Follow- up to the March 9, 2015 letter from EPA: Additional Comments on the Study Plan and 

Quality Assurance Project Plan for Octamethylcyclotetrasiloxane (D4) - February 2, 2015

Detailed Comments

Comments are divided into the following sections and presented in outline format for ease of 

review:

1. Duration Between Sampling Events

2. Normal Plant Operations

3. Representative D4 Release Rate

4. Fish Sampling – Technical Issues

5. Site-Specific Sampling Plans – Direct Discharge Sites

6. Site-Specific Sampling Plans - Non-Industrial and Indirect Discharge Sites

7. Pre-Mobilization Information Collection Logs

8. QAPP Project Staff Reporting Requirements and Additional QC Related Issues

9. Method Validation Study – Vial Headspace

10. QAPP Appendix C-2 – Technical Issues

11. Mixing Zone Modeling

12. Overview of EPA’s QAPP Review and Approval Process

1 Duration Between Sampling Events (Study Plan Section 3.2, Study Plan Sections 7.3 

through 21.3 and QAPP Section 2.6.2.2.). There is no site-specific information on the 

sampling schedule included in the Study Plan or QAPP.

ECA Requirement: The ECA (Appendices 1-3) specifies that samples shall be taken during 

two testing events at least three months apart and that the exact duration between sampling 

events for each site shall be determined in a detailed Sampling Plan included in the Study 

Plan and QAPP.

The Study Plan provides optimal time frames for monitoring based on low river flow (low 

dilution) and safety concerns. The provided optimal time periods consist of a two month 

period (June and July) and a four month period (August through November). Monitoring 

within these ranges allows for possible durations less than three months as required by the 

ECA. For example, sampling in July and again in August would result in two testing events 

only one month apart.

1.1 Please revise the Study Plan and QAPP to include an overall sampling schedule which lists 

the proposed dates for each sampling event for each site and sampling location. All task 

dependencies should be identified and captured in the schedule (e.g., sampling team 1 

requires X-days pre-/post-mobilization and cannot sample two sites simultaneously, and 

other dependencies such as sampling equipment, sampling platforms, holiday schedules, 

and laboratory capacity). 

1.2 EPA recommends that the Study Plan and QAPP be revised to include a discussion of 

contingency plans in place (e.g., alternative sampling schedules that could be implemented 

if initial sampling conditions are not met). EPA suggests that contingency planning include 

developing alternative sampling schedules based on the assumption that plant operations, 

weather, or river conditions will preclude sampling as initially planned. EPA also suggests 

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the inclusion of measures to be taken to minimize the potential for not achieving the 

required duration between sampling events (e.g., additional sampling teams, alternative 

laboratories), as well as the measures that will be taken if the sampling window will not be 

met.

2 Normal Plant Operations (Study Plan Section 3.2, Study Plan Sections 7.2.3 through 

21.2.3, QAPP Section 2.6.2.2 and QAPP Section 3.9). There is no site-specific 

documentation regarding the criteria or means that are used by the facilities to determine 

normal operating conditions in the Sampling Plans.

ECA Requirement: The ECA (Appendices 1-3) specifies that samples shall be collected 

during normal plant operations and during such times that effluent flow rates from the 

wastewater treatment system are representative of normal plant operations. The ECA 

(Appendices 4-8) also specifies that normal operating conditions will be established by 

consulting with the operator of each WWTP, indirect and direct discharge facility. Further, 

the ECA specifies that the criteria or means that are used by the facilities to determine 

normal operating conditions will be documented in the site-specific Sampling Plans and that 

confirmation will be obtained that the subject facility is operating under normal conditions 

prior to commencing sampling at a given location.

2.1 EPA recommends that the normal plant operations discussion be revised to include the 

following list of plant operations that are not normal:

• Exceeding WWTP design capacity (i.e., hydraulic, organic, and solids loading 

capacities, as applicable);

• Upsets, as defined by their discharge permits;

• Bypasses, as defined by their discharge permits;

• Utilizing emergency systems, as defined by their discharge permits;

• Noncompliance with any permit requirements or conditions; and

• Exceedance of any permit limits.

Each of these conditions should be defined for each plant, including discussion of how 

the conditions will be determined and how they will be documented during premobilization. For example, WWTP operators will provide plant design capacities, while 

discharge requirements, conditions, and limitations can be identified from the NPDES 

permit. These conditions and their pre-determined status or threshold should be captured 

on site-specific data collection forms. These forms would be pre-populated with each 

plant’s design capacities and permit limits; yes/no checkboxes would be provided to 

record upset, bypass, and emergency conditions, as well as compliance with other permit 

conditions. ERM would complete the site-specific forms during the pre-mobilization call, 

including recording actual plant loadings and effluent quality on the form at the time of 

the call. In the case of conditions that require extended periods of time to assess (e.g., 5-

day BOD testing), and in consideration of the hydraulic holding time of the treatment 

system and weather-induced variation, ERM should record conditions for several days 

prior to and including the day of the sampling event. 

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2.2 EPA recommends the following process for collecting and analyzing plant operations data:

1 Section 3.2 of the Study Plan (revised to incorporate EPA review recommendations) 

lists conditions under which D4 process operations and WWTPs may not be operating 

under normal operating conditions. This listing will provide a starting point for 

developing site-specific operation conditions and for defining normal operations. 

Each plant would start by developing a matrix listing all the parameters listed in 

Section 3.2.

2 Each site would then determine whether or not each of the listed parameters is 

applicable/relevant to their site; they can also add new, site-specific conditions to the 

list as appropriate.

3 For each applicable parameter, the site would then determine whether the parameter 

can be assessed quantitatively or only qualitatively. For parameters that can be 

assessed quantitatively, the site would determine whether normal operations for that 

parameter are best represented by a threshold (e.g., permit limits, design capacity) or 

a range of normal operation (e.g., MLSS or SRT). Finally, for parameters with a 

range of normal operation, the site would perform a statistical analysis of historic 

monitoring data, calculating, for example, mean and standard deviation. For 

parameters lacking normal distribution, the site can propose an alternative statistical 

representation of the data.

