EPA reviewed data and information contained in the NPDES permit fact sheets for two minor industrial dischargers to evaluate potential for impact under the proposed rule [KB Alloys, LLC (WA0002976), and Sandvik Special Metals, LLC (WA0003701)]. The primary pollutants of concern for which data were available are metals (e.g., aluminum, chromium, copper, cyanide, lead, nickel and zinc). For metals, aquatic life protection criteria are more stringent than the proposed human health criteria. For both facilities, due in part to the lack of background pollutant data (i.e., background was set equal to zero) and the dilution factors applied to each facility discharge, there was no reasonable potential to exceed water quality criteria for the metals. The NPDES permits include technology-based effluent limitations for the metals of concern.
Effluent data were not available for all other pollutants for which human health criteria are being proposed. In the fact sheets for each facility, Ecology had determined that discharges from each facility are unlikely to contain chemicals regulated to protect human health. Additional data would be needed to confirm or dispute this finding under the proposed rule.
Methods for Identifying Potential Costs: Nonpoint Sources
Changes in water quality criteria could result in incremental impacts on nonpoint sources of pollution, such as agriculture, urban areas, and forestry, through TMDLs or other pollution cleanup plans. Section 2.2 discusses the nonpoint sources of pollution, and Section 2.3 summarizes the process by which Ecology categorizes waterbodies. Ambient water quality data can be used to determine the impact that a change in human health criteria may have on the attainment of the criteria and thus the potential for incremental control strategies and costs for nonpoint sources.
Identifying Exceedances
EPA identified potential incremental impairments based on available data in EIM. According to the state's Water Quality Program Policy (Ecology, 2012d), Ecology generally uses the last ten years of data to determine impairment status of surface waters. EPA used available surface water monitoring data on pollutants of interest from EIM for the years 2005 to 2014. EPA acknowledges that Ecology uses fish tissue equivalent concentrations to trigger waterbody impairments based on the human health criteria in their 303(d) listing methodology, whereas for the purposes of this analysis, EPA identified potential incremental impairments using water column concentrations. For each monitoring station and parameter, EPA compared the pollutant concentration to both the existing baseline human health criteria and the proposed criteria. Station results that would represent impairment under the proposed criteria but not under the existing baseline criteria may represent potential incremental impairments.
Exhibit 5-1 shows the results of this analysis. Using the baseline criteria values, monitoring data indicate potential impairment on the basis of human health criteria exceedances in the water column at 205 stations. Using the proposed criteria, there would be exceedances in the water column at 254 stations, for a total of 49 potential incremental exceedances (or a 24% increase compared to the baseline).
Exhibit 5-1. Potential Incremental Impairments[1]
Parameter
Number of Locations
Potential Impairments

Baseline[2]
Proposed[3]
Incremental[4]
1,2-Dichloropropane
                                       D

1,3-Dichloropropene
                                       D

2,3,7,8-TCDD (dioxin)
                                       D

4,4'-DDT
                                      45
                                       7
                                      24
                                      17
Acenaphthene
                                       5
                                       0
                                       0
                                       0
Anthracene
                                       8
                                       0
                                       0
                                       0
Antimony
                                      49
                                       0
                                       0
                                       0
Arsenic
                                      178
                                      167
                                      167
                                       0
Benzo(a) anthracene
                                      16
                                       5
                                       7
                                       2
Benzo(a) pyrene
                                      10
                                       5
                                       7
                                       2
Benzo(b) fluoranthene
                                      10
                                       6
                                       7
                                       1
Benzo(k) fluoranthene
                                      15
                                       4
                                       5
                                       1
Bis(2-ethylhexyl) phthalate
                                      22
                                       0
                                      14
                                      14
Butylbenzyl phthalate
                                       6
                                       0
                                       2
                                       2
Chlordane
                                       D

Chrysene
                                      10
                                       5
                                       4
                                      -1
Copper[5]
                                      238
                                       0
                                       0
                                       0
Dibenzo(a,h) anthracene
                                       6
                                       2
                                       3
                                       1
Diethyl phthalate
                                       6
                                       0
                                       0
                                       0
Dimethyl phthalate
                                       2
                                       0
                                       0
                                       0
Di-n-butyl phthalate
                                      19
                                       0
                                       0
                                       0
Fluoranthene
                                      11
                                       0
                                       0
                                       0
Fluorene
                                       5
                                       0
                                       0
                                       0
Indeno(1,2,3-cd) pyrene
                                      15
                                       4
                                       6
                                       2
Nickel
                                      163
                                       0
                                       0
                                       0
Polychlorinated biphenyls (PCBs)
                                       D

Pyrene
                                      10
                                       0
                                       0
                                       0
Thallium
                                       6
                                       0
                                       0
                                       0
Zinc[5]
                                      201
                                       0
                                       0
                                       0
Mercury[6]
                                      18
                                       0
                                       8
                                       8
Source: Based on 2005 to 2014 surface water monitoring data from Washington's Environmental Information Management System (EIM).
D = EIM data are available, but all observations are unusable due to the study type (contaminated site), waterbody type (groundwater), or result qualifiers.
1. Blanks indicate that data are not available, or that EPA did not use all observations due to study, location, or data quality reasons.
2. Number of stations at which monitoring data indicate two or more exceedances of the baseline human health criteria within 3 years.
3. Number of stations at which monitoring data indicate two or more exceedances of the proposed human health criteria within 3 years.
4. Represents difference in results between baseline and proposed criteria.
5. For zinc, nickel, and copper, includes only freshwaters since the aquatic life criteria are more stringent than proposed human health criteria for marine waters.
6. Potential to exceed the proposed fish tissue criterion based on the projected water column target.

--------------------------------------------------------------------------------
Identifying Compliance Actions and Costs
EPA does not have data on all parameters for all waterbodies, or data on the sources of loadings to potentially impaired waterbodies. Additionally, Ecology is currently in the process of revising and updating its management plan for nonpoint source pollution (see Ecology, 2015b). Reductions in nonpoint source pollution loadings arising from this revised plan will occur in the absence of the proposed rule and represent baseline requirements.
If the revised criteria lead to additional waters being listed on the state's 303(d) list for exceedances of human health based water quality criteria, the magnitude of cost impacts to nonpoint sources depends on the extent to which additional practices are needed for compliance with the potential revisions in comparison to compliance with existing baseline standards.
If nonpoint sources are the primary cause of some incremental impairments, then the revised criteria may result in some costs to nonpoint sources, including:
Agricultural and forest lands  -  sediment and erosion controls beyond those specified under existing state and federal regulations and plans;
Mining  -  cleanup and remediation including excavation and onsite capping of contaminated soils, capping of onsite solid waste mining debris, regrading of tailings to mitigate mass wasting and off-site migration, and abatement and mitigation of physical hazards; and
Stormwater discharges  -  increased or additional nonstructural BMPs (e.g., institutional, education, or P2 practices designed to limit generation of runoff or reduce the pollutants load of runoff); and structural controls (e.g., engineered and constructed systems designed to provide water quantity or quality control).
Control of nonpoint sources of the pollutants of concern could reduce costs to point sources. In the context of a TMDL, load and wasteload allocations reflecting the source of the pollutant could result in less stringent limits for point sources than anticipated through the analysis of the sample facilities as described in Section 4.
If an additional number of TMDLs are needed under the revised criteria, there may be an increase in government regulatory costs. EPA (2001b) estimates that TMDL development costs per water body typically range from under $26,000 to over $500,000 depending on the number of TMDLs, the level of complexity, and the extent to which impaired waters are clustered together for TMDL development.

Potential Compliance Costs
This section summarizes the potential costs to point sources and nonpoint sources, and discusses the limitations and uncertainties associated with the analyses.
Point Sources
Costs for compliance with baseline criteria include costs associated with compliance with WQBELs reflective of existing criteria. Incremental costs associated with the potential revised criteria represent the costs of any additional actions or controls needed for compliance with revised WQBELs under the proposed rule. Exhibit 6-1 provides a summary of the potential total annual statewide costs. The low estimate represents the assumption that the projected control scenario will result in compliance with projected effluent limits; the high estimate includes the estimated cost of also obtaining a variance under the assumption that control actions will not result in compliance with very low limits. For the 73 major dischargers in the state, EPA estimates that the total annual cost may be in the range of $13 million.
Exhibit 6-1. Total Annual Costs by Discharger Type
Discharger Type
Statewide Annual Costs (millions; 2014$)

Low
High
Municipal
                                                                          $0.00
                                                                          $0.00
Industrial
                                                                         $13.03
                                                                         $13.06
Total
                                                                         $13.03
                                                                         $13.06

