sound Controlled

054 63 rd St SW PS Emerg

. Overflow Puget Sound Controlled

055 S.W. Alaska Street Overflow Puget Sound Controlled

056 Murray St PS Emerg

. Overflow Puget Sound Uncontrolled Control project underway

057 Barton St PS Emerg

. Overflow Puget Sound Uncontrolled Control project underwayFact Sheet for NPDES Permit WA 0029181 Page 26 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### B. Description of the r eceiving w ater

King County submitted ambient background data with the ir permit application in a report

called Receiving Water Characterization Study (June 2013). This report presented results of a characterization study of a mbient receiving water in central Puget So und, Elliott Bay, and the

Duwamish River.

West Point WWTP



### The West Point WWTP outfall discharges to central Puget Sound

. Other nearby point source

outfall s include King County’s South Plant outfall and Bainbridge Island’s WWTP outfall. Significant nearby non

- point sources of pollutants include stormwater runoff, industrial runoff, and maritime uses. Water quality impairments for this waterbody are discussed in

Section III.E of this fact sheet.

Ecology used a mbient data from sampling stat ion KSBP01 in King County's receiving water study to assess compliance with water quality standards. This sampling station is loca ted six

miles north of the West Point outfall (47. 743960  ̊,

- 121.4 28169  ̊)

.

Table 5

. West Point Ambient Background Data 1

Parameter Value

Temperat ure (h ighest annual 1

- DADMax) 1 4.0 o C (at 1.3 m below surface)

pH (Minimum / Maximum ) 7. 5 / 8. 0 s td units

Salinity ( minimum ) 26

. 1 p ss
Dissolved Oxygen ( 10 th percentile ) 6.1 mg/L

Total Ammonia (max ) 0.085 mg/L as N (from LSNT01)

Fecal Coliform (max) 4 / 100 m L

TSS ( max) 7 mg/L

Arsenic (90th percentile), Dissolved / Total 2 1.390 / 1.360 μg/L

Cadmium (90th percentile), Dissolved / Total 0.073 / 0.081 μg/L

Chromium (90th percentile), Dissolved / Total 0.148 / 0.159 μg/L

Copper (90th percentile), Dissolved / Total 0.363 / 0.410 μg/L

Lead (90th percentile), Dissolved / Total 0.005 / 0.044 μg/L

Mercury (90th percentile), Dissolved / Total 0.00020 / 0.00048 μg/L

Nickel (90th percentile), Dissolved / Total 0.424 / 0.437 μg/L

Silver (90th percentile), Dissolved / Total 0.027 / 0.028 μg/L

Zinc (90th percentile), Dissolved / Total 0.643 / 0.685 μg/L

1 Data s ource: King County Receiving Water Characterization Study

- Final Report , June 2013

. 2 Data reported in 2013 report shows 90 th percentile of dissolved fraction as slightly larger than total

concentration. This discrepancy is likely within the precision of the analytical method.



### Alki CSO Treatment Plant



### The Alki CSO treatment plant discharges to the Puget Sound

. Another nearby point source

outfall includes King County’s South Plant outfall. Significant nearby non

- point sources of pollutants include stormwater runoff.

Ecology used ambient data from sampling statio n LSNT01 in King County's receiving water study to assess compliance with water quality standards. This sampling station is located

three miles south of the Alki outfall (47. 533333  ̊,

- 121.4 33333  ̊).Fact Sheet for NPDES Permit WA 0029181 Page 27 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 6 . Alki Ambient Background Data 1

Parameter Value

Temperat ure (h ighest annual 1

- DADMax) 12.7 o C (at 1.3 m below surface)
pH (Minimum / Maximum) 7.4 / 8.0 std units
Salinity (minimum) 27.7 pss
Alkalinity (10 th percentile) 97.5 mg/L CaCO 3 Dissolved Oxygen (10 th percentile) 5.8 mg/L
Total Ammonia (max) 0.085 mg/L as N
Fecal Coliform (max) 1 / 100 mL
TSS (max) 7.5 mg/L
Antimony (90th percentile ), Dissolved / Total 0.172 / 0.178 μg/L
Arsenic (90th percentile), Dissolved / Total 1.450 / 1.450 μg/L
Cadmium (90th percentile), Dissolved / Total 0.073 / 0.081 μg/L
Chromium (90th percentile), Dissolved / Total 2 0.150 / 0.145 μg/L

Copper (90th percentile), Dissolved / Total 0.354 / 0.428 μg/L

Lead (90th percentile), Dissolved / Total 0.006 / 0.045 μg/L
Mercury (90th percentile), Dissolved / Total 0.00020 / 0.00038 μg/L
Nickel (90th percentile), Dissolved / Total 0.427 / 0.476 μg/L
Silver (90th percentile), Dissolved / Total 0.026 / 0.029 μg/L
Zinc (90th percentile), Dissolved / Total 2 0.605 / 0.538 μg/L

1 Data source: King County Receiving Water Characterization Study

- Final Report , June 2013.
2 Data reported in 2013 report shows 90 th percentile of dissolved fraction as slightly larger than total concentration. This discrepancy is likely within the precision of the analytical method.



### Carkeek CSO Treatment Plant



### The Carkeek CSO treatment plant discharges to Puget Sound

. Pipers Creek al so discharges to Puget Sound and affects water quality in this area. Significant nearby non

- point sources of pollutants include stormwater runoff.

Ecology used ambient data from sampling station KSBP01 in King County's receiving water study to assess compl iance with water quality standards. This sampling station is located two
miles northwest of the Carkeek outfall (47. 743960  ̊,

- 121.4 28169  ̊).

Table 7

. Carkeek Ambient Background Data 1

Parameter Value

Temperat ure (h ighest annual 1

- DADMax) 14.0 o C (at 1.3 m below surface)
pH (Minimum / Maximum) 7.5 / 8.0 std units
Salinity (minimum) 26.1 pss
Dissolved Oxygen ( 10 th percentile ) 6.1 mg/L

Total Ammonia (max) 0.085 mg/L as N

Fecal Coliform (max) 4 / 100 mL

TSS (max) 7 mg/L

Arsenic (90th percentile), Dissolved / Total 2 1.390 / 1.360 μg/L
Cadmium (90th percentile), Dissolved / Total 0.073 / 0.081 μg/L
Chromium (90th percentile), Dissolved / Total 0.148 / 0.159 μg/L
Copper (90th percentile), Dissolved / Total 0.363 / 0.410 μg/L
Lead (90th percentile), Dissolved / Total 0.005 / 0.044 μg/L
Mercury (90th percentile), Dissolved / Total 0.00020 / 0.00048 μg/L

Nickel (90th percentile), Dissolved / Total 0.424 / 0.437 μg/L
Silver (90th percentile), Dissolved / Total 0.027 / 0.028 μg/L
Zinc (90th percentile), Dissolved / Total 0.643 / 0.685 μg/L

1 Data source: King County Receiving Water Characterization Study

- Final Report , June 2013.
2 Data reported in 2013 report shows 90 th percentile of dissolved fraction as slightly larger than total concentration. This discrepancy is likely within the precision of the analytical method.Fact Sheet for NPDES Permit WA 0029181 Page 28 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Elliott West CSO Treatment Plant



### The Elliott West CSO treatment plant outfall discharges to Elliott Bay

. Significant nearby

non

- point sources of pollutants include stormwater runoff and maritime uses.

Ecology used ambient data from sampling station LTED0 4 in King County's receiving water study to assess compliance with water quality standards. This samp ling station is located one mile west of the Elliott West outfall (47. 603642  ̊,

- 121. 356514  ̊).

Table 8 . Elliott West Ambient Background Data

Parameter Value

Temperat ure (h ighest annual 1

- DADMax) 13

. 4 o C (at 1 m below surface)

pH (Minimum / Maximum) 7.4 / 8.0 std units

Salinity (minimum) 2 4

. 0 pss
Dissolved Oxygen ( 10 th percentile ) 5.7 mg/L

Total Ammonia (max) 0.085 mg/L as N (from LSNT01)

Fecal Coliform (geometric mean ) 2 / 100 mL

TSS (max) 8.1 mg/L

Arsenic (90th percentile), Dissolved / Total 1.388 / 1.407 μg/L

Cadmium (90th percentile), Dissolved / Total 0.072 / 0.079 μg/L

Chromium (90th percentile), Dissolved / Total 0.139 / 0.167 μg/L

Copper (90th percentile), Dissolved / Total 0.487 / 0.696 μg/L

Lead (90th percentile), Dissolved / Total 0.005 / 0.066 μg/L

Mercury (90th percentile), Dissolved / Total 0.00020 / 0.00039 μg/L

Nickel (90th percentile), Dissolved / Total 0.432 / 0.464 μg/L

Silver (90th percentile), Dissolved / Total 0.028 / 0.032 μg/L

Zinc (90th percentile), Dissolved / Total 0.995 / 0.903 μg/L

Data s ource: King County Receiving Water Characterization Study

- Final Report , June 2013

.



### Henderson/MLK CSO Treatment Plant



### The Henderson/MLK CSO treatment plant outfall discharges to the Duwamish waterway

. This discharge shares an outfall with Seattle’ s Norfolk stormwater outfall. Ano ther

s ignificant nearby source of pollutants is Boeing’s industrial stormwater outfal l

. Ecology used ambient da ta from sampling station LTXQ01 in King County's receiving water study to assess compliance with water quality standards. This sampling station is located approximately 600 feet downstream of the Henderson/MLK o utfall (47. 512269  ̊,

- 121.29970  ̊).Fact Sheet for NPDES Permit WA 0029181 Page 29 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Tab le 9

. Henderson/MLK Amb ient Background Data 1

Parameter Value

Temperat ure (h ighest annual 1

- DADMax) 18.7 o C (at 1 m below surface)

pH (Minimum / Maximum) 6. 8 / 7.3 std units

Salinity (minimum , 1⁄2 of DL ) 1

. 0 pss
Dissolved Oxygen ( 10 th percentile ) 7.5 mg/L

Fecal Coliform (max , minus outlier ) 110 / 100 mL

TSS ( 90 th percentile ) 20 mg/L

Arsenic (90th percentile), Dissolved / Total 0.555 / 0.796 μg/L

Cadmium (90th percentile), Dissolved / Total 2 0.020 / 0.018 μg/L

Chromium (90th percentile), Dissolved / Total 0.084 / 0.215 μg/L

Copper (90th percentile), Dissolved / Total 0.551 / 1.195 μg/L

Lead (90th percentile), Dissolved / Total 0.025 / 0.243 μg/L

Mercury (90th percentile), Dissolved / Total 0.00076 / 0.00175 μg/L

Nickel (90th percentile), Dissolved / Total 2 0.966 / 0.934 μg/L

Silver (90th percentile), Dissolved / Total 0.021 / 0.044 μg/L

Zinc (90th percentile), Dissolved / Total 1.135 / 1.810 μg/L

1 Data source: King County Receiving Water Characterization Study

- Final Report , June 2013.

2 Data reported in 2013 report shows 90 th percentile of dissolved fraction as slightly larger than total concentration. This discrepancy is likely within the precision of the analytical method.



### C

. Wastewater i nfluent c haracterization

King County reports influent pollutant concentration s in discharge monitoring reports. The following tables summarize influent wastewater quality for each facility for the period between July 2009 and October 2013

.

Table 10 . Influent Characterization

- West Point WWTP

Parameter Units # of Samples Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈260 1 93 270

lbs/day ≈260 137,112 168,700

CBOD 5 mg/L ≈1800 165 227

lbs/day ≈1800 117,115 147,500

TSS mg/L ≈1800 221 293

lbs/day ≈1800 161,975 191,645

Table 11 . Influent Characterization

- Alki

Parameter Units # of Samples Average Maximum

Volume MG 19 1 3.7 5 0.7

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈20 36 93

TSS mg/L ≈2 0 89 213Fact Sheet for NPDES Permit WA 0029181 Page 30 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 12 . Influent Characterization

- Carkeek

Parameter Units # of Samples Average Maximum

Volume MG 2 3 3 .8 1 8.5

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈25 147 658

TSS mg/L ≈25 208 1,016

Table 13 . Influent Characterization

- Elliott West

Parameter Units # of Samples Average Maximum

Volume MG 41 42 .5 200

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈ 41 77 391

TSS mg/L ≈ 41 150 706

Table 14 . Influent Characterization

- Henderson/MLK

Parameter Units # of Samples Average Maximum

Volume MG 11 4.7 2 0.8

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈ 11 23 45

TSS mg/L ≈11 55 104



### D. Wastewater e ffluent c haracterization

King County reported the concentration of pollutants in the discharge in the permit application and in discharge monitoring reports. The following tables summarize effluent quality for each facility from 2009

- 2013. The priority pol lutant data presented contains only detectable compounds and elements with existing water quality criteria

. More data is available in Appendix E

.Fact Sheet for NPDES Permit WA 0029181 Page 31 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 15 . Effluent Characterization

– West Point WWTP

Parameter Units # of Samples Maximum Average Monthly Maximum Average Weekly

C BOD 5 mg/L ≈200 14 27 lbs/day ≈200 13,000 33,200

TSS mg/L ≈200 21 45 lbs/day ≈200 21,500 61,300
Maximum Monthly Geometric Mean Maximum Weekly Geometric Mean

Fecal Coliform cfu/100 mL ≈200 16 45

Minimum Maximum pH Std Units continuous 6.0 7.8
Maximum Monthly Average Maximum Daily Maximum

Chlorine

, Total Residual μg/L continuous 139 340

Ammonia

, as N mg/L ≈ 60 29 32 lbs/day ≈ 60 19,867 27,700 Total Kjeldahl Nitrogen , as N mg/L ≈60 31 33

Nitrate + Nitrite , as N mg/L ≈60 10 10 Phosphorus, total , as P mg/L ≈60 3.4 3.4 Phosphate

, ortho, as P mg/L ≈60 4.0 4.9 Dissolved Oxygen Mg/L 3 8.4 10.6 Minimum Maximum
1,4

- Dichlorobenzene ug/L 9 1.0 10.2
2,4

- Dichlorophenol ug/L 9 0.12 0.96 2,4

- Dimethylphenol ug/L 9 0.24 0.48 Antimony, Total ug/L 15 0.30 0.63 Arsenic, Total ug/L 15 0.27 2.28 Bis(2

- Ethylhexyl)Phthalate ug/L 9 0.41 10.20 Boron, Total ug/L 8 110 200 Cadmium, Total ug/L 15 0.05 0.18
Chloroform ug/L 9 1.00 5.68 Chromium, Total ug/L 15 0.20 1.34 Copper, Total ug/L 15 0.40 16.30 Cyanide, w eak acid d iss

. mg/L 15 0.005 0.006 Diethyl Phthalate ug/L 9 0.120 0.850

Di

- N

- Octyl Phthalate ug/L 9 0.071 0.360 Iron, Total ug/L 8 110 661 Lead, Total ug/L 15 0.10 2.51 Magnesium, Total ug/L 8 6,040 10,300 Manganese, Total ug/L 8 8.7 71.1 Mercury, Total ug/L 27 0.002 0.016 Methylene Chloride ug/L 9 5.0 5.3 Molybdenum, Total ug/L 8 3.0 7.4 Naphthalene ug/L 9 0.14 0.76 Nickel, Total ug/L 23 0.1 6.5 Phenolics, Total mg/L 15 0.040 0.090 Potassium, Total ug/L 8 5,770 11,700 Pyrene ug/L 9 0.071 0.290 Selenium, Total ug/L 15 0.50 1.30 Silver, Total ug/L 15 0.04 0.15 Sodium, Total ug/L 8 34,200 54,700 Strontium, Total ug/L 8 107 277 Sulfur, Total ug/L 8 6,370 9,840 Thallium, Total ug/L 15 0.040 0.130 Titanium, Total ug/L 8 4.0 31.9

Toluene ug/L 9 1.0 1.1 Zinc, Total ug/L 23 10.7 54.2 Value Temperature

– 95 th percentile

1

- DADMAX °C continuous 2 1 .0Fact Sheet for NPDES Permit WA 0029181 Page 32 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 16 . Effluent Characterization

– Alki CSO TP

Parameter Units # of Samples Average Maximum

Volume MG 1 9 9.8 41.7

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈16 23 40

TSS mg/L ≈16 34 65

Maximum Monthly
Geometric Mean Maximum

Fecal Coliform cfu/100 mL 16 1 20,000

Minimum Maximum

pH Std Units continuous 5.8 8.4

Chlorine, Total Residual μg/L continuous 0 1708

Ammonia

, as N mg/L 1 2.18 2.18

Total Kjeldahl Nitrogen , as N mg/L 1 6.3 6.3

Nitrate + Nitrite , as N mg/L 1 0.8 0.8

Phosphorus, total , as P mg/L 1 0.84 0.84

Phosphate

, ortho, as P mg/L 1 0.6 0.6

Dissolved Oxygen mg/L 4 10.2 10.6

Hardness, calc mg CaCO 3 /L 1 35.6 35.6

Alkalinity, total mg CaCO 3 /L 1 40.2 40.2

Antimony, Total, ICP

- MS ug/L 7 0.48 0.7

Arsenic, Total, ICP

- MS ug/L 7 1.85 2.28

Benzyl Butyl Phthalate ug/L 7 0.071 0.43

Bis(2

- Ethylhexyl)Phthalate ug/L 7 0.46 3.65

Cadmium, Total, ICP

- MS ug/L 7 0.052 0.13

Chloroform ug/L 7 1.5 14

Chromium, Total, ICP

- MS ug/L 7 1.47 2.2

Copper, Total, ICP

- MS ug/L 7 8.93 12.3

Cyanide, weak acid diss. ug /L 6 5.0 18.3

Diethyl Phthalate ug/L 7 0.51 3.69

Lead, Total, ICP

- MS ug/L 7 2.55 4.7

Mercury, Total ug/L 7 0.021 0.025

Nickel, Total, ICP

- MS ug/L 7 2.83 3.37

Silver, Total, ICP

- MS ug/L 7 0.04 0.1

Zinc, Total, ICP

- MS ug/L 7 32.1 42.9

Value

Temperature

– 95 th
percentile 1

- DADMAX °C continuous No temp data available, used value from West

Pt WWTP effluent: 21 .0Fact Sheet for NPDES Permit WA 0029181 Page 33 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 17 . Effluent Characterization

– Carkeek CSO TP

Parameter Units # of Samples Average Maximum

Volume MG 23 3.2 17.4

Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈ 12 38 132

TSS mg/L ≈12 46 132

Minimum Monthly
Geometric Mean Maximum

Fecal Coliform cfu/100 mL 11 0 80,000

Minimum Maximum

pH Std Units continuous 5.1 7.9

Chlorine, Total Residual μg/L continuous 8 1370

Ammonia

, as N mg/L 4 1.66 3.35

Total Kjeldahl Nitrogen , as N mg/L 4 4.57 9.44

Nitrate + Nitrite , as N mg/L 4 1.18 2.15

Phosphorus, total , as P mg/L 4 0.67 1.18

Phosphate

, ortho, as P mg/L 4 0.51 0.90

Dissolved Oxygen mg/L 3 8.6 10.1

Hardness, calc mg CaCO 3 /L 4 35 48

Alkalinity, total mg CaCO 3 /L 4 27.5 49.3

2,4

- Dichlorophenol ug/L 9 0.12 0.89

Antimony, Total ug/L 10 0.47 1.03

Arsenic, Total ug/L 10 1.83 4.84

Benzo(b)fluoranthene ug/L 5 0.75 2.91

Benzo(k) fluoranthene ug/L 5 0.75 0.81

Benzyl Butyl Phthalate ug/L 9 0.14 4.46

Bis(2

- Ethylhexyl)Phthalate ug/L 9 0.41 3.65

Cadmium, Total ug/L 10 0.05 0.2

Chloroform ug/L 8 1.5 64.3

Chloromethane ug/L 8 1 1

Chromium, Total ug/L 10 0.91 5.68

Copper, Total ug /L 10 9.83 27.7

Cyanide, weak acid diss. ug/L 17 5.0 20.1

Di

- N

- Butyl Phthalate ug/L 9 0.12 0.63

Diethyl Phthalate ug/L 9 0.28 1.54

Lead, Total ug/L 10 1.55 11.3

Mercury, Total ug/L 10 0.05 0.051

Nickel, Total ug/L 10 1.71 4.63

Silver, Total ug/L 10 0.04 0.3

Toluene ug/L 8 1 3.52

Zinc, Total ug/L 10 34 85

Value

Temperature

– 95 th
percentile 1

- DADMAX °C continuous No temp data available, used value from West
Pt WWTP effluent: 21.0Fact Sheet for NPDES Permit WA 0029181 Page 34 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 18 . Effluent Characterization

– Elliott West CSO TP

Parameter Units # of Samples Average Maximum

Volume MG 27 20.1 97.4 Average Monthly Average Maximum Monthly Average

BOD 5 mg/L ≈27 69 191

TSS mg/L ≈ 27 144 708 Maximum Monthly Geometric Mean Maximum Weekly Geometric Mean

Fecal Coliform cfu/100 mL ≈ 26 400,000 412,500
Minimum Maximum
pH Std Units continuous 5.5 8.5

Chlorine, Total Residual μg/L continuous 607 860

Ammonia

, as N mg/L 2 2.54 2.68
Total Kjeldahl Nitrogen , as N mg/L 2 7.65 9.07

Nitrate + Nitrite , as N mg/L 2 0.35 0.45
Phosphorus, total , as P mg/L 2 1.04 1.14
Phosphate

, ortho, as P mg/L 2 0.04 0.64
Dissolved Oxygen mg/L 2 0.1 5.2
Alkalinity, total mg CaCO 3 /L 2 32.7 38.6

Hardness, calc mg CaCO 3 /L 1 31.9 31.9

1,4

- Dichlorobenzene ug/L 8 1 8.16

2,4

- Dichlorophenol ug/L 9 0.24 1
Antimony, Total, ICP

- MS ug/L 20 0.3 1.71

Arsenic, Total, ICP

- MS ug/L 20 0.46 2.66
Benzo(b)fluoranthene ug/L 8 0.75 2.93
Benzo(k)fluoranthene ug/L 8 0.75 1.6
Benzyl Butyl Phthalate ug/L 9 0.41 1.42

Bis (2

- Ethylhexyl)Phthalate ug/L 9 2.05 6.85

Bromodichloromethane ug/L 8 1 2

Cadmium, Total, ICP

- MS ug/L 20 0.05 0.617

Chloroform ug/L 8 5.41 35.8

Chloromethane ug/L 8 1 1.3

Chromium, Total, ICP

- MS ug/L 20 0.23 7.33
Copper, Total, ICP

- MS ug/L 20 23 86.7
Cyanide, weak acid diss. ug/L 1 1 5.0 19.3
Diethyl Phthalate ug/L 9 0.47 5.47
Dimethyl Phthalate ug/L 9 0.179 0.4

Fluoranthene ug/L 9 0.16 0.6

Lead, Total, ICP

- MS ug/L 20 0.39 26.8
Mercury, Total, CVAA ug/L 9 0.05 0.088
Mercury, Total, CVAF ug/L 1 0.0272 0.0272

Nickel, Total, ICP

- MS ug/L 20 0.1 6.34
Pentachlorophenol ug/L 9 0.47 1.91
Pyrene ug/L 9 0.18 0.6

Selenium, Total, ICP

- MS ug/L 20 0.5 0.61

Silver, Total, ICP

- MS ug/L 20 0.05 1.9

Thallium, Total, ICP

- MS ug/L 20 0.04 0.268

Toluene ug/L 8 1 32.8

Zinc, Total, ICP

- MS ug/L 20 2.8 162
Value
Temperature

– 95 th
percentile 1

- DADMAX °C continuous No temp data available, used value from West
Pt WWTP effluent: 21.0Fact Sheet for NPDES Permit WA 0029181 Page 35 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 19 . Effluent Characterization

– Henderson/MLK CSO TP

Parameter Units # of Samples Average Maximum

Volume MG 11 2.3 16.6

Minimum Maximum

BOD 5 mg/L ≈4 5 16

TSS mg/L ≈4 31 45

Fecal Coliform cfu/100 mL ≈ 4 1 302,667

pH Std Units ≈4 6.7 7.0

Chlorine, Total Residual μg/L ≈4 13 218

Ammonia

, as N mg/L 1 0.73 0.73

Total Kjeldahl Nitrogen , as N mg/L 1 3.86 3.86

Nitrate + Nitrite , as N mg/L 1 2.21 2.21

Phosphorus, total , as P mg/L 1 0.54 0.54

Phosphate

, ortho, as P mg/L 1 0.27 0.27

Dissolved Oxygen, mg/L mg/L 3 8.4 10.6

Hardness, calc mg CaCO 3 /L 1 48.3 48.3

Alkalinity, total mg CaCO 3 /L 1 33.5 33.5

2,4

- Dichlorophenol ug/L 3 0.24 2.54

Antimony, Total ug/L 3 0.77 0.89

Arsenic, Total ug/L 3 1.81 2.08

Bis(2

- Ethylhexyl)Phthalate ug/L 3 0.732 1.33

Bromodichloromethane ug/L 3 1 1.5

Cadmium, Total ug /L 3 0.05 0.073

Chloroform ug/L 3 1 50.1

Chromium, Total ug/L 3 1.56 2.4

Copper, Total ug/L 3 10.1 12.3

Cyanide, weak acid diss. ug/L 6 5.0 6.5

Di

- N

- Butyl Phthalate ug/L 3 0.24 1.49

Diethyl Phthalate ug/L 3 0.34 0.47

Dimethyl Phthalate ug/L 3 0.11 0.2

Lead, Total ug/L 3 3.02 4.23

Mercury, Total ug/L 3 0.05 0.05

Nickel, Total ug/L 3 1.92 3.31

Phenol ug/L 3 1.9 6.72

Zinc, Total ug/L 3 30.1 40.2

Value

Temperature

- 7

- DADMAX °C continuous No temp data available, used value from West

Pt WWTP effluent: 21.0



### W hole Effluent Toxicity Testing

- West Point WWTP

King County conducted a cute and chronic toxicity testing in January 2012, April 2012, July 2012, and October 2012. Acute toxicity tests were conducted with Daphnia pulex and fathead minnow. Chronic toxicity tests were conducted with Atlantic mysid and topsmelt

. See Appendix E for toxicity test results

.Fact Sheet for NPDES Permit WA 0029181 Page 36 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### For acute toxici ty, the performance standard requires median survival in 100% effluent at
levels equal to or greater tha n 80%

, and no individual test result showing less than 65%

survival in 100% effluent

. All toxicity tests performed in 2012 met these performance

standards

. For chronic toxicity, the performance standard requires that no chronic toxicity test

demonstrat es a statistically

- significant difference in response between the control and a test concentration equal to the acute critical effluent concentration (ACEC)

. West Point had no chronic toxicity anywhere near the ACEC of 3.1% effluent in any recent test

.

No WE T limit s are required

. The proposed permit includes the same set of WET tests at the

end of the next permit term to meet the application submission requirements

.

E. Sediment characterization

West Point WWTP Outfall



### Sediment testing in 1998 3 

### , 2000 4 

### , 2006 5



### , and 2011 6 

### occurred at 12 to 19 stations and included chemistry, bioassays, and benthic surveys as shown in Table 20

. The results are compared to

the Se diment Quality Standards (SQS) criteria for marine water. The sediment sampling

stations for the 2011 sampling report are shown in Figure 7

.