4 Each site would then develop site-specific data collection forms. These forms would 

include the site-specific listing of applicable parameters. For parameters measured 

qualitatively, the form would include yes/no checkboxes for ERM to report the 

plant’s pre-mobilization operating condition as either normal or not normal, as 

determined by the plant operator. For parameters that can be measured quantitatively, 

the form would display the pre-determined summary statistics and also provide space 

for ERM to collect and record the plant’s current operating conditions.

5 The bottom of the data collection form would include space to provide a narrative 

discussion of any qualitative parameters recorded as “not normal,” and any 

quantitative parameters measured beyond their threshold or more outside of a predetermined statistical range. The narrative discussions should describe the operating 

condition of concern, provide the rationale for determining whether or not operation 

is normal, and describe the anticipated impact on effluent quality. The rationale for 

determining normal versus not normal operation will be developed in consultation 

with the WWTP operator (as required by the ECA), and in compliance with 

conditions identified as NOT considered normal operations discussed above. If the 

cause of the operating condition of concern is unknown, or the impact unclear, 

monitoring should be postponed.

2.3 Additionally, the discussion of normal plant operations should extend beyond WWTP 

operations, focusing on activated sludge treatment. Revise this section to also address 

operating conditions at direct discharge sites, including D4 process operations and the 

types of wastewater treatment systems operated by these plants (i.e., chemical/physical 

treatment). This includes, for direct discharge sites, defining plant operations that are not 

normal, and listing items that indicate that plants may not be operating under normal 

operating conditions.

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3 Representative D4 Release Rate (Study Plan Sections 7.3 through 21.3). There is no sitespecific discussion on how the typical rate of release of D4 will be determined.

ECA Requirement: The ECA (Appendices 1-3) specifies that samples shall be collected at 

a time when the rate of D4 release is expected to be representative of the typical rate of 

release of D4 for that site. To meet this requirement, EPA recommends the selection criteria 

that follow.

3.1 Please revise the Study Plan (Sections 7.3 through 10.3) to demonstrate that the proposed 

sample collection schedule for direct discharge sites will meet the following criteria: 

1 Confirmation that the processes that generate D4 process wastewater are currently 

operating and generating wastewater that is being fed to the WWTP; and

2 Confirmation that these processes have been operating and generating wastewater as 

typical during the period of time prior to pre-mobilization equal to or greater than the 

hydraulic residence time of the WWTP.

3.2 Please revise the Study Plan (Sections 11.3 through 20.3) to demonstrate that the proposed 

sample collection schedule for the non-industrial and indirect discharge wastewater 

treatment sites will meet the following criteria:

1 The potential sources of D4 (residential use and/or industrial use), and

2 The days and times these wastewater sources are expected to be received at the 

POTW (e.g., diurnal cycle and days/hours of industrial operations). For example, if 

D4 is expected in consumer personal care products (such as deodorants and 

shampoos), D4 release rates from consumers might be expected in the morning when 

most people shower (and accounting for hydraulic residence time of the collection 

system).

4 Fish Sampling- Technical Issues

4.1 The QAPP and Study Plan state that the techniques and recommendations for fish 

collection described in the ECA (i.e., USEPA 2003a (Section 7.0 Procedures, pp. 3-5) and 

Powell and Woodburn (2009, Sample Collection, p. 8)) were generally followed. However, 

several other fish collection techniques (gillnets, trap/hoop/Fyke nets, and angling) that 

were not described in the ECA are also described for possible use based on site-specific 

conditions. These other commonly used fish collection procedures were based on EPA 

guidance (Fish Field Sampling, Operating Procedure SESDPROC-512-R3, EPA Region 4, 

April 2011).

ECA Requirement: The ECA (Appendix 8) states:

The exact method for collection of fish is a site-specific determination. During 

preparation of the site-specific Sampling Plans, the physical nature (e.g., width, depth, 

flow) of the receiving water will be determined and used to guide the selection of the 

appropriate method of sample collection. For each site, collection procedures will be 

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based, as appropriate to the characterization of the receiving water, on USEPA 2003a 

(Section 7.0 Procedures, pp. 3-5) and Powell and Woodburn (2009, Sample Collection, 

p. 8). This guidance identifies two main types of fish collection methods for relatively 

shallow and slow moving water and gives direction on choice of method, general 

practices, and other considerations for the field work. For each site, the exact collection 

method for fish samples will be detailed in the site-specific Sampling Plans and QAPP.

EPA recommends that the SOP be revised to include a description of the parameters and 

conditions under which each type of fish collection method would be preferred at each 

site. In addition, it is recommended that documentation be provided by the field crew 

describing the fish collection method used and the supporting rationale. This clarification 

should be made throughout the QAPP and Study Plan.

4.2 Sample Collection Procedures – Fish. The approach in the Study Plan and QAPP is 

inconsistent with the ECA requirements to focus first on collecting different trophic levels 

before collecting based on abundance (e.g., the study plans state throughout that the two 

most abundant species collected will be selected for analysis, and if practicable, they will 

represent two different trophic guilds). This needs to be modified throughout the QAPP 

and Study Plan.

ECA requirement: The ECA (Appendix 8) states:

On the day of field sampling at a given site, fish shall be collected and sorted by 

species. The taxonomic identification of each fish species shall be noted. Two species 

of fish from different trophic guilds, if practicable, collected in sufficient mass such 

that individual or composite samples can be prepared for the analysis of D4, shall be 

selected. If adequate quantities of fish from different trophic guilds are not available 

the two most abundant species will be selected. Information about the life history of 

the two species selected shall be included in study reports. The individual fish will be 

measured for length and weight.

The QAPP must also address the QA/QC of the taxonomic determinations of the fish made 

in the field. The QAPP should prescribe procedures for the review to ensure the collected 

fish are accurately identified and classified. This review step should preferably be 

performed in the field such that fish collection can be reattempted immediately if needed. 

If this review step is not performed until the laboratory, reattempt of fish collection may be 

difficult.