Of the costs shown in Exhibit 6-1, all costs are attributable to industrial dischargers, primarily for treatment of arsenic. Overall, 99% of the costs are attributable to the revised human health criteria for arsenic while the remaining 1% are attributable to the revised human health criteria for mercury.
Nonpoint Sources
Costs for compliance with baseline criteria include costs to nonpoint sources (e.g., agricultural and forest operations; contamination from historic mining sites), and municipal stormwater sources associated with implementation of existing programs and TMDLs.  Incremental costs associated with compliance with the potential revised criteria represent the costs of any actions or controls above and beyond those needed to meet baseline requirements. EPA did not estimate incremental costs for nonpoint sources for this preliminary analysis. However, if nonpoint sources are the primary source of the pollutants of concern, control of nonpoint sources could result in less stringent limitations and lower costs than estimated for point sources. For situations in which controls beyond those required under the baseline are necessary, controls could include the development and implementation of TMDLs.
Uncertainties and Quality Assurance
As noted previously, the proposed rule does not establish any requirements directly applicable to regulated entities or other sources of pollution. State implementation of the proposed rule may result in new or revised NPDES permit conditions for point source dischargers, and incremental control requirements for nonpoint sources. For point sources, EPA has estimated these impacts as the difference between compliance with the existing human health criteria and compliance with the proposed human health criteria. However, there is substantial uncertainty associated with actual state implementation of the proposed rule.
The proposed rule establishes human health criteria applicable to the waters in the state and as such there could be a need for additional controls on nonpoint sources of pollutant loadings to attain WQS. EPA estimated potential incremental impairments using readily available ambient water quality data. However, data are limited to identify specific incremental control actions and costs that may be required of nonpoint sources.
Exhibit 6-2 summarizes additional uncertainties and limitations in the analysis.
Exhibit 6-2. Uncertainties in Analysis of Costs
Uncertainty/Assumption
Effect on Cost Estimate
Notes
Sample facility costs are representative of all facilities in state (by category)
                                   Uncertain
Could result in an overestimate or underestimate of statewide costs if sample facilities are higher or lower than average costs. Does not account for new/expanding facilities.
Baseline controls
                                   Uncertain
EPA did not conduct extensive site-specific review of facility plans and information for addressing baseline water quality issues; thus, facility analyses could under- or overstate baseline and incremental actions and costs.
Means of addressing incremental impairments
                                 Overestimate
Under a TMDL, load and wasteload allocations may result in less stringent requirements for point sources if nonpoint sources are the cause of impairments.
Zero compliance costs for two sample facilities for which effluent data are not available
                                 Underestimate
If these facilities do need to take actions to comply with the revised requirements, the total cost of compliance would be greater than that estimated here.
Total arsenic and dissolved arsenic monitoring data represent only the inorganic fraction of arsenic
                                 Overestimate
Effluent and ambient monitoring data available for the analysis are in terms of total and dissolved arsenic; if some fraction of arsenic measured is in the organic form then this may result in an overestimate of costs since the proposed criterion is in terms of the inorganic form, which is more toxic than other forms.

EPA conducted quality assurance checks on the data, analyses, and results, consistent with the programmatic and project-specific quality assurance plans. In addition, the Agency used Ecology's permit-writing tool, ensuring consistency with state permitting approaches and calculations. EPA also used Washington-specific data sources as available, and for all data entry, EPA confirmed the accuracy of data sources and documentation following procedures described in the quality assurance plans. These procedures include checks on all inputs and calculations, and using multiple approaches to confirm results.

References
Bureau of Labor Statistics, United States Department of Labor. 2014. May 2014 State Occupational Employment and Wage Estimates: Washington. (available at: http://www.bls.gov/oes/current/oes_wa.htm)
Department of Ecology, State of Washington (Ecology). 2015a. Phase I Municipal Stormwater Permit. National Pollutant Discharge Elimination System and State Waste Discharge General Permit for Discharges from Large and Medium Municipal Separate Storm Sewer Systems. Modification Date: January 16, 2015.
Department of Ecology, State of Washington (Ecology). 2015b. Washington's Water Quality Management Plan to Control Nonpoint Sources of Pollution: Draft. Publication No. 15-10-015.
Department of Ecology, State of Washington (Ecology). 2015c. Water Quality Program Permit Writer's Manual. Publication Number 92-109.
Department of Ecology, State of Washington (Ecology). 2014a. Draft -- Washington Human Health Criteria Review Documents. Revised 8/8/2014.
Department of Ecology, State of Washington (Ecology). 2014b. Frequently Asked Questions, Water Quality Program: Municipal Stormwater Permits.
Department of Ecology, State of Washington (Ecology). 2014c. Western Washington Phase II Municipal Stormwater Permit. National Pollutant Discharge Elimination System and State Waste Discharge General Permit for Discharges from Small Municipal Separate Storm Sewers in Western Washington. Modification Date: January 16, 2014.
Department of Ecology, State of Washington (Ecology). 2014d. Industrial Stormwater General Permit. A National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permit for Stormwater Discharges Associated with Industrial Activities. Issuance Date: December 3, 2014.
Department of Ecology, State of Washington (Ecology). 2014e. Water Quality Improvement Project Deschutes River Watershed Area: Multi-Parameter. Available at: http://www.ecy.wa.gov/programs/wq/tmdl/deschutes/index.html (accessed 4/7/2015).
Department of Ecology, State of Washington (Ecology). 2012a. 2012 Stormwater Management Manual for Western Washington. Amended in December 2014. Publication Number 14-10-055.
Department of Ecology, State of Washington (Ecology). 2012b. Eastern Washington Phase II Municipal Stormwater Permit. National Pollutant Discharge Elimination System and State Waste Discharge General Permit for Discharges from Small Municipal Separate Storm Sewers in Eastern Washington. Issuance Date: August 1, 2012.
Department of Ecology, State of Washington (Ecology). 2012c. Water Quality Improvement Project, Yakima Watershed Area: Toxics. Available at: http://www.ecy.wa.gov/programs/wq/tmdl/yakima_wq/YakToxicsTMDL.html (accessed 4/7/2015).
Department of Ecology, State of Washington (Ecology). 2012d. Water Quality Program Policy: Assessment of Water Quality for the Clean Water Act Section 303(d) and 305(b) Integrated Report. Chapter 1: WQP Policy 1-11.
Department of Ecology, State of Washington (Ecology). 2010. Yakima River Pesticides and PCBs Total Maximum Daily Load. Volume 1: Water Quality Study Findings. Publication No. 10-03-018.
Department of Ecology, State of Washington (Ecology). 2007a. Palouse River Chlorinated Pesticides and PCBs Total Maximum Daily Load: Water Quality Improvement Report and Implementation Plan. Publication No. 07-03-018.
Department of Ecology, State of Washington (Ecology). 2007b. Mission Creek Watershed DDT Total Maximum Daily Load: Water Quality Improvement Report. Publication No. 07-10-046.
Department of Ecology, State of Washington (Ecology). 2006a. Walla Walla River Chlorinated Pesticides and PCBs Total Maximum Daily Load (Water Cleanup Plan): Submittal Report. Publication No. 05-10-079.
Department of Ecology, State of Washington (Ecology). 2006b. Lake Chelan Watershed DDT and PCB Total Maximum Daily Load: Water Quality Improvement Report. Publication No. 06-10-022.
Department of Ecology, State of Washington (Ecology). 2005. Lower Okanogan River Basin DDT and PCBs Total Maximum Daily Load: Submittal Report. Publication No. 04-10-043.
Department of Ecology, State of Washington (Ecology). 2004a. Stillaguamish River Watershed Fecal Coliform, Dissolved Oxygen, pH, Mercury, and Arsenic Total Maximum Daily Load (Water Cleanup Plan): Submittal Report. Publication No. 05-10-044.
Department of Ecology, State of Washington (Ecology). 2004b. Lower Similkameen River Arsenic Total Maximum Daily Load: Submittal Report for Joint Issuance. Publication Number 03-10-074.
Department of Ecology, State of Washington (Ecology). 2001. Inner Bellingham Bay Contaminated Sediments Total Maximum Daily Load: Submittal Report. Publication Number 99-58-WQ.
Department of Ecology, State of Washington (Ecology). 1999. Spokane River Dissolved Metals Total Maximum Daily Load: Submittal Report. Publication Number 99-49-WQ.
Department of Ecology, State of Washington (Ecology). 1992a. Total Maximum Daily Load. TMDL Number: 07-001.
Department of Ecology, State of Washington (Ecology). 1992b. Total Maximum Daily Load. TMDL Number: 10-001.
United States Environmental Protection Agency (U.S. EPA). 2014. Toxicity and Bioaccumulation Factors Used in the Draft 2014 Updated Ambient Water Quality Criteria for the Protection of Human Health. (available from: http://water.epa.gov/scitech/swguidance/standards/criteria/current/hhdraft.cfm)
United States Environmental Protection Agency (U.S. EPA). 2012. Water: Contaminated Sediments. Basic Information. (available from: http://water.epa.gov/polwaste/sediments/cs/aboutcs.cfm)
United States Environmental Protection Agency (U.S. EPA). 2008. Cost of Compliance with Water Quality Criteria for Toxic Pollutants for Oregon Waters. Prepared by Science Applications International Corporation.
United States Environmental Protection Agency (U.S. EPA).  2002.  National Recommended Water Quality Criteria: 2002.  Human Health Criteria Calculation Matrix.  EPA 822-R-02-012.  November.
United States Environmental Protection Agency (U.S. EPA).  2001a.  Water Quality Criterion for the Protection of Human Health: Methylmercury.  EPA-823-R-01-001.  January.
United States Environmental Protection Agency (U.S. EPA).  2001b.  The National Costs of the Total Maximum Daily Load Program (Draft Report).  EPA 841-D-01-003.  August.
United States Environmental Protection Agency (U.S. EPA).  1995.  Interim Economic Guidance for Water Quality Standards Workbook.  EPA 823-B-95-002.  March.
United States Environmental Protection Agency (U.S. EPA). 1991. Technical Support Document for Water Quality-Based Toxics Control. EPA/505/2-90-001.
United States Environmental Protection Agency (U.S. EPA). 1980. Guidelines and Methodology Used in the Preparation of Health Effect Assessment Chapters of the Consent Decree Water Criteria Documents. Federal Register 45: 79347, Appendix 3.