Table 20

. West Point WWTP

– Sediment Test Results

Year Chemistry

# of stations Bioassays

# of stations Benthic

Surveys * SQS Hits Stations

2011

- July 1 8

– Larval

echinoderm only 0 Bioassays WP430S (no chemistry hits to support toxicity , and TIE conducted by King County indicates toxicity

was likely due to sample turbidity and not chemically induced )

2011

- April 8 8 0 Chemistry & Bioassays WP230P : Total PCB

WP 420NW : Total PCB

WP215N : Dimethyl Phthalate

2006 19 10 10 Bioassays WP280W

WP230P

WP215N

2000 12 2 6 Bioassays WP230P

WP430N

1998 12 2 5 Chemistry & Bioassays WP230P

WP430N

* Unable to determine compliance with Sediment Management Standards for the benthic surveys due to lack of

reference station.

3 King County 1998. SEDQUAL data WPNT98.

4 King County 2000. SEDQUAL data WPNT00.

5 King County 2006. West Point Wastewater Treatment Plant 2006 Outfall Sediment Sampling Event Final Report.

6 King County , letters to Ecology (Henley) dated July 12, 2011 and February 16, 2012

. EIM data WPNT00Fact Sheet for NPDES Permit WA 0029181 Page 37 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 7 . Sediment sampling locations for West Pt WWTP outfall



### A ll detected concentrations have met the SQS chemical numeric standards (1988 Lowest Apparent Effects Threshold

- LAET) except for one station in 1998 and 3 stations in April

2011

. Due to low organic carbon content, chemical concentrations were compared to the 1988 LAET dry weight thresholds that are the basis for the organic carbon

- normalized criteria in the Sediment Management Standards

. Testing in April 2011 resulted in tota l PCB exceedances at stations WP230P and WP420NW, and a dimethyl phthalate exceedance at

station WP215N. Although a few stations had elevated levels of Polycyclic Aromatic Hydrocarbons (PAH), all met the chemical criteria in 2006

. In 2000, some samples had Method Detection Limits (MDL) above SQS for Hexachlorobutadiene, but it also was not

detected in the influent or effluent

. In 1998, there were 42 non

- detects and 5 detected concentrations above SQS

. The five detected exceedances all occurred at one statio n, WP230P, and included b enzo(g,h,i)perylene, f luoranthene, i ndeno(c,d)pyrene, phenanthrene, and p yrene (all PAH compounds).

Bioassay test result s have shown toxicity at several stations over the years

. The following

stations have failed one or more bioas say test: WP280W, WP230P, WP215N, and

WP430N

. Some of these stations coincide with elevated concentrations of PAH compounds

. The sediments at Station WP280W failed all three bi oassay tests in 2006, but

no elevated chemicals were detected

. The sediments at s tation WP230P failed bioassay

tests in 1998, 2000, and 2006, but passed in 2011

. In April 2011, Station WP430S showed a bioassay hit but again toxicity was not supported with e levated chemical concentration s, and a TIE (toxics identification evaluation) c onducted by King County showed that the toxicity was likely a result of physical characteristics (i.e., sample turbidity) and not chemically induced.

In 1998 and 2000, benthic surveys showed benthic abundance and diversity were reduced at two stations (WP2 30P, WP430N) compared to the other sites near the outfall

. These two stations also had bioassay toxicity

. In 2006, no differences were evident between the stations

. Ecology cannot compare benthic data to the SQS criteria because no reference station data

w as collected. Benthic surveys were not conducted in 2011.

In summary, King County has conducted sediment analyses near the West Point WWTP

outfall five times in the past sixteen years (1998, 2000, 2006

, April 2011 , and July 2011 )

. Many of the stations have consistently shown no indication of chemical or biological effects

.Fact Sheet for NPDES Permit WA 0029181 Page 38 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Except for one station in 1998 and three stations in 2011 , all detected concentrations met the SQS chemical numeric standards

. Bioassay test result s have consistently shown apparent
sedim ent toxicity at a few stations

, but cause of toxicity is unclear based on chemistry results and on the TIE conducted by King County in 2011

. Benthic surveys showed that in 1998 and 2000, benthic abundance and diversity were reduced at the two stations that also had bioassay toxicity (WP230P, WP430N), but this was not evident in 2006

. Sediment monitoring will continue in the vicinity of the outfall with more focus on investigating the area which has shown some evidence of sediment impacts.

Alki CSO Treatment Plant Outfall



### King County has sampled sediments near the Alki CSO treatment plant on several occasions,

most recent ly in October 2001. The study evaluated sediments at six stations; five of the stations formed a transect perpendicular to the end of the outfall and the sixth station was located approximately 1,500 feet from the outfall. All detected chemical concentrations were less than their respective SQS criteria or LAET values. Data from this sampling event can be found in EIM under User Study ID ALKI01. 7 

### No additional sediment monitoring is planned

at this outfall because there were no SMS exceedances in the last round of sampling and

source conditions have not changed

Carkeek CSO Treatment Plant Outfall



### King County has sampled sediments near the Carkeek CSO treatment plant on several occasions, most recently in October 2000. The study evaluated sediments at six stations; five

of the stations formed a transect perpendicular to the end of the outfall and the sixth station was located approximately 1,500 feet from the outfall in the direction of the prevailing current. All detected chemical concentrations were less than their respective SQS criteria or

LAET values . Data from this sampling event can be found in EIM under User Study ID

CARKEK00

. 7 

### No additional sediment monito ring is planned at this outfall because there

we re no SMS exceedances in the last round of sampling and source conditions have not changed

.

Elliott West CSO Treatment Plant Outfall



### King County has sampled sediments near the Elliott West CSO t reatment plant and the Denny Way

CSO extensively. The most recent sediment monitoring program has been in effect since 2001 as part of the Denny Way/Lake Union CSO Control Project long

- term sediment monitoring program. The County collected s amples from 16 locations near the two outfalls in 2001, 2003, 2004, 2006,
2007, 2008, and 2009 7 

### . Several chemicals exceed ed either SQS and/or Clean

- up Screening Level ( CSL ) chemical criteria at one or more locations. These include total PCBs

, benzo(a)anthracene

, benzo(a)pyrene

, benzo(g,h,i)perylene

, benzyl butyl phthalate

, bis(2

- ethylhexyl) phthalate

, chrysene

, dibenzo(a,h)anthracene

, fluroanthene

, indeno(1,2,3

- c,d)pyrene

, a nd mercury

. Sedime nt characterization is ongoing and an interim cleanup plan has been developed for this outfall and the Denny Way Regulator

. 8 

### Since sediment characterization is on

- going and an interim cleanup plan has been developed as part of cleanup eff orts, additional sediment monitoring requirements have not been imposed in this permit. Table 21 details King County’s sediment remediation activity in the vicinity o f the Elliott West CSO treatment plant outfall.

7 King County, Comprehensive Sediment Quality Summary Report for CSO Discharge Locations , 2009.

8 King County, Post Construction Monitoring Plan for King County CSO Controls , Sept 2012.Fact Sheet for NPDES Permit WA 0029181 Page 39 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 21 . Elliott West CSO treatment plant outfall

– sediment remediation activity 7

1986 Metro began a trial program to identify and reduce toxicant inputs to the sewer system discharging

th rough the Denny Way CSO.

1990 King County and the U.S. Army Corps of Engineers (Corps) sponsored the Denny Way CSO capping

project to test the feasibility of capping contaminated sediments in Elliott Bay with clean dredged
material from the Duwamish Waterway. A 3

- foot layer of clean sand, dredged from the upper Duwamish Waterway during routine maintenance, was placed over a 3

- acre area in water depths ranging from approximately

- 25 to

- 60 feet mean lower low water (MLLW). Monitoring r esults s how that the cap was stable, wa s not eroding, and ha d successfully isolated the und erlying contaminated sediments 9

. However, chemical concentrations on the cap surface layer (offshore of the Denny Way CSO) increased after cap construction, suggesting possi ble recontamination from the continued CSO discharges from Denny Way or potential redistribution of remaining contaminated sediments from the intertidal area and

the inshore edge of the cap.

1997 King County characterized the nature and extent of surface and subsurface sediment contamination in

the outfall area and in areas inshore and offshore of the existing sediment cap 10

. Follow

- up sediment sampling conducted by King County in 2005 demonstrated that chemical concentrations in the offshore

areas declined over time due to a combination of natural processes, including biodegradation of chemicals, accumulation and mixing of clean sediment, and reduction of contaminant sources 9 . Thus,

monitored natural recovery is a prospective cleanup remedy for the offshore areas.

S ediments sampled within inshore areas of the site contained concentrations of cadmium, copper, lead, mercury, silver, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), bis(2

- ethylhexyl)phthalate, and butyl benzyl phthalate that exceeded SQS chemical criteria. Contaminant
concentrations above SQS chemical criteria were present to a depth of approximately 10 feet below the existing mudline. Unlike offshore areas of the site, natural recovery rates in the inshore sediment areas appeared to be progressing relatively slowly. In order to accelerate cleanup of the site and minimize the

risk of future recontamination to other site areas, including the offshore cap, an interim sediment cleanup action plan for the site was developed by King County and Ecology in 2007 that i ncluded dredging to the

maximum extent practicable to remove contaminated sediments and backfilling to rest ore the grade to

close to pre

- project conditions.

2002 T he County constructed a new outfall to extend CSO discharge location further offshore.

2006 P rimary treatment and disinfection began for most of the discharges from this CSO (Elliott West CSO)

. 2007

- 2008 Under an Ecology Agreed Order, the County completed an interim action to clean up contaminated

sediments in two near

- shore areas in the immediate vicinity of th e former Denny Way CSO outfall. A combination of dredging, backfilling, and armoring w as employed to remediate the near

- shore areas.
King County dredged a pproximately 13,700 c ubic y ards of contaminated sedi ments and associated side slopes . The dredged area was backfilled and armored with an average thickness of more than 8 feet of

material. Approximately 11,886 cy of well

- graded clean sand was armored with approximately 4,821 cy of sandy

- gravel habitat mix and with large cobbles and boulders. An additional 1,540 cy of well

- graded clean sand was placed in an approximate 6

- inch

- thick layer around the perimeter of the dredge prism to address any residuals that may have resulted from the dredging. S ediment monitoring continue d until 2012 to satisfy the National Marine Fisheries Service Biological Opinion. 11



### Henderson/MLK CSO Treatment Plant Outfall



### Table 22 summarizes sediment remediation activity for the Henderson/MLK outfall area. Sediment sampling in this part of the Duwamish River has been characte rized by

Windward 12 

### as part of the ongoing Lower Duwamish Waterway Superfund action. Sediment sampling off the Norfolk CSO/storm drain was conducted over three rounds from 1994

9 King County. 2005

. The Denny Way sediment cap

– 2000 data

– final monitoring report.

10 King County. 1999. Sediment remediation plan, Denny Way/Lake Union CSO Control Project.

11 King County 2008. Denny Way CSO and Elliott West CSO Treatment Facility, Post

- Construction Se diment Monitoring Sampling and Analysis Plan

. 12 Windward Environmental LLC. 2008. Lower Duwamish Waterway remedial investigation, remedial investigation report , draft final (internal).Fact Sheet for NPDES Permit WA 0029181 Page 40 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### through 1995 under the Elliott Bay/Duwamish Restoration Program 13 

### . Both surface a nd subsurface sampling was extensively conducted with in several hundred feet of the outfall to

determine the remediation boundaries. SMS exceedances i ncluded mercury, total PCBs, 1, 4 dichlorobenzene, and bis(2

- ethylhexyl)phthalate. The SQS was used to set the remediation

boundaries. Data from this study may be found in EIM under User Study ID NRFK9495

. 7



### The 1999 remediation project was monitored for a period of five years to evaluate possible

recontamination of the backfill sediment as a result of continuing CSO discharges. The monitoring wa s completed in 2005. The site is now under evaluation as part of the early action sites in the Superfund area. More information on Norfolk CSO sediment remediation can be found on King County’s website at:
http://www.kingcounty.gov/environment/wastewater/SedimentManagement/Projects/Norfolk/Library.aspx

. 

### Ecology does not expect significant recontamination from the CSO discharges during this permit term for the following reasons:

 T he Henderson/MLK CSO facility discharges infrequently, only 1

- 3 times each year,

 T he basin that feeds the facility is largely residential with few industrial users, therefore toxic pollutant loads are expected to be smaller

,

 T he facility provides some settling therefore fewer solids are discharged,

 T he facility often retains ‘first flush’ stormwate r (when the tunnel fills but does not discharge) and sends th e s e more contaminated flow s to a wastewater treatment plant

for additional treatment.

Since the site is under sediment evaluations as part of Superfund cleanup efforts, additional sediment monitoring at the Norfolk CSO outfall is not required in this permit. A dditional

sediment conc erns from other contaminant sources will be addressed through Lower Duwamish Waterway sediment cleanup projects

.

Table 22

. Henderson/MLK CSO treatment plant outfall

– sediment remediation activity 7

1991 To implement the requirements of a 1991 Consent Decree defining the terms of a natural resources

damage agreement, the Elliott Bay/Duwamish Restoration Program (EBDRP) was established. P rogram oversight is provided by the EBDRP Panel, which is composed of federal, state, and tribal natural

resource trustees, the Municipality of Metropolitan Seattle (which subsequently became part of King County government and is now the King County Depart ment of Natural Resources and Parks (KCDNRP), and the City of Seattle (City). The goals of the EBDRP include remediation of contaminated sediments associated with KCDNRP and City CSOs and storm drains, restoration of habitat in Elliott Bay and the Duwamish River, and control of potential sources of contaminants from the outfalls.

1992 A Sediment Remediation Technical Working Group (SRTWG) was established by the EBDRP Panel to

address contaminated sediment issues. The SRTWG identified 24 potential sediment remediation sites associated with KCDNRP and City CSOs and storm drains. These sites were evaluated against several criteria, which included extent of contamination, degree of source control near sites, and public input, as reported in the Final Concept Do cument.
Ultimately, the SRTWG selected three sites (the Duwamish Pump Station CSO and Diagonal Way CSO/storm drain, the Norfolk CSO, and the Seattle Waterfront) for further investigation.

1994 A plan to investigate the extent of contamination at the Nor folk CSO was prepared by KCDNRP (then

Metro) on behalf of the EBDRP Panel. KCDNRP implemented field data collection activities between August 1994 and December 1995. The primary goals were to determine the extent of sediment

contamination around the Norfolk CSO outfall, based on co mparison to SMS criteria and to determine a preferred remedial alternative for the site.

13 King County. 1996. Norfolk CSO cleanup study report.Fact Sheet for NPDES Permit WA 0029181 Page 41 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

1999 Site remediation began in February 1999 and was completed in March 1999. Activities consisted of

dredging approximately 2 acres of contaminated sediment and backfilling the dredged area to original grade with clean sediment. A dredging dept of 3

- 9 feet resulted in 5,190 cubic yards of sediment

removal.

2003 Elevated PCB concentrations ( greater than the SQS criterion or LAET ) indicated that cap

recontamination was occurring

. In response, Boeing conducted a cleanup of river sediments at a stormwater outfall adjacent to the Norfolk CSO outfall using a specialized vacuum excavator; approximately 100 cubic yards of sediment were re moved

. 2004 King County completed p ost

- remedial monitoring at the Norfolk outfall , and reported ( King County, June

2005 ) sporadic SMS exceeda nces on the sediment cap without a consistent upward trend. T he five

- year monitoring period did not show s urface recontamination f r om CSO discharges to levels approaching
SQS chemical criteria.



### Untreated CSO Outfalls



### Sediment monitoring at CSO locations is a complex situation at many locations, some in different stages of cleanup under different authorities. Severa l CSOs discharge into Superfund cleanup site s so King County is coordinating with other agencies on source control and cleanup of larger area s . Cleanups done under CERCLA and MTCA may have

short

- term monitoring, but rely on other authorities, such as NPDES permits under the Clean Water Act to address long

- term monitoring. Th is NPDES permit has a role in assuring discharges are in compliance with the Sediment Management Standards , but it is necessary to coordinate these efforts with cleanup investigations an d actions under state and federal

authorities.

The County’s 1999 Sediment Management Plan 14 

### developed remedial strategies for correcting short

- and long

- term hazards associated with contaminated sediments near King County CSO sites. In 2011 and 2013 t he Cou nty collected s ediment data at several CSO

outfall locations to update the ir Sediment Management Plan ( SMP )

. King County is using

this data to calibrate and validate a near

- field sediment model that will be used to evaluate

rec ontamination potential for CS Os following control and sediment remediation projects. An updated SMP is expected in 2015.

In 2009 King County provided Ecology with a Comprehensive Sediment Quality Summary Report that summarize s sediment data collected up until 2009 for all of King County’s CSO

outfall s. The County has conducted s ediment monitoring at most CSO outfall s to assess CSO impacts and to determine if remediation is needed. King County’s 2012 Post Construction Monitoring Plan also provides a brief summary of the sediment sam ples that have been

collected near each CSO discharge location.

King County outlined their post construction monitoring program for sediments in their 2012 Post Construction Monitoring Plan (PCMP). Post construction sediment monitoring requires

site chara cterization using modeling and /or sediment quality samples. King County, in consultation with Ecology, will determine what comprises an adequate site characterization on a site specific basis. Based on the site characterization, certain CSO discharge locat ions may exceed Sediment Management Standards (SMS). For these locations, King County will develop site

- specific sediment clean

- up plan s . Clean

- up plans will contain actions required to
meet the SMS as well as a sampling program to ensure the outcome has b een achieved and recontamination is not occurring.

14 King County

, 1999

.Fact Sheet for NPDES Permit WA 0029181 Page 42 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### For untreated CSOs discharging to the Puget Sound, sediment data show either no exceedances of SQS or a single exceedance of a phthalate compound , except for the Barton

CSO site . For the Barton CSO outfal l, the 2011 sediment monitoring results show multiple exceedances of SQS and CSL for several parameters (likely contributed to by other sources).

For untreated CSOs discharging to Elliott Bay and the Duwamish River, sediment quality data show multiple exce edances of SQS, often including PAHs, total PCBs, phthalate compounds, and some metals. CSOs discharging into Lake Washington and the Ship Canal have multiple

exceedances of the freshwater sediment guidelines for metals, total PCBs, PAHs, phthalate

compoun ds, and other organic compounds.

Table 23 lists sediment remediation activities King County has undertaken to improve sediment quality near untreated CSO outfall locations.

Based on the County’s 2009 Sediment Quality Summary Report

, Ecology prioritized sampling at the County’s 38 untreated CSO locations into categories of high, medium, or low ( Ecology memo, Podger, 2010 ). Ecology based prioritization on discharge characteristics (volume and frequency, treatment), past sediment data re sults, and impact of other activities (cleanups pending or completed, construction pending, monitoring under other authorities). However the predominant metric used for ranking was average discharge flow from 2001

- 2007, in which discharges less than 1 mill ion gallons (MG) average per year were rated low, 1

- 10 MG/year were rated as medium, and >10 MG/year were rated as high priority. Locations with primary treatment and with diffusers were also rated lower than untreated single

- pipe discharges. CSOs ranked w ith high and medium priorities are listed in Table 24 along with sampling results from 2011 and 2013. The table also lists low priority CSOs that were tested in 2011/2 013.

Table 23

. Untreated CSO outfalls

– sediment remediation activity

1999 King County developed a Sediment Management Plan that identified seven contaminated sediment sites near CSO discharges. 15 Fo ur of those sites have cleanup actions planned or completed including Denny Way, Norfolk, Diagonal/Duwamish, and Hanford/Landers.

2000 King County, t he Boeing Company, the City of Seattle (the City) , and the Port (the Lower Duwamish

Waterway Group or LDWG) completed a voluntary agreement to begin investigation of the LDW sediments, toward an ultimate waterway cleanup plan.

2003 T he Diagonal/Duwamish cleanup included dredging and capping of seven acres of contaminated

sediment along the Lower Duwamish River. Post

- cleanup monitori ng continue d for five years. 16

2003

- 2006 The County and City , as operators of the local sanitary sewer and stormwater drainage systems, worked

together to inspect more than 1,000 Lower Duwamish Waterway businesses to reduce pollutants discharged to the Lo wer Duwamish.

2003

- present The County worked in partnership with the Port on the Harbor Island Superfund project. The project w ill

remediate sediments at the County’s Lander St and Hanford St CSOs.

2004 The County participated in two early action sites

— the Diagonal/Duwamish CSO/Storm Drain and Slip 4

CSO. King County removed 66,000 cubic yards of contaminated sediment at the Duwamish CSO outfall and Diagonal storm drain.

2005 King County placed a thin sand layer over four acres adjacent to the Duwamish CSO outfall and

Diagonal storm drain cleanup site to control residuals from the dredging and to compare enhanced natural recovery to monitored natural recovery in that portion of the LDW.

2007

- present T he County’s Industrial Waste Program work s with other agencies to conduct pollution source control

inspections at Lower Duwamish Waterway businesses as part of the Urban Waters Initiative, an interagency coordination effort of Ecology. The initiative provides increased resources to speed up pollution reduction efforts to benefit the waters, sediments, and human and marine inhabitants of the Lower Duwamish Waterway.

15 King County 1999. King County Department of Natural Resources Year 2000 CSO Plan Update Project, Sediment Management Plan

. 16 Ecology 2002. Final Sediment Management Standards Cleanup Action Decision Duwamish/Diagonal CSO/SD.Fact Sheet for NPDES Permit WA 0029181 Page 43 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

2008

- 2009 As part of the Duwamish East Wate rway Superfund site, the County remov ed approximately 20,000

cubic yards of sedimen t in front of th e Lander CSO

. 2012 WTD partnered with the City, the Port, and Boeing under a consent agreement with EPA and Ecology to

prepare a remedial investigation and feasibility study for the Lower Duwamish Waterway Superfund Site. The feasibility study described 11 cleanup alternatives . In 2012 EPA proposed a cleanup plan based on

the 2010 Lower Duwamish Waterway Draft Final Feasibility Study

.

2012 King County developed a sediment transport model to better assess impacts from CSO discharges.

present Ecology le ads the Source Control Work Group that includes EPA , Seattle Public Utilities (SPU), the King

County Industrial Waste Program, the Port of Seattle, the Puget Sound Clean Air Agency, and the City of Tukwila. This group meets monthly to coordinate source con trol efforts and make it easier for businesses to identify and control pollutant sources. The group’s first priority is to address the early action areas identified for sediment cleanup. The group is working on controlling sources of contaminants that may pose health or environmental problems if they accumulate in waterway sediments. More information is available on the group’s website at: http://www.ldwg.org/ and at http://www.ecy.wa.gov/programs/tcp/sites_brochure/lower_duwamish/lower_duwamish_hp.html

. present The County is in the process of updating its 1999 Sediment Management Plan in coordination with new

requirements for characterization and Post

- Construction Monitoring.

present The Wastewater Division's Sediment Management Program is coordinating expanded source control to

identify and control the sources of pollution that may pose health or environmental problems if they accumulate in Duwamish Waterway sediments or re contaminate cleanup areas. The Industrial Wa ste Program, Water and Land Resources Division and KC Airport are some of the groups involved with the current expanded source control efforts in King County.

Table 24 . Sediment test ing priorities for CSO outfalls & sampling results from 2011 & 2013

CSO Outfall 2010 Comments from Ecology 1 2011 & 2013 Sampling Results 2 Future Monitoring / Cleanup

High Priority

028

- King Street 15+ year old sediment data

with multiple hits, not cleanup site. Not tested. Treatment plant constructed
in 2026. Sediments to be sampled prior to construction. 029

- Kingdome

036

- Chelan Harbor Island superfund

site. Sediment impairment in 1996 samples but EPA signed a ‘No Further Action’

on the site. No additional monitoring planned. 2011: 5 of the 6 sites exceeded SQS for 2 to
several chemicals , 1 site exceeded CSL for 1

chemical (many NDs exceeded criteria)

. 2013: 1 site had dimethyl phthalate SQS exceedance, many NDs exceed criteria

. HPAHs, PCBs, p hthalates Storage tank constructed in

2023. Sediments to be sampled post

- construction.

0 37

- Harbor

Avenue Not tested. Area

- wide cleanup in progress. To be sampled when complete or when CSO

controlled

. 041

- Brandon
Street Large discharge with high

metals concentrations, little

sediment data available. 2011: 4 of the 6 sites exceeded SQS for 1 to

several chemicals , 3 sites exceeded CSL for

1 to several chemicals

. HPAHs, LPAH, PCBs, p hthalate Treatment plant constructed by 2022. Sediments to be sampled prior to construction

or with area

- wi de clean

- up effort.

015

- University Large discharge with no

recent sed iment data 2011: 5 of the 7 sites had S CO or CSL
exceedances

. 2013: 3 of the 5 sites had SCO or CSL
exceedances. Phthalates, mercury, lead, nickel, silver, PCBs Storage tank constructed in
202 8 . Sediments to be sampled post

- constructio n or with area

- wide clean

- up effort.

014

- Montlake Medium discharges and 10

-

20 year old sediment data

show elevated PAH and other chemicals. [Last sampled in 2001, single site ( KC 2009

) ]. 2011: 2 of the 7 sites had S CO exceedances

,

no sites had CSL exceedances

. Arsenic, lead Storage tank constructed in

202 8 . Sediments to be sampled post

- construction or

with area

- wide effort.

008

- 3 rd Ave

West 2011: 6 of the 7 sites exceeded SQS levels
for 3 to 5 chemicals

, 6 sites exceeded CSL

for 2

- 5 chemicals

. Phthalates, nickel, silver, PCBs, phenol, t otal PAHs, mercury Storage tank constructed in

202 3 . Sediments to be sampled post

- construction or

with area

- wide effort.Fact Sheet for NPDES Permit WA 0029181 Page 44 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

CSO Outfall 2010 Comments from Ecology 1 2011 & 2013 Sampling Results 2 Future Monitoring / Cleanup

009

- Dexter Ave Not tested. Area

- wide cleanup projects expected. CSO projects completed but not yet

deemed controlled.
Sediments to be sampled

after outfalls deemed

controlled or area

- wide cleanup projects completed. 003

- Ballard

013 /045

- MLK

and Henderson
PS CSO controlled since 2005

but had medium discharges in the past. Sediment data from 2005 had high PAH, phthalates, zinc. Not tested. Sediments characterized during this permit term.

Medium Priority

044

- Norfolk Sediment data with hits or

increasing trends. Not tested. CSO treatment plant outfall.

Area

- wide clean

- up and monitoring complete. See
discussion for Henderson/

MLK TP above.

038

- Terminal

115 Not tested. Storage pipe constructed by

202 5 . Sediments to be sampled prior to construction

or with area

- wide clean

- up effort.

039

- S Michigan Not tested. Treatment plant constructed by 2022. Sediments to be sampled prior to construction

or with area

- wide clean

- up effort.

Low Priority ( does not include all outfalls, only sites tested in 2011/ 2013 and those with proposed monitoring )

048

- North

Beach 2011: No SMS exceed a nces at 6 sites.

2013: No SMS exceed a nces at 5 sites. CSO project in progress. No
further action.

006

- South Magnolia 2011: No SMS exceed a nces at 6 sites.
2013: No SMS exceedances at 1 site

. CSO project in progress. No

further action.

056

- Murray

Avenue 2011: Benzyl Butyl Phthalate exceeded SQS at 1 site, no exceedances at remaining 6

sites. 2013: 1 site had SQS and CSL exceedances,

no exceedance s at remaining 5 sites

. Phthalate, LPAHs, HPAHs CSO project in progress. Site evaluation and possible

c lean

- up plan as required by
PCMP

.

057

- Barton
Street 2011: 6 of 6 sites exceeded several SQS and
CSL criteria. HPAHs, LPAHs

, phthalates, dibenzofuran CSO project in progress. Site evaluation and possible

c lean

- up plan as required by
PCMP

. 052

- 53rd

Avenue 2011: No SMS exceed a nces at 6 sites. CSO controlled. No further

action.