4.3 Sample Collection Procedures – Benthic Organisms (QAPP Section 3.2.1.5). The 

QAPP states, “in the event that 100 grams of benthic organisms cannot be obtained, the 

absolute minimum mass of benthic organisms required is 25 grams.

ECA Requirement: The ECA (Appendix 8, Figure 5) specifies that a total mass off 100 

grams of benthic organisms should be collected.

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EPA emphasizes, as discussed previously, that if grab does not yield sufficient sample 

mass, then the effort should be repeated in an adjacent location. Please revise the Study 

Plan and QAPP as appropriate.

5 Site-Specific Sampling Plans - Direct Discharge Sites

Comments 5.1.1 and 5.1.2 within this section are ECA requirements that must be addressed. 

The remaining comments within this section (Comments 5.1.3 through 5.1.6) are considered 

technical deficiencies that should be addressed, unless previously identified as an ECA 

requirement (e.g. comments pertaining to “normal plant operations” must be addressed).

5.1.1 Study Plan Sections 7.2.3 through 10.2.3. Please revise to describe how each of the 

criteria and conditions listed in Study Plan Section 3.2 will be evaluated specific to each 

site. Additionally, please develop site-specific call log forms for insertion into Study Plan 

Sections 7.2.3 throughn10.2.3, listing each of these criteria and conditions and their predetermined range or threshold for acceptable sampling (i.e., normal plant operations, 

duration between sampling events, typical and unusual weather conditions, period since 

unusual weather, and representativeness of typical rates of release of D4).

5.1.2 Study Plan Sections 7.3 through 10.3. Please revise to incorporate how an assessment 

of normal operating conditions will be considered in determining sampling timing and 

schedule.

5.1.3 Study Plan Sections 7.5 through 10.5 and Figures 7-1 through 10-1. Please revise 

“Sampling Locations Description” sections and “Site Location: figures to include greater 

detail.

5.1.4 Study Plan Figures 7-2 through 10-2. Please revise “Wastewater Treatment Plant 

Process Flow Diagram” figures to clearly indicate sampling and flow measurement 

locations. 

5.1.5 Study Plan Section 9.2.2 and Figure 9-2. The “Wastewater Treatment Plant Process 

Flow Diagram” figure appears to show primary clarifiers following neutralization and 

before equalization; however, this treatment step is not included in the “WWTP Process 

Description” section. Please correct this oversight.

5.1.6 Study Plan Section 10.2.2 and Figure 10-2. The “Wastewater Treatment Plant Process 

Flow Diagram” figure remains largely illegible, but appears to show primary clarification 

between the oil/water separator and the air stripper; however, this treatment step is not 

included in the “WWTP Process Description” section. Additionally, the chemical 

precipitation and flocculation-sedimentation treatment steps included in the “WWTP 

Process Description” section do not appear to be included in the indicated “Wastewater 

Treatment Plant Process Flow Diagram” figure. Please correct this oversight.

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6 Site-Specific Sampling Plans - Non-Industrial and Indirect Discharge Sites

6.1.1 Study Plan Sections 11.5 through 21.5, Figures 11-1 through 21-1 and Figures 11-2 

through 21-2. The “Sampling Locations Description” sections and “Site Location” 

figures lack sufficient detail. Please revise text and figures as appropriate. Additionally, 

please revise the “Process Flow Diagram” figure for each site to clearly indicate sampling 

and flow measurement locations.

6.1.2 Study Plan Sections 11.3 through 21.3. Please revise the “Sampling Timing and 

Schedule” section to incorporate how assessment of “Normal Operating Conditions” will 

be considered in determining sampling timing and schedule.

6.1.3 Study Plan Sections 11.2.3 through 21.2.3. Several of the selected WWTPs are served 

by combined sewage systems with permitted combined sewer overflows (CSOs). For 

these WWTPs, please revise “Normal Operating Conditions” sections to describe the 

combined sewage systems, the CSOs, and the historical frequency, extent, and conditions 

of CSO discharges (e.g., intensity and duration of precipitation events). Describe the fate 

and transport of discharges from known and likely D4 industrial users under CSO 

discharge conditions. Describe the criteria that will be used to determine whether and 

under what conditions periods of CSO discharges will be considered normal operating 

conditions. Furthermore, for indirect discharge WWTPs (Study Plan Sections 17.2.3 

through 21.2.3), describe the criteria that will be used to determine that the WWTP 

influent shall reasonably be expected to contain D4. Describe how these conditions and 

determinations will be documented during pre-mobilization. If sampling is conducted

conditions of CSO discharges, describe how these conditions (extent and nature) will be 

documented in the field notes and final report.

6.1.4 Study Plan Sections 11.2.3 through 21.2.3. Certain of the selected WWTPs have 

treatment system bypasses used during emergency conditions. Please revise the “Normal 

Operating Conditions” section to indicate that use of these bypasses is not considered 

normal operating conditions. Additionally, please describe how these conditions will be 

documented during pre-mobilization.

6.1.5 Study Plan Tables 12-2, 15-2, 16-2, and 18-2. Please confirm whether historical 

monitoring data provided is for BOD5 or CBOD5 and revise tables as appropriate.

6.1.6 Study Plan Section 11.2.2. Please revise the “WWTP Process Description” section to 

describe the Emergency/Polishing Pond and its historical frequency, extent, and 

conditions of use. Describe the criteria that will be used to determine whether and under 

what conditions use of the pond will be considered normal operating conditions. If 

sampling is conducted during use of the pond, describe how these conditions (extent and 

nature) will be documented in the field notes and final report, and how flows to and/or 

from the pond will be accounted for when reporting the influent and effluent flow rates.

6.1.7 Study Plan Figure 11-2. Please provide a replacement “Process Flow Diagram” as tank 

volumes and other small text are not discernible.

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6.1.8 Study Plan Section 12.2.2. Please revise the “WWTP Process Description” section to 

provide additional information regarding the planned addition of an external carbon 

dosing facility (e.g., chemical/source name, construction dates, date dosage is scheduled 

to commence).

6.1.9 Study Plan Section 12.0, Appendix I. Boulder’s discharge permit indicates that flow 

measurement occurs only at the wastewater influent. Please describe how effluent flow 

will be measured or estimated.