 -  Facility Analyses
This appendix provides detailed analyses for the sample facilities in alphabetical order by municipal dischargers first followed by industrial dischargers.
Chambers Creek Regional Wastewater Treatment Facility
The Chambers Creek Regional Wastewater Treatment Facility (WWTF; NPDES permit WA0039624) provides wastewater treatment to 65,000 households and 2,000 businesses in DuPont, Lakewood, Tacoma, University Place, Steilacoom, and other unincorporated areas. The facility also treats wastewater from five industrial users, including the Boeing Corporation Skin and Spar fabrication facility, the Land Recovery Incorporated Hidden Valley Landfill, James Hardie Building Products, and Fredrickson Power. The facility discharges a maximum monthly flow of 14 to 20 mgd (dry weather flow and maximum monthly flow, respectively) to Puget Sound Gordon Point Area.
Treatment Processes
The 2008 permit fact sheet indicates that the current treatment consists of screening equipment and primary sedimentation; secondary treatment includes bioselectors, secondary clarifiers and ultraviolet disinfection.
Effluent Data
No recent effluent monitoring data for the WWTF were available for any of the pollutants for which human health criteria are being proposed.
Receiving Water
The facility discharges to Puget Sound Gordon Point Area, which is a Class AA extraordinary receiving water. According to the 2008 permit fact sheet, Commencement Bay (monitoring station BRW-COMMENCEBAY) is the nearest monitoring station with available water column data. Exhibit A-1 summarizes the available ambient receiving water concentrations for the station based on data from Ecology's Environmental Information Management System between 2008 and 2009.
Exhibit A-1. Ambient Receiving Water Concentrations: Commencement Bay
Pollutant
Water Column Concentration (ug/L)

Maximum
Average
Copper
                                      1.3
                                     0.837
Zinc
                                     2.91
                                     1.515
Source: Washington State Department of Ecology Environmental Information Management System, 2008 to 2009 data for station BRW-COMMENCEBAY.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. The necessary data to confirm the reasonable potential analysis under the baseline scenario were not available.
Policy Scenario
EPA did not have the necessary data to perform the reasonable potential analysis under the policy scenario. Thus, it could not determine reasonable potential or calculate permit limits and costs.
King County South WWTP and CSO System
The King County Department of Natural Resources and Parks (Wastewater Treatment Division) operates the King County South WWTP (NPDES permit WA0029581), which serves 25 jurisdictions and utility districts, including Seattle, across 152 square miles. The majority of flow to the treatment facility is from separated sanitary systems, with approximately 4% coming from a combined system in Seattle. Average WWTP flow is 76 mgd.
Treatment Processes
The 2009 permit fact sheet reports that primary treatment consists of screening and settling followed by primary clarification. Secondary treatment is an activated sludge process and includes aeration and secondary clarification. After disinfection (using sodium hypochlorite), effluent is discharged to Puget Sound.
Effluent Data
Exhibit A-2 summarizes the last three years of effluent data for the treated wastewater for the pollutants of concern for which data are available, based on Ecology's priority pollutant monitoring data and reasonable potential analysis (Appendices C and H in the 2009 permit fact sheet).
Exhibit A-2. Summary of Effluent Data: King County South WWTP[1]
Pollutant
Observations
QL (ug/L)
Summary of Detected Values (ug/L)[2]

Total
Nondetect

Median
Average
95th Percentile
Max
1,1,2,2-Tetrachloroethane
                                      23
                                      23
                                       1

1,1,2-Trichloroethane
                                      23
                                      23
                                       1

1,2,4-Trichlorobenzene
                                      24
                                      24
                                   0.57-0.71

1,2-Trans-dichloroethylene
                                      23
                                      23
                                       1

2,4-Dimethylphenol
                                      24
                                      24
                                 0.94  -  1.2

2,4-Dinitrophenol
                                      24
                                      24
                                  1.9  -  2.4

2-Chlorophenol
                                      24
                                      24
                                  1.9  -  2.4

Acenaphthene
                                      24
                                      24
                                   0.57-0.71

Acrolein
                                      23
                                      23
                                       5

Acrylonitrile
                                      23
                                      23
                                       5

Antimony
                                      32

                                      0.5
                                     0.25
                                   <0.51
                                     0.514
                                     0.67
Arsenic
                                      34

                                      0.5

                                     1.26
                                     1.516
                                     1.60
Benzene
                                      23
                                      23
                                       1

Benzidine
                                      24
                                      24
                                     23-28

Benzo(a) anthracene
                                      24
                                      24
                                   0.57-0.71

Bromoform
                                      23
                                      23
                                       1

Carbon tetrachloride
                                      23
                                      23
                                       1

Chloroform
                                      23

                                     1.32
                                      1.3
                                   <1.32
                                     2.034
                                     2.18
Copper
                                      32

                                      0.4

                                     16.5
                                     31.34
                                     42.4
Cyanide
                                      33

                                     0.005
                                     .0025
                                   <0.008
                                     0.019
                                     0.028
Dichlorobromomethane
                                      23
                                      23
                                       1

Ethylbenzene
                                      23
                                      23
                                       1

Fluoranthene
                                      24
                                      24
                                   0.57-0.71

Fluorene
                                      24
                                      24
                                   0.57-0.71

Hexachlorocyclopentadiene
                                      24
                                      24
                                   0.94-1.2

Hexachloroethane
                                      24
                                      24
                                   0.94-1.2

Indeno(1,2,3-cd) Pyrene
                                      24
                                      24
                                   0.94-1.2

Isophorone
                                      24
                                      24
                                   0.94-1.2

Methyl bromide
                                      23
                                      23
                                       5

Methylene chloride
                                      23

                                       5
                                      2.5
                                   <4.74
                                      2.5
                                       7
Nickel
                                      33

                                      0.3
                                     2.90
                                     2.99
                                     4.004
                                     4.45
Nitrobenzene
                                      24
                                      24
                                   0.94-1.2

N-Nitrosodimethylamine
                                      24
                                      24
                                    3.8-4.7

N-Nitrosodi-n-propylamine
                                      24
                                      24
                                   0.94-1.2

N-Nitrosodiphenylamine
                                      24
                                      24
                                   0.94-1.2

Pentachlorophenol (PCP)
                                      24
                                      24
                                   0.94-1.2

Phenol
                                      24
                                      24
                                      3.9

Pyrene
                                      24
                                      24
                                   0.57-0.71

Selenium
                                      33
                                      33
                                      1.5

Tetrachloroethylene
                                      23
                                      23
                                       1

Thallium
                                      33
                                      33
                                   0.04-0.2

Toluene
                                      23

                                       4
                                       2
                                   <1.45
                                     3.41
                                     3.86
Trichloroethylene
                                      23
                                      23
                                       1

Vinyl Chloride
                                      23
                                      23
                                       1

Zinc
                                      33

                                      0.5

                                      29
                                     49.34
                                      68
Mercury
                                      33

                                     0.05
                                     0.025
                                   <0.05
                                     0.052
                                     0.058
Source: 2009 permit fact sheet (Appendix C and H).
QL = quantitation level
1. Blanks indicate unreported data.
2. Metal concentrations are total recoverable form.

Receiving Water
The facility discharges to Puget Sound, which Ecology has designated as an extraordinary marine water. Exhibit A-3 summarizes the available ambient receiving water concentrations based on 2011 to 2012 data from Ecology's Environmental Information Management System (monitoring station LSNT01, identified in the permit fact sheet as the most appropriate monitoring station for ambient data).
Exhibit A-3. Ambient Receiving Water Concentrations (2011 to 2012): Puget Sound
Pollutant
Water Column Concentration (ug/L)1

Minimum
Median
Geometric Mean
90th Percentile
Maximum
Antimony
                                     0.143
                                     0.158
                                     0.158
                                     0.172
                                     0.173
Arsenic
                                     1.22
                                      1.4
                                     1.364
                                     1.45
                                     1.46
Copper
                                     0.231
                                     0.287
                                     0.296
                                     0.355
                                     0.387
Cyanide
                                      nd
                                      nd
                                      nd
                                      nd
                                      nd
Mercury
                                      nd
                                      nd
                                      nd
                                      nd
                                      nd
Nickel
                                     0.39
                                    0.4115
                                  0.410904577
                                    0.4275
                                     0.43
Zinc
                                     0.27
                                     0.395
                                  0.428224144
                                     0.605
                                     0.707
Source: based on data from Ecology's Environmental Information Management System, monitoring station LSNT01.
nd=nondetect
1. Metal concentrations are dissolved.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Exhibit A-4 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-2 and available ambient data in Exhibit A-3, there is reasonable potential to exceed the baseline human health criteria for arsenic.
Exhibit A-4. Human Health Reasonable Potential Analysis for King County South WWTP  -  Baseline Scenario[1]
Parameter
Effluent Conc. (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     1.26
                                     1.364
                                     1.364
                                     0.14
1. See effluent concentrations in Exhibit A-2 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-3.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 428.
3. Consumption of organisms only.