012 /049

- Belvoir & 30 th

Ave NE PS 2013: 1 site tested; 2 SCO and no CSL

exceedances. Total DDEs, bis(2

- ethylhexyl)phthalate CSO controlled. Sediments to
be characterized during this permit term due to SMS

exceedances.

011

- E. Pine Street PS Emergency Overflow Not tested. CSO s controlled. Low volume discharge s with n o recent
data. Sediments to be characterized during this permit term to confirm meet water quality standards

, consistent with County’s 2012 018

- Matthews

Park P S Emergency
Overflow Not tested.Fact Sheet for NPDES Permit WA 0029181 Page 45 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

CSO Outfall 2010 Comments from Ecology 1 2011 & 2013 Sampling Results 2 Future Monitoring / Cleanup

033

- Rainier

Avenue P S Emergency
Overflow Not tested. PCMP.

1 Source: Ecology TCP memo on review of KC’s 2009 Sediment Quality Report (Podger), 2010.

2 Sampling performed according to Ecology

- approved KC CSO Sediment Quality Characterization Final Sampling and Analysis Plan, August 2011

.



### King County must model and /or sample sediments in accordance with the approved 2012 Post Construction Monitoring Plan or any approved plan revisions

. Post construction monitoring of sediments is required with the completion of CSO projects once the CSO has

been deemed controlled. I f an area

- wide cleanup project is planned, sediment samples must be collected once the project is complete.

During this permit term, the CSO s listed in Table 25 are scheduled to be controlled. The proposed permit requires submittal of a Post

- Construction Summary Report that summarizes post construction sediment data and any clean

- up actions performed

. Anticipated monitoring

is also described in the table.

Table 25

. CSO outfalls scheduled to be controlled during this permit term

CSO Outfall Anticipated Sediment Monitoring / Cleanup

Dexter Avenue Regulator (DSN 009) Area

- wide clean

- up anticipated.

Denny Way Regulator (DSN 027a) Area

- wide clean

- up in progress.

Harbor Avenue Regulator (DSN 037) Area

- wide clean

- up in progress.

Ballard Siphon Regulator (DSN 003) Area

- wide clean

- up anticipated.

Barton (DSN 057) Post Construction monitoring and clean

- up plan required by PCMP

. Murray (DSN 056)

South Magnolia (DSN 006) No additional sediment monitoring; p re

- project monitoring showed no SMS exceedances. North Beach (DSN 048)



### Hanford # 1

- Construction of the Hanford #1 CSO project will begin during this permit term and must be completed by December 31, 2019 according to the County’s consent decree

. Since the project does not include in

- water work the County will not perform pre

- project sediment monitoring according to their PCMP (King County, September 2012). An area

wide cleanup effort is in progress in the vicinity of the diagonal stormwater drain outfall through which the Hanford #1 CSO discharges

. According to the PCMP, the County will

assess sediment quality in the vicinity of the outfall following completion of the CSO control project or cleanup project . This assessment will be conducted by modeling, collect ing

sediment samples

, and/ or assessing recent sediment data

. No pre

- project monitoring is requi red with the proposed permit

. A post

- construction monitoring report will be required in the next permit term.Fact Sheet for NPDES Permit WA 0029181 Page 46 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### F

. Summary of c ompliance with p revious p ermit i ssued

Ecology assess ed compliance based the facilities’ discharge monitoring reports (DMRs), annual CSO report s , and inspections.

West Point WWTP



### The West Point WWTP consistently complied with the effluent limits and permit conditions throughout the duration of the permit term. The County reported no effluen t limit violations

for CBOD 5 

### , TSS, pH, total residual chlorine, or fecal coliform for the period July 1 , 200 9 to
October 20 13

.

Alki CSO Treatment Plant



### For the Alki CSO treatment plant, t he previous permit placed effluent limits on TSS, fecal coliform, set tleable solids, pH, and chlorine. Table 26 summarizes the violations and permit triggers that occurred from July 2009 through September 2013

.

Table 26 . Alki CSO Treatment Plant

– Permit Violations

Date Parameter Statistical Base Units Value Limit

10/1/2009 Fecal Coliform Geometric Mean #/100ml 20000 400

11/1/2009 Chlorine, Total residual Daily Maximum μg/L 684 234

1/1/2010 Chlorine, Total residual Daily Maximum μg/L 1708 234

11/1/2010 Chlorine, Total residual Daily Maximum μg/L 513 234

12/1/2010 Chlorine, Total residual Daily Maximum μg/L 503 234

3/1/2011 pH, Daily Min Minimum Std Units 5.8 6 .0

- 9.0

11/1/2011 Fecal Coliform Geometric Mean #/100ml 18150 400

1/1/2012 Fecal Coliform Geometric Mean #/100ml 2157 400

9/1/2013 pH, Daily Min Minimum Std Units 5.8 6.0

- 9.0



### In 2009 and 2010 the facility struggled to meet chlorine limits, as shown in Table 26 . The facility exceeded chlorine limits by a wide margin four times during this period. King County responded to these violations by correcting a PLC programming error and by

incre asing SBS dosing capacity.

The facility continues to experience occasional fecal coliform exceedances . D u ring this compliance period the facility exceeded the fecal limit three times

. In response to these permit violations the County increased chlorine resi dual levels . They also lowered the hypochlorite solution concentration from 4% to 2% to allow for finer control, minimizing the risk of overdosing. The County also improved s ample collection procedures to
minimize cross

- contamination

.Fact Sheet for NPDES Permit WA 0029181 Page 47 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Twice during th e compliance period effluent pH dropped below 6.0 due to sodium bisulfate

feed rates and low

- alkalinity stormwater. The County is currently improving the sodium bisulfate feet system to prevent these violations.

T he County is in the process of upgrad ing th ree pump station s upstream of the 63 rd 

### Avenue PS (53 rd 

### , Murray , and Barton). These projects will increase the storage upstream of the 63 rd


### Avenue Pump Station, helping to reduce untreated combined sewer overflows

. It may also

tend to increase the volume tr eated at Alki

. The County will need to review operational strategies at 63 rd 

### Avenue PS, the inlet regulator gate, and the West Seattle PS/Tunnel as these projects move forward.

Annual Limits

- Between 2009 and 2012 there were 27 filling events and 19 discharge events,

and the Alki facility met all annual permit limits for settleable solids and TSS removal. During this time period, the CSO facility prevented 6 7 million gallons of combined sewage from discharging into the Puget Sound.

5

- Year Limits

- The long

- term average (i.e. permit cycle length) effluent discharge volume and number of events is limited to 108 million gallons (MG) and 29 discharge events, respectively

. During the current permit cycle the Alki CSO treatment plant met these limits

with an average annual discharge volume of 52 MG and average of 5 discharge events per

year

.

Carkeek CSO Treatment Plant



### For the Carkeek CSO treatment plant, the previous permit placed effluent limits on TSS, fecal coliform, sett leable solids, pH, and chlori ne

. Table 27 summarizes the violations and permit triggers that oc curred from July 2009 through September 2013

.

Table 27 . Carkeek CSO Treatme nt Plant

– Permit Violations

Date Parameter Statistical Base Units Value Limit

1/1/2010 Fecal Coliform Geometric Mean #/100ml 755 400

12/1/2010 Chlorine, Total residual Maximum μg/L 1370 490

12/1/2010 Fecal Coliform Geometric Mean #/100ml 752 400

11/1/2012 Chlorine, Total residual Maximum μg/L 723 490

12/1/2012 pH, Daily Min Minimum Std Units 5.1 6



### From 2009 to 2013, the Carkeek CSO plant exceeded fecal coliform and chlorine limits each

twice. In 2011 King County retrofitted their sampling procedures and installed new auto

samplers that are capable of notifying the SCADA system when the sampl ing system fails. I n 2013 the County upgraded the hypochlorite feed pump system with a pump upgrade, line flushing improvemen ts, and a new hypochlorite flow meter.

Annual Limits

- Between 2009 and 2012 there were 50 filling events and 23 discharge events,

and the Carkeek facility met all annual permit limits for settleable solids and TSS removal. During this time period, the CSO facility prevented 17 million gallons of combined sewage from discharging into the Puget Sound.

5

- Year Limits

- The long

- term average (i.e. permit cycle length) effluent discharge volume and number of events is limited to 46 million gallons (MG) and 10 discharge events, respectively. During the current permit cycle the Carkeek CSO treatment plant met these

limits averaging 6 discharge events per year with an average annual discharge volume of

19 MG

.Fact Sheet for NPDES Permit WA 0029181 Page 48 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Elliott West CSO Treatment Plant



### For the Elliott West CSO treatment plant, the previous permit placed effluent limits on TSS, fecal coliform, sett leable solids, pH, and chlorine

.
Table 28 summarizes the violations and permit triggers that occurred from July 2009 through September 2013

.

Table 28 . Elliott West CSO Treatment Plant

– Permit Violations and Permit Triggers

Date Parameter Statistical Base Units Value Limit

10/1/09 Fecal Coliform Geometric Mean #/100ml 5889 400

10/1/09 Settleable Solids Maximum mL/L 6 1.9

11/1/09 Settleable Solids Maximum mL/L 10 1.9

2009 TSS, Annual % removal Annual Ave % 41.6 >50

2009 Settleable Solids Annual Ave mL/L 2.3 0.3

1/1/10 Settleable Solids Maximum mL/L 9 1.9

4/1/10 Settleable Solids Maximum mL/L 2 1.9

9/1/10 Fecal Coliform Geometric Mean #/100ml 5,099 400

9/1/10 Settleable Solids Maximum mL/L 2 1.9

11/1/10 Fecal Coliform Geometric Mean #/100ml 2,439 400

11/1/10 Settleable Solids Maximum mL/L 2.5 1.9

12/1/10 Chlorine, Total residual Maximum μg/L 158 104

2010 Settleable Solids Annual Ave mL/L 1.5 0.3

3/1/11 Fecal Coliform Geometric Mean #/100ml 553 400

4/1/11 pH, Daily Min Minimum Std Units 5.5 6

4/1/11 Settleable Solids Maximum mL/L 4.5 1.9

5/1/11 Fecal Coliform Geometric Mean #/100ml 400,000 400

12/1/11 Chlorine, Total residual Maximum μg/L 259 104

12/1/11 Fecal Coliform Geometric Mean #/100ml 17000 400

2011 Settleable Solids Annual Ave mL/L 0.8 0.3

1/1/12 Chlorine, Total residual Maximum μg/L 231 104

1/1/12 Settleable Solids Average mL/L 1 0.3

7/1/12 Settleable Solids Maximum mL/L 5.5 1.9

10/1/12 pH, Daily Min Minimum Std Units 5.7 6

11/1/12 pH, Daily Min Minimum Std Units 5.7 6

12/1/12 Chlorine, Total residual Maximum μg/L 407 104

12/1/12 pH, Daily Min Minimum Std Units 5.76 6

12/1/12 Settleable Solids Maximum mL/L 3.7 1.9

2012 Settleable Solids Annual Ave mL/L 1.2 0.3

1/1/13 pH, Daily Min Minimum Std Units 5.9 6

3/1/13 Chlorine, Total residual Maximum μg/L 435 104

3/1/13 pH, Daily Min Minimum Std Units 5.95 6

3/1/13 Settleable Solids Maximum mL/L 2 1.9

4/1/13 pH, Daily Min Minimum Std Units 5.93 6

9/1/13 Chlorine, Total residual Maximum μg/L 860 104

9/1/13 Fecal Coliform Geometric Mean #/100ml 700 400Fact Sheet for NPDES Permit WA 0029181 Page 49 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 8 . Fecal Coliform data for Elliott West CSO TP.

Figure 9 . Residual chlorine data for Elliott West CSO TP. 

### S everal contributory factors affected permit compliance, including equipment performance (auto samplers, sampling pumps, dewatering pumps, flap gate failure, drain gate failure ), poor mixing of chemicals, and hydraulic gradient issues that were causing surcharging

at the dechlorination and outfall

transition structures

. The County has hired consultant engineers and implemented many projects to address the performance conc erns.

Fecal Coliform

- As shown in

Table 28 and Figure 8 the facility exceeded

fecal coliform limits seven times between

October 2009 and Octobe r 2013. In 2011 the County rebuilt all th r e e hypochlorite pumps , modified the hypo system plumbing, a nd started exercising the pumps on a regular

schedule. In 2012 the County added new chemical flowmeters, increased chlorine contact time by moving the hypo injection point upstream,

added an initial chlorine

- demand analyzer, and converted the hypochlorite and bisulfite dosing control programs to compound loop

controls. T hese improvements have

resulted in somewhat lower fecal

coliform levels and improved compliance , as can be seen in Figure 8

.
Residual Chlorine

- As shown in

Table 28 and Figure 9 the facility exceeded chlorine limits six times between October 2009

and October 2013. To address this, in 2011 the County improve d the sodium bisulfite system plumbing and initiat ed a standa rd procedure to manually flush the line s periodically to prevent freezing . The County also installed a pressure gauge to monitor for line constrictions. In 2012 the County converted the hypochlorite and bisulfite dosing controls as discussed

above

. pH

- P rior to 2011 pH fluctuated around 6.5

. Since 2011 , however, low pH has plagued this facility with the effluent frequently drop ping below 6.0. These d rops are likely a result of

sodium bisulfate feed rates , but th e situation is compounded by the lack of alk alinity in

Seattle’s stormwater.Fact Sheet for NPDES Permit WA 0029181 Page 50 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Settleab l e Solids

- The facility also has difficulty meeting settleable solids limits. Table 28 shows 11 monthly exceedances and 4 annual exceedances . In 201 3 the County repaired the discharge line drain gate through which marine water was enter ing the effluent line and sampling well. A utomated tunnel flushing schedules implemented in 201 3 will hopefully send more solids to West Point treatment plant after each CSO event

. In addition, the County started turning on the tunnel’s dewatering pumps sooner and leaving them on during a discharg e event to enhance settled solids transfer to the West Point Treatment Plant. Also, the

marine transition flap gate repair in December 2013 will keep marine water and solids out of the effluent tunnel and sampling well.

Additionally, the County installed a new effluent sample pump in 2010 and implemented procedures to make sure the pump is regularly inspected and tested. In February 2013 the County completed an effluent sampling improvement project and the County continues to provide annual sampling refresh er training courses for operators.

The facility met the annual TSS removal requirement every year except 2009 in which the facility only achieved 42% removal.

Between 2009 and 2012 the Elliott West facility experienced 158 filling events and 45 discharge events

. During this period, the CSO facility prevented 889 million gallons of combined sewage from discharging into Elliott Bay. However, t he Elliott West CSO treatment plant continues its struggle to meet permit limits for fecal coliform, pH, c hlorine,

and settleable solids.

Henderson/MLK CSO Treatment Plant



### For the Henderson/MLK CSO treatment plant, the previous permit placed effluent limits on TSS, fecal coliform, sett leable solids, pH, and chlorine

. Table 29 summarizes the violations and permit triggers that occurred from July 2009 through September 2013

.

Table 29 . Henderson/MLK CSO Treatment Plant

– Permit Violations and Permit Triggers

Date Parameter Statistical Base Units Value Limit Violation

10/1/2010 Fecal Coliform Geometric Mean #/100ml 302

, 667 400 Numeric effluent

violation

11/1/2012 Chlorine, Total residual Maximum μg/L 218 39 Numeric effluent

violation



### Annual Limits

- Between 2009 and 2012 t here were twelve filling events and four discharge

events , and the Henderson/MLK facility met all annual permit limits for settleable solids and TSS removal. During this time period, the CSO facility prevented 24 million gallons of combined sewage from discharging into the Duwamish River.

G

. S tate e nvironmental p olicy a ct (S EPA ) c ompliance

State law exempts the issuance, reissuance or modification of any wastewater discharge permit from the SEPA process as long as the permit contains conditions are no less stringent than federal and state rules and regulations (RCW 43.21C.0383). The exemption applies only to existing disc harges, not to new discharges.Fact Sheet for NPDES Permit WA 0029181 Page 51 of 1 75

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## III. P roposed Permit Limits

Federal and s tate regulations require that effluent limits in an NPDES permit be either

tec hnology

- or water quality

- based

.

 

### Technology

- based limits are based upon the treatment methods available to treat specific pollutants

. Technology

- based limits are set by the EPA and published as a regulation, or Ecology develops the limit on a case

- by

- case basis (40 CFR 125.3, and chapter

173

- 220 WAC)

.

 

### Water quality

- based limit s are calculated so that the effl uent will comply with the Surface Water Quality Standards ( c hapter 173

- 201A WAC), Ground Water Standards ( c hapter

173

- 200 WAC), Sediment Quality Standards ( c hapter 173

- 204 WAC)

, or the National Toxics Rule (40 CFR 131.36)

.

 

### Ecology must apply the most str ingent of these limits to each parameter of concern

. These

limits are described below.

The limits in this permit reflect information received in the application and from supporting reports (engineering, hydrogeology, etc.)

. Ecology evaluated the permit app lication and determined the limits needed to comply with the rules adopted by the s tate of Washington

. Ecology does not develop effluent limits for all reported pollutants

. Some pollutants are not treatable at the concentrations reported, are not controllable at the source, are not listed in regulation, and do not have a reasonable potential to cause a water quality violation

. Ecology does not usually develop limits for poll utants not reported in the permit application but may be present in the discharge

. T he permit does not authorize discharge of the non

- reported pollutants

. During the five

- year permit term, the facility’s effluent discharge conditions may change

from those conditions reported in the permit application. The facility must notify Ecology if significant changes occur in any constituent [40 CFR 122.42(a)]

. Until Ecology modifies the permit to reflect additional discharge of pollutants, a permitted facility could be violating its permit.

A. Design criteria

Under WAC 173

- 220

- 150 (1)(g), flows and waste loadings must not exceed approved design

criteria

.

West Point WWTP



### The design criteria for the West Point WWTP listed in Table 30 are taken from the 199 1 Plans

titled West Point Treatment Plant Secondary Treatment Facilities, Liquids Stream

, prepared by

CH 2 

### M Hill, KCM, and others

. Ecology erroneously put the wrong desig n criteria in the previous permit; the values were taken from the same document but for the ‘saturation/future’ loading levels instead of the actual ‘design’ levels. The proposed permit corrects this mistake by reducing the TSS and BOD 5 

### design loadings to those listed in Table 30

.

Table 30

. West Point WWTP Design Criteria

Parameter Design Quantity

Monthly average flow (maximum month) 215 MGD

Average wet weather flow (non

- storm) 133 MGD

Instantaneous peak flow (combined) 440 MGD

BOD 5 influent loading ( maximum month ) 201 ,000 lbs/day

TSS influent loading ( maximum month ) 218 ,000 lbs/dayFact Sheet for NPDES Permit WA 0029181 Page 52 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Permit Condition S10 authorizes CSO

- related bypasses of the secondary treatment portion of

the West Point WWTP when the instantaneous flows to the WWTP exceed 300 MGD as a result of precipitation. The wastewater that bypasses secondary treatment must recei ve solids and floatables removal, primary clarification, and disinfection. The final combined discharge

must at all times meet the effluent limits listed in S1. EPA’s 1994 CSO Control Policy allows

for “CSO

- related bypass” under certain conditions.

EPA's CSO Guidance for Permit Writers (EPA

- 832

- B

- 95

- 08) states that a "CSO

- related bypass" at the wastewater treatment plant can only occur if there is no feasible alternative

and the no feasible alternatives analysis is part of the administrative record . The no feasible alternative requirement can be met if “ the record shows that the secondary treatment system is properly operated and maintained, that the system has been designed to meet secondary limits for flows greater than the peak dry weather flow, plus an appropriate quantity of wet weather flow, and that it is either technically or financially infeasible to provide secondary treatment at the existing facilities for greater amounts of wet weather flow.”

Ecology is confident the West Point WWTP is well operated and maintained based on monthly DMR and annual CSO reporting, frequent meetings, and inspections. As recommended by EPA’s guidance, the West Point WWTP “meets secondary limits for flows greater than the peak dry weather flow plus an appropri ate wet weather flow” (i.e., the facility provides secondary treatment to flows up to 300 MGD , which is greater than the

maximum month wet weather flow of 215 MGD and meets secondary limits under all CSO conditions). When Metro designed the facility it was deemed infeasible to provide secondary treatment to peak wet weather flows from the combined system due to concerns that peak flows would wash out the secondary process.

King County submitted to Ecology a no feasibility alternatives analysis in 2009 (Kin g County, 2009) per the CSO Control Policy requirements. As part of this permit development

process Ecology reviewed this document again and concluded it still applies since there have

been no major capacity changes at the facility . The document provides a dequate justification

to continue to authorize the CSO

- related bypass for this permit cycle

. Additionally, t he collection system storage projects planned and in progress will likely result in fewer bypass

events allow ing the West Point facility to provide secondary treatment to more CSO flows than previous ly assess ed in the 2009 analysis

. Ecology will likely require a n update to the no feasible alternatives analysis in the next permit which will be issued in 2019

- 2020

.

Alki CSO Treatment Plant



### Ecology obtained the design criteria the Alki facility , listed in Table 31

, from the Facilitie s Plan for Alki Transfer/CSO Project prepared by HDR Engin eering, Inc. a nd dated October

1992.

Table 31

. Alki CSO Treatment Plant

– Design Criteria

Parameter Design

Peak storm water flow to treatment p lant 65 MGD

TSS influent loading (average annual) 9,580 lbs/day



### Carkeek CSO Treatment Plant



### Ecology obtained the design criteria for the Carkeek Storage and CSO Treatment Plant , listed

in Table 32

, from the Facility Plan for the Carkeek Transfer/CSO Faciliti es Project prepared by Brown and Caldwell Consulting Engineers and dated December 1988

.Fact Sheet for NPDES Permit WA 0029181 Page 53 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 32 . Carkeek CSO Treatment Plant

– Design Criteria

Parameter Design Quantity

Peak wet weather flow 20 MGD

TSS influent loading 5,100 lbs/day



### EWCSO CSO Treatment Plant



### Ecology obtained the design criteria for the EWCSO Satellite CSO Treatment Plant , listed in

Table 33

, from the Denny Way/Lake Union CSO Control Facilities Plan

, dated July 1988

.

Table 33 . EWCSO Treatment Plant

– Design Criteria

Parameter Design

Tunnel Diameter 14’ 8”

Tunnel Length 6,200’

Total Volume 7.2 MG



### Henderson/MLK CSO Treatment Plant



### Ecology obtained t he design criteria for the Henderson/MLK CSO treatment plant , listed in

T able 34

, from the Henderson/ML King CSO Control Facilities Plan (approved March 5, 2002).

T able 34

. Henderson/MLK CSO Treatment Plant

– Design Criteria

Parameter Design

Tunnel Diameter 14’ 8”

Tunnel Length 3,100’

Total Volume 4 MG



### B. T echnology

- b ased e ffluent l imit s

Federal and state regulations define technology

- based effluent limits for municipal wastewater treatment plants

. These effluent limits are given in 40 CFR Part 133 (federal) and in chapter 173

- 221 WAC (state)

. These regulations are performance standards that constitute all known, available, a nd reasonable methods of prevention, control, and treatment (AKART) for municipal wastewater.

The federal CSO Control Policy ( 

### 59 FR 18688) also requires entities with Combined Sewer Overflows to implement “ Nine Minimum Controls” as technology

- based perform ance standards for CSO discharges. Nine Minimum Controls are discussed in more detail in

Section V .G of this fact sheet.

West Point WWTP



### The table below identifies technology

- based limits for pH, fecal coliform, C BOD 5 

### , and TSS, as listed in chapter 173

- 221 WAC for secondary wastewater treatment plants

. Section III.F of

this fact sheet describes the potential for water quality

- based limits

.Fact Sheet for NPDES Permit WA 0029181 Page 54 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 35 Technology

- based Limits (West Point WWTP)

Parameter Average Monthly Limit Average Weekly Limit

C BOD 5 25 mg/L 40 mg/L

In addition

, the C BOD 5 effluent concentration must not exceed : 15% of the average influent concentration from May

- October, and

20 % of the average influent concentration from November

- April

. TSS 30 mg/L 45 mg/L

In addition

, the TSS effluent concentration must not exceed : 15% of the average influent concentration from May

- October, and

20 % of the average influent concentration from November

- April

. Chlorine 0.5 mg/L 0.75 mg/L

Parameter Monthly Geometric Mean Limit Weekly Geometric Mean Limit

Fecal Coliform Bacteria 200 organisms/100 mL 400 organisms/100 mL

Parameter Daily M inimum Daily Maximum

pH 6.0 standard units 9.0 standard units



### Ecology derived the technology

- based monthly average limit for chlorine from standard operating practices

. The Water Pollution Control Federation's Chlorination of Wastewater (1976) states that a properly designed and maintained wastewater treatment plant can achieve adequate disinfection if a 0.5 mg/L chlorine residual is mai ntained after fifteen minutes of contact time. See also Metcalf and Eddy, Wastewater Engineering, Treatment, Disposal and

Reuse , Third Edition, 1991

. A treatment plant that provides adequate chlorination contact time can meet the 0.5 mg/L chlorine limit on a monthly average basis

. According to WAC

173

- 221

- 030(11)(b), the corresponding weekly average is 0.75 mg/L.

Technology

- based mass limits are based on WAC 173

- 220

- 1 30(3)(b) and 173

- 221

- 0 30(11)(b)

. Ecology calculated the monthly and weekly average mass li mits for C BOD 5 

### and Total Suspended Solids as follows:

Mass Limit = CL x DF x CF

where:

CL = Technology

- based concentration limits listed in the above table

DF = Maximu m Monthly Average Design flow ( MGD)

CF = Conversion factor of 8.34

Table 36

. Technology

- based Mass Limits

Parameter Concentration Limit (mg/L) Mass Limit (lbs/day)

C BOD 5 Monthly Average 25 44,800

C BOD 5 Weekly Average 4 0 71,700

TSS Monthly Average 30 53,800

TSS Weekly Average 45 80,700



### WAC 173

- 221

- 050 subsection (3) states that, “for domestic wastewater facilities which receive flows from combined sewer, Ecology shall decide on a case

- by

- case basis whether any attainable percent removal can be defined during wet weather.” The West Point WWTP receives a more dilute influent during wet weather due to a collection system that combinesFact Sheet for NPDES Permit WA 0029181 Page 55 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### both sanitary sewage and storm water

. A dilute influent can make the 85% removal criteria

for CBOD 5 

### and TSS difficult to achieve

.
Calculations show that due to dilute influent at West Point during wet weather months

, effluent TSS and CBOD 5 

### average monthly effluent concentrations would have to be 13% and 19% lower, on average, than their respective discharge limits (30/25 mg/L) 36 and 49 percent of the time, re spectively, to meet the 85% removal requirement. Ecology calculated these values using average monthly influent concentrations over the past 5 years. According to the

EPA Permit Writer's Manual (page 5

- 11), this criteria qualifies the West Point facility f or less stringent percent removal requirements, consistent with 40 CFR 13 3.103(a). Ecology has

assessed historical data and concluded that the West Point facility can consistently achieve

80% TSS and CBOD 5 

### removal during the wet weather m onths of November through April; the 85% removal requirement applies during the remaining months.

F ederal CSO statute requires as one of the Nine Minimum Controls ( 9 MC No. 4) that King County maximizes flows to the plant during the wet season in order to minimize CSO

discha rges

. Ecology recognizes that increased flows and more dilute flows to the treatment plant over time may impact the achievable removal efficiency during wet weather conditions

. In accordance with the EPA CSO guidance document, Ecology will re

- evaluate wet season percent removal requirement s each permit cycle based on recent plant performance data.