6.1.10 Study Plan Section 13.2.3. Please revise the “Normal Operating Conditions” section to 

provide additional information regarding the planned biosolids loading facility and cogeneration engines (e.g., construction and implementation dates) and the anticipated 

“short-duration interruptions” (e.g., interruption of the entire WWTP only sludge 

management) and their impacts on sampling.

6.1.11 Study Plan Section 13.5. Please revise the “Sampling Locations Description” section to 

clarify whether the effluent sampling location is before or after 

chlorination/dechlorination. Additionally, please discuss the representativeness of the 

selected biosolids sampling location, as Study Plan Section 13.5 indicates samples will be 

collected as the biosolids exit the belt filter presses, while Study Plan Section 13.2.2 and 

Figure 13-2, “Process Flow Diagram” describe that digested sludge is dewatered via 

centrifuges or belt filter presses.

6.1.12 Study Plan Section 14.0, Appendix I. Please revise Appendix I to include this WWTP’s 

discharge permit.

6.1.13 Study Plan Section 14.2.3. Please revise the “Normal Operating Conditions” section to 

provide additional information, regarding the planned centrifuge dewater system and 

polymer change (e.g., installation/construction and implementation dates, does the 

polymer contain D4).

6.1.14 Study Plan Section 16.2.2 and Figure 16-2. Sludge thickening using dissolved air 

floatation is discussed within the “WWTP Process Description” section but is not 

included in the “Process Flow Diagram” figure. Additionally, flocculation is not 

discussed in the “WWTP Process Description” section but is present on the “Process 

Flow Diagram” figure. Please revise the text and figure as appropriate.

6.1.15 Study Plan Section 17.2.2. Please revise the “WWTP Process Description” section to 

describe the “high strength” wastewater sources and their management, including the use 

and objectives of the “BAR” treatment unit indicated on Figure 17-2. Additionally, 

please revise text to discuss sludge thickening using the rotary drum thickener.

6.1.16 Study Plan Section 17.2.2. The narrative is inconsistent regarding the use of polymers. 

Text within the “WWTP Process Description” section states “Polymers are not used at 

the WWTP.... No information is available on the presence of siloxanes in the polymers 

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used at the WWTP.” Also, Study Plan Section 17.5 mentions “the polymer tank room.” 

Please address this oversight.

6.1.17 Study Plan Section 17.5. The description of the biosolids sampling location is unclear. 

Please clarify what is meant by the “post belt processing machine.”

6.1.18 Study Plan section 18.1 and Table 18-2. There is a discrepancy in the reported 2013 

average flow (65.7 MGD v.s. 71.96). Please correct this oversight. 

6.1.19 Study Plan Section 18.5. Please revise the “Sampling Locations Description” section to 

better describe the effluent and biosolids sampling locations.

6.1.20 Study Plan Section 19.1 and Appendix I. The “Site Description” section describes a 

design average flow rate of 32 and 40 MGD for dry and wet conditions, respectively. 

However, the discharge permit specifies a design average flow rate of 54 MGD. Please 

revise the text as appropriate.

6.1.21 Study Plan Section 19.9.2 and Figure 19-2. The text states “sludge that settles in the 

intermediate...clarifiers is returned to the tricking filters...”; however, the process flow 

diagram shows that sludge from the intermediate clarifiers is returned to the bar screens. 

Please correct this oversight and revise text and figure as appropriate.

6.1.22 Study Plan Section 21.0, Appendix I. Please revise Appendix I to include this WWTP’s 

discharge permit.

6.1.23 Study Plan Section 21.2.2, Study Plan Section 21.5 and Figure 21-2. The “Process 

Flow Diagram” figure depicts and the “WWTP Process Description” section describes 

that digested sludge is dewatered via centrifuges or lagoons, while text within the 

“Sampling Locations Description” section specifies that samples will be collected as the 

biosolids exit the post-digestion centrifuges. Please revise text and figure to discuss the 

representativeness of the selected biosolids sampling location.

7 Pre-Mobilization Information Collection Logs (Study Plan Appendix G)

7.1 EPA recommends that site-specific call logs for the direct, indirect and non-industrial sites 

be developed based upon comments above for Study Plan Sections 7 through 21. The sitespecific call logs for indirect and non-industrial discharge sites will record both influent 

and effluent flows, while the logs for the direct discharge sites will only record effluent 

flows. Appendix G of the Study Plan provides an example call log form.

7.2 Study Plan Appendix G (Pre-Mobilization Information Collection Logs) for Direct 

Discharger WWTP #DD1, Adrian, MI. The call log form for this direct discharger 

should record flows for both Outfall 001A (process wastewater discharge compliance 

point) and Outfall 001B (treated ground water); daily flow measurements at these outfalls 

are required by the plant’s NPDES permit. The plant’s call log form should also indicate 

whether “High-Strength Wastewater” is being routed to the WWTP at the time of sampling 

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and during the period of time prior to pre-mobilization equal to or greater than the 

hydraulic residence time of the WWTP.

7.3 Study Plan Appendix G (Pre-Mobilization Information Collection Logs) for Direct 

Discharger WWTP #DD2, Carrollton, KY. The call log form for this direct discharger 

should record flows at the time of sampling for both Outfall 001 (compliance point) and 

Outfall 002 (internal compliance point); continuous flow measurements at these outfalls 

are required by the plant’s NPDES permit.

8 QAPP Project Staff Reporting Requirements and Additional Quality Control Related 

Issues

8.1.1 QAPP Section 2.4. Descriptions of the how communications and any reporting 

relationships between the ERM QA Unit and the ALS QA Managers will be handled are 

needed in the QAPP. The signoff or approval trail of project QA and management 

personnel indicating that the data generated are appropriate for use needs to be 

documented. For example, it is stated in the body of the QAPP that the ERM Data QA 

Manager will communicate with the ALS quality staff, but that communication is not 

reflected in Figure 1-1. Further, the independence of the ALS QA Unit Managers with

those ALS staff working directly on the project analyses needs to be documented.