Exhibit A-5 summarizes the calculated permit limits for arsenic under the baseline scenario.
Exhibit A-5. Human Health Based Effluent Limitations for King County South WWTP  -  Baseline Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                     0.14
                                     0.16
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the baseline scenario, the discharger would have to meet an average monthly effluent limit (AML) of 0.14 ug/L and a maximum daily effluent limitation (MDL) of 0.16 ug/L. Since the average effluent concentration is 1.26 ug/L and the maximum effluent concentration is 1.6 ug/L, which are greater than the projected baseline permit limitations, the discharger will need to reduce arsenic in its effluent to ensure that permit limitations are consistently met.
Arsenic and arsenic-containing chemicals are not used in wastewater treatment. However, the facility has a large industrial base and regulates 65 industrial users of which 27 are significant industrial users and 19 are categorical industrial users (i.e., users subject to EPA's national pretreatment standards), including 32 in the electroplating and metal finishing categories. Thus, a source control program that targets or imposes more stringent limits on the most likely indirect industrial dischargers of arsenic to the plant could reduce arsenic concentrations to the necessary levels. Costs for such a program would depend on the number of arsenic sources and the measures that could be implemented at those sources to reduce arsenic. However, without more detailed information on these industrial users and King County's pretreatment program (e.g., flows and arsenic concentrations for each industrial user, local limits for arsenic, ordinances, etc.), it is not possible to estimate pretreatment or P2 costs to indirect dischargers.
Other potential sources of arsenic to the treatment plant are water and groundwater infiltration. Details on the drinking water sources for the municipalities served by King County South, including whether these sources are surface water or groundwater and levels of arsenic in these sources, were not evaluated. The drinking water maximum contaminant level is 10 ug/L, which is higher than current wastewater effluent concentrations and human health criteria. EPA did not attempt to determine with any certainty whether drinking water is contributing to high arsenic levels in the wastewater effluent. However, if the facility determines that drinking water is the source of high arsenic values in the wastewater, it is likely that the facility would pursue a variance.
The fact sheet for the facility's 2009 permit indicates that 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 a regional I&I control program to reduce the amount of peak wet weather flow entering the County's wastewater conveyance. 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 began in 2000 and culminated with the County Executive's recommendation for a regional I&I control program.
The study included: defining levels of I&I for each local agency tributary to the regional system through an extensive flow monitoring and modeling program; constructing 10 pilot projects in 12 local agency jurisdictions to demonstrate the effectiveness of collection system rehabilitation projects and to test various technologies and gain cost information; developing model standards, procedures, policies, and guidelines for use by local agencies to reduce I&I in their systems; performing a cost-benefit analysis to determine the cost-effectiveness of I&I reduction; developing a long-term regional I&I control plan; working with the local sewer agencies to conduct an I&I reduction feasibility analysis; and performing several I&I reduction projects.
As the focus of these studies and analyses were on reduction of peak flows to minimize combined sewer overflows, it is uncertain whether this I&I reduction program and these modifications to the collection system would address arsenic levels (there are a number of modifications that can correct I&I issues that would not necessarily reduce arsenic concentrations). If groundwater infiltration is causing the high arsenic effluent levels, the facility may have to implement modifications to the existing I&I reduction program for compliance with the baseline scenario criteria.
Due to the fact that ambient receiving water concentrations exceed the baseline human health criteria, the discharger may pursue obtaining a water quality standards variance. The one-time cost associated with pursuing a variance is estimated to be $426,000, with minimal costs associated with renewal. If the arsenic effluent levels are the result of infiltration of arsenic-contaminated groundwater, total costs could be $10,600,000 for a comprehensive I&I reduction program that includes source identification and pipe rehabilitation for a system with 145 miles of sewer pipes (approximately $1,000,000 per year annualized at 7% over 20 years). Note that if groundwater infiltration is not the only source of arsenic to the treatment plant, an I&I reduction program alone may not be sufficient for compliance and the discharger would not likely undertake such a program for compliance with toxic criteria alone.
Policy Scenario
Exhibit A-6 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-2 and available ambient data in Exhibit A-3, there is reasonable potential to exceed the proposed human health criteria for arsenic.
Exhibit A-6. Human Health Reasonable Potential Analysis for King County South WWTP  -  Policy Scenario[1]
Parameter
Baseline Average Monthly Effluent Limit  (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     0.14
                                     1.364
                                     1.364
                                    0.0059
1. See effluent concentrations in Exhibit A-2 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-3.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 428.
3. Consumption of organisms only.

Exhibit A-7 summarizes the calculated permit limits for arsenic under the policy scenario.
Exhibit A-7. Human Health Based Effluent Limitations for King County South WWTP  -  Policy Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                    0.0059
                                    0.0069
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the policy scenario, the discharger would have to meet an AML of 0.0059 ug/L and a MDL of 0.0069 ug/L. Under the baseline scenario, the projected effluent limitations are below the analytical quantitation level (QL) and EPA estimated that the discharger would incur costs for I&I control as well as pursuit of a variance in order to ensure compliance with effluent limitations below the QL. Since the projected effluent limitations under the policy scenario are also below the QL, no additional compliance strategy would be required under the policy scenario (i.e., the discharger would not pursue a second variance).
King County West Point WWTP and CSO System
King County provides wholesale wastewater treatment services to 17 cities, 16 local sewer utilities, and one Indian tribe. The King County West Point WWTP and Combined Sewer Overflow (CSO) System (NPDES permit WA0029181) 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 WWTP discharges to the Puget Sound, and the CSO treatment plants discharge to the Puget Sound, Elliot Bay, and Duwamish Waterway. Average annual WWTP flow is 95 mgd.
Treatment Processes
The 2014 permit fact sheet for the facility indicates that the West Point WWTP treats 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 Puget Sound. The Alki, Carkeek, Denny/Elliott West, and Henderson/MLK CSO treatment plants have primary treatment with disinfection.
Effluent Data
Exhibit A-8 summarizes effluent monitoring data for the WWTP from the permit fact sheet, which reports detected concentrations only for the pollutants of concern.
Exhibit A-8. Summary of Effluent Data (2009-2013): King County West Point WWTP
Pollutant
Number of Observations
Effluent Concentration (ug/L)[1]

Minimum
Median
95[th] Percentile
Maximum
1,4-Dichlorobenzene
                                       9
                                      1.0

                                     10.2
                                     10.2
2,4-Dichlorophenol
                                       9
                                     0.12

                                     0.96
                                     0.96
2,4-Dimethylphenol
                                       9
                                     0.24

                                     0.48
                                     0.48
Antimony
                                      15
                                     0.30
                                     0.44

                                     0.63
Arsenic
                                      15
                                     0.27

                                     2.196
                                     2.28
Bis(2-ethylhexyl) phthalate
                                       9
                                     0.41

                                     7.332
                                     10.20
Chloroform
                                       9
                                     1.00

                                     5.68
                                     5.68
Copper
                                      15
                                     0.40

                                     16.3
                                     16.3
Cyanide
                                      15
                                      5.0

                                      6.0
Diethyl phthalate
                                       9
                                     0.120

                                     0.85
                                     0.85
Mercury
                                      21
                                     0.002
                                     0.005
                                    0.0155
                                     0.016
Methylene chloride
                                       9
                                      5.0

                                      5.3
                                      5.3
Nickel
                                      23
                                      0.1
                                     2.81
                                     5.999
                                      6.5
Phenol
                                       9
                                      40

                                     0.95
                                      90
Pyrene
                                       9
                                     0.071

                                     0.29
                                     0.290
Selenium
                                      15
                                     0.50
                                      0.5
                                     0.74
                                     1.30
Thallium
                                      15
                                     0.040
                                     0.050

                                     0.130
Toluene
                                       9
                                      1.0

                                      1.1
                                      1.1
Zinc
                                      23
                                     10.7

                                     50.78
                                     54.2
Source: Summarized data from 2014 Fact Sheet, Table 15 and Appendix F.
1. Metal concentrations are total recoverable form.

Receiving Water
Exhibit A-9 summarizes the available ambient receiving water concentrations based on data from the 2014 Fact Sheet for the permit and King County Department of Natural Resources (2013).
Exhibit A-9. Ambient Receiving Water Concentrations: Puget Sound
Pollutant
Water Column Concentration (ug/L)[1]

Minimum
Median
Mean
90[th] Percentile
Maximum
Arsenic
                                     1.15
                                     1.33
                                     1.29
                                     1.36
                                     1.43
Copper
                                     0.234
                                     0.308
                                     0.322
                                     0.41
                                     0.617
Mercury
                                      nd
                                      nd
                                      nd
                                      nd
                                      nd
Nickel
                                     0.387
                                     0.407
                                     0.408
                                     0.437
                                     0.443
Zinc
                                     0.170
                                     0.417
                                     0.438
                                     0.685
                                     0.694
nd = nondetect
Source: King County Department of Natural Resources (2013; Table 3-2) and 2014 Fact Sheet (for 90[th] percentile values only); based on 12 samples (9 with detectable concentrations of total mercury).
1. Metal concentrations are dissolved.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Exhibit A-10 summarizes the reasonable potential analysis under the baseline scenario. Based on effluent concentrations in Exhibit A-8 and available ambient data in Exhibit A-9, there is reasonable potential to exceed the baseline human health arsenic criterion.
Exhibit A-10. Human Health Reasonable Potential Analysis for King County West Point WWTP  -  Baseline Scenario[1]
Parameter
Effluent Conc. (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     0.27
                                     1.33
                                     1.33
                                     0.14
1. See effluent concentrations in Exhibit A-8 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-9.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 324.
3. Consumption of organisms only.