CSO Treatment Plants



### The specific technology

- based limits that apply to CSOs are the nine minimum controls

. Also, CSO treatment plants must provide “primary treatment” which is defined in WAC

173

- 245

- 020(16) as “any process which removes at least 50% of the total suspended solids from the waste stream, and discharges less that 0.3 ml/L/hr of settleable solids.” Additionally, Ecology’s C riteria for Sewage Works Design clarifies that the 50% removal is to be assessed on an annual average basis.

Table 37

. Technology & Guidance

- based Limits for CSO Treatment Plants

Parameter Limit

TSS a 50% removal, annual average

Settleable Solids a 0.3 ml/L/hr, annual average

Fecal Coliform Bacteria b 400 /100 mL

a WAC 173

- 245

- 020(16)

b Washington State Department of Ecology, Criteria for Sewage Works Design , December 1998, p C3

- 21.



### Total Suspended Solids: The County’s four CSO treatment plants provide primary treatment which consists of sedimentation of solids and disinfection of the effluent prior to discharge

. In order to comply with Washington State regulation, the limit for all CSO treatment plants is based on overall p ercent removal of total suspended solids of 50% or greater

. The overall percent removal on an annual basis includes the removal achieved at the CSO treatment plant

and that achieved at the West Point WWTP.

Settleable Solids: Ecology evaluates compliance of the CSO treatment plant effluent with the 0.3 ml/l/hr of settleable solids limit based on a yearly average due to the intermittent and highly variable operation of the CSOs

. Ecology removed the settleable solids event
maximum limit of 1.9 ml/l/hr because the re is no basis in regulation for an event maximum

settleable solids limit.Fact Sheet for NPDES Permit WA 0029181 Page 56 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Fecal Coliform: Ecology’s technical guidance document ( Criteria for Sewage Works Design

, C3

- 3.3.8 ) states that an appropriate performance criteri on for end

- of

- the

- pipe CS O treatment for

fecal coliform is 400 cfu/100 mL

. Ecology believes t h is criteri on is appropriate and achievable

for the Alki, Carkeek , and Henderson/MLK facilit ies based on data collected between September 2009 and September 2013 . During this time, Alki me t the fecal coliform criteria 13 of the 16 months in which discharges occurred

, t he Carkeek facility met the criteria 9 of the 11 months in which discharges occurred , and the Henderson/MLK facility met the criteria 3 of the

4 months in which discharges occ urred

. Additionally, King County has recently upgraded equipment and improved SOPs at these facilities to improve future performance

. For Elliott West, the technical guidance

- based limit is applied as Ecology views this limit as more appropriate and prote ctive of water quality than the previous final limit. For further discussion, refer to sub

- section F below and Appendix F.

C. Surface w ater q uality

- b ased e ffluent l imit s

The Washington State surface water quality standards ( c hapter 173

- 201A WAC) are designed to protect existing water quality and preserve the beneficial uses of Washington 's

surface waters

. W aste discharge permits must include conditions that ensure the discharge

will meet the s urface w ater q uality s tandards (WAC 173

- 201A

- 510 )

. W ater qu ality

- based

effluent limits may be based on an individual waste load allocation or on a waste load

allocation developed during a basin wide total maximum daily load study (TMDL).

Numerical criteria for the protection of aquatic life and recreation

Numerica l water quality criteria are listed in the water quality standards for surface waters ( c hapter 173

- 201A WAC)

. They specify the maximum levels of pollutants allowed in receiving water to protect aquatic life and recreation in and on the water

. Ecology uses

n umerical criteria along with chemical and physical data for the wastewater and receiving water to derive the effluent limits in the discharge perm it

. When surface water quality

- based limits are more stringent or potentially more stringent than technology

- based limits

, the discharge must meet the water quality

- based limits

. Federal regulation (40 CFR 122.45(c)) require s Ecology to express effluent limits for metals in the form of total recoverable. However, the 1992 revision of the Washington Water Quality Standards express metals criteria in the dissolved form . Ecology therefore uses metal translators to predict the dissolved to total recoverable fraction in the receiving water. For marine waters, these translators are provided in WAC 173

- 201A

- 240(3) . Howev er, Ecology’s Permit Writer’s Manual recommends using the fraction of dissolved to total recoverable measured in the receiving water during the critical condition if data is available. King County provided both the dissolved and total recoverable fractions of several metals in

their 2013 Receiving Water Study and Ecology chose to use these ratios where applicable , as summarized in Table 38

.

Numerical criteria for the protection of human health

The U.S. EPA has published 91 numeric water quality criteria for the protection of human health that are applicable to dischargers in W ashington State (EPA, 1992). These criteria are designed to protect humans from exposure to pollutants linked to cancer and other diseases, based on consuming fish and shellfish and drinking contaminated surface waters. The water quality standards also inc lude radionuclide criteria to protect humans from the effects of

radioactive substances.Fact Sheet for NPDES Permit WA 0029181 Page 57 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 38

. Metal Translators U sed in Reasonable Potential Analyses

Metal Ecology Translators a Wt Point &
Carkeek Alki Elliott

West Henderson

/ MLK b Acute Chronic

Arsenic 1.000 1.000 1.000 0.980 1.000 1.000

Cadmium 0.994 0.994 0.980 0.950 0.960 0.994

Chromium 0.993 0.993 0.96 0 0.993 0.993 0.993

Copper 0.830 0.830 0. 79 0 0.9 2 0 0. 79 0 0.830

Lead 0.951 0.951 0.951 0.951 0.951 0.951

Mercury 0.850 n/a 0.850 0.850 0.850 0.850

Nickel 0.990 0.990 1.000 0.950 0.970 0.990

Silver 0.850 n/a 0.850 0.850 0.850 0.850

Zinc 0.946 0.946 0.946 0.946 0.946 0.946

a From WAC 173

-

201A

- 240(3)

b Used Ecology's marine translators for all metals for this outfall because critical condition was not fully characterized with receiving water data ( e.g., unclear how partitioning is affected by salinity fluctuations).



### Narrative criteria

Narrative water quality criteria (e.g., WAC 173

- 201A

- 240(1); 2006) limit the toxic, radioactive, or other deleterious material concentrations that the facility may discharge to levels below those which have the potential to:

• Adversely affect designated water uses.

• Cause acute or chronic toxicity to biota.

• Impair aesthetic values.

• Adversely affect human health.

Narrative criteria protect the specific designated uses of all fresh waters (WAC 173

- 201A

- 200, 2006) and of all marine waters (WAC 173

- 201A

- 210

, 2006) in the s tate of Washington.

Antidegradation

De scription

-- The purpose of Washington's Antidegradation Policy (WAC 173

- 201A

- 300

- 330; 2006) is to:

• Restore and maintain the highest possible quality of the surface waters of Washington.

• Describe situations under which water quality may be lowered from its c urrent condition.

• Apply to human activities that are likely to have an impact on the water quality of surface

water.

• Ensure that all human activities likely to contribute to a lowering of water quality, at a minimum, apply all known, available, and reasona ble methods of prevention, control, and treatment (AKART).

• Apply three t iers of protection (described below) fo r surface waters of the state.

Tier I ensure s existing and designated uses are maintained and protected and applies to all waters and all sources of pollutions

. Tier II ensure s that waters of a higher quality than the criteria assigned are not degraded unless such lowering of water quality is necessary and in the overriding public interest

. Tier I I applies only to a specific list of polluting activities

. TierFact Sheet for NPDES Permit WA 0029181 Page 58 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### III prevent s the degradation of waters formally listed as "outstanding resource waters," and applies to all sources of pollution.

A facility must prepare a Tier II analysis when a ll three of t he following conditions are met :

• The facility is planning a new or ex panded action

.

• Ecology regulates or authorizes the action.

• The action has the potential to cause measurable degradation to existing water quality at the edge of a chronic mixing zone.

Fa cility Specific Requirements

-- Th e facilities covered by this permit must meet Tier I requirements

.

• Dischargers must maintain and protect existing and designated uses

. Ecology must not allow any degradation that will interfere with, or become injurious to, existing or designated uses, except as provided for in chapter 173

- 201A WAC

. Ecology’s analysis described in this section of the fact sheet demonstrates that the proposed permit conditions will protect existing and designated uses of the receiving water

.

Combined Sewer Overflows

Chapter 173

- 245 WAC requires that “ a ll CSO sites shall achieve and at least maintain the greatest reasonable reduction, and neither cause violations of applicable water quality standards, nor restrictions to the characteristic use s of the receiving water, nor accumulation of deposits which: (a) e xceed sediment criteria or standards; or (b) have an adverse biological

effect.” The greatest reasonable reduction means control of each CSO outfall such that an average of no more than one untreated discharge may occur per year

. Ecology includes specific conditions in the proposed permit to ensure that the Permit t ee continues to make progress towards meeting water quality goals for each CSO outfall in its system

. Section V of

this fact shee t contains more detailed information on these CSO requirements

.

Mixing z ones

A mixing zone is the defined area in the receiving water surrounding the discharge port(s), where wastewater mixes with receiving water

. Within mixing zones the pollutant

concen trations may exceed water quality numeric standards, so long as the discharge doesn’t

interfere with designated uses of the receiving water body ( for example

, recreation, water supply , and aquatic life and wildlife habitat , etc .) The pollutant concentrations outside of the mixing zones must meet water quality numeric standard s.

State and federal rules allow mixing zones because the concentrations and effects of most pollutants diminish rapidly after discharge, due to dilution

. Ecology defines mi xing zone sizes to limit the amount of time any exposure to the end

- of

- pipe discharge could harm water quality, plants, or fish.

The state’s water quality standards allow Ecology to authorize mixing zones for the facility’s permitted wastewater discharges only if those discharges already receive all known, available, and reasonable methods of prevention, control

, and treatment (AKART)

. Mixing zones typically require compliance with water quality criteria within a specified distance from the point of dischar ge and must not use more than 25% of the available width of the water body for dilution [ WAC 173

- 201A

- 400 (7)(a)(ii

- iii) ]

.Fact Sheet for NPDES Permit WA 0029181 Page 59 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Ecology uses modeling to estimate the amount of mixing within the mixing zone

. Through modeling Ecology determine s the potential fo r violating the water quality standards at the edge of the mixing zone and derive s any necessary effluent limit s

. Steady

- state models are the most frequently used tools for conducting mixing zone analyses

. Ecology chooses values

for each effluent and for receiving water variable s that correspond to the time period when

the most critica l condition is likely to occur (see Ecology’s Permit Writer’ s Manual )

. Each critical condition parameter

, by itself

, has a low probability of occurrence and the resulting

dil ution factor is conservative

. The term “ reasonable worst

- case ” applies to these values.

The mixing zone analysis produces a numerical value called a dilution factor (DF)

. A

d ilution factor represents the amount of mixing of effluent and receiving water that occurs at the boundary of the mixing zone

. For example, a dilution factor of 10 means the effluent is 10% and the receiving water is 90% of the total volume of water at the boundary of the mixing zone

. Ecology uses d ilution factor s with the water qual ity criteria to c al culate reasonable potentials and effluent limits

. Water quality standards include both aquatic

life

- based criteria and human health

- based criteria

. The former are applied at both the acute and chronic mixing zone boundaries ; the latter are applied only at the chronic boundary

. The concentration of pollutants at the boundar ies of any of these mixing zones may not exceed

the numerical criteria for that zone

.
Most of the aquatic life acute criteri a are based on the assumption that organism s are not exposed to that concentration for more than one hour and more often than one exposure in three years

. Most of the aquatic life chronic criteri a are based on the assumption that organisms are not exposed to that concentration for more than four consecutive days and

more often than once in three years

. The two types of human health

- based water quality criteria distinguish between those pollutants linked to non

- cancer effects (non

- carcinogenic) and those linked to cancer effects (carcinogenic)

. Th e human health

- based water quality criteria incorporate several exposure and risk assumptions

. These assumptions include:

• A 70

- year lifetime of daily exposures

.

• A n ingestion rate for fish or shellfish measured in kg/day

.

• A n ingestion rate of two liters/day for drinking water

.

• A one

- in

- one

- million cancer r isk for carcinogenic chemicals.

This permit authorizes acute mixing zone s for each outfall, surrounded by chronic mixing

zone s around each point of discharge ( WAC 173

- 201A

- 400 )

. The water quality standards impose certain conditions before allowing discharger s a mixing zone:

1. Ecology must specify both the allowed size and location in a permit.

Th e proposed permit specifies the size s and location s of the allowed mixing zone s (as specified below)

.

2. The facility must f

ully apply “all known

, available

, and reasonable methods of prevention,

control and treatment” (AKART) to its discharge s

. Ecology has determined that the treatment provided meet s the requirements of AKART

.

3. Ecology must c onsider critical disc harge condition s

. Surface water quality

- based limits are derived for the water body’s critical condition ( the receiving water and waste discharge condition with the highest potential for adverse impactFact Sheet for NPDES Permit WA 0029181 Page 60 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### on the aquatic biota, human health, and existing or des ignated water body uses )

. The critical discharge condition is of

ten pollutant

- specific or water body

- specific.

Critical discharge conditions are those conditions that result in reduced dilution or increased effect of the pollutant

. Factors affecting dilution include the depth of water, the density stratification in the water column, the currents

, and the rate of discharge

. Density stratification is determined by the salinity and temperature of the receiving water

. Temperatures are warmer

in the surface waters in summer

. Therefore, density stratification is generally greatest during

the summer months

. Density stratification affects how far up in the water col umn a freshwater plume may rise

. The rate of mixing is greatest when an effluent is rising

. The effluent stops rising when the mixed effluent is the same density as the surrounding water

. After the effluent stops rising , the rate of mixing is much more gradual

. Water depth can affect dilution when a plume might rise to the surface when there is little or no stratification

. Ecology uses the water depth at mean lower low water (MLLW) for marine waters

. Ecology’s Permit Writer’s

Manual describes additional guidance on criteria/design conditions for dete rmining dilution

factors

. The m anual can be obtained from Ec ology’s website at:

http://www.ecy.wa.gov/biblio/92109.html



### .

West Point WWTP



### King County modeled the West Point WWTP discharge using the critical conditions listed in

Table 39

.

Table 39

. West Point WWTP

- Critical Conditions Used to Model the Discharge

.

Critical Condition Value

Water depth at MLLW 230 feet

Number of diffuser ports 200

Diffuser port diameter 4.5”

- 5.75“

Acute Condition:

Density profile with a difference of 0. 1 sigma

- t units between 246 feet and the surface ( Dec )

10 th or 90 th percentile current speeds 0. 428

- 0. 49 m/sec

Maximum daily effluent flow 404 MGD

Chronic and Human Health Condition s : Density profile with a difference of 1.5 sigma

- t units between 246 feet and the surface (July)

50th percentile current speeds for chronic and human health mixing zones 0. 252

- 0. 264 m/sec

Maximum ave monthly effluent flow for chronic and human health non

- carcinogen 87 MGD

Annual average flow for human health carcinogen (design average annual flow) 142 MGD

Source: King County’s 2013 Effluent Dilution Modeling Report for the West Point WWTP Outfall



### CSO Treatment Plants



### King County derived the chronic and acute dilution factors for the intermittent CSO discharges using effluent flow rates calculated according to guidance in Ecology’s Permit Writer’s Manual, Appendix 6

. Table 40 summarizes t he very conservative methodology King County used to assess treatment plant flows for these intermittent discharges.

Table 40

. CSO discharge flows used in dilution calculations

Acute E quivalent 24

- hour A verage Flow = total event volume divided by total event duration

. King

County used the event with the highest equivalent 24

- hr flow for each assessment.

Chronic E quivalent M onthly A verage Flow = T otal volume of all discharge events in a month divided by

the total hours of discharge in that month. King County used the highest equivalent monthly average flow from the previous 3 years of operation for each assessment.Fact Sheet for NPDES Permit WA 0029181 Page 61 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### King County modeled the Alki , Carkeek, Elliott West, and Henderson /MLK CSO treatment plant discharges using the critical conditions listed in Table 41 through Table 44

.

Table 41

. Alki CSO TP: Critical Conditions Used to Model th e Discharge

Critical Condition Value

Water depth at MLLW 143 feet

Number of diffuser ports 8

Diffuser port diameter 12”

Acute Condition:

Density profile with a difference of 0. 7 sigma

- t units between 147 feet and the surface

10 th or 90 th percentile current speeds 0.05 m/sec

Maximum equivalent 24

- hour flow 52 MGD

Chronic Condition:

Density profile with a difference of 0

. 04 sigma

- t units between 147 feet and the surface

50th percentile current speeds 0. 16 m/sec

Maximum equivalent monthly average effluent flow 33 MGD

Source: King County’s 2013 Effluent Dilution Modeling Report for the Alki CSO TP Outfall

Table 42

. Carkeek CSO TP: Critical Conditions Used to Model the Discharge

Critical Condition Value

Water depth at MLLW 195 feet

Number of diffuser ports 13

Diffuser port diameter 5.5

- 10 ”

Acute Condition:

Density profile with a difference of 0.25 sigma

- t units between195 feet and the surface

10 th or 90 th percentile current speeds 0.02 & 0.15 m/sec

Maximum equivalent 24

- hour flow 9.5 MGD

Chronic Condition:

Density p rofile with a difference of 0.5 sigma

- t units between195 feet and the surface

50th percentile current speeds 0.05 m/sec

Maximum equivalent monthly average effluent flow 9.3 MGD

Source: King County’s 2013 Effluent Dilution Modeling Report for the Carkeek CSO TP Outfall

Table 43

. Elliott West CSO TP: Critical Conditions Used to Model the Discharge

Critical Condition Value

Water depth at MLLW 60 feet

Number of diffuser ports 1

Diffuser port diameter 90 ”

Acute Condition:

Density profile with a difference of 0.9 sigma

- t units between 60 feet and the surface

10 th or 90 th percentile current speeds 0.0 2 5 & 0.1 m/sec

Maximum equivalent 24

- hour flow 67 MGD

Chronic Condition:

Density profile with a difference of 1. 4 sigma

- t units between 60 feet and the surface

50th percentile current speeds 0.05 m/sec

Maximum equivalent monthly average effluent flow 58 MGD

Source: King County’s 2013 Effluent Dilution Modeling Report for the Elliott West CSO TP OutfallFact Sheet for NPDES Permit WA 0029181 Page 62 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 44

. Henderson/MLK CSO TP: Critical Conditions Used to Model the Discharge

Critical Condition Value

Number of diffuser ports 1

P ort diameter 84 ”

50 th percentile current speed for chronic mixing zone 0.21 m/s

10 th & 90 th percentile current speeds for acute mixing zone 0. 0 78 & 0.39 m/s

Maximum average monthly effluent flow for chronic = used chronic facility design flow 25 MGD

Maximum daily flow for acute mixing zone

– used acute facility design flow 77 MGD

Source: King County’s 2013 Effluent Dilution Modeling Report for the Henderson/MLK CSO TP Outfall

. Ambient data at critical conditions in the vicinity of the outfall were taken from the Henderson/MLK

Pre

- design Report.



### 4. Supporting information must clearly indicate the mixing zone would not:

• H ave a reasonable potential to c ause the loss of sensitive or important habitat.

• S ubstantially interfere with the existing or characteristi c uses.

• R esult in damage to the ecosystem

.

• A dversely affect public health.

Ecology established Washington State water quality criteria for toxic chemicals using

EPA criteria

. EPA developed the criteria using toxicit y tests with numerous organisms

and set the criteria to generally protect the species tested and to fully protect all commercially and recreationally important species

.

EPA sets a cute criteria for toxic chemicals assuming organisms are exposed to the pollutant at the criteria concentration for one hour

. They set chronic standards assuming organisms are exposed to the pollutant at the criteria concentration for four day s

.

T he discharge plume does not impact d rifting and non

- strong swimming organisms because they cannot stay in the plume close to the outfall long enough to be affected

. Strong swimming fish could maintain a position within the plume, but they can also

avo id the discharge by swimming away

. M ixing zone s generally do not affect b enthic organisms (bottom dwellers) because the buoyant plume rises in the water column

. Ecology has additionally determined that the effluent will not exc eed 33 degrees C for

more tha n two seconds after discharge; and that the temperature of the water will not create lethal conditions or blockages to fish migration

. Ecology evaluates the cumulative toxicity of an effluent by testing the discharge with

w hole effluent toxicity (WET) tes ting

. Ecology reviewed the above information, the specific information on the characteristics of the discharge, the receiving water characteristics

, and the discharge location

. Based on

this review

, Ecology concluded that the discharge does not have a reasonable potential to cause the loss of sensitive or important habitat, substantially interfere with existing or characteristics uses, result in damage to the ecosystem

, or adversely affect public health if the permit limits are met

.

5. T he discharge/receiv ing water mixture must not exceed w ater quality criteria outside the boundary of a mixing zone.

Ecology conducted a reasonable potential analysis, using procedures established by the

EPA and by Ecology , f

or each pollutant and concluded the discharge/receiv ing water

mixture will not violate water quality criteria outside the boundary of the mixing zone if permit limits are met

.Fact Sheet for NPDES Permit WA 0029181 Page 63 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 6. The size of the mixing zone and the concentrations of the pollutants must be minimized.

At any given time, the effluent plume uses o nly a portion of the acute and chronic mixing zone, which minimizes the volume of water involved in mixing

. Because tidal currents change direction, the plume orientation within the mixing zone changes

. The plume

mixes as it rises throu gh the water column therefore much of the receiving water volume at lower depths in the mixing zone is not mixed with discharge

. Similarly, because the discharge may stop rising at some depth due to density stratification, waters above that depth will not mix with the discha rge

. Ecology determined i t is impractical to specify in the permit the actual, much more limited volume in which the dilution occurs as the plume rises and moves with the current

. Ecology minimizes the size of mixing zones by requiring dischargers to inst all diffusers when they are appropriate to the discharge and the receiving waterbody

. When a diffuser

is installed

, the discharge is more completely mixed with the receiving water in a shorter

time

. Ecology also minimizes the size of the mixing zone (in th e form of the dilution factor) using design criteria with a low probability of occurrence

. For example, Ecology uses the expected 95th percentile pollutant concentration, the 90th percentile background concentration, the centerline dilution factor

, and the lowest flow occurring once in every

ten years to perform the reasonable potential analysis.

Because of the above reasons, Ecology has effectively minimized the size s of the mixing

zone s authorized in the proposed permit

.

7. Maximum size of mixing zone

.
The authorized mixing zone s do not exceed the maximum size restriction s

. Mixing zone dimensions are depicted in Figure 10 through Figure 14

.

8. Acute m ixing z one

.

• The discharge/receiving water mixture must comply with acute criteria as near to the point of discharge as practicably attainable.

For each outfall, Ecology determined whether t he acute criteria w ould be met at 10% of the distance or volume fraction of the chronic mixing zone

.

• The pollutant concentration, duration, and frequency of exposure to the discharge will not create a barrier to migration or translocation of indigenous organisms to a degree that has the potential to cause damage to the ecosystem.

As described above, the toxicity of any pollutant depends upon the exposure, the pollutant concentration, and the time the organism is exposed to that concentration

. Authorizing a limited acute mixing zone for this discharge assures that it will not create a barrier to migration

. The effluent from this discharge will rise as it enters the receiving water, assuring that the rising effluent will not cause translocation of indigenou s organisms near the point of discharge (below the rising effluent).

• Comply with size restrictions.

The mixing zone authorized for this discharge complies with the size restrictions published in chapter 173

- 201A WAC.

9. Overlap of mixing zones

.
The mixing zone s authorized in this permit do not overlap other mixing zone s

.Fact Sheet for NPDES Permit WA 0029181 Page 64 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Diffuser: Diameter = 42”, Length = 120’ with 8 (12”) Ports, 2,000’ offshore Plan View 806 ft

Side View

- 143 ft MLLW

0 ft MLLW Acute Mixing Zone Boundary

189 ft
188.6ft Chronic Mixing Zone Boundary 686 ft 68.6 ft 188.6 ft

Not to Scale Figure 10 . West Point’s WWTP’s Mixing Zone

Figure 11

. Alki’s Mixing ZoneFact Sheet for NPDES Permit WA 0029181 Page 65 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 12 . Carkeek’s Mixing Zone Zone

Figure 13 . Elliott West Mixing Zone 96 inch Outfall Pipe w/ open end port Plan View 520 ft

Chronic Mixing

Zone Boundary

Side View

- 60 ft MLLW 52 ft

0 ft MLLW Acute Mixing

Zone Boundary Diffuser length = 50 ft. Diffuser Dia. = 33in. 13 ports, 5

- 10 inches in diameter. Plan View 840 ft

Side View

- 195 ft MLLW

0 ft MLLW Acute Mixing

Zone Boundary

129 ft Chronic Mixing

Zone Boundary 790 ft 79 ft 129 ft

Not to ScaleFact Sheet for NPDES Permit WA 0029181 Page 66 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Figure 14 . Henderson/MLK Mixing Zones



### D. Designated u ses and s urface w ater q uality c riteria

Applicable designated uses and surface water quality criteria are defined in c hapter

173

- 201A WAC

. In addition, the U.S. EPA set human health criteria for toxic pollutants (EPA 1992)

. The descriptions and table s below summarize the c riteria applicable to the receiving water’s designated uses

.

Puget Sound Discharges:

Aquatic life uses are designated usin g the following general categories

. All indigenous fish

and non

- fish aquatic species must be protected in waters of the state.

a. Extraordinary quality salmonid and other fish migration, rearing, and spawning; clam, oyster, and mussel rearing and spawning; cr ustaceans and other shellfish (crabs, shrimp, crayfish, scallops, etc.) rearing and spawning.

b. Excellent quality salmonid and other fish migration, rearing, and spawning; clam, oyster, and mussel rearing and spawning; crustaceans and other shellfish (crabs, shrimp, crayfish, scallops, etc.) rearing and spawning.

c. Good quality salmonid migration and rearing; other fish migration, rearing, and spawning; clam, oyster, and mussel rearing and spawning; crustaceans and other shellfish (crabs, shrimp, crayfish, scal lops, etc.) rearing and spawning.

d. Fair quality salmonid and other fish migration.

The West Point WWTP, Alki CSO TP , and the Carkeek CSO TP discharge to Extraordinary

Marine waters. The Aquatic Life Uses and the associated criteria for this receiving water are identified in Table 45

. Plan View

- not to scale Dilution Zone = 300 ft + diffuser depth = 312 ft

Width of plume =

74 feet (from
CORMIX model) Max. = 100 ft.

50 th % current = 0.21 m/s

10 th and 90 th % currents = 0. 078 & 0. 39 m/s

River width =
300 ft

Outfall is located at bank.

Pipe is 8 ” diameter cast iron. Acute Zone
= 31 ftFact Sheet for NPDES Permit WA 0029181 Page 67 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 45 . Marine Aquatic Life Uses and Criteria

- Wes t Point WWTP, Alki, and Carkeek

Extraordinary Quality

Temperature Criteria

– Highest 1D MAX 13°C (55.4°F)

Dissolved Oxygen Criteria

– Lowest 1

- Day Min 7.0 mg/L

Turbidity Criteria • 5 NTU over background when the background is 50 NTU or less; or

• A 10 percent increase in turbidity when the background turbidity is more than 50 NTU.

pH Criteria pH must be within the range of 7.0 to 8.5 with a human

- caused variation within the above range of less than 0.2 units.



### The Elliott West CSO TP discharge s to Excellent Marine waters. The Aquatic Life Uses and

th e associated criteria for this receiving water are identified in Table 46

.