8.1.2 QAPP Section 2.8.2. The QAPP states that the validation study will be repeated at 

ALS/SLC in early 2015. Please provide validation results for ALS Salt Lake City.

8.1.3 QAPP Section 2.9.3 and Appendix D. It is stated that a description of the EQUIS EDD 

format will be provided in Appendix D. This Appendix only contains a listing of several 

data elements. There is no description of the format of all data elements that will be 

submitted to EPA. Please provide this information. 

8.1.4 QAPP Section 3.5 and Appendix F. Corrective Actions for sample QC failure are not 

defined in the QAPP, analytical SOPs in Appendix F, Section 14 of all analytical SOPs, 

and Section 13 for SOP OE-DC-LIPIDS. The SOPs mention that if QC fails, 

Nonconformity and Corrective Action Reports (NCAR) are required and routine 

corrective actions are part of normal operating procedures and no other documentation 

(other than laboratory or maintenance logs) are necessary. If there are known routine 

corrective actions that are part of the operating procedures, they are not mentioned in the 

SOPs, which is where this type of information should be located. For example, if a CCV 

percent recovery fails, it is common practice that samples that are bracketed within a 

passing CCV and a failing CCV are re-analyzed. If CCVs continue to fail, the instrument 

can undergo a cleaning or maintenance cycle or the CCV solution can be re-prepared.

Please revise the SOPs to include guidance as to what is routinely done when a QC fails 

and if there are different steps for different failed QC samples. This is to ensure that the 

laboratory will re-analyze samples if QC fails or if they flag samples and what they 

commonly do in such occasions. Additionally, please include corrective action 

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procedures for all types of QC in case of failure, such as IS, CCVs, Blanks, field spikes 

and surrogates, hold times, and anything that has acceptance criteria.

9 Method Validation Study – Vial Headspace (QAPP Section 3.4.3 and Appendix C). The 

QAPP states that D4 analytical SOPs were prepared for the water matrices, solid matrices 

and tissue samples. EPA expects clarification of the issues surrounding headspace in sample 

vials that were expressed in the March 9, 2015 letter. Specifically, it is expected that SEHSC 

will revise the Study Plan and QAPP to include an explanation (and relevant documentation) 

of how the analytical techniques will account for the headspace.

ECA Requirement: The ECA (Appendix 4) specifies that the commercial laboratory will 

develop a method for analyzing D4 that shall be adapted from the analytical method 

specified in Knoerr (2013). The ECA further specifies:

The Knoerr (2013) analytical method utilizes pieces of LDPE film to act as a sorbent 

and partial barrier to prevent loss of analyte to the headspace of the sample container. 

Immediately after collection, a water sample is placed into a container containing 

pieces of LDPE, which adsorbs the D4. In the laboratory, the water sample and the 

LDPE sorbent are solvent extracted and processed for analysis with GC-MS.

10 QAPP Appendix C-2 – Technical Issues

10.1 The method validation reports fail to provide the date and time of analysis following 

sample preparation. Were the samples analyzed immediately after preparation, or did the 

study authors use a holding time that would mimic the actual holding times that would be 

experienced when field samples are taken?

10.2 Suggest adding to all validation reports in Appendix C2 a summary of quality control 

sample results and passing criteria, such as Internal Standard (IS) added to samples not just 

in calibration curve, field spike (if it was added), pre/post-extraction spiked surrogates, and 

blanks.

10.3 Validation Reports are vague on how each calibration point was obtained. The validation 

reports should provide the weight of standard (the actual not just target weight).

10.4 Provide an example of the sequence including calibration, QC samples, and blanks in the 

order these are analyzed in SOPs or Reports.

10.5 Define what is a long sequence and when multiple Procedural Blanks (PBs) between 

samples are required.

• Provide number of PBs analyzed and analysis position in the sequence.

• Suggest analyzing PBs at the end of each sequence.

10.6 Provide volume of extracted sample poured into autosampler vial. A large sample was 

prepared and 50 mL were used for each sample, but how much of each sample was poured 

into the autosampler vials?

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10.7 Provide date and time, and volume of solution and vial for the following:

• Prepared bulk sample

• Individual 50 mL samples (only volume was provided)

• Autosampler vials ready for analysis

10.8 Recommend that a set of samples is analyzed the same day of preparation and another set 

should be analyzed after a period of time that equals the amount of days that real samples 

will be from collection to analysis.

10.9 Provide date and time of sample analysis.

10.10 Provide calibration standards and QC samples preparation date and expiration date.

10.11 Provide total run time.

11 Mixing Zone Modeling (Study Plan Section 2.5.6 and Appendix F) Comments in this 

section are based upon the following ECA requirements:

1. Samples are to be collected from the receiving water environment (i.e., surface water, 

sediment, and benthic) at a location as near to the outfall as is possible after “adequate” 

mixing of the discharge plume and ambient flow has occurred.

2. Monitoring shall not occur within three days of an unusual weather event, such as heavy 

rain storm. Thus, receiving water flows used in the modeling effort should be consistent 

with typical dry weather flows for the time of year in which monitoring will occur.

11.1 Summary Comments

11.1.1 The Study Plan fails to provide justification for applying the 100-meter downstream 

sampling location to the direct discharge, non-industrial and indirect discharge 

wastewater treatment plant sites.

11.1.2 EPA recommends that “adequate mixing” be evaluated on the basis of complete vertical 

mixing unless modeling produces unreliable or unfeasible results. Tracer studies should 

be considered for sites if modeling is inapplicable. 

ECA Requirement: The ECA (Appendix 8) specifies:

At each site, benthic organisms shall be collected as close as reasonably possible to the 

effluent outfall provided adequate mixing of the discharge and receiving water has 

occurred and where adequate benthic organism sample masses are obtained. Each site 

specific sampling plan will identify where the effluent and receiving stream are 

adequately mixed and the basis for the determination. At each site fish, surface water 

and sediment shall also be collected at approximately the same location.

11.1.3 The Study Plan does not provide adequate details on the modeling inputs and the 

rationale for the chosen values for the direct discharge sites.