Exhibit A-11 summarizes the calculated permit limits for arsenic under the baseline scenario.
Exhibit A-11. Human Health Based Effluent Limitations for King County West Point WWTP  -  Baseline Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                     0.14
                                     0.28
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the baseline scenario, the discharger would have to meet an AM) of 0.14 ug/L and a MDL of 0.28 ug/L. Since the average effluent concentration is not listed in the fact sheet and the maximum effluent concentration is 2.28 ug/L, which is greater than the projected baseline permit limitations, the discharger will need to reduce arsenic in its effluent to ensure that permit limitations are consistently met.
Arsenic and arsenic-containing chemicals are not used in wastewater treatment.  However, the facility has a large industrial base and regulates 48 industrial users of which 27 are significant industrial users and 39 are categorical industrial users (i.e., users subject to EPA's national pretreatment standards), including 16 in the electroplating and metal finishing categories. West Point receives an estimated daily flow of 9.6 MGD from these industrial users. Thus, a source control program that targets or imposes more stringent limits on the most likely indirect industrial dischargers of arsenic to the plant could reduce arsenic concentrations to the necessary levels. Costs for such a program would depend on the number of arsenic sources and the measures that could be implemented at those sources to reduce arsenic. However, without more detailed information on these industrial users and King County's pretreatment program (e.g., flows and arsenic concentrations for each industrial user, local limits for arsenic, ordinances), it is not possible to estimate pretreatment or P2 costs to indirect dischargers.
Other potential sources of arsenic to the treatment plant are drinking water and groundwater infiltration. Details on the drinking water sources for the municipalities served by West Point, including whether these sources are surface water or groundwater and levels of arsenic in these sources, were not evaluated. The drinking water maximum contaminant level is 10 ug/L, which is higher than current wastewater effluent concentrations and human health criteria. EPA did not attempt to determine with any certainty whether drinking water is contributing to high arsenic levels in the wastewater effluent. However, if the facility determines that drinking water is the source of high arsenic values in the wastewater, it is likely that the facility would pursue a variance.
The fact sheet for the facility's 2014 permit indicates that King County created a Regional I&I Control Program in 1999 as part of the Regional Wastewater Services Plan (RWSP) to explore the feasibility of a regional I&I control program to reduce the amount of peak wet weather flow entering the County's wastewater conveyance. 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 began in 2000 and culminated with the County Executive's recommendation for a regional I&I control program.
The study included: defining levels of I&I for each local agency tributary to the regional system through an extensive flow monitoring and modeling program; constructing 10 pilot projects in 12 local agency jurisdictions to demonstrate the effectiveness of collection system rehabilitation projects and to test various technologies and gain cost information; developing model standards, procedures, policies, and guidelines for use by local agencies to reduce I&I in their systems; performing a cost-benefit analysis to determine the cost-effectiveness of I&I reduction; developing a long-term regional I&I control plan; working with the local sewer agencies to conduct an I&I reduction feasibility analysis; and performing several I&I reduction projects.
As the focus of these studies and analyses were on reduction of peak flows to minimize combined sewer overflows, it is uncertain whether this I&I reduction program and these modifications to the collection system would address arsenic levels (there are a number of modifications that can correct I&I issues that would not necessarily reduce arsenic concentrations). If groundwater infiltration is causing the high arsenic effluent levels, the facility may have to implement modifications to the existing I&I reduction program for compliance with the baseline scenario criteria.
Due to the fact that ambient receiving water concentrations exceed the baseline human health criteria, the discharger may pursue obtaining a water quality standards variance. The one-time cost associated with pursuing a variance is estimated to be $426,000, with minimal costs associated with renewal. If the arsenic effluent levels are the result of infiltration of arsenic-contaminated groundwater, total costs could be $11,650,000 for a comprehensive I&I reduction program that includes source identification and pipe rehabilitation for a system with 165 miles of sewer pipes (approximately $1,100,000 per year annualized at 7% over 20 years). Note that if groundwater infiltration is not the only source of arsenic to the treatment plant, an I&I reduction program alone may not be sufficient for compliance and the discharger would not likely undertake such a program for compliance with toxic criteria alone.
Policy Scenario
Exhibit A-12 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-8 and available ambient data in Exhibit A-9, there is reasonable potential to exceed the proposed human health criteria for arsenic.
Exhibit A-12. Human Health Reasonable Potential Analysis for King County West Point WWTP  -  Policy Scenario[1]
Parameter
Baseline Average Monthly Effluent Limit (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     0.14
                                     1.33
                                     1.33
                                    0.0059
1. See effluent concentrations in Exhibit A-8 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-9.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 324.
3. Consumption of organisms only.

Exhibit A-13 summarizes the calculated permit limits for arsenic under the policy scenario.
Exhibit A-13. Human Health Based Effluent Limitations for King County West Point WWTP  -  Policy Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                    0.0059
                                     0.012
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the policy scenario, the discharger would have to meet an AML of 0.0059 ug/L and a MDL of 0.012 ug/L. Under the baseline scenario, where the projected effluent limitations are below the analytical QL, EPA estimated that the discharger would incur costs for I&I control as well as pursuit of a variance in order to ensure compliance with effluent limitations below the QL. Since the projected effluent limitations under the policy scenario are also below the QL, no additional compliance strategy would be required under the policy scenario (i.e., the discharger would not pursue a second variance).
Pasco Wastewater Treatment Works
The Pasco Wastewater Treatment Works (NPDES permit WA0044962) provides wastewater treatment to 43,500 people in the City of Pasco and two permitted industrial users (Easterday Farms Produce Company and A1 Quality Services, a truck washing facility). The Wastewater Treatment Works discharges an annual average flow of 4.5 mgd to the Lake Wallula reach of the Columbia River.
Treatment Processes
The 2014 permit limits evaluation indicates that treatment processes include headworks with traveling screens, grit removal, primary clarifiers, a trickling filter, an intermediate clarifier, aeration basins, and secondary clarifiers followed by disinfection.
Effluent Data
Exhibit A-14 summarizes available effluent monitoring data for the Wastewater Treatment Works from 2012 through 2014.
Exhibit A-14. Summary of Effluent Data (2012-2014): Pasco Wastewater Treatment Works
Pollutant
Number of Observations
Effluent Concentration (ug/L)[1]

Median
Average
95[th] Percentile
Maximum
Arsenic
                                       3
                                      1.0
                                      1.5
                                     2.35
                                      2.5
Chloroform
                                       6

                                     1.65

                                     1.94
Copper
                                      15
                                     40.7
                                    42.013
                                     53.57
                                     54.9
Cyanide
                                      15
                                      10
                                      10
                                      10
                                      10
Mercury
                                      27

                                    0.0004

                                     0.012
Methylene chloride
                                       2

                                     0.72

                                     0.76
Phenol
                                       2

                                     0.77

                                     0.87
Selenium
                                       3
                                       3
                                      5.3
                                     9.21
                                      9.9
Zinc
                                       3
                                     42.1
                                    54.167
                                     74.68
                                     78.3
Source: Discharge monitoring reports for 2012 through 2014 (for arsenic, copper, cyanide, selenium, and zinc), a 2014 permit application (for chloroform and mercury), and a 2014 permit limit evaluation (for methylene chloride and phenol).
1. Metal concentrations are in total recoverable form.

Receiving Water
Exhibit A-15 summarizes the available ambient receiving water concentrations based on data from Ecology's Environmental Information Management System between 2004 and 2014.
Exhibit A-15. Ambient Receiving Water Concentrations: Columbia River
Pollutant
Water Column Concentration (ug/L)

90[th] Percentile
Average
Arsenic
                                     0.77
                                    0.6175
Copper
                                      1.1
                                     0.677
Mercury
                                     0.002
                                     0.002
Nickel
                                     0.71
                                    0.6183
Zinc
                                      6.2
                                     3.77
Source: Washington State Department of Ecology Environmental Information Management System, 2004 to 2014 data for station 36A070.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Exhibit A-16 summarizes the reasonable potential analysis under the baseline scenario. Based on effluent concentrations in Exhibit A-14 and available ambient data in Exhibit A-15, there is reasonable potential to exceed the baseline human health arsenic criterion.
Exhibit A-16. Human Health Reasonable Potential Analysis for Pasco Wastewater Treatment Works  -  Baseline Scenario[1]
Parameter
Effluent Conc. (ug/L)
Ambient Conc. (ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     2.35
                                    0.6175
                                    0.6178
                                     0.018
1. See effluent concentrations in Exhibit A-14 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the median) and available ambient concentrations in Exhibit A-15.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 8477 for carcinogens and 3077 for non-carcinogens.
3. Consumption of water and organisms.