Table 46

. Marine Aquatic Life Uses and Associated Criteria

- Elliott West

Excellent Quality
Temperature Criteria

– Highest 1D MAX 16°C (60.8°F)
Dissolved Oxygen Criteria

– Lowest 1

- Day Min 6.0 mg/L
Turbidity Criteria • 5 NTU over background when the background is 50 NTU or less; or

• A 10 percent increase in turbidity when the background turbidity is more than 50 NTU.
pH Criteria pH must be within the range of 7.0 to 8.5 with a human

- caused variation within the above range of less than 0.5 units.



### To protect shellfish harvesting in the receiving waters around the West Point WWTP, Alki, Carkeek, and Denny/Elliott West CSO treatment plants, fecal coliform organism levels must not exceed a geometric m ean value of 14 colonies/100 mL and not have more than 10 percent of all samples (or any single sample when less than ten sample points exist) obtained for calculating the geometric mean value exceeding 43 colonies/100 mL.

R ecreational uses include primary contact and secondary contact recreation . The recreational

use for receiving waters around the West Point WWTP, Alki, Carkeek, and Elliott West CSO treatment plant outfall s is primary contact as identified in Table 47

.
Miscellaneous marine water uses include wildlife habitat, harvesting, commerce and navig ation, boating, and aesthetics.

Table 47

. Recreational Uses

- West Point WWTP, Alki, Carkeek, and Elliott West

Recreational Use Criteria

Primary Contact

Recreation Fecal coliform organism levels must not exceed a geometric mean value of 14
colonies/100 mL , with not more than 10 percent of all samples (or any single sample when less than ten sample points exist) obtained for calculating the geometric mean value exceeding 43 colonies /100 mL.



### Duwamish River Discharge (Henderson/MLK) :

The Henderson /MLK CSO TP discharges to the Duwamish River. Ecology designated this portion of the river with an Aquatic Life Use of rearing and migration only and a R ecreation

U se of secondary contact

. However, salinity data from King County’s 2012 Receiving Water Study an d other sources indicates that the receiving water in the vicinity of the Henderson/MLK outfall is tidally influenced and meets the salinity requirements of WACFact Sheet for NPDES Permit WA 0029181 Page 68 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 173

- 201a

- 260. This means that the marine criteria apply to this waterbody for all parameters

ex cept for fecal coliform

. The criteria for Excellent Aquatic Life Uses are listed in Table 48

.

Table 48

. Receiving Water Criteria Comparison for Henderson /MLK

Aquatic Life Uses Marine Criteria: Excellent

Temperature 16°C (60.8°F)

– Highest 1D MAX

Dissolved Oxygen 6.0 mg/L

– Lowest 1

- Day Minimum

Turbidity • 5 NTU over background when the background is 50 NTU or less; or

• A 10 percent increase in turbidity when the background turbidity is more than 50 NTU.

pH pH must be within the range of 7.0 to 8.5 with a human

- caused variation within the above range of less than 0.5 units.

Recreational Use Freshwater Criteria: Secondary Contact

Fecal Coliform Fecal coliform organism levels must not exceed a geometric mean value of 200 colonies/100 mL, with not more than 10 percent of all samples (or any single sample when less than ten sample points exist) obtained for calculating the g eometric mean value exceeding 400 colonies /100 mL

.



### For fecal coliform, WAC 173

- 201a

- 260 states that freshwater criteria must be applied when ninety

- five percent of the salinity values are less than ten parts per thousand (based on vertically averaged daily maximum salinity values). Ecology placed freshwater criteria in the proposed permit, consistent with the existing permit. This decision is supported by the fact that this treatment facility only discharges once or twice each year and during very larg e storm events when the river flow is likely high from significant storm runoff. Under these circumstances the salinity component of the receiving water is most likely quite insignificant. As discharges from the facility increase with future CSO correction projects, Ecology may require future ambient salinity testing to support this decision.

The miscellaneous fresh water uses for the Henderson/MLK receiving water are wildlife habitat, harvesting, commerce and navigation, boating, and aesthetics.

E. Water q uality and sediment i mpairments

Central Puget Sound, South Puget Sound, and Elliott Bay are listed on Ecology’s 2012 303(d) list a s impaired for fecal coliform in the vicinities of the West Point WWTP, Alki, Carkeek, and E l liott West CSO outfalls. Ecology is not currently conducting a fecal coliform Total Maximum Daily Load (TMDL) a nalysis for these areas. I nstead , Ecology is focusing

on the South Puget Sound Dissolved Oxygen study ; this study should be finalized in the next few years

.
The Duwamish River is listed as impaired for high pH in the vicinity of the Henderson/MLK

CSO outfall. Downstream of the outfall in the lower Duwamish

, sediments and fish tissue are listed as impaired for a wide range of contaminants due to decades of industrial activity and

run off from industrial areas. These contaminants include PCBs (polychlorinated biphenyls), PAHs (polycyclic aromatic hydrocarbons), chlorinated dioxins & furans, arsenic and other metals, pesticides and phthalates. EPA is leadi ng the sediment contamination investigation for the Lower Duwamish Waterway site with support from Ecology. In 2001, EPA added the Lower Duwamish Waterway site to the Superfund National Priorities List; Ecology added the site to the Washington Hazardous Si tes l ist in 2002. More information on the Lower Duwamish Waterway Superfund site can be found on EPA’s web page: Lower Duwamish Waterway site . More information on the sediment contaminat ion clean

- up can be found onFact Sheet for NPDES Permit WA 0029181 Page 69 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### the following sites: Duwamish River Cleanup Coalition ( http://www.duwamishcleanup.org ) the Lower Duwamish Work Group ( http://www.ldwg.org ), and Ec ology’s LDW webpage (http://www.ecy.wa.gov/programs/tcp/sites_brochure/lower_duwamish/lower_duwamish_hp.html).



### In 1992 Ecology issued an ammonia

- nitrogen TMDL in the Green/Duwamish system that

identified a zero ammonia

- nitrogen wasteload allocation for Kin g County’s Renton South WWTP ( except during emergencies and planned short

- term maintenance). King County responded to this TMDL by relocating their South Plant WWTP outfall to the Puget Sound.

F. Evaluation of s urface w ater q uality

- b ased e ffluent l imits for n umeric c riteria

Pollutants in an effluent may affect the aquatic environment ne ar the point of discharge (near

- field) or at a considerable distance f rom the point of discharge (far

- field)

. Toxic pollutants, for exam ple, are near

- field pollutants ; their adverse effects diminish rapidly with mixing in the receiving water

. Conversely

, a pollutant such as bio chemical oxygen demand (BOD) is a far

- field pollutant whose adverse effect occurs away from the discharge even

after dilution has occurred

. Thus , the method of ca lculating surface water quality

- based effluent limits varies with the point at which the pollutant has its maximum effect.

With technology

- based controls (AKART), predicted p ollutant concentrations in the discharge exceed water quality cr iteria

. Ecology therefore authorizes a mixing zone in accordance with the geometric configuration, flow restriction, and other restrictions imposed on mixing zones by c hapter 173

- 201A WAC.

Estuarine Mixing Zones (West Point WWTP, Alki, Carkeek, and Elliott West)

Chronic

-- WAC 173

- 201A

- 400(7)(b) specifies that mixing zones must not extend in any horizontal direction from the discharge ports for a distance greater than 200 feet plus the depth of water over the discharge ports as measured during MLLW

. The mixing zone extends from the top of the discharge ports to the water surface.

Acute

- WAC 173

- 201A

- 400(8)(b) specifies that in estuarine waters a zone where acute criteria may be exceeded must not extend beyond 10% of the distance established for the chronic zone

.

We st Point WWTP



### The diffuser at outfall 001 is 600 feet long with 200 ports spaced equally on alternating sides with diameters ranging between 4.5 and 5.75

- inches. The mean lower low water (MLLW) diffuser depth is 230 feet. Ecology obtained this information from King County’s 2013 Effluent Dilution Modeling for West Point Treatment Plant Outfall Report

. The horizontal distance of the chronic mixing zone is 430 feet from any discharge port

. The acute mixing zone extends 43 feet in any directio n from any discharge port.

Alki CSO



### The Alki outfall ends in a multi

- port diffuser at a depth of 43.6m (143 ft) MLLW. The diffuser is 120 feet long with eight 12

- inch diameter diffuser ports. The first six ports are directed to alternating sides of the ou tfall. The two end ports formed a ‘Y’ at the end of the diffuser. Ecology obtained this information from King County’s 2013 Effluent Dilution Modeling

-

Alki CSO Treatment Facility Marine Outfall Report

. The horizontal distance of the chronic mixing zone is 340 feet

. The acute mixing zone extends 34 feet in any direction from any discharge port.Fact Sheet for NPDES Permit WA 0029181 Page 70 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Carkeek CSO Outfall



### The Carkeek outfall ends in a multi

- port diffuser at a depth of 59.5m (195 ft) MLLW. The diffuser is 50 feet long with 13 diffuser ports varying b etween 5.5

- inches and 10.0

- inches in diameter. The ports are equally spaced on alternating sides. A port diameter of 6.57 inches corresponds to the average port area. Ecology obtained this information from King County’s

2013 Effluent Dilution Modeling

- Cark eek CSO T reatment Facility Marine Outfall Report

. The horizontal distance of the chronic mixing zone is 395 feet from any discharge port

. The acute mixing zone extends 39.5 feet in any direction from any discharge port.

Elliott West CSO Outfall



### The Elliott West outfall ends with a single 90 inch diameter port at a depth of 60 ft MLLW, approximately 490 ft offshore. Several years ago King County removed a duckbill valve from the end of the port to reduce back pressure caused by the valve. Ecology obtained th is information from King County’s 2013 Effluent Dilution Modeling

- Elliott West CSO Treatment Facility Marine Outfall Report

. The horizontal distance of the chronic mixing zone is 260 feet from any discharge port

. The acute mixing zone extends 26 feet in any direction from any discharge port.

Freshwater Mixing Zone ( Henderson /MLK)

While the mari ne water quality criteria apply for the Henderson/MLK discharge, Ecology applied the freshwater mixing zone sizing criteria to the Henderson/MLK outfall because

WAC 173

- 201A

- 400(8)(a) states that riverine size criteria “may also be applied to estuaries having flow characteristics resembling rivers ”.

Chronic

-- WAC 173

- 201A

- 400(7)(a) specifies that mixing zones must not extend in a

downstream direction from the dischar ge ports for a distance greater than 300 feet plus the depth of water over the discharge ports or extend upstream for a distance of over 100 feet

, not utilize greater than 25% of the flow, and not occupy greater than 25% of the width of the water body

.

Ac ute

-- WAC 173

- 201A

- 400(8)(a) specifies that in rivers and streams a zone where acute toxics criteria may be exceeded must not extend beyond 10% of the distance towards the upstream and downstream boundaries of the chronic zone, not use greater than 2.5% of the flow and not occupy greater than 25% of the width of the water body

.
The Henderson/MLK effluent discharges through an 84

- inch, single

- port pipe, located at the

Norfolk outfall. The Norfolk outfall is located on the north bank of the Duwamish River approximately at river km 10.5. The 84

- inch diameter outfall approaches the river bank at a

90

- degree a ngle to the river flow and is flush with the bank. There is a flap gate on the end of the pipe that is assumed to be completely open during discharge events.

For the Henderson/MLK CSO t reatment p lant outfall, the chronic mixing zone is 312 feet long (downs tream) and 74 feet wide

. The acute mixing zone is 31.2 feet long

. Both mixing

zone s extend from the river bottom to the top of the water surface. The dilution factor s are based on dilution at th e downstream distance or where the plume width reaches 25% of the river width, whichever is more conservative

.

Dilution Factors

King County calculated the dilution factors that occur within these zones at the critical conditions using Visual Plumes (UM3 and RSB model components) for all outfalls exceptFact Sheet for NPDES Permit WA 0029181 Page 71 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Henderson/MLK, for which the County used the CORMIX model

. Table 49 compares the proposed dilution factors to the dilution factors in the current permit.

Ecology rev iew ed the County’s data, dilution factors, and modeling in November 2013. Ecology verified that the County used conservative assumptions and provided rigorous modeling to obtain dilution factors

. There are differences between the dilution factors used in the previous permit and the dilution factors used in the proposed permit as described below

. Ecology revised the dilution factors because calculations were performed with 1 ) updated receiving water current and density data

, and 2) updated effluent flow data obtained during the previous permit cycle

. Ecology considers the dilution factors in the proposed permit to be

more up

- to

- date and representative than the factors in the previous permit. Ecology notes that

three of the dilution factors increased and four dilution factors decreased from the previous permit.

Table 49 . Comparison of Dilution Factors

Chronic Dilution

Factor Acute Dilution

Factor Human Health,

Carcinogen Human Health,

Non

- carcinogen

Current

Permit Proposed

Permit Current

Permit Proposed

Permit Current

Permit Proposed

Permit Current

Permit Proposed

Permit

West Point WWTP 181 188 28 28 330 324 330 324

Alki CSO 61 99 17.5 20 * * * *

Carkeek CSO 146 104 93 75 * * * *

Elliott West CSO 11 9 .7 7.8 8 .4 * * * *

Henderson /MLK 10.3 10.3 1.9 1.9 * * * *

* Human Health dilution factors not assessed for CSO treatment plants . Ecology used chronic dilution factor s for reasonable potential assessments

.



### Changes in the proposed dilution factors can be explained as follows:

1. West Point WWTP

– Updated effluent and receiving water data resulted in a larger chronic dilution factor compared to the previous analysis. In the recent analysis, receiving water density data show that the receiving water is most stratified in July. This stratification results in reduced plume mixing and therefore lower dilution factors than those calculated during winter months. As a result, the maximum average monthly flow

used in the dilution ca lculation decreased from 204 MGD in the previous analysis to 87 MGD (max flow during July in past 3 years). This in combination with the updated receiving water density profile resulted in a slightly higher dilution factor. No change is proposed for the ac ute dilution factor.

2. Alki CSO

– Updated effluent and receiving water data resulted in larger chronic and acute dilution factors compared to the previous analysis.

3. Carkeek CSO

– Updated effluent and receiving water data resulted in reduced chronic

and acut e dilution factors compared to the previous analysis.

4. Elliott West CSO

– Updated effluent and receiving water data resulted in a reduced

chronic and a slightly larger acute dilution factor compared to the previous analysis.

5. Henderson/MLK CSO

– No dilution factors changes are proposed.

Ecology assessed the impacts of the treatment plant discharges on receiving water dissolved oxygen deficiency, pH, fecal coliform, turbidity, toxics ( ammonia, chlorine

, metals, and other priority pollutants), and temp erature using the dilution factors listed in Table 49

. TheFact Sheet for NPDES Permit WA 0029181 Page 72 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### following tables describe this assessment for each treatment plant. The derivation of any surface water qual ity

- based limits also takes into account the variability of pollutant concentrations in both the effluent and the receiving water.

West Point Wastewater Treatment Plant

Dissolved Oxygen

- BOD 5 and

Ammonia
Effects Natural decomposition of organic material in wastewater effluent impacts dissolved

oxygen (DO) in the receiving water at distances far outside of the regulated mixing

zone. The 5

- day Biochemical Oxygen Demand (BOD 5 ) of an effluent sample indicates the amount of biodegradable material in the wastew ater and estimates the magnitude of oxygen consumption the wastewater will generate in the receiving water. The

amount of ammonia

- based nitrogen in the wastewater also provides an indication of oxygen demand potential in the receiving water.

Ecology modele d the impact of BOD 5 on the receiving water using a simple mixing

model and an estimated oxidation rate at critical conditions (see Appendix F )

. Based on King County’s receiving water study, dissolved oxygen in the vicinity of the outfall is frequently below the water quality criteria of 7 mg/L. King County’s data shows the 10 th
percentile dissolved oxygen value as 6.1 mg/L. Under critical conditi ons, assuming a typical technology

- based weekly average effluent limit of 45 mg/L, t he mixing model

shows that dissolved oxygen decreases by 0. 0 7 mg/L at the chronic mixing zone

. Ecology is in the process of modeling the impacts of nutrient discharges from wastewater treatment plants and non

- point sources on dissolved oxygen levels in the

south Puget Sound. Ecology plans to publish the results of this study in the next several years. The results may impact nutrient control in future permit s but since the

st udy is not yet complete, the proposed permit does not include nutrient limit s. The proposed permit requires nutrient monitoring to provide data to better inform future permitting decisions.

pH Compliance with the technology

- based limits of 6.0 to 9.0 will assure compliance with

the water quality standards of surface waters because of the high buffering capacity of

marine water. For calculations see Appendix F.

Fecal
Coliform Ecology modeled receiving water fecal coliform by simple mixing analysis and a mbient

data from King County’s 2013 Receiving Water Characterization Study

. With a dilution

factor of 18 8 , a technology

- based limit of 400/100 mL, and an ambient fecal

concentrat ion of 4 /100 mL, Ecology calculated a fecal coliform concentration at the edge of the mixing zone boundary of 6 /100 mL, well below the water quality standard
of 14 colonies/100 mL (for primary contact recreation)

. Therefore, the proposed permit

includes the technology

- based effluent limit s for fecal coliform bacteria.

Turbidity Ecology evaluated the impact of turbidity based on the range of total suspended solids

in the effluent and turbidity of the receiving water. Ecology expects no violations of the

t urbidity criteria outside the designated mixing zone provided the facility meets its technology

- based total suspended solids permit limits.

Toxics Federal regulations (40 CFR 122.44) require Ecology to place limits in NPDES permits

on toxic chemicals in an effluent whenever there is a reasonable potential for those chemicals to exceed the surface water quality criteria

. Ecology does not exempt facilities with technology

- based effluent limits from meeting the surface water quality

standards.

The following toxic pollutants were detected in West Point WWTP’s discharge: ammonia, 1,4 dichlorobenzene, 2,4 dichlorophenol, 2,4 dimethylphenol, antimony, arsenic, bis(2

- ethylhexyl)phthalate, cadmium, chromium (hex), copper, cyanide, diethylphthalate, lead, manganese , methylene chloride, mercury, nickel, phenol, pyrene, selenium, silver, thallium, toluene, zinc, chlorine . Ecology conducted a reasonable potential analysis ( s ee Appendix F) on these parameters to assess whether
effluent limits would be require d.Fact Sheet for NPDES Permit WA 0029181 Page 73 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point Wastewater Treatment Plant

King Co unty provided ambient data in t heir 2013 receiving water study and the following parameters were detected in the receiving water: ammonia, arsenic, cadmium, chromium (hex), copper , lead, m ercury, nickel, silver, and zinc . Ecology

used the 90% concentrations for these pollutants in the reasonable poten tial analysis

and assumed zero for ambient concentrations if data was not available.

Ecology determined that none of the toxics detected in the effluent pose a reasonable potential to exceed the wa ter quality criteria at the critical condition using procedures given in EPA, 1991. Ecology’s determination assumes that this facility meets the other effluent limits of this permit.

Ecology derive d effluent limits for chlorine using methods from EPA, 1991 as shown in Appendix F. Ecology derived the new limits based on the state water quality standards of 13 μg/L for acute and 7.5 μg/L for chronic along with an acute dilution factor of 28

and a chronic dilution factor of 18 8

. The proposed effluent limits ar e 139 μg/L (average monthly limit) and 364 μg/L ( m aximum d aily l imit ).

Temperature The state te mperature standards ( WAC 173

- 201A

- 200

- 210 and 600

- 612 ) include

multiple elements: a nnual summer maximum threshold criteria, s upplemental spawning and rearing season criteria, i ncremental warming restrictions, and p r otections against
acute effects. Ecology evaluates each criterion independently to determine reasonable potential and derive permit limits.

Annual summer maximum and supplementary spawning/rearing criteria

- Each water body has an annual maximum temperature criterion [WAC 173

- 201A

- 200(1)(c), 210(1)(c), and Table 602]. These threshold criteria protect specific categories of aquatic life by controlling the effect of hum an actions on summer temperatures.

Some waters have an additional threshold criterion to protect the spawning and incubation of salmonids (9°C for char and 13°C for salmon and trout) [WAC 173

- 201A

- 602, Table 602]. These criteria apply during specific dat e

- windows.

The threshold criteria apply at the edge of the chronic mixing zone. Criteria for most fresh waters are expressed as the highest 7

- Day average of daily maximum temperature (7

- DADMax). The 7

- DADMax temperature is the arithmetic average of

seven c onsecutive measures of daily maximum temperatures. Criteria for marine waters and some fresh waters are expressed as the highest 1

- Day annual maximum temperature (1

- DMax).

Incremental warming criteria

- The water quality standards limit the amount of warm ing human sources can cause under specific situations [WAC 173

- 201A

- 200(1)(c)(i)

- (ii), 210(1)(c)(i)

- (ii)]. The incremental warming criteria apply at the edge of the chronic mixing zone.

At locations and times when background temperatures are cooler than th e assigned threshold criterion, point sources are permitted to warm the water by only a defined increment. These increments are permitted only to the extent doing so does not cause temperatures to exceed either the annual maximum or supplemental spawning c riteria.

At locations and times when a threshold criterion is being exceeded due to natural conditions, all human sources, considered cumulatively, must not warm the water more than 0.3°C above the naturally warm condition.

When Ecology has not yet comple ted a TMDL, our policy allows each point source to warm water at the edge of the chronic mixing zone by 0.3°C. This is true regardless of the background temperature and even if doing so would cause the temperature at the edge of a standard mixing zone to e xceed the numeric threshold criteria. Allowing a 0.3°C warming for each point source is reasonable and protective where the dilution factor is based on 25% or less of the critical flow. This is because the fully mixed effect on temperature will only be a f raction of the 0.3°C cumulative allowance (0.075°C or less) for all human sources combined.

Protections for temperature acute effects

– Instantaneous lethality to passing fish: The upper 99 th percentile daily maximum effluent temperature must not exceed 33°C, unless a dilution analysis indicates ambientFact Sheet for NPDES Permit WA 0029181 Page 74 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point Wastewater Treatment Plant

temperatures will not exceed 33°C two seconds after discharge.

General lethality and migration blockage: Measurable (0.3°C) increases in tempe rature at the edge of a chronic mixing zone are not allowed when the receiving water temperature exceeds either a 1DMax of 23°C or a 7DADMax of 22°C.

Lethality to incubating fish: Human actions must not cause a measurable (0.3°C) warming above 17.5°C at locations where eggs are incubating.

Reasonable Potential Analysis for Annual summer maximum and incremental warming criteria: Ecology calculated the reasonable potential for the discharge to exceed the annual summer maximum and the incremental warming criteria at the edge of the chronic mixing zone during critical conditions (see Appendix F ). No reasonable potential exists to exceed the temperature cri terion where:
(Criterion + 0.3) > [Criterion + (Teffluent 95

– Criterion)/DF]. ( 13 + 0.3) > ( 13 + ( 21.0

– 13.0 )/ 188 )

13.3 > 13.04
Therefore, the proposed permit does not include a temperature limit. King County reported temperature data with th eir monthly discharge monitoring reports; Ecology used the 95 th percentile of the 1DADmax value reported. Using a dilution f a ctor
of 18 8 and maximum daily temperature of 1 4 .0 °C for the receiving water, the predicted maximum daily temperature inside the dilution zone is 1 4

. 04 °C

. Thus, under the worst case scenario, the effluent discharge from this facility results in warming of the ambient temperature by 0.0 4 °C, which is less than the allowable warming temperature of 0.3°C.

Alki CSO Treatment Plant

Dissolved Oxygen

- BOD 5 Calculations show there is no reasonable potential for the Alki CSO treatment plant to

violate DO water quality standards. For calculations see Appendix F.

pH Compliance with the technology

- based limits of 6.0 to 9.0 will assure compliance with

the water quality standards of surface waters because of the high buffering capacity of

marine water

. For calculations see Appendix F.

Fecal
Coliform With the dilution factor of 99

, the guidance

- based limit of 400/1 00mL, and an ambient

fec al concentration of 1 /100 mL (from KC’s 2013 receiving water study ) , Ecology calculated a fecal coliform concentration at the edge of the mixing zone boundary of

5 /100 mL, which is below the water quality standard of 14 colonies/100 mL (see Appendix F )

. Therefore, the proposed permit includes the technology

- based effluent limit for fecal coliform bacteria, on a monthly basis, since it is protective of water quality and more stringent than the water

- quality based limit.

For CSO treatment plants that have technology/guidance

- based limits for fecal coliform, the calculation method only includes discharge days. Non

- discharge days are not included in the calculation, as the technology/guidance

- based limit applies only when

di scharges are occurring with the reasoning that the plant is capable of achieving the technology/guidance limit on any given day.

Toxics The following toxic pollutants are present in the Alki C SO treatment plant’s discharge:

ammonia, antimony, arsenic, b is(2

- ethylhexyl)phthalate, butylbenzyl phthalate, cadmium, chlorine, chloroform, chromium (hex), copper, diethylphthalate, lead, mercury, nickel, silver, and zinc. Ecology conducted a reasonable potential analysis (see Appendix F) on these parameters to as sess whether effluent limits would be required.

King County provided ambient data in their 2013 receiving water study and the following parameters were detected in the receiving water: ammonia, antimony, arsenic, cadmium, chlorine, chromium (hex), copper, lead, mercury, nickel, silver, and zinc. Ecology used the 90% concentrations for these pollutants in the reasonable potential analysis and assumed zero for ambient concentrations if data was not available.Fact Sheet for NPDES Permit WA 0029181 Page 75 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment Plant

Ecology determined that none of the toxics detecte d in the effluent, except chlorine,

pose a reasonable potential to exceed the water quality criteria at the critical condition using procedures given in EPA, 1991

. Ecology’s determination assumes that this facility meets the other effluent limits of this p ermit.

Ecology derived effluent limits for the toxic pollutant chlorine using methods from EPA, 1991 as shown in Appendix F. The calculated maximum daily water

- quality

- based limit
for chlorine based on the revised dilution factors is 260 μg/L. The previous permit

included a water

- quality based limit of 234 μg/L based the dilution factor in the 2009 permit. The anti

- backsliding provision under the federal regulations [CFR 122.44(l)] requires that the chlorine limit be based on the more stringent limit establ ished in the previous permit since it has been shown to be technologically achievable.

Temperature The County was not required to collect temperature data for this facility so Ecology

used West Point data for this assessment

. Using t he 95 th percentile of West Point’s

1DADmax (21.0°C) and a dilution factor of 99, no reasonable potential exists to exceed the temperature criterion where:
0.3 > (Teffluent95

– Tambient90)/DF 0.3 > (21.0

– 12.7)/99

0.3 > 0.08

U nder the se assumptions , the effluen t discharge from this facility results in warming of the ambient temperature by 0.0 8 °C, which is less than the allowable warming temperature of 0.3°C. Therefore, the proposed permit does not include a temperature

limit

.

Carkeek CSO Treatment Plant

Dissolved Oxygen

- BOD 5 Calculations show there is no reasonable potential for the Carkeek CSO treatment plant

to violate DO water quality standards. For calculations see Appendix F.

pH Compliance with the technology

- based limits of 6.0 to 9.0 will assure compliance with

the water quality standards of surface waters because of the high buffering capacity of marine water. For calculations see Appendix F.

Fecal Coliform With the dilution factor of 104

, the guidance

- based limit of 400/100mL, and an ambient

f ecal concentration of 4 /100 mL (obtained from King County’s 2013 ambient monitoring report ) , Ecology calculated a fecal coliform concentration at the edge of the mixing zone boundary of 8 /100mL, which is below the water quality standard of 14 colonies/100 mL (see Appendix F )

. Therefore, the proposed permit includes the guidance

- based effluent limit for fecal coliform bacteria, on a monthly basis, since it is protective of water quality and more stringent than the water quality

- based limit

. For CSO treatment plants that have technology/guidance

- based limits for fecal coliform, the calculation method only includes discharge days. Non

- discharge days are not included in the calculation, as the technology/guidance

- based limit applies only when

di scharges are occurring with the reasoning that the plant is capable of achieving the technology/gu idance limit on any given day.