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11.1.4 While the choice of 100 m for the direct discharge sites appears more appropriate than 

the other two approaches proposed by the Study Plan (constant dilution factor and 

complete mixing), this distance may result in more dilution than is necessary and may be 

inconsistent with the goals of the ECA. 

11.1.5 Monitoring at multiple distances downstream could compensate to some degree for the 

uncertainty of determining when mixing has reached the benthic layer.

11.2 Dilution Summary and Recommendation

11.2.1 As stated above in Summary Comment 9.1.2, EPA recommends that “adequate mixing” 

be evaluated on the basis of complete vertical mixing unless modeling produces 

unreliable or unfeasible results (i.e., sampling location on the order of kilometers 

downstream). In instances where modeling is inappropriate, due to channel geometry or 

other confounding factors, mixing should be evaluated using field studies and best 

professional judgment.

11.2.2 EPA cannot make recommendations regarding the non-industrial and indirect discharge 

wastewater treatment plant (WWTP) sites based on information presented in Study Plan 

Section 2.5.6.2, as no modeling was performed or data reported for these sites. 

EPA recommends that either modeling and/or field studies be completed for the nonindustrial and indirect discharge WWTP sites. Dilution modeling is site-specific. Mixing 

zone simulations performed for the direct discharge (DD) sites are not applicable to the 

non-industrial and indirect discharge WWTP sites described in the Study Plan, unless 

there is a high degree of correspondence between the discharges and receiving water 

bodies.

11.3 General Comments

11.3.1 As stated above in Comment 9.1.2 and Comment 9.2.1, “adequate mixing” should 

include vertical mixing consideration. To fully characterize and evaluate the resulting 

exposure of aquatic and sediment dwelling organisms, the sampling location should 

ensure sediment dwelling organisms are exposed to the effluent plume. For the intent of 

the ECA Testing Program, EPA recommends that “adequate mixing” be defined at or 

beyond the point of complete vertical mixing unless it violates another part of the Study 

Plan. Other considerations may be applicable, and should be discussed within the SiteSpecific Sampling Plans. 

11.3.2 Benthic organisms’ exposure to the discharge will be limited until the spreading line of 

the plume reaches a riverbed. Exposure will be maximized once complete vertical mixing 

has occurred. For three of the four direct discharge facilities (#DD1-Adrian, #DD2-

Carrollton, and #DD4-Waterford), the Study Plan assumes an equal effluent density to 

receiving water density and discharges occur at the surface of the receiving water, which 

is likely to indicate these effluent will mix in the vertical at a slow rate. For #DD3-

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Friendly, the effluent is buoyant and discharged from a submerged single point outfall 

located just above the bottom of the stream which will tend to produce rapid vertical 

mixing rates.

11.3.3 The Study Plan defines dilution factor as the ratio of ambient receiving water to effluent 

flow in the plume at the location of interest (Study Plan Section 2.5.1.2, page 32). The 

Cormix User Manual uses a slightly different definition of dilution, which differs from 

the Study Plan definition by one unit (i.e., Study Plan Dilution = Cormix Dilution – 1). 

The Study Plan does not explicitly state that they have corrected for this difference in the 

Study Plan.

11.3.4 The Study Plan does not specify whether centerline dilution (i.e., peak concentration at a 

downstream distance) or flux-averaged dilution (i.e., average concentration at 

downstream distance) is being specified. At any given downstream location, the 

centerline dilution would be more stringent than (i.e., less than) the flux-averaged 

dilution. Please refer to Figure 11-1 for further illustration. Outside of the jet region of 

the plume, Cormix calculates flux-averaged dilution so this is likely to be the value

presented in the Study Plan since the distances being discussed are hundreds to thousands 

of meters downstream.

Figure 11-1. Centerline versus Flux-Averaged Dilution

11.4 Study Plan Section 2.5.6

The Study Plan asserts that it is necessary to identify the mixing zone for each WWTP and 

direct discharge effluent discharge to be sampled, and that the availability of well-defined 

mixing zones, such as those established in an NPDES permit, was determined during site 

visits.

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Typical mixing zones established in NPDES permits are not optimal for purposes of 

characterizing average, long-term exposure in the receiving water environment. Regulatory 

mixing zones in permits are typically based on reasonable worst-case conditions applicable 

to acute and/or chronic conditions with reoccurrence intervals corresponding to water 

quality standards (for instance, 1-day out of three year returns). The use of regulatory 

mixing zones may not be consistent with “normal operations” or typical dry weather 

receiving water flows specified within the ECA.

11.5 Study Plan Section 2.5.6.1

11.5.1 The Study Plan asserts that the inputs to the model were based on best estimates of 

realistic conditions of the river at each facility and various flow rates. Limited rationale is 

provided for the modeling inputs, and we were unable to substantiate the use of many of 

the individual model inputs (for further discussion on inputs, please refer to Section 9.6). 

This conclusion is based upon a review of Study Plan Section 2.5.6, Study Plan Section 

7.0, Study Plan Section 10.0 and Appendix F.

11.5.2 The Study Plan states that model output was evaluated to develop a consistent approach 

to determine the zone of “adequate” mixing for all DD sites. The Study Plan explores 

three approaches:

1. Complete mixing – Complete mixing is defined by the Study Plan in Appendix F 

as “where the plume is uniform both vertically and horizontally throughout the 

river cross-section.” Modeling estimates show complete mixing did not occur 

within 100 km downstream under any of the modeled river flow rates for the 

#DD2-Carrollton facility, nor for the highest modeled river flow rate for the 

#DD3-Friendly facility. The distance to complete mixing for the #DD4-Waterford 

facility exceeded 3 km.

At the distances required for complete mixing, the Study Plan finds that several 

other contributing sources (both point source discharges and tributary inflow) to 

the rivers occur between the outfall and the complete mixing distance. These 

additional contributing sources introduce confounding effects that cannot be 

overcome. The Study Plan concludes that in order to have consistency between 

sites and to help ensure that sampling is not conducted too close to the effluent 

outfall or too far downstream, the distance to complete mixing could not be used 

as the point of adequate mixing.