Exhibit A-17 summarizes the calculated permit limits for arsenic under the baseline scenario.
Exhibit A-17. Human Health Based Effluent Limitations for Pasco Wastewater Treatment Works -  Baseline Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
0.018
0.036
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the baseline scenario, the discharger would have to meet an AML of 0.018 ug/L and a MDL of 0.036 ug/L. Since the average effluent concentration is 1.5 ug/L and the maximum effluent concentration is 2.5 ug/L, which are greater than the projected baseline permit limitations, the discharger will need to reduce arsenic in its effluent to ensure that permit limitations are consistently met.
Arsenic and arsenic-containing chemicals are not used in wastewater treatment and the facility has only two permitted industrial users, one of which is a produce company. If the produce is treated with arsenic-containing pesticides, then any wash water from the packaging operations could contribute to the high effluent arsenic levels. Thus, a source control program that targets the most likely indirect industrial dischargers of arsenic to the plant could reduce arsenic concentrations to the necessary levels. Costs for such a program would depend on the number of arsenic sources and the measures that could be implemented at those sources to reduce arsenic. Without specific information on the types of industrial dischargers that may need controls, it is not possible to estimate pretreatment or P2 costs to indirect dischargers.
Other potential sources of arsenic to the treatment plant include drinking water and groundwater infiltration. Details on the drinking water source(s) for the City of Pasco, including whether these sources are surface water or groundwater and levels of arsenic in these sources, were not evaluated. The drinking water maximum contaminant level is 10 ug/L, which is higher than current wastewater effluent concentrations and human health criteria. EPA did not attempt to determine with any certainty whether drinking water is contributing to high arsenic levels in the wastewater effluent. However, if the facility determines that drinking water is the source of high arsenic values in the wastewater, it is likely that the facility would pursue a variance.
The wastewater treatment plant exceeded 85% of the design maximum month in October, November and December 2008, likely due to infiltration. The City has been working on relining old sewer lines to prevent I&I. It is uncertain whether this I&I reduction program would address arsenic levels (there are a number of modifications that can correct I&I issues that would not necessarily reduce arsenic concentrations). If groundwater infiltration is causing the high arsenic effluent levels, the facility may have to implement modifications to the existing I&I reduction program for compliance with the baseline scenario criteria.
Due to the fact that ambient receiving water concentrations exceed the baseline human health criteria, the discharger may pursue obtaining a water quality standards variance. The one-time cost associated with pursuing a variance is estimated to be $180,000, with minimal costs associated with renewal. If the arsenic effluent levels are the result of infiltration of arsenic-contaminated groundwater, total costs could be $16,200,000 for a comprehensive I&I reduction program that includes source identification and pipe rehabilitation for a system with 307 miles of sewer pipes (approximately $1,530,000 per year annualized at 7% over 20 years). Note that if groundwater infiltration is not the only source of arsenic to the treatment plant, an I&I reduction program alone may not be sufficient for compliance and the discharger would not likely undertake such a program for compliance with toxic criteria alone.
Policy Scenario
Exhibit A-18 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-14 and available ambient data in Exhibit A-15, there is reasonable potential to exceed the proposed human health criteria for arsenic.
Exhibit A-18. Human Health Reasonable Potential Analysis for Pasco Wastewater Treatment Works  -  Policy Scenario[1]
Parameter
Baseline Average Monthly Effluent Limit (ug/L)
Ambient Conc. (ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion3 (ug/L)
Arsenic
                                     0.018
                                    0.6175
                                    0.6178
                                    0.0045
1. See effluent concentrations in Exhibit A-14 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the median) and available ambient concentrations in Exhibit A-15.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 8477 for carcinogens and 3077 for non-carcinogens.
3. Consumption of water and organisms.

Exhibit A-19 summarizes the calculated permit limits for arsenic under the policy scenario.
Exhibit A-19. Human Health Based Effluent Limitations for Pasco Wastewater Treatment Works  -  Policy Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                    0.0045
                                    0.0091
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the policy scenario, the discharger would have to meet an AML of 0.0045 ug/L and a MDL of 0.0091 ug/L. Under the baseline scenario, where the projected effluent limitations are below the analytical QL, EPA estimated that the discharger would incur costs for I&I control as well as pursuit of a variance in order to ensure compliance with effluent limitations below the QL. Since the projected effluent limitations under the policy scenario are also below the QL, no additional compliance strategy would be required under the policy scenario (i.e., the discharger would not pursue a second variance).
Puyallup WWTP
The City of Puyallup owns and operates a municipal WWTP (NPDES permit WA0037168) that provides primary and secondary treatment. The WWTP discharges an annual average flow of 4.07 mgd to the Puyallup River within the Puyallup Reservation. The EPA has authority to issue permits for the facility based on the Puyallup Tribe's WQS, pursuant to a memorandum of understanding among the EPA, the Puyallup Tribe, and Ecology.
Treatment Processes
The 2014 fact sheet for the permit states that the facility uses preliminary treatment consisting of fine screening for solids removal, and primary treatment includes clarification, sludge/grit centrifugal separation, and grit disposal. Secondary treatment consists of activated sludge, secondary clarification, and ultraviolet light disinfection.
Effluent Data
Exhibit A-20 summarizes available effluent monitoring data for the WWTP from 2012 through 2014.
Exhibit A-20. Summary of Effluent Data (2012-2014): Puyallup WWTP
Pollutant
Number of Observations
Effluent Concentration (ug/L)[1]

Median
Average
95[th] Percentile
Maximum
Copper
15
5.60
5.39
6.34
6.90
Mercury
15
0.00180
0.00183
0.00279
0.00300
Zinc
15
33.90
33.83
43.93
44.70
Source: Discharge monitoring reports for 2012 through 2014.
1. Metal concentrations are in total recoverable form.

Receiving Water
Exhibit A-21 summarizes the available ambient receiving water concentrations based on data from Ecology's Environmental Information Management System from 2009.
Exhibit A-21. Ambient Receiving Water Concentrations: Puyallup River
Pollutant
Water Column Concentration (ug/L)

90[th] Percentile
Average
Arsenic
0.90
0.62
Di(2-ethylhexyl) phthalate
0.07
0.07
Copper
11.60
3.36
Zinc
12.66
5.28
Source: Washington State Department of Ecology Environmental Information Management System, 2009 data for station PSTLA-RIV05.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Based on effluent concentrations in Exhibit A-20 and available ambient data in Exhibit A-21, there is no reasonable potential to exceed the proposed human health criteria for pollutants for which effluent data are available (copper, mercury, and zinc). Thus, there are no permit limits or costs associated with the baseline scenario.
Policy Scenario
Based on effluent concentrations in Exhibit A-20 and available ambient data in Exhibit A-21, there is no reasonable potential to exceed the proposed human health criteria for pollutants for which effluent data are available (copper, mercury, and zinc). Thus, there are no permit limits or costs associated with the policy scenario.
Redondo WWTP
The Lakehaven Utility District owns and operates the Redondo WWTP (NPDES permit WA0023451) which serves residential and commercial customers. The WWTP discharges an annual average flow of 2.8 mgd to Puget Sound  -  Poverty Bay.
Treatment Processes
The 2013 fact sheet for the permit (Washington Department of Ecology, 2013a) indicates that the facility employs primary and secondary treatment consisting of screening, grit removal and comminution, primary clarification, biological treatment using plastic media trickling filters, secondary clarification, and ultraviolet disinfection (p. 8).
Effluent Data
Exhibit A-22 summarizes available effluent monitoring data for the WWTP from 2009 through 2012.
Exhibit A-22. Summary of Effluent Data (2009-2012): Redondo WWTP
Pollutant
Number of Observations
Detected Value (ug/L)1

Total
Nondetect
QL (ug/L)
Maximum
Average
1,1,2,2-Tetrachloroethane
                                       3
                                       3
                                       1

1,1,2-Trichloroethane
                                       3
                                       3
                                       1

1,1-Dichloroethylene
                                       3
                                       3
                                       1

1,2,4-Trichlorobenzene
                                       3
                                       3
                                     0.29

1,2-Dichloropropane
                                       3
                                       3
                                       1

1,2-Diphenylhydrazine
                                       3
                                       3
                                     0.95

1,2-Trans-dichloroethylene
                                       3
                                       3
                                       1

1,3-Dichlorobenzene
                                       3
                                       3
                                       1

1,4-Dichlorobenzene
                                       3
                                       3
                                       1

2,4,6-Trichlorophenol
                                       3
                                       3
                                      1.9

2,4-Dichlorophenol
                                       3
                                       3
                                      0.4

2,4-Dinitrotoluene
                                       3
                                       3
                                     0.16

2-Chloronaphthalene
                                       3
                                       3
                                     0.24

2-Chlorophenol
                                       3
                                       3
                                       1

3,3'-Dichlorobenzidine
                                       3
                                       3
                                     0.48

4,4'-DDD
                                       3
                                       3
                                     0.024

4,4'-DDE
                                       3
                                       3
                                     0.024

4,4'-DDT
                                       3
                                       3
                                     0.024

Acenaphthene
                                       3
                                       3
                                     0.029

Acrolein
                                       3
                                       3
                                       5

Acrylonitrile
                                       3
                                       3
                                       5

Aldrin
                                       3
                                       3
                                     0.024

alpha-BHC
                                       3
                                       3
                                     0.024

alpha-endosulfan
                                       3
                                       3
                                     0.024

Anthracene
                                       3
                                       3
                                     0.29

Antimony
                                       3
                                       3
                                      0.3