Toxics The following toxic pollutants were detected in Carkeek CSO treatment plant’s

discharge: ammonia, antimony, arsenic, benzo(b)fluoranthene, benzo(k)fluoranthene, bis(2

- ethylhexyl)phthalate, butybenzyl phthalate, cadmium, chloroform, chromium (hex), copper, 2

- 4 dichlorophenol, diethylphthalate, di

- n

- butyl phthalate, lead, mercury, nickel,

silver , toluene, zinc, and chlorine. Ecology conducted a reasonable potential analysis (see Appendix F) on these parameters to assess whether effluent limits would be required.
King County provided ambient data in their 2013 receiving water study and the followi ng parameters were detected i n the receiving water: ammonia, arsenic, cadmium

, chromium (hex), copper, lead, mercury, nickel, silver, and zinc. Ecology used the 90% concentrations for these pollutants in the reasonable potential analysis and assumed
zero f or ambient concentrations if data was not available.Fact Sheet for NPDES Permit WA 0029181 Page 76 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plant

Ecology determined that none of the toxics detected in the effluent, except chlorine, pose a reasonable potential to exceed the water quality criteria at the critical condition using procedures given in EPA, 1991. Ecology’s determination assumes that this facility meets the other effluent limits of this permit.
Ecology derived effluent limits for the toxic pollutant chlorine, determined to have a reasonable potential to cause a violation of the water qual ity standards

. Ecology calculated effluent limits using methods from EPA, 1991 as shown in Appendix F. The

calculated maximum daily water

- quality

- based limit for chlorine based on the revised mixing zone is 975 μg/L

. The technology

- based maximum daily limi t for chlorine is more stringent than the water

- q uality

- based limit at 750 μg/L

. The previous permit included a

water

- quality based limit of 490 μg/L based on the dilution factor in th e 2004 permit

. The

anti

- backsliding provision under the federal regulati ons [CFR 122.44(l)] requires that the more stringent limit established in the previous permit be applied since it has been shown to be technologically achievable.

Temperature The County was not required t o collect temperature data for this facility so Ecology used

West Point data for this assessment. Using the 95 th percentile of West Point’s 1DADmax (21.0°C) and a dilution factor of 104, no reasonable potential exists to exceed the temperature criterion whe re: 0.3 > (Teffluent95

– Tambient90)/DF 0.3 > (21.0

– 14.0)/104

0.3 > 0.07
Under these assumptions, the effluent discharge from this facility results in warming of the ambient temperature by 0.0 7 °C, which is less than the allowable warming temperature of 0.3°C. Therefore, the proposed permit does not include a temperature

limit

.

Elliott West CSO Treatment Plant

Dissolved Oxygen

- BOD 5 Preliminary c alculations show there could be a reasonable potential for the effluent

from the Elliott West CSO treatment plant to violate DO water quality standards ( see Appendix F )

. Ecology could not make a reliable assessment due to very limited DO

data for this facility

. The proposed permit requi res additional DO monitoring so Ecology can better assess the impacts of BOD on dissolved oxygen in the receiving water at the next permit issuance. The Elliott West CSO treatment plant was originally designed
for CSO treatment and not designed to remove B OD. Ecology is addressing the impact

of effluent nutrients on Puget Sound DO in the ongoing South Puget Sound DO Study.

pH Compliance with the technology

- based limits of 6.0 to 9.0 will assure compliance with

the water quality standards of surface waters because of the high buffering capacity of marine water. For calculations see Appendix F.

Fecal
Coliform With the chronic dilution factor of 9 .7 , the guidance

- based limit of 400/100mL, an

ambient fecal concentration of 2/100 mL (obtained from King County’s 2013 ambient monitoring report), and an assumption that the facility discharges three times each month for a period of 24 hours

, Ecology calculated a monthly geometric mean for fecal coliform at the edge of the mixing zone boundary of 2. 4 /100mL . This easily meets the water quality standard of 14 colonies/100 mL (see Appendix F for calculations). Therefore, the proposed permit includes the guidance

- based effluent limit for fecal coliform bacteria, on a monthly basis, since it is protective of water qua lity and more stringent than the water quality

- based limit. The previous permit included this same guidance

- based limit for a n interim period followed by a less stringent WQ

- based limit

that included non

- discharge days in the calculation. Ecology now belie ves this guidance

- based limit is more appropriate and more protective of the water quality in Elliott Bay and therefore proposes this limit in the proposed permit.
For CSO treatment plants that have technology/guidance

- based limits for fecal

coliform , the calculation method only includes discharge days. Non

- discharge days are not included in the calculation, as the technology/guidance

- based limit applies onlyFact Sheet for NPDES Permit WA 0029181 Page 77 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment Plant

when discharges are occurring with the reasoning that the plant is capable of achieving

the t echnology/guidance limit on any given day. Compliance with this limit must be calculated using the geo metric mean of all fecal coliform samples taken during each

calendar month a discharge occurs

. Toxics The following toxic pollutants were detected in El liott West CSO treatment plant’s

discharge: ammonia, antimony, arsenic, bis(2

- ethylhexyl)phthalate, butylbenzyl phthalate, cadmium, chloroform, chromium (hex), copper, 1

- 4 dichlorobenzene, dichlorobromomethane, 2

- 4 dichlorophenol, diethylphthalate, dimeth ylphthalate, fluoranthene, lead, mercury, nickel, pentachlorophenol, pyrene, selenium, silver, thallium, toluene, zinc, chlorine , and cyanide (weak acid dissociable)

. King County provided ambient data in their 2013 receiving water study and the following parameters were detected in the receiving water: ammonia, arsenic, cadmium, chromium (hex), copper, lead, mercury, nickel, silver, and zinc. Ecology used the 90% concentrations for these pollutants in the reasonable potential analysis

and assumed zero for ambient concentrations if data was not available.

Ecology conducted a reasonable potential analysis (see Appendix F) on these parameters to determine if they pose a reasonable potential to exceed the water quality criteria at the critical condition using p rocedures given in EPA, 1991. Ecology

determined that the only toxics detected in the effluent that pose a reasonable potential

are chlorine

, copper , and cyanide

. Ecology’s determination assumes that this facility

meets the other effluent limits of th e per mit.

Ecology derived an effluent limit for chlorine using methods from EPA, 1991 as shown in Appendix F. The proposed chlorine effluent limit is based on the revised dilution

factor s King County calculated using recent effluent flow data. The resultant maximum daily effluent limit for chlorine is 109 μg/L

.
Calculations also showed a reasonable potential for copper

. The copper levels in the
Elliott West effluent are consistently five to six times higher than those from other King County outfalls

. The Cou nty suspects this is a sampling anomaly caused by contamination within the sampl ing collection system. The proposed permit requires

additional copper monitoring using an improved sampling technique

, along with a study

to evaluate copper reduction strategies includ ing source control options

, copper removal at the facility

, and improved outfall mixing

.
C yanide (weak acid dissociable) concentrations in the effluent were below detection (<5 μg/L) for 8 out of 11 samples; th e th ree detected s a mples measured 7 .3 (estimate)

, 11.8, and 19.3 μg/L. The proposed permit requires additional monitoring to better

assessment cyanide concentrations in the Elliott West effluent

. Temperature The County was not required to collect temperature data for this facility so Ecology

used West Point data for this assessment. Using the 95 th percentile of West Point’s 1DADmax (21.0°C) and a dilution factor of 9, no reasonable potential exists to exceed the temperature criterion where :

Max Incremental increase = 12 / (T

- 2) where T = ambient temp = 12 / (13.4

- 2)

= 1.05°

Max Incremental increase > (Teffluent95

– Tambient90 )/DF

1.05° > (21.0

– 1 3

. 4 ) / 9 .7

1.05° > 0. 78 °

This calculation is based on the requirements of WAC 173

- 201a

- 210(1)(c)(ii)(A)]. Under these assumptions, the effluent discharge from this facility results in warming of the ambient temperature by 0. 78 °C, which is less than the allowable warming temperature of 1.05 °C. Therefore, the proposed permit does not include a temperature

limit

.Fact Sheet for NPDES Permit WA 0029181 Page 78 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Henderson /MLK CSO Treatment Plant

Dissolved Oxygen

- BOD 5 Calculations show there is no reasonable potential for the Henderson/MLK CSO

treatment plant to violate DO water quality standards. For calculations see Appendix F.

pH Ecology modeled the impact of the effluent pH on the receiving water using the

calculations from EPA, 1988, and the ch ronic dilution factor of 10.3 (see Appendix F ). The receiving water input variables used were obtained from King County’s 2013

receivi ng water study and the effluent characteristics were obtained from DMRs. Using

the assumed values, Ecology predicts no violation of the pH criteria under critical

conditions

. Therefore, the proposed permit includes technology

- based effluent limits for pH.

Fecal
Coliform Ecology modeled the numbers of fecal col iform by simple mixing analysis. With the

dilution factor o f 10.3

, the guidance

- based limit of 400/100mL, and an ambient fecal
concentration of 110 /100 mL obtained from King County’s 2013 receiving water study

, Ecology calculated a fecal coliform concentration at the edge of the mixing zone boundary of 138 /100mL, which is below the water quality standard of 200 colonies/100 mL (for freshwater recreational s econdary contact)

. Therefore, the proposed permit includes the guidance

- based effluent limit for fecal coliform bacteria, on a monthly basis, since it is protective of water quality and more stringent than the water quality

based limit

. Toxics Based on three sampling events, t he following toxic pollutants were detected in the

Henderson/MLK CSO treatment plant’s discharge: ammonia, antimony, arsenic, bis(2

- ethylhexyl)phthalate, cadmium, chlorine, chloroform, chromium (hex), chromium (tri), copper, dichlo robromomethane, 2

- 4 dichlorophenol, diethylphthalate, dimethylphthalate, di

- n

- butyl phthalate, lead, mercury, nickel, phenol, zinc, and cyanide

. Ecology did not conduct a reasonable potential analysis on these parameters because it would not be prudent to set a limit based on three data points. Instead, Ecology is requiring the County to sample for priority pollutants during the next permit cycle for re

assessment with the next permit issuance.

Ecology derived an effluent limit for chlorine using methods fr om EPA, 1991 as shown in Appendix F. The proposed chlorine effluent limit is based on the dilution factors King County calculated using recent effluent flow data. The resultant maximum daily

average effluent limit for chlorine is 25 μg/L

, but since the chlorine analyzers cannot

accurate ly measure in this range the limit was kept at 39 μg/L. This limit will be protective of the maximum daily water quality criteria since additional chlorine decay occurs in the 5000 foot outfall line. Also, t he Henderson/MLK facility typically discharges for less than 24 hours, therefore, if the proposed limit is met, the daily average concentration will be less than 25 μg/L.

Temperature The County was not required to collect temperature data for this facili ty so Ecology

used West Point data for this assessment. Using the 95 th percentile of West Point’s 1DADmax (21.0°C) and a dilution factor of 10.3, no reasonable potential exists to exceed the temperature criterion where:

0.3 > (Teffluent95

– Tambient9 0 )/DF

0.3 > (21.0

– 18.7 )/10.3

0 .3 > 0.2 Under these assumptions, the effluent discharge from this facility results in warming of the ambient temperature by 0. 22 °C, which is less than the allowable warming temperature of 0.3°C. Therefore, the proposed permit does not include a temperature

limit

.Fact Sheet for NPDES Permit WA 0029181 Page 79 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### G. Human h ealth

Washington’s water quality standards include 91 numeric human health

- based criteria that Ecology must consider when writing NPDES permits

. These criteria were established in

1992 by th e U.S. EPA in its National Toxics Rule (40 CFR 131.36)

. The National Toxics

Rule allows states to use mixing zone s to evaluate whether discharges comply with human

health criteria.

Ecology determined the effluent s for the West Point WWTP, Alki CSO TP, Carkeek CSO TP, Elliott West CSO TP, and the Henderson/MLK CSO TP may contain chemicals of concern for human health, based on (1) the facilit ie s ’ status as EPA major discharger s
, or (2) data or information indicating regulated chemicals occur in the discha rge s . Ecology evaluated the discharges ’ potential to violate the water quality standards as required by 40 CFR 122.44(d) by following the procedures published in the Technical Support Document for Water Quality

- Based Toxics Control (EPA/505/2

- 90

- 001) and E cology's Permit Writer's

Manual to make reasonable potential determination s (Appendix F)

. For all facilities listed above, the evaluation s showed that the discharge s ha ve no reasonable potential to cause

violation of the human health water quality standar d s and effluent limits are not needed

.

H. Sediment q uality

The aquatic sediment standards ( c hapter 173

- 204 WAC) protect aquatic biota and human

health

. Under t hese standards Ecology may require a facility to evaluate the potential for its discharge to cause a violation of sediment standards (WAC 173

- 204

- 400). You can obtain additional information about sediments at the Aquatic Lands Cleanup Unit website

. http://www.ecy.wa.go v/programs/tcp/smu/sediment.html



### Ecology determined that the West Point WWTP discharge has potential to cause a violation of the sediment quality standards because:

 Past sediment testing near the outfall has shown some inconclusive evidence of toxicity to benthic organisms (refer to Section II.E for more information)

.

 Past sediment testing near CSO locations has shown exceedances of the Sediment Management Standard.

The proposed permit includes a condition requiring King County to:

 Continue sediment and e ffluent testing to investigate the source and extent of toxicity at the West Point WWTP outfall.

 Provide a n update to the 2009 CSO sediment report that summarizes activities and existing data for sediment quality at the CSO locations

.

 Submit a post

- constr uction monitoring summary report for CSO outfalls that will be controlled during this permit term.

 Mo del or sample sediments at five controlled CSO outfall location s: E. Pine Street Pump Station Emergency Overflow (011), Belvoir (012)/30 th 

### Ave NE Pump Stat ion (049), Martin Luther King (013)/Henderson Pump Station (045), Matthews Park Pump Station Emergency Overflow (018), and Rainier Avenue Pump Station Emergency Overflow (033)

.Fact Sheet for NPDES Permit WA 0029181 Page 80 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### I. Whole e ffluent t oxicity

The water quality standards for surface waters forbid discharge of effluent that has the potential to cause toxic effects in the receiving waters

. Many toxic pollutants cannot be measured by commonly available detection methods

. However, laboratory tests c an measure toxicity directly by exposing living organisms to the wastewater and measuring their

responses

. These tests measure the aggregate toxicity of the whole effluent, so this approach is called whole effluent toxicity (WET) testing

. Some WET tests me asure acute toxicity and other WET tests measure chronic toxicity.

• Acute toxicity tests measure mortality as the significant response to the toxicity of the

effluent

. Dischargers who monitor their wastewater with acute toxicity tests find early

indications of any potential lethal effect of the effluent on organisms in the receiving

water.

• Chronic toxicity tests measure various sublethal toxic responses , such as reduced growth or reproduction

. Chronic toxicity tests often involve either a complete life cycle test on an organism with an extremely short life cycle, or a partial life cycle test during a critical stage of a test organism's life

. Some chronic toxicity tests also measure organism

survival.

Laboratories accredited by Ecology for WET testing know how to use the proper WET testing protocols, fulfill the data requirements, and submit results in the correct reporting

format

. Accredited laboratory staff know about WET testing and how to calculate an NOEC, LC50, EC50, IC25, etc

. Ecology gives all accredite d labs the most recent version of Ecology Publication No. WQ

- R

- 95

- 80, Laboratory Guidance and Whole Effluent Toxicity Test

Review Criteria ( http://www.ecy.wa.gov/biblio/9580.html 

### ), which is referenced in the permit

. Ecology recommends that King County send a copy of the acut e or chronic toxicity sections of its NPDES permit to the laboratory.

WET testing conducted during effluent characterization at the West Point WWTP showed no reasonable potential to ca use receiving water acute or chronic toxicity , therefore t he proposed permit does not include WET li mit s

. King County must retest the West Point WWTP effluent before submitting an application for permit renewal.

• If this facility makes process or material changes which, in Ecology's opinion, increase the potential for effluent toxicity, then Ecology may (in a regulatory order, by permit modification, or in the permit renewal) require the facility to conduct additional effluent

characterization

. King County may demonstrate to Ecology that effluent toxicity has not increased by performing additional WET testing and / or chemical analyses after the process or material changes have been made

. Ecology recommends that the Permittee

check first to make sure that Ecol ogy will consider the demonstration adequate to support a decision to not require an additional effluent characterization.

• If WET testing conducted for submittal with a permit application fails to meet the performance standards in WAC 173

- 205

- 020, Ecology will assume that effluent toxicity

has increased

. King County may demonstrate to Ecology that effluent toxicity has not increased by performing additional WET testing after the process or material changes

have been made.Fact Sheet for NPDES Permit WA 0029181 Page 81 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### J. Groundwater q uality l imits

The groundwater quality s tandards (c hapter 173

- 200 WAC) protect beneficial uses of groundwater

. Permits issued by Ecology must not allow violations of those standards (WAC

173

- 200

- 100). King County does not discharge wastewater to the ground

. N o permit limits are required to protect groundwater

.

K. Comparison of e ffluent l imits w ith t he p revious permit

The proposed limits are compared to those of the current permit in Table 50 through Table

54

. For the CSO treatment plants, Ecology evaluates settleable solids compliance using the

0.3 ml/l/hr yearly average limit due to the intermittent and highly variable operation of the

CSOs. Eco logy removed the settleable solids event maximum limit of 1.9 ml/l/hr because there is no basis in regulation for an event maximum limit.

Table 50

. Comparison of Previous and Proposed Effluent Limits

- West Point WWTP

Parameter Basi s of Limit Previous Effluent Limits Proposed Effluent Limits
Average Monthly Average

Weekly Average

Monthly Average

Weekly

CBOD (5

- day) Technology 25 mg/L, 44,800 lb/day

80% removal (Nov

- April)

85% removal (May

- Oct) 40 mg/L,

71,700 lb/day 25 mg/L,

44,800 lb/day

80% removal (Nov

- April)

85% removal (May

- Oct) 40 mg/L,

71,700 lb/day

TSS Technology 30 mg/L, 53,800 lb/day

80% removal (Nov

- April)

85% removal (May

- Oct) 45 mg/L,

80,700 lb/day 30 mg/L,

53,800 lb/day

80% removal (Nov

- April)

85% removal (May

- Oct) 45 mg/L,

80,700 lb/day

Fecal Coliform
Bacteria Technology 200/100 mL 400/100 mL 200/100 mL 400/100 mL

pH Technology Daily Minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0
Average Monthly Maximum

Daily Average

Monthly Maximum Daily

Total Residual Chlorine Water Quality

Based 139 μg/L 364 μg/L 139 μg/L 364 μg/L

Table 51

. Comparison of Previous and Proposed Effluent Limits

- Alki CSO T P

Previous Effluent Limits Proposed Effluent Limits

Parameter Monthly

Average Annual

Average Long

- Term

Average Monthly

Average Annual

Average Long

- Term

Average

TSS Removal Efficiency, % NA 50% NA NA 50% NA

Settleable Solids (mL/L/hr) 1.9 Maximum

per event 0.3 NA no limit 0.3 NA

Fecal Coliform Bacteria 400/100mL NA NA 400/100mL NA NA

Number of events per year NA NA 29/yr NA NA 29/yr

Average Vol. per yr, MG NA NA 108 MG/yr NA NA 108 MG/yr

pH Daily Minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0
Average Monthly Maximum Daily Average Monthly Maximum Daily

Total Residual Chlorine NA 234 μg/L NA 234 μg/LFact Sheet for NPDES Permit WA 0029181 Page 82 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 52

. Comparison of Previous and Proposed Effluent Limits

- Carkeek CSO TP

Previous Effluent Limits Proposed Effluent Limits

Parameter Monthly Average Annual

Average Long

- Term

Average Monthly

Average Annual

Average Long

- Term

Average

TSS Removal Efficiency, % NA 50% NA NA 50% NA

Settleable Solids (mL/L/hr) 1.9 Maximum per event 0.3 NA no limit 0.3 NA

Fecal Coliform Bacteria 400/100mL NA NA 400/100mL NA NA

Number of events per year NA NA 10/yr NA NA 10/yr

Average Vol. per yr, MG NA NA 46 MG/yr NA NA 46 MG/yr

pH Daily Minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0 Average Monthly Maximum Daily Average Monthly Maximum Daily

Total Residual Chlorine NA 490 μg/L NA 490 μg/L

Table 53

. Comparison of Previous and Proposed Effluent Limits

- Elliott West CSO T P

Previous Effluent Limits Proposed Effluent Limits

Parameter Monthly Average Annual

Average Long

- Term

Average Monthly

Average Annual

Average Long

- Term

Average

TSS Removal Efficiency, % Report 50% NA Report 50% NA

Settleable Solids (mL/L/hr) 1.9 Maximum per event 0.3 NA n o limit 0.3 NA

Fecal Coliform Bacteria Interim

400/100 mL

Final 154/100 mL (calcul a ted w/ ‘ 1 ’ for non

discharge days) NA NA 400/100 mL ( not calculated w/ ‘1’ for non

discharge days) NA NA

Number of events per year NA Report NA NA Report NA

Average Vol. per
yr, MG NA Report NA NA Report NA

pH Daily Minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0 Average Monthly Maximum Daily Average Monthly Maximum Daily

Total Residual Chlorine NA 104 μg/L NA 109 μg/L

Table 54

. Comparison of Previous and Proposed Effluent Limits

– Henderson /MLK T P

Previous Effluent Limits Proposed Effluent Limits

Parameter Monthly Average Annual

Average Long

- Term

Average Monthly

Average Annual

Average Long

- Term

Average

TSS Removal Efficiency, % NA 50% NA NA 50% NA

Settleable Solids (mL/L/hr) 1.9 Maximum

per event 0.3 NA n o l imit 0.3 NA

Fecal Coliform Bacteria 400/100 mL Report NA 400/ 100 mL Report NA

Number of events per year NA Report NA NA Report NA

Average Vol. per yr, MG NA Report NA NA Report NA

pH Daily Minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0 Average Monthly Maximum Daily Average Monthly Maximum Daily

Total Residual Chlorine NA 39 μg/L NA 39 μg/LFact Sheet for NPDES Permit WA 0029181 Page 83 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## IV. Monitoring Requirements

Ecology requires m onitoring, recording, and reporting (WAC 173

- 220

- 210 and 40 CFR 122.41) to verify that the treatment process is functioning correctly and that the discharge complies with the permit’s effluent limits

.
If a facility uses a contract laboratory to monitor wastewater, it must ensure that the laboratory uses the methods and meets or exceeds the method detection levels required by the permit. The permit describes when facilities may use alternative methods

. It al so describes what to do in certain situations when the laboratory encounters matrix effects

. When a facility uses an alternative method as allowed by the permit, it must report the test method, DL, and QL on the discharge monitoring report or in the requir ed report.

A. Wastewater m onitoring

The monitoring schedule is detailed in the proposed permit under Special Condition S2

. Specified monitoring frequencies take into account the quantity and variability of the discharge s , the treatment method s , past compli ance, significance of pollutants, and cost of monitoring

. The required monitoring frequency for the West Point WWTP is consistent with

or more conservative than agency guidance given in Ecology’s Permit Writer's Manual (Publication Number 92

- 09) for munici pal activated sludge facilities with design flows greater than 5 MGD

. Ecology has included some additional monitoring of nutrients in the proposed permit to establish a baseline for this discharger

. Ecology will use this data if TMDLs for dissolved

oxygen are developed and waste load allocations for nutrients are established

. Monitoring of sludge quantity and quality is necessary to determine the appropriate uses of

the biosolids

. Biosolids monitoring is required by the current state and local solid waste management program and also by EPA under 40 CFR 503.

As a pretreatment publicly owned treatment works (POTW), King County is required to sample influent, primary clarifier effluent, final effluent, and sludge for toxic pollutants in

order to characterize the industrial input

. Sampling is also done to determine if pollutants interfere with the treatment process or pass

- through the plant to the sludge or the receiving

water

. King County will use the monitoring data to develop local limits which commercial

and industrial users must meet.

The proposed permit requires King County to monitor for sediments, whole effluent toxicity, and priority pollutants to further characterize the discharge s . These pollutants could have a significant impact on the quality of the surface water.

B

. Lab accreditation

Ecology requires that facilities must use a laboratory registered or accredited under the provisions of chapter 173

- 50 WAC, Accreditation of Envi ronmental Laboratories

, to prepare all monitoring data (with the exception of certain parameters)

. Ecology accredited the laboratory at this facility for the parameters listed in Table 55

.Fact Sheet for NPDES Permit WA 0029181 Page 84 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Table 55

. Lab Accredited Parameters

Parameter Name Analyte ID Method Name Method Code

Solids, Total Volatile 1970 EPA 160.4_1971 10010409

Chemical Oxygen Demand (COD) 1565 HACH 8000 90004005

Alkalinity 1505 SM 2320 B

- 97 20045607

Hardness, Total (as CaCO3) 1755 SM 2340 C

- 97 20047603

Specific Conductance 1610 SM 2510 B

- 97 20048606

Solids, Total 1950 SM 2540 B

- 97 20049405

Solids, Total Dissolved 1955 SM 2540 C

- 97 20050402

Solids, Total Suspended 1960 SM 2540 D

- 97 20051201

Solids, Settleable 1965 SM 2540 F

- 97 20052204

Chlorine (Residual), Total 1940 SM 4500

- Cl D

- 00 20080108

Chlorine (Residual), Total 1940 SM 4500

- Cl E

- 00 20080415

Chloride 1575 SM 4500

- Cl ̄ C

- 97 20085205

pH 1900 SM 4500

- H+ B

- 00 20105219

Ammonia 1515 SM 4500

- NH3 E

- 97 20110605

Nitrogen, Total Kjeldahl 1795 SM 4500

- Norg B

- 97 20119204

Dissolved Oxygen 1880 SM 4500

- O G

- 01 20121408

Orthophosphate 1870 SM 4500

- P E

- 99 20124214

Phosphorus, Total 1910 SM 4500

- P E

- 99 20124214

Sulfate 2000 SM 4500

- SO4 ̄ E

- 97 20132803

BOD, Carbonaceous BOD (CBOD) 1532 SM 5210 B

- 01 20135006

Fecal coliform

- count 2530 SM 9221 E2 (A1) + C MPN 20196207

Total coliforms

- count 2500 SM 9222 B (M

- endo)

- 97 20203207



## V. Other Permit Conditions

A. R eporting and record keeping

Ecology base d Special C ondition S3 on its authority to specify any appropriate reporting and

record keeping requirements to prevent and control waste discharges (WAC 173

- 220

- 210).

B. Prevention of facility overloading

Overloading of the treatment plant is a violation of the terms and conditions of the permit

. To prevent this from occurring, RCW 90.48.110 and WAC 173

- 220

- 150 require King County

to :

• Take the actions detailed in proposed permit Special C ondition S4.

• Design and construct expansions or modifications before the treatment plant reaches existing capacity.

• Report and correct conditions that could result in new or increased discharges of pollutants.

Special Condition S4 restricts the amount of flow.Fact Sheet for NPDES Permit WA 0029181 Page 85 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### If a municipality intends to apply for Ecology

- administered funding for the design or construction of a facility project, the pl an must meet the standard of a Facility Plan , as defined in WAC 173

- 98

- 030. A complete Facility Plan includes all elements of an Engineering Report along with State En vironmental Review Process (SERP) documentation to demonstrate compliance with 40 CFR 35.3140 and 40 CFR 35.3145, and a cost effectiveness analysis as required by WAC 173

- 98

- 730. The municipality should contact Ecology’s regional office as early as practic al before planning a project that may include Ecology

- administered funding.