EPA agrees that the long distances necessary for complete mixing are 

inappropriate for the purpose and intent of the ECA Testing Program. 

Additionally, the available dilution factors associated with complete mixing 

exceed 100:1 (i.e., the ratio of receiving water to effluent), and are not consistent 

with “low dilution” as specified within the ECA Testing Program.

2. Constant dilution factor – The Study Plan proposes the consideration of a constant 

dilution factor to determine the point of “adequate mixing”. The Study Plan points 

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out that the #DD4-Waterford facility did not achieve a dilution of 10 until just 

past 150 m from the discharge point at the lowest modeled river flow rate, while 

the #DD1-Adrian facility was predicted to achieve a dilution factor of 10 in just 

2.4 m. The Study Plan asserts that at a distance of 2.4 m the receiving water will 

be mostly effluent which, since it is in direct contravention of the modeled 

estimate, indicates a lack of faith in the reliability of the modeling results.

The Study Plan does not provide rationale for why they find a distance of 150 m 

too far away and leaves the assertion unsubstantiated. However, EPA agrees with 

the Study Plan’s conclusion based on the requirements of the ECA that the 

monitoring location be as close to the effluent outfall as possible, and that 

unnecessary dilution be minimized.

Based on the Study Plan’s modeling results for the #DD1-Adrian facility, at a 

distance of 2.4 m downstream of the effluent outfall, the receiving water is 

expected to be mostly receiving water (i.e., a dilution factor of 11:1). Based on the 

model, the assertion that the receiving water will be mostly effluent is 

unsubstantiated and unlikely. This was the Study Plan’s sole rationale for 

discounting the constant dilution factor approach, and is further referenced as 

rationale for supporting the third and chosen approach.

Performing monitoring based on a constant dilution factor, irrespective of the 

behavior of the effluent plume and the exposure to target organisms, is not 

consistent with the intent of the ECA Testing Program. The use of a constant 

dilution factor may result in monitoring locations where benthic organisms are not 

exposed to the effluent plume. Thus, we agree that the use of a consistent dilution 

factor is inappropriate for determining adequate mixing.

3. Use of a constant distance (100 m) - The approach eventually accepted by the 

Study Plan to define “adequate” mixing was the use of a constant distance of 100 

m downstream of the effluent outfall. The chosen approach seems to rely on three 

claims:

a. No other discharges to the receiving rivers were identified within 100 m of 

any of the direct discharge WWTP sites.

b. This distance was neither too close to the facilities effluent (as would be 

the case if a specific dilution factor were used) or too far away (as would 

be the case if complete mixing were used).

c. The other two options (complete mixing and constant dilution factor) have 

been determined to be inadequate.

That there are no other discharges to the receiving rivers within 100 m of any of 

the direct discharge WWTP sites is an important consideration but is not 

sufficient in and of itself to define adequate mixing. The Study Plan does not 

discuss the appropriateness of the approach in regards to collecting data adequate 

to address the purpose and intent of the ECA Testing Program. Specifically, 

whether benthic organisms are exposed to the effluent plume within 100 m of the 

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effluent outfall and whether the effluent diluted more than reasonably necessary at 

100 m.

Adequate mixing must be defined and evaluated consistent with the purposes and 

intent of the ECA. Identification of a sampling location consistent with purposes 

and intent of the ECA should result in a sampling location where benthic 

organisms are exposed to the effluent plume and should not result in significantly 

more dilution than necessary at that location.

11.6 Study Plan Section 2.5.6.2

11.6.1 The Study Plan states that because of difficulties encountered during modeling of the 

selected DD facilities, and the lack of correspondence between the predicted and actual 

location of the plume at a field training site (#DD2-Carrollton facility), the mixing zone 

for the municipal POTWs were not modeled. Instead, the same 100 m downstream 

distance is proposed as the potential sampling location for all sites.

The lack of correspondence between the modeling results and the field observations at 

the #DD2-Carrollton facility may indicate inappropriate input values were used in the 

modeling effort or that an incorrect Cormix module was used. The Study Plan should 

provide further discussion regarding the difficulties encountered and explanation for the 

lack of correspondence between the modeling results and the field observations. At a 

minimum, the Study Plan should evaluate and document whether effluent and receiving 

water conditions were representative of model inputs on the date field observations were 

made.

Additional discussion should be given to explaining the infeasibility of resolving the 

identified issues with the modeling effort. For instance, could field testing be used to 

calibrate the Cormix simulation and, if not, why is this standard technique inappropriate 

or infeasible in this instance?

11.6.2 For the non-industrial and indirect discharge WWTP sites that were not subject to 

dilution modeling, it is not ideal to assume monitoring at 100 m downstream of the 

effluent outfall is adequate for the purposes and intent of the ECA Testing Program. 

Without additional data to evaluate the effluent plume, there is no supporting evidence to 

suggest that benthic organisms are exposed to the effluent plume at 100 m at each of the 

facilities. Mixing processes are site-specific. The downstream distance need to reach 

complete vertical mixing at one site will have no bearing on another site. With the direct 

discharge facilities, site-specific modeling data indicated that vertical mixing had 

occurred prior to the sampling location, but there is no evidence to support such a finding 

for the remaining facilities.

However, due to cost considerations, it may be practical to assume vertical mixing has 

occurred within a given receiving stream at a downstream distance of 100 m if the 

following holds:

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• The receiving water to effluent flow ratio is low when compared to the DD 

facilities;

• Stream depths are consistent with the characteristics of the DD facilities receiving 

streams; and

• The effluent is not excessively buoyant.

11.6.3 For the non-industrial and indirect discharge WWTP sites that were not modeled, the 

Study Plan does not provide information regarding the presence or absence of additional 

point sources or non-trivial tributary flows into the 100 m downstream mixing intervals. 

If additional point sources or tributary inflows are identified between the effluent outfall 

and the receiving water monitoring location, the potential impacts of those point sources 

should be evaluated.

EPA concludes that due to the lack of data and analysis provided within the report for the 

non-industrial and indirect discharge WWTP sites, it is not possible to evaluate 

consistency with the ECA Testing Program requirements that facilities be selected with 

low dilution, and that the receiving water location be located as close as possible to the 

effluent outfall where adequate mixing occurs.