Arsenic
                                       5

                                     2.39
                                     1.61
Benzene
                                       3
                                       3
                                       1

Benzidine
                                       3
                                       3
                                      11

Benzo(a) anthracene
                                       3
                                       3
                                     0.29

Benzo(a) pyrene
                                       3
                                       3
                                     0.48

beta-BHC
                                       3
                                       3
                                     0.024

beta-endosulfan
                                       3
                                       3
                                     0.024

Bis(2-chloroethyl) ether
                                       3
                                       3
                                     0.29

Bis(2-Ccloroisopropyl) ether
                                       3
                                       3
                                     0.29

Bis(2-ethylhexyl) phthalate
                                       3

                                     3.69
                                     2.88
Bromoform
                                       3
                                       3
                                       1

Butylbenzyl Phthalate
                                       3
                                       2
                                     0.29
                                     0.76
                                     0.39
Carbon Tetrachloride
                                       3
                                       3
                                       1

Chlorobenzene
                                       3
                                       3
                                       1

Chlorodibromomethane
                                       3
                                       3
                                       1

Chloroform
                                       3
                                       3
                                       1

Chrysene
                                       3
                                       3
                                     0.29

Copper
                                       5

                                     68.7
                                     42.1
Cyanide
                                       3
                                       3
                                       5

Dichlorobromomethane
                                       3
                                       3
                                       1

Dieldrin
                                       3
                                       3
                                     0.024

Diethyl Phthalate
                                       3
                                       3
                                     0.48

Dimethyl Phthalate
                                       3
                                       3
                                     0.19

Di-n-Butyl Phthalate
                                       3
                                       3
                                     0.48

Endosulfan Sulfate
                                       3
                                       3
                                     0.024

Endrin
                                       3
                                       3
                                     0.024

Endrin Aldehyde
                                       3
                                       3
                                     0.024

Ethylbenzene
                                       3
                                       3
                                       1

Fluoranthene
                                       3
                                       3
                                     0.29

Fluorene
                                       3
                                       3
                                     0.29

Heptachlor
                                       3
                                       3
                                     0.024

Heptachlor epoxide
                                       3
                                       3
                                     0.024

Hexachlorobenzene
                                       3
                                       3
                                     0.29

Hexachlorobutadiene
                                       3
                                       3
                                     0.48

Hexachlorocyclopentadiene
                                       3
                                       3
                                     0.48

Hexachloroethane
                                       3
                                       3
                                     0.48

Indeno(1,2,3-cd) pyrene
                                       3
                                       3
                                     0.48

Isophorone
                                       3
                                       3
                                     0.48

Mercury
                                       5

                                    0.0851
                                    0.0341
Methyl Bromide
                                       3
                                       3
                                       5

Nickel
                                       5

                                     2.05
                                     1.60
Nitrobenzene
                                       3
                                       3
                                     0.48

N-Nitrosodi-n-propylamine
                                       3
                                       3
                                     0.48

N-Nitrosodiphenylamine
                                       3
                                       3
                                     0.48

Pentachlorophenol (PCP)
                                       3
                                       3
                                     0.48

Phenol
                                       3
                                       3
                                      1.9

Pyrene
                                       3
                                       3
                                     0.29

Selenium
                                       5

                                     0.51
                                     0.50
Tetrachloroethylene
                                       3
                                       3
                                       1

Toluene
                                       3
                                       3
                                     0.38

Thallium
                                       3
                                       3
                                     0.04

Toxaphene
                                       3
                                       3
                                       1

Trichloroethylene
                                       3
                                       3
                                       1

Vinyl chloride
                                       3
                                       3
                                       1

Zinc
                                       3

                                     57.4
                                     51.0
Source: 2013 Fact Sheet, Appendix D.
QL = quantitation level
1. Metal concentrations are in total recoverable form.

Receiving Water
Exhibit A-23 summarizes the available ambient receiving water concentrations in Puget Sound based on data from Ecology's Environmental Information Management System from 2011 to 2013.
Exhibit A-23. Ambient Receiving Water Concentrations (2011 to 2013): Puget Sound
Pollutant
Water Column Concentration (ug/L)1

90th Percentile
Average
Antimony
                                     0.172
                                   0.158625
Arsenic
                                     1.45
                                    1.36625
Copper
                                    0.3545
                                     0.299
Cyanide
                                      nd
                                      nd
Mercury
                                      nd
                                      nd
Nickel
                                    0.4275
                                   0.411125
Zinc
                                     0.662
                                   0.604167
nd=nondetect
Source: Environmental Information Management System data (NPDES receiving water characterization study).
1. Metal concentrations are dissolved form.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Exhibit A-24 summarizes the reasonable potential analysis under the baseline scenario. Based on effluent concentrations in Exhibit A-22 and available ambient data in Exhibit A-23, there is reasonable potential to exceed the baseline human health criterion for arsenic.
Exhibit A-24. Human Health Reasonable Potential Analysis for Redondo WWTP  -  Baseline Scenario[1]
Parameter
Effluent Conc. (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     2.39
                                    1.3663
                                     1.371
                                     0.14
1. See effluent concentrations in Exhibit A-22 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-23.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 182.
3. Consumption of organisms only.

Exhibit A-25 summarizes the calculated permit limits for arsenic under the baseline scenario.
Exhibit A-25. Human Health Based Effluent Limitations for Redondo WWTP  -  Baseline Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit (total; ug/L)[1]
Arsenic
                                     0.14
                                     0.28
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the baseline scenario, the discharger would have to meet an AML of 0.14 ug/L and a MDL of 0.28 ug/L. Since the average effluent concentration is 1.61 ug/L and the maximum effluent concentration is 2.39 ug/L, which are greater than the projected baseline permit limitations, the discharger will need to reduce arsenic in its effluent to ensure that permit limitations are consistently met.
Arsenic and arsenic-containing chemicals are not used in wastewater treatment and the facility does not have any significant or categorical industrial users. However, drinking water and groundwater infiltration are two potential sources of arsenic to the treatment plant.
Details on the drinking water sources for the communities served by the Redondo WWTP, including whether these sources are surface water or groundwater and levels of arsenic in these sources, were not evaluated. The drinking water maximum contaminant level is 10 ug/L, which is higher than current wastewater effluent concentrations and human health criteria. EPA did not attempt to determine with any certainty whether drinking water is contributing to high arsenic levels in the wastewater effluent. However, if the facility determines that drinking water is the source of high arsenic values in the wastewater, it is likely that the facility would pursue a variance.
The fact sheet for the facility's 2013 permit indicates that the District completed a comprehensive wastewater system plan in 1999. A collection system analysis found that I&I is a significant problem at this plant, and it recommended various I&I and flow reduction programs. The District incorporated an I&I rehab program focusing on the Redondo basin areas. It is uncertain whether this I&I reduction program and these modifications to the collection system would address arsenic levels (there are a number of modifications that can correct I&I issues that would not necessarily reduce arsenic concentrations). If groundwater infiltration is causing the high arsenic effluent levels, the facility may have to modify or expand the existing I&I reduction program for compliance with the baseline scenario criteria.
Due to the fact that ambient receiving water concentrations exceed the baseline human health criteria, the discharger may pursue obtaining a water quality standards variance. The one-time cost associated with pursuing a variance is estimated to be $180,000, with minimal costs associated with renewal. If the arsenic effluent levels are the result of infiltration of arsenic-contaminated groundwater, total costs could be $6,020,000 for a comprehensive I&I reduction program that includes source identification and pipe rehabilitation for a system with 114 miles of sewer pipes (approximately $568,000 per year annualized at 7% over 20 years). Note that if groundwater infiltration is not the only source of arsenic to the treatment plant, an I&I reduction program alone may not be sufficient for compliance and the discharger would not likely undertake such a program for compliance with toxic criteria alone.
Policy Scenario
Exhibit A-26 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-22 and available ambient data in Exhibit A-23, there is reasonable potential to exceed the proposed human health criterion for arsenic.
Exhibit A-26. Human Health Reasonable Potential Analysis for Redondo WWTP  -  Policy Scenario[1]
Parameter
Baseline Average Monthly Effluent Limit (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     0.14
                                    1.3663
                                     1.371
                                    0.0059
1. See effluent concentrations in Exhibit A-22 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-23.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 182.
3. Consumption of organisms only.