C. Operation and maint enance

The proposed permit contains Special Condition S 5 as authorized under R CW 90.48.110,

WAC 173

- 220

- 150, c hapter 173

- 230 WAC, and WAC 173

- 240

- 080

. Ecolog y included it to ensure proper operation and regular maintenance of equipment, and to ensure that King County takes adequate safeguards so that it uses constructed facilities to their optimum potential in terms of pollutant capture and treatment

.

D. Pretreatment

Duty to enforce discharge prohibitions

This provision prohibits the publicly owned treatment works ( POTW ) from authorizing or permitting an industrial discharger to discharge certain types of waste into the sanitary sewer

.

• The first section o f the pretreatment requirements prohibits the POTW from accepting pollutants which causes “ pass

- through” or “interference ”

. This general prohibition is from 40 CFR §403.5(a)

. Appendix C of this fact sheet defines these terms.

• The second section reinforces a number of specific state and federal pretreatment prohibitions found in WAC 173

- 216

- 060 and 40 CFR §403.5(b)

. These reinforce that the POTW may not accept certain wastes, which:

a. Are prohibited due to dangerous waste rules.

b. Are explosive or flammable.

c. Ha ve too high or low of a pH (too corrosive, acidic or basic).

d. May cause a blockage such as grease, sand, rocks, or viscous materials.

e. Are hot enough to cause a problem.

f. Are of sufficient strength or volume to interfere with treatment.

g. Contain too much pet roleum

- based oils, mineral oil, or cutting fluid.

h. Create noxious or toxic gases at any point.

40 CFR Part 403 contains the regulatory basis for these prohibitions, with the exception of the pH provisions which are based on WAC 173

- 216

- 060.

• The third sect ion of pretreatment conditions reflects state prohibitions on the POTW accepting certain types of discharges unless the discharge has received prior written authorization from Ecology

. These discharges include:

a. Cooling water in significant volumes.

b. Storm water and other direct inflow sources.Fact Sheet for NPDES Permit WA 0029181 Page 86 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### c. Wastewaters significantly affecting system hydraulic loading, which do not require

treatment.

Ecology delegated authority to King County for permitting, monitoring, and enforcement over industrial users discharging t o their treatment system to provide more direct and effective control of pollutants

. Ecology oversees the delegated Industrial Pretreatment Program to assure compliance with federal pretreatment regulations (40 CFR Part 403) and categorical standards and s tate regulations (chapter 90.48 RCW and chapter 173

- 216 WAC).

As sufficient data becomes available, King County must, in consultation with Ecology, reevaluate its local limits in order to prevent pass

- through or interference

. If any pollutant

causes pass

- through or interference, or exceeds established biosolids standards, King County must establish new local limits or revise existing local limits as required by 40 CFR 403.5

. In addition, Ecology may require revision or establis hment of local limits for any pollutant that causes a violation of water quality standards or established effluent limits, or that causes whole effluent toxicity

.

E. Solid waste s

To prevent water quality problems the facility is required in permit Special Condition S7 to store and handle all residual solids (grit, screenings, scum, sludge, and other solid waste) in accordance with the req uirements of RCW 90.48.080 and state water quality s tandards.

The final use and disposal of biosolids from this f acility is regulated by U.S. EPA under 40 CFR 503, and by Ecology under chapter 70.95J RCW, c hapter 173

- 308 W AC “Biosolids Management,” and c hapter 173

- 350 WAC “Solid Waste Handling Standards .” The disposal of other solid waste is under the jurisdiction o f Public Health

- Seattle and King County

. Requirements for monitoring biosolids and record keeping are included in this permit

. Ecology

will use t his information , required under 40 CFR 503

, to develop or update local limits.

F. Spill p lan

The permitted facilities store a quantity of chemicals on

- site that have the potential to cause water pollution if accidentally released

. Ecology can require a facility to develop best management plans to pr event this accidental release [S ection 402(a)( 1) of the Federal Water Pollution Control Act (FWPCA) and RCW 90.48.080].

King County developed a plan for preventing the accidental release of pollutants to state waters and for minimizing damages if such a spill occurs

. The proposed permit requires the facility to review the plan annually and send revised plans to Ecology when significant changes are made

.

G

. Combined sewer overflows

Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewat er in the same piping system

. Most of the time, combined sewer systems transport all wastewater to a sewage treatment plant, where it is treated and then discharged to a water body

. During periods of heavy rainfall or snowmelt, however, the

wastewater volu me in a combined sewer system can exceed the capacity of the combined

sewer system or treatment plant

. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, orFact Sheet for NPDES Permit WA 0029181 Page 87 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### othe r water bodies

. Chapter 173

- 245 WAC and EPA’s CSO control policy (59 FR 18688) identify the required measures for control of overflows from combined sewer systems

.

CSO Reduction Plan/Long

- Term Control Plan and CSO Reduction Plan Amendments

Ecology require s municipalities to initially develop combined sewer overflow ( CSO ) reduction plans per chapter 173

- 245 WAC requirements

. These plans are substantially equivalent to the long

- term control plan (LTCP) as defined by EPA in its CSO control policy

. Chapter 173

- 245 WAC requires that “ a ll CSO sites shall achieve and at least maintain the greatest reasonable reduction, and neither cause violations of applicable water quality standards, nor restrictions to the characteristic uses of the receiving water, nor accu mulation of deposits which: (a) e xceed sediment criteria or standards; or (b) have an adverse biological effect.” The greatest
reasonable reduction means control of each CSO outfall such that an average of no more than one untreated discharge may occur per year

.
Under EPA’s CSO Control Policy’s presumption approach, CSO controls are presumed to attain WQS if certain performance criteria are met

. Ecology presumes that a program that meets the criteria specified in WAC 173

- 245 and EPA’s CSO control policy pr ovides an adequate level of control to meet the water quality

- based requirements of the Clean Water Act

. This presumption must be verified via a post

- construction monitoring program by characterization, monitoring, and modeling of the system, including con sideration of sensitive areas.

King County submitted a CSO reduction plan amendment in 2012 (King County’s 2012 Long

Term CSO Control Plan Amendment ). The proposed permit requires King County to submit an amendment of its CSO reduction plan in conjunction with its application for permit renewal

. The amendment must include an assessment of the effectiveness of the CSO reduction plan, a re

evaluation of CSO project priorities, and a list of projects to be completed in the next five years. In addition, King Co unty must identify newly corrected or controlled CSOs that meet the state’s one untreated discharge per year per CSO standard in the CSO Reduction Plan Amendment.

Nine Minimum Controls

Municipalities with combined sewer overflow outfalls must implement nin e minimum controls as technology

- based standards for CSO discharges

. The nine minimum controls are largely programmatic policies and practices designed to minimize the impacts untreated CSOs have on

human health and the environment

. It is not possible with current knowledge and technology to

calculate numeric water quality

- based effluent limits for CSOs

.

The nine minimum controls include:

1. Use proper operations and maintenance practices within the combined collection system to reduce the magnitude, frequenc y and duration of CSOs.

2. Implement procedures that maximize storage capacity of the combined collection system.

3. Minimize pollution from non

- domestic wastewater sources through close management of

a pretreatment program.

4. Maximize treatable flow to the wastewater treatment plant during wet weather.

5. Prevent CSO discharges during dry weather and properly report any dry weather CSO discharges immediately to Ecology.

6. Implement procedures to control solid and floatable materials in CSOs.

7. Implement and maintai n a pollution prevention program designed to keep pollutants from entering the combined sewer system.Fact Sheet for NPDES Permit WA 0029181 Page 88 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 8. Establish a process to notify the public when and where CSOs occur.

9. Monitor CSO outfalls to characterize CSO impacts and the efficacy of CSO controls,

inc luding event

- based monitoring of all CSO flow quantity, frequency and duration.

CSO Monitoring

The proposed permit requires King County to monitor the volume, duration

, and precipitation associated with each CSO discharge event at each identified outfall

.

Annual CSO Report

King County must submit annual reports according to the requirements of WAC 173

- 245

- 090(1)

. This report: (a) details the past year’s frequency and volume of combined sewage discharge from each CSO site, (b) explains the previous year’s CSO reduction accomplishments, and (c) lists the projects planned for the next year

. The report must indicate whether a CSO site has increased

over the baseline annual condition

. The report must document implementation of the nine minimum controls, and we t weather operation (flow blending) at the West Point WWTP

. King County must also assess in its annual reports and CSO reduction plan amendment whether identified outfalls meet the state standard of one untreated discharge per year per CSO

. Assessment may be based on a long

- term average

, which is defined as a 20

- year averaging period.

King County may choose to indicate in the annual report which CSO events were exacerbated. For this purposes, e xacerbated CSO shall mean any overflow at a CSO outfall that, w hile already discharging as a result of precipitation, is worsened by mechanical failures, blockages, power outages, and/or human error.

Post

- Construction Monitoring Program

The f ederal CSO control policy (59 FR 18688) requires post

- construction monitoring to verify implemented CSO control strategies comply with water quality standards

. Post

- construction monitoring applies to any CSO outfall that is controlled to meet the “greatest reasonable reduction” of combined sewer overflows, as defined in chapter 173

- 245 WAC

. Implementation requires development of a monitoring plan and completion of a data report that documents compliance

. The proposed permit requires King County to implement their 2012 Post Construction Monitoring Plan and to submit any plan modifica tions to Ecology for review and approval.

H

. O utfall e valuation

The proposed permit requires King County to conduct outfall inspection s of the West Point

WWTP and CSO treatment plant outfall s and submit a report detailing the findings of th ose inspection s ( Special Condition S 14 )

. The inspection s must evaluate the physical condition of

the discharge pipe s and diffusers

, and evaluate the extent of sediment accumulations in the vicinity of the outfall s

.

I. Elliott West CSO treatment plant

– copper reduction as sessment

King County must assess copper discharges from the Elliott West CSO treatment plant and

submit a Copper Reduction Assessment Report to Ecology

. The County has consistently measured copper conce ntrations from the facility at five times higher than other CSO

facilities. The proposed permit requires the County to determine if these measurementsFact Sheet for NPDES Permit WA 0029181 Page 89 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### accurately reflect copper concentrations in the effluent or if there is sample interference . The study also requires the County to evaluate various copper reduction strategies.

J. Elliott West CSO treatment plant

– settleable solids removal assessment

The Elliott West CSO treatment facility has difficulty meeting its annual settleable solids limit. The proposed permit requires the County to as sess ways to reduce settleable solids from its discharge.

K

. G eneral c onditions

Ecology bases the standardized G eneral Conditions on state and federal law and regulations

. They are included in all individual domestic wastewater NPDES permits issued by Ecology

.



## VI. Permit Issuance Procedures

A. P ermit m odifications

Ecology may modify this permit to impose numerical limit s , if necessary to comply with water quality standards for s urface waters, with s ediment q uality s tandards, or with water quality standards for groundwater s, based on new information from sources such as inspections, effluent monitoring, outfall studies, and effluent mixing studies.

Ecology may also modify this permit to comply with new or amended state or federal regulations.

B. Proposed perm it issuance

This proposed permit meets all statutory requirements for Ecology to authorize a wastewater discharge

. The permit includes limit s and conditions to protect human health and aquatic life,

and the be neficial uses of waters of the s tate of Washing ton

. Ecology proposes to issue this permit for a term of 5 years.



## VII. References f or Text a nd Appendices

Ecology. Laws and Regulations ( http://www.ecy.wa.gov/laws

- rules/index.html )



### Ecology. Permit and Wastewater Related Information
( http://www.ecy.wa.gov/programs/wq/permits/guidance.html )



### Ecology 1995. Sediment Management Standards . Chapter 173

- 204 WAC. Amended December 1 995. http://www.ecy.wa.gov/programs/tcp/smu/sed_standards.htm

Ecology 1998. Chapter E

- 1, Criteria For Sewage Works Design , Ecology Publication # 98

- 37.

Ecology 2002. Final Sediment Management Standards Cleanup Action Decision Duwamish/Diagonal CSO/SD. Dep artment of Ecology NWRO TCP. July 25, 2002.

Enviro nmental Protection Agency (EPA). 1983. Water Quality Standards Handbook . USEPA Office of Water, Washington, D.C.

EPA, 1985. Water Quality Assessment: A Screening Procedure for Toxic and Conventional

Polluta nts in Surface and Ground Water . EPA/600/6

- 85/002a.

EPA, 1991. Technical Support Document for Water Quality

- based Toxics Control . EPA/505/2

- 90

- 001.Fact Sheet for NPDES Permit WA 0029181 Page 90 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### EPA, 1992. National Toxics Rule. Federal Register, V. 57, No. 246, Tuesday, December 22, 1992.

EPA, 1995. Combined Sewer Overflow Guidance for Permit Writers , EPA, August 1995

. King County. 1996. Norfolk CSO cleanup study report. Prepared for Elliott Bay/Duwamish Restoration Program Panel. Panel Publication 13. King County Department of Natural Resources, Seat tle, WA.
( http://www.kingcounty.gov/environment/wastewater/SedimentManagement/Projects/Norfolk/Library.aspx )



### King County, 1999. King County Depa rtment of Natural Resources Year 2000 CSO Plan Update Project, Sediment Management Plan. Prepared by Anchor Environmental and Herrera Environmental Consultants in collaboration with King County. June 1999.

King County, 1999. Sediment remediation plan, Denn y Way/Lake Union CSO Control Project. Prepared for King County and Black and Veatch. Seattle, Washington.

King County. 2005. The Denny Way sediment cap

– 2000 data

– final monitoring report. King County Department of Natural Resources. Seattle, Washington.

King County. June 2005. Norfolk CSO Sediment Remediation Project Five

- Year Monitoring Program, Final Monitoring Report, Year Five

. Prepared for the E l liott Bay/Duwamish Restoration Program Panel, Panel Publication 38. King County Department of Natural Resources. Seattle, Washington.

King County 2006. West Point Wastewater Treatment Plant 2006 Outfall Sediment Sampling Event Final Report. King County Department of Natural Resources and Parks, Marine and Sediment Assessment Group, September 2007. SEDQUAL data WPNT06.

King County 2008. Denny Way CSO and Elliott West CSO Treatment Facility, Post

- Construction Sediment Monitoring Sampling and Analysis Plan. Prepared by King County Department of Natural Resources and Parks Marine and Sediment Assessment Group. March 2008.

King County, CSO Sediment Quality Characterization Final Sampling and Analysis Plan , Aug 2011.

King County, Technical Memorandum

- Feasible Alternatives Analysis for CSO

- Related Secondary Process Diversion at West Point Treatment Plant , May 21, 2009.

King County, 2009 Comprehensive Sediment Quality Summary Report for CSO Discharge Locations,

Dec 2009.

King County, CSO Sediment Quality Characterization Final Sampling and Analysis Plan , Aug 2011.

King County, Post Construction Monitoring Plan for King County CSO Controls , Sept 2012.

King County, 2012 Long Term CSO Control Plan Amendment

, October 20 12

. King County, CSO Sediment Quality Characterization, 2011 Sediment Sampling Event , Dec 2012.

King County, 2013 Receiving Water Characterization Study, King County NPDES Monitoring Program, Final Report for Brightwater, South, Vashon, and West Point Treatment Plants and Alki,
Carkeek, Elliott West, and Henderson/MLK CSO Storage and Treatment Facilities, June 2013.

King County, Effluent Dilution Modeling Report for the West Point WWTP Outfall, 2 013.

King County, Effluent Dilution Modeling Report for the Alki CSO Treatment Plant Outfall, 2013.

King County, Effluent Dilution Modeling Report for the Carkeek CSO Treatment Plant Outfall, 2013.

King County, Effluent Dilution Modeling Report for the Elliott West CSO Treatment Plant Outfall, 2013.

King County, Effluent Dilution Modeling Report for the Henderson/MLK CSO Treatment Plant Outfall, 2013.Fact Sheet for NPDES Permit WA 0029181 Page 91 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Washington State Department of Ecology. Permit Writer’s Manual . Publication Number 92

- 109,

December 2011. ( http://www.ecy.wa.gov/biblio/92109.html )



### Washington State Department of Health, 1994. Design Criteria for Municipal Wastewater Land

Treatment

. Water Pollution Control Federation, Chlorination of Wastewater , 1976.

Windward Environmental LLC. 2008. Lower Duwamish Waterway remedial investigation, remedial investigation report, draft final (internal). Prepared for submittal to EPA and Ecology.
( http://yosemite.epa.gov/r10/CLEANUP.NSF/LDW/Lower+Duwamish+Waterway+Draft+Phase+II+ Remedial+Investigation+Report/$FILE/draft_riII.pdf )Fact Sheet for NPDES Permit WA 0029181 Page 92 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix A

— Public Involvement Information

Ecology proposes to reissue a permit to King County. The permit includes was tewater discharge

limit s and other conditions

. This fact sheet describes the facility and Ecology’s reasons for requiring permit conditions

. Ecology place d a Public Notice of Draft on October 30, 2014

, in the Seattle Times to inform the public and to invite comment on the proposed draft National Pollutant Discharge Elimination System permit a nd fact sheet

.
The n otice:

• Told where copies of the draft permit and fact s heet we re available for public evaluation (a loc al public library, the closest r egional or field office, posted on our website ).

• O ffered to provide the documents in an alternate format to accommodate special needs.

• A sked people to tell us how well the proposed permit would protect the receiving water.

• I nvited people to suggest fairer conditions, limits, and requirements for the permit.

• I nvited comments on Ecology’s determination of compliance with antidegradation rules.

• U rged people to submit their comments, in writing, before the end of the comment p eriod

.

• T old how to request a public hearing a bout the proposed NPDES p ermit.

• E xplained the next step(s) in the permitting process.

Ecology has published a document entitled Frequently Asked Questions about Effective Public Commenting

, which is available on our websit e at http://www.ecy.wa.gov/biblio/0307023.html



### . You may obtain f

urther inform ation from Ecology by telephone, 425

- 649

- 7201

, or by writing to

the address listed below

. Water Quality Permit Coordinator Department of Ecology Northwest Regional Office
3190 160th Avenue SE Bellevue, WA 98008

- 5452



### The primary author of t his permit and fact sheet is Alison Evans, PE

.Fact Sheet for NPDES Permit WA 0029181 Page 93 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix B

— Your Right to Appeal

You have a right to appeal this permit to the Pollution Control Hearing Board (PCHB) within 30 days of the date of receipt of the final permit

. The appeal process is governed by c hapter 43.21B

RCW and c hapter 371

- 08 WAC

. “Date of receipt” is defined in RCW 43.21B.001(2) (see glossary)

. To appea l you must do the following within 30 days of the date of receipt of this permit :

 

### File your appeal and a copy of this permit with the PCHB (see addresses below)

. Filing means actual receipt by the PCHB during regular business hours.

 

### Serve a copy of your a ppeal and this permit on Ecology in paper form

- by mail or in person

. (See addresses below.) E

- mail is not accepted.

You must also comply with other applicable requirements in c hapter 43.21B RCW and c hapter

371

- 08 WAC.

Street Addresses Mailing Addresses

Department of Ecology Attn: Appeals Processing Desk
300 Desmond Drive SE Lacey, WA 98503 Department of Ecology Attn: Appeals Processing Desk
PO Box 47608 Olympia, WA 98504

- 7608

Pollution Control Hearings Board
1111 Israel RD SW
STE 301 Tumwater, WA 98501 Pollution Control Hearings Board
PO Box 40903 Olympia, WA 98504

- 0903Fact Sheet for NPDES Permit WA 0029181 Page 94 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System 

## Appendix C

— Glossary

1

- DMax or 1

- day maximum temperature

-- The highest water temperature reached on any given day. This measure can be obtained using calibrated maximum/minimum thermometers or continuous monitoring probes having sampling intervals of thirty minutes or less.

7

- DADMax or 7

- day average of the daily maximum temperatures

-- The arithmetic average of seven consecutive measures of daily maximum temperatures. The 7

- DADMax for any individual day is calculated by averaging that day's daily maximum temperature with the daily maximum temperatures of the three days prior and the three days after that date.

Acute toxicity

-- The lethal effect of a compound on an organism that occurs in a short time period, usually 48 to 96 hours.

AKART

-- The acronym for “all known, available, and reasonable methods of preventio n, control and treatment.” AKART is a technology

- based approach to limiting pollutants from wastewater discharges, which requires an engineering judgment and an economic judgment

. AKART must be applied to all wastes and contaminants prior to entry into wa ters of the state in accordance with RCW 90.48.010 and 520, WAC 173

- 200

- 030(2)(c)(ii), and WAC 173

- 216

- 110(1)(a).

Alternate point of compliance

-- An alternative location in the groundwater from the point of compliance where compliance with the groundwater standards is measured. It may be

established in the groundwater at locations some distance from the discharge source, up to, but not exceeding the property boundary and is determined on a site specific basis following an AKART analysis. An “early warning value” must be used when an alternate point is

established. An a lternate point of compliance must be determined and approved in

accordance with WAC 173

- 200

- 060(2).

Ambient water quality

-- The existing environmental condition of the water in a receiving water body.

Ammonia

-- Ammonia is produced by the breakdown of nit rogenous materials in wastewater

. Ammonia is toxic to aquatic organisms, exerts an oxygen demand, and contributes to eutrophication

. It also increases the amount of chlorine needed to disinfect wastewater

. Annual average design flow (AADF )

-- The average of the daily flow volumes anticipated to occur over a calendar year.

Average monthly (intermittent) discharge limit

-- The average of the measured values obtained over a calendar months time taking into account zero discharge days.

Average monthly dischar ge limit

-- The average of the measured values obtained over a

calendar month's time.

Background water quality

-- The concentrations of chemical, physical, biological or radiological

constituents or other characteristics in or of groundwater at a particula r point in time upgradient of an activity that has not been affected by that activity [WAC 173

- 200

- 020(3)]. Background water quality for any parameter is statistically defined as the 95% upper tolerance interval with a 95% confidence based on at least eigh t hydraulically upgradient water quality samples

. The eight samples are collected over a period of at least one year, with no more than one sample collected during any month in a single calendar year.

Best management practices (BMPs)

-- Schedules of activi ties, prohibitions of practices, maintenance procedures, and other physical, structural and/or managerial practices to prevent or reduce the pollution of waters of the state

. BMPs include treatment systems, operatingFact Sheet for NPDES Permit WA 0029181 Page 95 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### procedures, and practices to control: plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage

. BMPs may be further categorized as operational, source control, erosion and sediment control, and treatment BMPs.

BOD 5 

### -- Determining the five

- day Bioche mical Oxygen Demand of an effluent is an indirect way of measuring the quantity of organic material present in an effluent that is utilized by

bacteria

. The BOD5 is used in modeling to measure the reduction of dissolved oxygen in receiving waters after eff luent is discharged

. Stress caused by reduced dissolved oxygen levels makes organisms less competitive and less able to sustain their species in the aquatic

environment

. Although BOD 5 

### is not a specific compound, it is defined as a conventional pollutant un der the federal Clean Water Act.

Bypass

-- The intentional diversion of waste streams from any portion of a treatment facility.

Categorical pretreatment standards

-- National pretreatment standards specifying quantities or concentrations of pollutants or p ollutant properties, which may be discharged to a POTW by existing or new industrial users in specific industrial subcategories.

Chlorine

-- A chemical used to disinfect wastewaters of pathogens harmful to human health. It is also extremely toxic to aquati c life.

Chronic toxicity

-- The effect of a compound on an organism over a relatively long time, often 1/10 of an organism's lifespan or more

. Chronic toxicity can measure survival, reproduction or growth rates, or other parameters to measure the toxic effects of a compound or combination of compounds

.
Clean water act (CWA )

-- The f ederal Water Pollution Control Act enacted by Public Law

92

- 500, as amended by Public Laws 95

- 217, 95

- 576, 96

- 483, 97

- 117; USC 1251 et seq.

Compliance inspection

- without samp ling

-- A site visit for the purpose of determining the compliance of a facility with the terms and conditions of its permit or with applicable statutes and regulations.

Compliance inspection

- with sampling

-- A site visit for the purpose of determining the compliance of a facility with the terms and conditions of its permit or with applicable statutes and regulations

. In addition it includes as a minimum, sampling and analysis for all parameters with limits in the permit to ascertain compliance with those l imits; and, for municipal facilities, sampling of influent to ascertain compliance with the 85 percent removal requirement

. Ecology may conduct additional sampling.

Composite sample

-- A mixture of grab samples collected at the same sampling point at

diffe rent times, formed either by continuous sampling or by mixing discrete samples

. May be

"time

- composite" (collected at constant time intervals) or "flow

- proportional" (collected either as a constant sample volume at time intervals proportional to stream flo w, or collected by increasing the volume of each aliquot as the flow increased while maintaining a constant time interval between the aliquots).

Construction activity

-- Clearing, grading, excavation, and any other activity, which disturbs

the surface of t he land

. Such activities may include road building; construction of residential houses, office buildings, or industrial buildings; and demolition activity.

Continuous monitoring

-- Uninterrupted, unless otherwise noted in the permit.

Critical condition

-- The time during which the combination of receiving water and waste discharge conditions have the highest potential for causing toxicity in the receiving waterFact Sheet for NPDES Permit WA 0029181 Page 96 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### environment

. This situation usually occurs when the flow within a water body is low, thus, its

ab ility to dilute effluent is reduced.

Date of receipt

– This is defined in RCW 43.21B.001(2) as five business days after the date of mailing; or the date of actual receipt, when the actual receipt date can be proven by a preponderance of the evidence. The r ecipient's sworn affidavit or declaration indicating the date of receipt, which is unchallenged by the agency, constitutes sufficient evidence of actual receipt. The date of actual receipt, however, may not exceed forty

- five days from the date of mailing.

Detection limit

-- The minimum concentration of a substance that can be measured and reported with 99 percent confidence that the pollutant concentration is above zero and is determined from analysis of a sample in a given matrix containing the pollutant.

Dilution factor (DF)

-- A measure of the amount of mixing of effluent and receiving water that occurs at the boundary of the mixing zone

. Expressed as the inverse of the percent effluent fraction, for example, a dilution factor of 10 means the effluent com prises 10% by volume and the receiving water 90%.

Distribution uniformity

-- The uniformity of infiltration (or application in the case of sprinkle or trickle irrigation) throughout the field expressed as a percent relating to the average depth

infiltrated in the lowest one

- quarter of the area to the average depth of water infiltrated.

Enforcement limit

-- The concentration assigned to a contaminant in the groundwater at the point of compliance for the purpose of regulation, [WAC 173

- 200

- 020(11)]. This limi t
assures that a groundwater criterion will not be exceeded and that background water quality will be protected.

Engineering report

-- A document that thoroughly examines the engineering and administrative aspects of a particular domestic or industrial was tewater facility

. The report must contain the appropriate information required in WAC 173

- 240

- 060 or 173

- 240

- 130.

Exacerbated CSO

-- A ny overflow at a CSO outfall that, while already discharging as a result of precipitation, is worsened by mechanical failu res, blockages, power outages, and/or

human error.

Fecal coliform bacteria

-- Fecal coliform bacteria are used as indicators of pathogenic bacteria

in the effluent that are harmful to humans

. Pathogenic bacteria in wastewater discharges are controlled by d isinfecting the wastewater

. The presence of high numbers of fecal coliform bacteria in a water body can indicate the recent release of untreated wastewater and/or the presence of animal feces.

Grab sample

-- A single sample or measurement taken at a specific time or over as short a period of time as is feasible.

Groundwater

-- Water in a saturated zone or stratum beneath the surface of land or below a surface water body.