11.7 Appendix F

11.7.1 Model Selection – The author does not indicate which Cormix module is utilized for each 

modeling effort.

11.7.1.1 Cormix1 should be used in instances where the discharge is emitted from a single port 

diffuser (either submerged or plunging), which has a substantial jet or momentum 

component into flowing unstratified or stratified receiving water environments. 

Facilities that appear applicable based on Appendix F summaries: Friendly, WV

Figure 11-2 Cormix1

11.7.1.2 Cormix2 should be used with submerged multiport diffusers under the same general 

characteristics as CORMIX1. This model does not appear to be applicable any of the 

four facilities described in Appendix F.

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11.7.1.3 Cormix3 should be used when an effluent enters a larger water body laterally, through a 

canal, channel, or near-surface pipe without a substantial jet component and is also 

positively or neutrally buoyant. Facilities that appear applicable based on Appendix F 

summaries: Adrian, MI Site; Carrollton, KY; Waterford, NY.

Figure 11-3 Cormix3

11.7.2 Effluent and Receiving Water Flow Inputs – Selected flow inputs used in the modeling, 

broadly speaking, should reflect the issue under investigation. For instance, when 

investigating acute mixing conditions, flow inputs should typically be based on a 

reasonable, worst-case scenario (i.e., high effluent flow rates and low/dry-weather 

receiving water flow rates). When investigating average long-term exposure (as is the 

case under this ECA), inputs should be based on long-term averages (i.e., average dry 

weather effluent flow rate and median/harmonic mean/geometric mean receiving water 

flow rates). Section 2.5.6.1 of the Study Plan states that inputs to the model were based 

on best estimates of realistic conditions of the river at each WWTP and various flow 

rates. However, it is unclear from Section 2.5.6.1 and the Appendix F memos how 

effluent and receiving water inputs were selected. For instance, were the effluent flow 

inputs developed based on an analysis of flow data and, if so, what was the analysis and 

why are the selected flows appropriate?

For the Carrollton facility, the receiving water high flow inputs represent the 90th

percentile of the daily mean flow rates; this is inconsistent with the Waterford facility 

where the 80th percentile of daily flow rates was used. Low and high flows are undefined 

for the Adrian and Friendly facilities. The Study Plan should define the ranges of 

acceptable receiving water flows, and provide the rationale for the asserted ranges in 

regards to the intent of the ECA Testing Program.

Were effluent flow inputs based on design capacities or some other assumed value? If 

inputs are not to be based on averages or typical values, input parameters could also be 

selected such that they roughly approximate typical seasonal conditions anticipated 

during the period in which sampling is anticipated to occur. The ECA requires the 

monitoring occur at least 3 days following unusual weather, thus dry weather receiving 

water flows would be most appropriate.

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Appendix F should provide the rationale to support each of the individual modeling 

inputs for the intended purposes of investigating “normal” operating conditions and 

typical dry weather stream flow.

11.7.3 Stream Geometry – The Cormix models assume fairly regular channel geometries, which 

are unrealistic over the distances (i.e., kilometers) discussed in the Study Plan. In winding 

streams and river, Cormix will produce more accurate results within the nearfield (i.e., 

dozens of meters downstream) than in the farfield (hundreds of meters downstream). In 

channels with many interruptions (i.e., sandbars) near the discharge location, modeled 

estimates of mixing are unlikely to produce reliable estimates of mixing.

11.7.4 Disjunction Between Modeled Plume Location And Field Observed Location – The 

modeling efforts will provide reasonable estimates of plume location under circumstances 

where inputs are similar to conditions on the day of sampling. It is rarely the case that 

models and reality correspond cleanly. Given the incomplete and limited mixing 

predicted by the models and the irregularity of some channels described, use of a tracer 

test to confirm the sampling location is within the influence of the discharge at each site 

is recommended.

12 Overview of EPA’s QAPP Review and Approval Process

12.1.1 QAPPs document the what, how, where, why and when of a project in addition to noting 

the specific QA system that governs the project and the quality control activities that have 

been put in to place to detect, manage and correct actions that need fixing. QAPPs reflect 

the current state of the project and are designed to accommodate the need to change 

procedures during the course of the study, if warranted. QAPPs are living documents that 

are kept current over the conduct of the study.

12.1.2 It is critical that those who will approve the QAPP understand the process that will be 

followed to make changes to study protocols. In many cases minor changes can be made 

during the conduct of the work (with the needed approvals) and then are reported in 

interim and final reports. Major changes must be documented and approved by those who 

approved the original (or previous revision) QAPP before the change is implemented. In 

some cases such changes can be approved via phone or email in real time, following up 

with the appropriate documentation and signatures.

12.1.3 The implementation of QAPPs follows a change process that ensures that users of the 

QAPP are aware of the changes made in real time, and clearly when a new revision is 

issued and approved. Revisions in this context generally reflect major changes to study 

protocols for data collection, analysis, use and reporting. These changes are reported in a 

Revision History that accompanies the QAPP. The Revision History documents the 

change(s) made, the reason for the change and where the change was made in the 

document (via the page number). This allow users to quickly learn of changes made, to 

track them, and to easily locate the revised text in the document. One approach often used 

when revised QAPPs are sent to the project team for review and specifically to those who 

will approve the QAPP is to provide a “Markup” copy of the QAPP, in addition to the 

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“Clean” version. New signature pages documenting that all signers of the QAPP have 

reviewed and approved of the changes are also prepared.

12.1.4 The first version of a QAPP is often submitted for review several times before it is

approved. The first version of an approved QAPP is documented as Revision 0. After 

each revision is approved, the Revision Number increases by one. For this reason, the 

QAPP that is currently under review will be considered Revision 0 once it is approved by 

EPA.

12.1.5 Further details are needed describing how EPA will be informed in a timely manner on 

significant quality control issues that arise during the conduct of the project activities and 

that require corrective actions that deviate from procedures that are documented in the 

QAPP.

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