Exhibit A-27 summarizes the calculated permit limits for arsenic under the policy scenario.
Exhibit A-27. Human Health Based Effluent Limitations for Redondo WWTP  -  Policy Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit (total; ug/L)[1]
Arsenic
                                    0.0059
                                     0.012
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the policy scenario, the discharger would have to meet an AML of 0.0059 ug/L and a MDL of 0.012 ug/L. Under the baseline scenario, where the projected effluent limitations are below the analytical QL, EPA estimated that the discharger would incur costs for I&I control as well as pursuit of a variance in order to ensure compliance with effluent limitations below the QL. Since the projected effluent limitations under the policy scenario are also below the QL, no additional compliance strategy would be required under the policy scenario (i.e., the discharger would not pursue a second variance).
Salmon Creek WWTP
The Salmon Creek WWTP (NPDES permit WA0022772), operated by the Southwest Suburban Sewer District (District), serves households and some commercial customers in King County. The facility does not serve any industrial customers. It has an average wet weather flow of 3.6 mgd.
Treatment Processes
According to a 2009 inspection report, treatment at the facility includes screening, grit removal, primary clarification, biological treatment, secondary clarification, and chlorine disinfection.
Effluent Data
Exhibit A-28 summarizes available effluent monitoring data for the WWTP from 2010 through 2012.
Exhibit A-28. Summary of Effluent Data (2010-2012): Salmon Creek WWTP
Pollutant
Number of Observations
Effluent Concentration (ug/L)1

Maximum
Average
Antimony
                                       3
                                     0.55
                                     0.45
Arsenic
                                       3
                                     2.37
                                     1.76
Bis(2-ethylhexyl) phthalate
                                       3
                                      1.5

Copper
                                       3
                                     11.6
                                     8.62
Nickel
                                       3
                                      2.3
                                     1.87
Selenium
                                       3
                                      1.4
                                     1.14
Thallium
                                       3
                                     0.017
                                     0.017
Toluene
                                       3
                                      1.1
                                      1.1
Zinc
                                       3
                                     44.2
                                     37.7
Mercury
                                       3
                                    0.0074
                                    0.0064
Source: 2012 priority pollutant monitoring report; bis(2-ethylhexyl) phthalate data are from 2013 fact sheet  addendum.
1. Metal concentrations are in total recoverable form.

Receiving Water
The facility discharges to Puget Sound, which is designated as a Class AA receiving water in the vicinity of the outfall. Exhibit A-29 summarizes the available ambient receiving water concentrations in Puget Sound based on data from Ecology's Environmental Information Management System from 2011 to 2013.
Exhibit A-29. Ambient Receiving Water Concentrations (2011 to 2013): Puget Sound
Pollutant
Water Column Concentration (ug/L)[1]

90th Percentile
Average
Antimony
                                     0.172
                                   0.158625
Arsenic
                                     1.45
                                    1.36625
Copper
                                    0.3545
                                     0.299
Cyanide
                                      nd
                                      nd
Mercury
                                      nd
                                      nd
Nickel
                                    0.4275
                                   0.411125
Zinc
                                     0.662
                                   0.604167
nd=nondetect
Source: Environmental Information Management System data (NPDES receiving water characterization study).
1. Metal concentrations are dissolved form.

Baseline Scenario
The permit does not include any WQBELs based on the existing human health criteria for the pollutants of concern. In this case, EPA performed a reasonable potential analysis for each pollutant based on the baseline (i.e., existing) human health criteria to confirm whether a WQBEL would have been included in the NPDES permit. In cases of reasonable potential, EPA calculated a WQBEL using the existing human health criteria and evaluated compliance with this baseline WQBEL.
Exhibit A-30 summarizes the reasonable potential analysis under the baseline scenario. Based on effluent concentrations in Exhibit A-28 and available ambient data in Exhibit A-29, there is reasonable potential to exceed the baseline human health arsenic criterion.
Exhibit A-30. Human Health Reasonable Potential Analysis for Salmon Creek WWTP  -  Baseline Scenario[1]
Parameter
Effluent Conc. (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
2.37
1.3663
1.368
0.14
1. See effluent concentrations in Exhibit A-28 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-29.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 1025.
3. Consumption of organisms only.

Exhibit A-31 summarizes the calculated permit limits for arsenic under the baseline scenario.
Exhibit A-31. Human Health Based Effluent Limitations for Salmon Creek WWTP  -  Baseline Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
0.14
0.28
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the baseline scenario, the discharger would have to meet an AML of 0.14 ug/L and a MDL of 0.28 ug/L. Since the average effluent concentration is 1.76 ug/L and the maximum effluent concentration is 2.37 ug/L, which are greater than the projected baseline permit limitations, the discharger will need to reduce arsenic in its effluent to ensure that permit limitations are consistently met.
Arsenic and arsenic-containing chemicals are not used in wastewater treatment and the facility does not have any significant or categorical industrial users. However, drinking water and groundwater infiltration are two potential sources of arsenic to the treatment plant.
Details on the drinking water sources for the communities served by the Salmon Creek WWTP, including whether these sources are surface water or groundwater and levels of arsenic in these sources, were not evaluated. The drinking water maximum contaminant level is 10 ug/L, which is higher than current wastewater effluent concentrations and human health criteria. EPA did not attempt to determine with any certainty whether drinking water is contributing to high arsenic levels in the wastewater effluent. However, if the facility determines that drinking water is the source of high arsenic values in the wastewater, it is likely that the facility would pursue a variance.
The fact sheet for the facility's 2003 permit indicates that the District had performed an evaluation of I&I attributed to direct storm runoff and that I&I flow for the Salmon Creek basin was 48%. The District obtained funds for a major rehabilitation program for the Salmon Creek basin and identified a list of collection system rehabilitation projects in its Comprehensive Sewer Plan to address I&I. It is uncertain whether this I&I reduction program and these modifications to the collection system would address arsenic levels (there are a number of modifications that can correct I&I issues that would not necessarily reduce arsenic concentrations). If groundwater infiltration is causing the high arsenic effluent levels, the facility may have to modify or expand its existing I&I reduction program for compliance with the baseline scenario limitations.
Due to the fact that ambient receiving water concentrations exceed the baseline human health criteria, the discharger may also pursue obtaining a water quality standards variance. The one-time cost associated with pursuing a variance is estimated to be $180,000, with minimal costs associated with renewal. If the arsenic effluent levels are the result of infiltration of arsenic-contaminated groundwater, total costs could be $6,810,000 for a comprehensive I&I reduction program that includes source identification and pipe rehabilitation for a system with 129 miles of sewer pipes (approximately $643,000 per year annualized at 7% over 20 years). Note that if groundwater infiltration is not the only source of arsenic to the treatment plant, an I&I reduction program alone may not be sufficient for compliance and the discharger would not likely undertake such a program for compliance with toxic criteria alone.
Policy Scenario
Exhibit A-32 summarizes the reasonable potential analysis under the policy scenario. Based on effluent concentrations in Exhibit A-30 and available ambient data in Exhibit A-31, there is reasonable potential to exceed the proposed human health arsenic criterion.
Exhibit A-32. Human Health Reasonable Potential Analysis for Salmon Creek WWTP  -  Policy Scenario[1]
Parameter
Baseline Average Monthly Effluent Limit (total; ug/L)
Ambient Conc. (dissolved; ug/L)
Conc. at Edge of Mixing Zone[2] (ug/L)
Human Health Criterion[3] (ug/L)
Arsenic
                                     0.14
                                    1.3663
                                     1.368
                                    0.0059
1. See effluent concentrations in Exhibit A-28 (reasonable potential analysis uses the maximum or 95[th] percentile concentration if the number of observations is less than 10, and otherwise uses the geometric mean) and available ambient concentrations in Exhibit A-29.
2. Based on Washington Department of Ecology's Permit writer spreadsheet tool using a dilution factor of 1025.
3. Consumption of organisms only.

Exhibit A-33 summarizes the calculated permit limits for arsenic under the policy scenario.
Exhibit A-33. Human Health Based Effluent Limitations for Salmon Creek WWTP  -  Policy Scenario
Parameter
Average Monthly Effluent Limit (total; ug/L)[1]
Maximum Daily Effluent Limit
(total; ug/L)[1]
Arsenic
                                    0.0059
                                     0.012
1. Based on Washington Department of Ecology's Permit writer spreadsheet tool.

Under the policy scenario, the discharger would have to meet an AML of 0.0059 ug/L and a MDL of 0.012 ug/L. Under the baseline scenario, where the projected effluent limitations are below the analytical QL, EPA estimated that the discharger would incur costs for I&I control as well as pursuit of a variance in order to ensure compliance with effluent limitations below the QL. Since the projected effluent limitations under the policy scenario are also below the QL, no additional compliance strategy would be required under the policy scenario (i.e., the discharger would not pursue a second variance).
BP Cherry Point Refinery
The BP Cherry Point Refinery (NPDES permit number WA0022900) encompasses 740 acres in a rural area of Whatcom County. The facility's wastewater treatment plant treats process water, ballast water from tankers, tank water draws, and stormwater that falls in process areas of the site. The permit also authorizes treatment of wastewater from the Praxair, Inc. Ferndale facility and a proposed cogeneration facility. The facility discharges treated effluent into the Strait of Georgia. The facility's average flow is 3.87 million gallons per day (mgd).
Treatment Processes
The 2012 NPDES permit for the facility lists current treatment processes as four parallel oil/water separators, two induced gas floatation units, an equalization tank, a complete mix activated sludge unit, a secondary clarifier, and two clarification ponds.
Effluent Data
Exhibit A-34 summarizes the last three years of effluent data for the treated wastewater for the pollutants of concern for which data are available.
Exhibit A-34. Summary of Effluent Data (2012-2014): BP Cherry Point Refinery, Outfall
Parameter
Number of Observations
Summary of Detected Values (ug/L)

Total
Nondetect
QL (ug/L)
Maximum
Geometric Mean
Minimum
1,1,2,2-Tetrachloroethane
                                       1
                                       1
                                      0.4

1,1,2-Trichloroethane
                                       1
                                       1
                                      0.4

1,1-Dichloroethylene
                                       1
                                       1
                                      0.4

1,2,4-Trichlorobenzene
                                       1
                                       1
                                      0.4

1,2-Dichlorobenzene
                                       1
                                       1
                                      0.4