Industrial user

-- A discharger of wastewater to the sanitary sewer that is not sanitary wastewater or is not equivalent to sanitary wastewater in character.

Industrial wastewater

-- Water or liquid

- carried waste from industrial or commercial processes,

as distinct from domestic wastewater

. These wastes may result from any process or activity of industry, manufacture, trade or business; from the development of any natural resource; or from animal operations such as feed lots, poultry houses, or dairies

. The term includes

contaminated storm w ater and, also, leachate from solid waste facilities.Fact Sheet for NPDES Permit WA 0029181 Page 97 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Interference

-- A discharge which, alone or in conjunction with a discharge or discharges from other sources, both:

 Inhibits or disrupts the POTW, its treatment processes or operations, or its sludge

pr ocesses, use or disposal; and

 Therefore is a cause of a violation of any requirement of the POTW's NPDES permit (including an increase in the magnitude or duration of a violation) or of the prevention of sewage sludge use or disposal in compliance with the following statutory provisions and regulations or permits issued thereunder (or more stringent State or local regulations): Section 405 of the Clean Water Act, the Solid Waste Disposal Act (SWDA) (including title II, more commonly referred to as the Resou rce Conservation and Recovery Act (RCRA), and including State regulations contained in any State sludge management plan prepared pursuant to subtitle D of the SWDA), sludge regulations appearing in 40 CFR Part 507, the Clean Air Act, the Toxic Substances C ontrol Act, and the Marine Protection, Research and Sanctuaries Act.

Local limits

-- Specific prohibitions or limits on pollutants or pollutant parameters developed by

a POTW.

Major facility

-- A facility discharging to surface water with an EPA rating sco re of > 80 points based on such factors as flow volume, toxic pollutant potential, and public health impact.

Maximum daily discharge limit

-- The highest allowable daily discharge of a pollutant measured during a calendar day or any 24

- hour period that re asonably represents the calendar day for purposes of sampling

. The daily discharge is calculated as the average measurement of the pollutant over the day

. Maximum day design flow (MDDF )

-- The largest volume of flow anticipated to occur during a

one

- day p eriod, expressed as a daily average.

Maximum month design flow (MMDF)

-- The largest volume of flow anticipated to occur during a continuous 30

- day period, expressed as a daily average.

Maximum week design flow (MWDF )

-- The largest volume of flow anticipa ted to occur during a continuous 7

- day period, expressed as a daily average.

Minor facility

-- A facility discharging to surface water with an EPA rating score of < 80 points based on such factors as flow volume, toxic pollutant potential, and public healt h impact.

Mixing zone

-- An area that surrounds an effluent discharge within which water quality criteria may be exceeded

. The permit specifies the area of the authorized mixing zone that Ecology defines following procedures outlined in state regulations ( chapter 173

- 201A WAC).

National pollutant discharge elimination system (NPDES)

-- The NPDES (Section 402 of the Clean Water Act) is the federal wastewater permitting system for discharges to navigable

waters of the United States

. Many states, including the state of Washington, have been delegated the authority to issue these permits

. NPDES permits issued by Washington State permit writers are joint NPDES/State permits issued under both state and federal laws.

pH

-- The pH of a liquid measures its acidity o r alkalinity

. It is the negative logarithm of the hydrogen ion concentration. A pH of 7 is defined as neutral and large variations above or below this value are considered harmful to most aquatic life.

Pass

- through

-- A discharge which exits the POTW into waters of the State in quantities or concentrations which, alone or in conjunction with a discharge or discharges from other sources, is a cause of a violation of any requirement of the POTW's NPDES permitFact Sheet for NPDES Permit WA 0029181 Page 98 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### (including an increase in the magnitude or duratio n of a violation), or which is a cause of a violation of State water quality standards.

Peak hour design flow (PHDF)

-- The largest volume of flow anticipated to occur during a

one

- hour period, expressed as a daily or hourly average.

Peak instantaneous de sign flow (PIDF)

-- The maximum anticipated instantaneous flow.

Point of compliance

-- The location in the groundwater where the enforcement limit must not be exceeded and a facility must comply with the Ground Water Quality Standards. Ecology

determines t his limit on a site

- specific basis. Ecology locates the point of compliance in the groundwater as near and directly downgradient from the pollutant source as technically, hydrogeologically, and geographically feasible, unless it approves an alternative poi nt of compliance.

Potential significant industrial user (PSIU)

-- A potential significant industrial user is defined as an Industrial User that does not meet the criteria for a Significant Industrial User, but which discharges wastewater meeting one or more of the following criteria:

a. Exceeds 0.5 % of treatment plant design capacity criteria and discharges <25,000 gallons per day ; or

b. Is a member of a group of similar industrial users which, taken together, have the potential to cause pass through or int erference at the POTW (e.g. facilities which develop photographic film or paper, and car washes).

Ecology may determine that a discharger initially classified as a potential significant industrial user should be managed as a significant industrial user.

Quantitation level (QL)

-- Also known as Minimum Level of Quantitation (ML)

– The lowest level at which the entire analytical system must give a recognizable signal and acceptable calibration point for the analyte

. It is equivalent to the concentration of the lowest calibration standard, assuming that the lab has used all method

- specified sample weights, volumes, and cleanup procedures. The QL is calculated by multiplying the MDL by 3.18 and rounding the result to the number nearest to (1,2,or 5) x 10 n 

### , whe re n is an integer (64 FR 30417).

ALSO GIVEN AS: The smallest detectable concentration of analyte greater than the Detection Limit (DL) where the accuracy (precision & bias) achieves the objectives of the intended purpose. ( Report of the Federal Advisory Committee on Detection and Quantitation Approaches and Uses in Clean Water Act Programs Submitted to the US Environmental Protection Agency

, December 2007).

Reasonable potential

-- A reasonable potential to cause a water quality violation, or loss of

sens itive and/or important habitat.

Responsible corporate officer

-- A president, secretary, treasurer, or vice

- president of the corporation in charge of a principal business function, or any other person who performs similar policy

- or decision

- making functio ns for the corporation, or the manager of one or more manufacturing, production, or operating facilities employing more than 250 persons or have gross annual sales or expenditures exceeding $25 million (in second quarter 1980 dollars), if authority to sign documents has been assigned or delegated to the manager in accordance with corporate procedures (40 CFR 122.22).

Significant industrial user (SIU)

--
1) All industrial users subject to Categorical Pretreatment Standards under 40 CFR 403.6 and 40 CFR Chap ter I, Subchapter N ; andFact Sheet for NPDES Permit WA 0029181 Page 99 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 2) Any other industrial user that: discharges an average of 25,000 gallons per day or more of process wastewater to the POTW (excluding sanitary, nonc ontact cooling, and boiler

blow

- down wastewater); contributes a process waste stream that makes up 5 percent or more of the average dry weather hydraulic or organic capacity of the POTW treatment plant; or is designated as such by the Control Authority* on the basis that the industrial user has a reasonable potential for adversely a ffecting the POTW's operation or for violating any pretreatment standard or requirement [ in accordance with 40 CFR 403.8(f)(6) ]

. Upon finding that the industrial user meeting the criteria in paragraph 2, above, has no reasonable potential for adversely af fecting the POTW's operation or for violating any pretreatment standard or requirement, the Control Authority* may at any time, on its own initiative or in response to a petition received from an industrial user or POTW, and in

accordance with 40 CFR 403.8 (f)(6), determine that such industrial user is not a significant industrial user.

*The term "Control Authority" refers to the Washington State Department of Ecology in

the case of non

- delegated POTWs or to the POTW in the case of delegated POTWs.

Slug discharge

-- Any discharge of a non

- routine, episodic nature, including but not limited to an accidental spill or a non

- customary batch discharge to the POTW

. This may include any pollutant released at a flow rate that may cause interference or pass t hrough with the POTW or in any way violate the permit conditions or the POTW’s regulations and local limits

.
Solid waste

-- All putrescible and non

- putrescible solid and semisolid wastes including, but not limited to, garbage, rubbish, ashes, industrial wa stes, swill, sewage sludge, biosolids, demolition and construction wastes, abandoned vehicles or parts thereof, contaminated soils and contaminated dredged material, and recyclable materials.

Soluble BOD 5 

### -- Determining the soluble fraction of Biochemical Oxygen Demand of an effluent is an indirect way of measuring the quantity of soluble organic material present in an effluent that is utilized by bacteria. Although the soluble BOD 5 

### test is not specifically described in Standard Methods, filtering the raw s ample through at least a 1.2 um filter prior to running the standard BOD 5 

### test is sufficient to remove the particulate organic fraction.

State waters

-- Lakes, rivers, ponds, streams, inland waters, underground waters, salt waters, and all other surface waters and watercourses within the jurisdiction of the state of Washington.

Stormwater

-- That portion of precipitation that does not naturally percolate into the ground or evaporate, but flows via overland flow, interflow, pipes, and other features of a storm water drainage system into a defined surface water body, or a constructed infiltration facility.

Technology

- based effluent limit

-- A permit limit b ased on the ability of a treatment method to reduce the pollutant.

Total coliform bacteria

-- A microbiological test, which detects and enumerates the total coliform group of bacteria in water samples.

Total dissolved solids

-- That portion of total solids in water or wastewater that passes through a specific filter.

Total maximum daily load (TMDL)

-- A determination of the amount of pollutant that a water body can receive and still meet water quality standards.

Total suspended solids (TSS)

-- Total suspended s olids is the particulate material in an effluent

. Large quantities of TSS discharged to a receiving water may result in solids accumulation

.Fact Sheet for NPDES Permit WA 0029181 Page 100 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Apart from any toxic effects attributable to substances leached out by water, suspended solids may kill fish, shell fish, and other aquatic organisms by causing abrasive injuries and by clogging the gills and respiratory passages of various aquatic fauna

. Indirectly, suspended solids can screen out light and can promote and maintain the development of noxious

conditions through oxygen depletion

. Upset

-- An exceptional incident in which there is unintentional and temporary noncompliance with technology

- based permit effluent limits because of factors beyond the reasonable

control of the Permittee

. An upset does not inclu de noncompliance to the extent caused by operational error, improperly designed treatment facilities, lack of preventative maintenance, or careless or improper operation.

Water quality

- based effluent limit

-- A limit imposed on the concentration of an effl uent parameter to prevent the concentration of that parameter from exceeding its water quality criterion after discharge into receiving waters.Fact Sheet for NPDES Permit WA 0029181 Page 101 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix D

— Receiving Water DataFact Sheet for NPDES Permit WA 0029181 Page 102 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix E

— Facility DataFact Sheet for NPDES Permit WA 0029181 Page 103 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 104 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point WWTP

– Plant DataFact Sheet for NPDES Permit WA 0029181 Page 105 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 106 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 107 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 108 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point WWTP

- Influent DataFact Sheet for NPDES Permit WA 0029181 Page 109 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point WWTP

- Effluent DataFact Sheet for NPDES Permit WA 0029181 Page 110 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point WWTP

- Effluent Data (continued)Fact Sheet for NPDES Permit WA 0029181 Page 111 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

West Point WWTP

- Effluent Data (continued)Fact Sheet for NPDES Permit WA 0029181 Page 112 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment Plant

– Plant DataFact Sheet for NPDES Permit WA 0029181 Page 113 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment Plant

- Influent vs

. EffluentFact Sheet for NPDES Permit WA 0029181 Page 114 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment Plant

- Effluent DataFact Sheet for NPDES Permit WA 0029181 Page 115 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plant

– Plant DataFact Sheet for NPDES Permit WA 0029181 Page 116 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plant

- Influent vs. EffluentFact Sheet for NPDES Permit WA 0029181 Page 117 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plant

- Effluent DataFact Sheet for NPDES Permit WA 0029181 Page 118 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment Plant

– Plant DataFact Sheet for NPDES Permit WA 0029181 Page 119 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment Plant

- Influent vs. EffluentFact Sheet for NPDES Permit WA 0029181 Page 120 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment Plant

- Effluent DataFact Sheet for NPDES Permit WA 0029181 Page 121 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 122 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Henderson / MLK CSO Treatment Plant

– Plant DataFact Sheet for NPDES Permit WA 0029181 Page 123 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Henderson/MLK CSO Treatment Plant

- Influent vs. EffluentFact Sheet for NPDES Permit WA 0029181 Page 124 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Henderson/MLK CSO Treatment Plant

- Effluent DataFact Sheet for NPDES Permit WA 0029181 Page 125 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Untreated CSO Discharges

- DataFact Sheet for NPDES Permit WA 0029181 Page 126 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 127 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix F

— Technical Calculations

Several of the Excel® spreadsheet tools used to evaluate a discharger’s ability to meet Washington State water quality standards can be found on Ecology ’s homepage at

http://www.ecy.wa.gov/programs/eap/pwspread/pwspread.html



### .

Simple Mixing:



### Ecology uses simple mixing calculations to assess the impacts of certain conservative pollutants, such as the expected increase in fecal coliform bacteria at the edge of the ch ronic mixing zone boundary. Simple mixing uses a mass balance approach to proportionally distribute a pollutant load from a discharge into the authorized mixing zone. The approach assumes no decay or generation of the pollutant of concern within the mixing zone. The predicted concentration at the edge of a mixing zone (MC) is based on the following calculation:

MC = [EC + (AC x DF)]/(1 + DF)

where:

EC = Effluent Concentration

AC = Ambient Concentration

DF = Dilution Factor

Reasonable Potential Analysis:



### The process and formulas for determining reasonable potential and effluent limits are taken directly from the Technical Support Document for Water Quality

- based Toxics Control , (EPA 505/2

- 90

- 001). The adjustment for autocorrelation is from EPA (1 996a), and EPA (1996b).

Calculation of Water Quality

- Based Effluent Limits:



### Water quality

- based effluent limits are calculated by the two

- value wasteload allocation process as described on page 100 of the TSD (EPA, 1991) and shown below.

1. Calculate the acu te wasteload allocation WLA

a 

### by multiplying the acute criteria by the acute dilution factor and subtracting the background factor. Calculate the chronic wasteload allocation (WLA

c 

### ) by multiplying the chronic criteria by the chronic dilution factor and subt racting the background factor.

WLA a = (acute criteria x DF a )

– [(background conc.x (DF a - 1)]

WLA c = (chronic criteria x DF c )

– [(background conc. x (DF c - 1)]

where: DF a = Acute Dilution Factor

DF c = Chronic Dilution Factor



### 2. Calculate the long term averages (LTA

a 

### and LTA

c 

### ) which will comply with the wasteload allocations WLA

a 

### and WLA

c 

### .
LTA a = WLA a  e [0.5  2

- z  ] where:  2 = ln[CV2 + 1]

z = 2.326
CV = coefficient of variation = std. dev./mean

LTA c = WLA c  e [0.5  2

- z  ] where:  2 = ln [(CV2  4) + 1]

z = 2.326Fact Sheet for NPDES Permit WA 0029181 Page 128 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 3. Use the smallest LTA of the LTA

a 

### or LTA

c 

### to calculate the maximum daily effluent limit and the monthly average effluent limit.

Maximum Daily Limit = MDL

MDL = LTA x e [Z σ

- 0.5 σ 2] where:  2 = ln[CV 2 + 1] z = 2.326 (99 th percentile occurrence) LTA = Limiting long term average

Average Monthly Limit = AML

AML = LTA x e [Zσ

n - 0.5σ

n 2] where:  n 2 = ln[(CV2 

###  n) + 1] n = number of samples/month z = 1.645 (95 th percentile occurrence) LTA = Limiting long term average

West Point WWTP

- CalculationsFact Sheet for NPDES Permit WA 0029181 Page 129 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 130 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 131 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 132 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 133 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 134 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 135 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 136 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment Plant

- CalculationsFact Sheet for NPDES Permit WA 0029181 Page 137 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 138 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 139 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 140 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 141 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 142 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 143 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plant

- CalculationsFact Sheet for NPDES Permit WA 0029181 Page 144 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 145 of 1 75

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 146 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 147 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 148 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 149 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 150 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment Plant

- CalculationsFact Sheet for NPDES Permit WA 0029181 Page 151 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 152 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 153 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 154 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 155 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 156 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 157 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 158 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Henderson/MLK CSO Treatment Plant

- CalculationsFact Sheet for NPDES Permit WA 0029181 Page 159 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 160 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 161 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 162 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 163 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix G

— Significant Industrial Users

Company Name Permit

Number Local

Limits Categorical

Limits If categorical, which category and

sub

- category

Acu

- Line Corporation 7231

- 04 No Yes Metal Finishing

- CFR 433 PSNS Alaskan Copper Works

- 6th Ave. 7238

- 05 No Yes Metal Finishing

- CFR 433 Alaskan Copper Works

- Marginal Way 7201

- 04 No Yes Metal Finishing

- CFR 433 Amgen Corporation (Seattle) 7785

- 02 Yes No Art Brass Plating, Inc. 7722

- 04 No Yes Metal Finishing

- CFR 433 PSNS ASKO Processing Inc. 7728

- 03 No Yes Metal Finishing

- CFR 433 BNSF Railway Co.

- Interbay Facility 7872

- 01 Yes No Boeing Commercial Airplane

- North Field 7594

- 05 No Yes Metal Finishing

- CFR 433 Boeing Company

- Plant 2 Facility 7811

- 03 No Yes Metal Finishing

- CFR 433 PSNS
BP West Coast Products, LLC 7592

- 04 Yes No Carl Zapffe, Inc. 7654

- 03 No Yes Metal Finishing

- CFR 433 PSNS Ceradyne Inc.

- Viox Glass Technology 7507

- 04 Yes No Darigold, Inc.

- Rainier Plant 7116

- 05 Yes No

Emerald Services Inc.

- Airport Way Facility 7884

- 01 No Yes Centralized Waste Treatment 437,ABC PSES

Emerald Services Inc.

- Marginal Way Facility 7725

- 04 Yes No
Encore Oils, LLC 7751

- 04 Yes No Foss Maritime Company 7703

- 04 Yes No

Glacier Northwest Inc. 7740

- 03 Yes No GM Nameplate Inc. 7187

- 05 No Yes Metal Finishing

- CFR 433

Industrial Container Services 7130

- 04 Yes No IRIS Holdings LLC

- 5th Ave. N. Ph 2 Construction Site 7871

- 01 Yes No Kerry Food & Beverage 7854

- 01 Yes No King County SWD

- Shoreline Transfer Station 7587

- 05 Yes No King County SWD

- Vashon Transfer Station 7675

- 04 Yes No King County WTD

- Ballard Siphon Replacement Project 7849

- 01 Yes No Magnetic and Penetrant Services Co. 7873

- 01 No Yes Metal Finishing

- CFR 433 PSNS
Marel Seattle, Inc. 7821

- 02 No Yes Metal Finishing

- CFR 433 PSNS
Marine Vacuum Service, Inc. 7676

- 05 No Yes Centralized Waste Treatment 437D
PSES Mastercraft Metal Finishing, Inc. 7233

- 03 No Yes Electroplating

- CFR 413

National Products Inc. 7834

- 02 No Yes Metal Finishing

- CFR 433 PSNS

Pacific Iron and Metal 7577

- 04 Yes No Pepsi Beverages Company

- Seattle Facility 7820

- 02 Yes No

Pioneer Industries 7723

- 04 No Yes Metal Finishing

- CFR 433 PSNS Rabanco Recycling Company 7595

- 05 Yes No Seattle Barrel Company 7113

- 03 Yes No Seattle, City of

- SDOT

- Mercer Corridor Improvements 7863

- 01 Yes No Seattle, City of

- SPU

- South Transfer Station 7878

- 01 Yes No
Skills, Inc.

- Ballard Facility 7552

- 03 No Yes Electroplating

- CFR 413

Sound Transit

- Capitol Hill Station Location 7860

- 02 Yes No

Sound Transit

- U830 Tunneling Pine Street Location 7859

- 01 Yes No

Sound Transit

- University of Washington Station Location 7861

- 02 Yes No TOC Holdings Co. 7689

- 07 Yes No U.S. Starcraft Corporation 9711

- 01 No Yes Metal Finishing

- CFR 433 University of Washington Microfabrication Facility 7800

- 02 No Yes Electronic Components

- CFR 469 University of Washington School of Dentistry 7797

- 03 Yes No Vigor Shipyards, Inc. 7782

- 06 Yes No

WSDOT

- Alaskan Way Viaduct Replacement Project,
SR99 Bored Tunnel 7875

- 01 Yes No

WSDOT

- Viaduct

- S. Holgate St. to S. King St. Stage 3 Atlantic Bypass Project 7877

- 01 Yes NoFact Sheet for NPDES Permit WA 0029181 Page 164 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix H

— Process Flow Diagrams

West Point WWTPFact Sheet for NPDES Permit WA 0029181 Page 165 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Alki CSO Treatment PlantFact Sheet for NPDES Permit WA 0029181 Page 166 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Carkeek CSO Treatment Plan tFact Sheet for NPDES Permit WA 0029181 Page 167 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Elliott West CSO Treatment PlantFact Sheet for NPDES Permit WA 0029181 Page 168 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



## Appendix I

— Response to Comments

King County Entity Review Comments Significant comments are listed below ; comments that provided clarification and/or corrections are not listed.Fact Sheet for NPDES Permit WA 0029181 Page 169 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 170 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 171 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow SystemFact Sheet for NPDES Permit WA 0029181 Page 172 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System

Public Review Comments



### Ecology received two comments during the 30

- day public review period : one from EPA Region

10 and the other from Seattle Public Utilities.

Comment #1: EPA
The U.S. Environmental Protection Agency reviewed the above

- referenced draft permit pursuant to the NPDES Memorandum of Agreement between the Washington Department of Ecology and United States Environmental Protection Agency Region 10 (MOA) and the EPA’s obligation to oversee implementation
of the NPDES programs by delegated states. The EPA reviewed the draft permit for consistency w ith the Clean Water Act and NPDES implementing regulations and with the Department of Ecology’s (Ecology)
regulations and permit writing guidance.

The EPA completed a screening

- level review of the above

- mentioned draft NDPES permit. Although our

review was not comprehensive, the following concern must be addressed to ensure consistency with the CWA and NPDES regulations.

The proposed draft permit removes discharge event maximum settleable solids effluent limits of 1.9 mL/L for all four CSO treatment pl ant discharges. Presumably these limits were developed in a previous version of the NPDES permit as a technology

- based effluent limit based on best professional judgment (BPJ). CWA section 402(o) expressly prohibits backsliding from certain existing effl uent limitations. The fact sheet must explain how removal of these effluent limits is consistent with CWA section 402(o) and exceptions to the general prohibition outlined in part (2) of that section or anti

- backsliding regulation at 40 CFR 122.44(l). Re fer to EPA’s Permit Writers’ Manual
( http://www.epa.gov /npdes/pubs/pwm_2010.pdf ), section 7.2, for information about applying the anti

backsliding provisions in NPDES permitting.

Please let me know if you have any questions regarding these comments. Sincerely, Karen

KAREN BURGESS, P.E

. NPDES Permits Unit

- State Oversight Lead
EPA Region 10

206

- 553

- 1644 | Burgess.Karen@epa.gov U.S. Environmental Protection Agency
Office of Water and Watersheds, M/S OWW

- 130 1200 Sixth Avenue, Suite 900
Seattle, Washington 98101 http://www.epa.gov



### Ecology’s response to Comment #1: Ecology proposes to regulate settleable solids discharges from the CSO treatment plants in King County’s collection system using the annual average limit of 0.3 mL/L/hr instead of both the per event limit of 1.9 mL/L/hr and annual average limit of 0.3 mL/L/hr, as instated in the previous permit

. The Clean Water Act (CWA) section 402(o) expressly prohibits backsliding from certain existing effluent limits including:

1. To revise an existing technology

- based effluent limit (TBEL) that was developed on a

case

- by

- case basis using best professional judgment (BPJ) to reflect subsequently promulgated effluent limitations guidelines and standards (effluent guidelines) that would result in a less stringent effluent limitation, andFact Sheet for NPDES Permit WA 0029181 Page 173 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### 2. Relaxation of an effluent limitation that is based on state standards, suc h as water quality standards or treatment standards, unless the change is consistent with CWA section 303(d)(4).

The discharge event maximum settleable solids limit that Ecology is proposing to remove is not a state standard (i.e. not in state regulation) and is not a guidance

- based or a water quality

- based limit, but instead a case

- by

- case limit developed using best professional judgment (BPJ). Therefore the exception allowances of 40 CFR 122.44(l) apply.

40 CFR 122.44(l)(2)(i)(B)(1) allows an exception t o anti

- backsliding policies when “i nformation is available which was not available at the time of permit issuance (other than revised regulations, guidance, or test methods) and which would have justified the application of a less stringent effluent limita tion at the time of permit issuance”. When Ecology originally issued the settleable solids per event limit of 1.9 mL/L/hr it was unaware of the extreme variability in volume and quality (physical and chemical characteristics) of CSO influent flows. In addi tion, the event maximum limit appears to have been developed with data for continuously operated facilities (i.e. Carkeek primary plant), which does not fit the intermittently operated CSO

facilities. The CSO trea tment plants cannot always meet the treatme nt demands of these highly fluctuating, intermittent influent flows when averaged over short periods such as 1 to 2 hours as is often the case for CSO events. This especially applies when “first flush” conditions occur and settleable solids levels are part icularly high. Averaging treatment performance over a longer time period provides a more representative assessment of a facility’s performance capability under these instances. Therefore Ecology is proposing to require the annual average limit of 0.3

mL/L/ hr and not include the maximum per event limit.

This decision is consistent with Ecology’s regulation to require on

- site treatment of CSOs to provide treatment equivalent to primary treatment which is defined in WAC 173

- 245

- 020(16) as ”any process which re moves at least 50% of the total suspended solids from the waste stream, and discharges less that 0.3 ml/L/hr of settleable solids”. The proposed permit restricts the facility to an annual average limit of 0.3 mL/L/hr to meet this design standard.

The remov al of the discharge event maximum settleable solids limit for the four CSO satellite treatment plants is consistent with CWA section 402(o) and exceptions to the general prohibition

outlined in anti

- backsliding regulation at 40 CFR 122.44(l).Fact Sheet for NPDES Permit WA 0029181 Page 174 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Comment # 2: Seattle Public UtilitiesFact Sheet for NPDES Permit WA 0029181 Page 175 of 175

West Point Wastewater Treatment Plant and Combined Sewer Overflow System



### Ecology’s response to Comment #2 Ecology has revised the sentence to indicate “appropriate BMPs” instead of “applicable BMPs”. Ecology did not intend to invoke the meaning of “applicable” as used in Volume IV of Ecology’s St ormwater Management Manual for Western Washington (2012).

Ecology agrees that stormwater management manuals approved by Ecology under a Phase I Municipal Stormwater Permit also contain appropriate BMPs. Such BMPs are determined to be functionally equivalen t to the relevant portion of Ecology’s Stormwater Management Manual for Western Washington through a process associated with the Phase I Municipal

Stormwater Permit.

For this CSO

- related permit requirement, Ecology agrees that use of Ecology’s Stormwater Management Manual for Western Washington and/or use of functionally equivalent manuals approved by Ecology under a Phase I Municipal Stormwater Permit is acceptable for reference purposes in identifying “appropriate” BMPs.

Ecology would also like to prov ide the following definitions of stormwater BMPs:

Stormwater Best Management Practices (BMPs) means schedules of activities, prohibitions of practices, maintenance procedures, and structural and/or managerial practices to prevent or reduce the release of pollutants. BMPs include treatment systems, operating procedures, and practices to control: fa cility site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.

Equivalent BMPs means operational, source control, treatment or innovative BMPs which result in equal or better quality of stormwater discharge from a site than BMPs selected from the Ecology Stormwater Management Manual for Western Washington.