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New York, City of (SPDES) - 6th Interim Decision, April 16, 1998

6th Interim Decision, April 16, 1998

50 Wolf Road
Albany, New York 12233-1010

In the Matter of the Application to Renew the State Pollutant Discharge Elimination System (SPDES) Permits Pursuant to ECL Article 17 and 6 NYCRR Parts 750 et seq. For New York City's 14 Publicly Owned Sewage Treatment Plants by CITY OF NEW YORK DEPARTMENT OF ENVIRONMENTAL PROTECTION (NYCDEP)


Case No. 0026131

April 16, 1998


Because the Commissioner served as the Department's General Counsel at times when hearings in this matter took place, responsibility to make the decision in this matter has been delegated to the Deputy Commissioner for Water Quality and Environmental Remediation.


This Decision is the latest of a series of Commissioner Interim Decisions and Administrative Law Judge Rulings concerning the terms and conditions of wastewater discharge permits for New York City's fourteen sewage treatment plants. Ten years ago, this Department, on notice but without a hearing, renewed the City's State Pollutant Discharge Elimination System ("SPDES") permits for its fourteen plants. The Interstate Sanitation Commission ("ISC") objected and obtained an order from State Supreme Court on April 17, 1989 that directed the Department to hold a hearing to consider modifying the 1988 permits, as provided by 6 NYCRR 757.2.

Since 1989, this proceeding has continued to consider, and to adopt in part, certain modifications to the SPDES permits for the City's sewage treatment plants. There have been five Interim Decisions of the Commissioner, each of which dealt with specific aspects of the City's SPDES permits.See Footnote 1 of ALJ O'Connell's attached Issues Ruling. At the conclusion of each phase, permit modifications were implemented as deemed necessary.During the proceeding, the City's SPDES permits were modified as follows. The Commissioner's Second Interim Decision dated July 16, 1991 incorporated new conditions and modified others as part of a settlement of the issues related to numeric toxic limits, and industrial pretreatment requirements. The Fourth Interim Decision dated January 28, 1994 incorporated conditions for controlling nitrogen loading. In the Fifth Interim Decision dated October 7, 1996 the Commissioner determined that the proposed March 1996 Modification to the June 1992 Consent Order resolved all issues related to untreated discharges from combined sewer outfalls. In 1996, the permits were administratively renewed without prejudice to the ongoing proceedings. The City's permits are now due for review and modification in accordance with the Environmental Benefit Permit Strategy (EBPS) Priority Ranking System.

This decision deals both with the appeals from Administrative Law Judge ("ALJ") Daniel P. O'Connell's September 4, 1997 "Issues Ruling on Remaining Issues," and with the process for review and modification of the City's permits.

The appeals from the three "remaining" issues designated in the Rulings are:

  1. Flow measurement;
  2. Plant capacity; and
  3. Whole effluent toxicity, sometimes abbreviated as "WET."

These three matters are first discussed in this Decision.

The process for review and modification of the City's SPDES permits is discussed at the end of this decision in light of the outcome of these appeals.

The ALJ's Issues Ruling

The ALJ's Issues Ruling concluded that a substantive and significant factual disagreement had surfaced in filings made by the parties with respect to an aspect of flow measurement. Specifically, this item deals with the method being used by the City to calculate dry weather flows. While concluding that this issue is factual and appropriate for adjudication, the ALJ urges the ISC and DEP staff to seek to resolve it by consensus if possible.

The ALJ also reported that there is a remaining dispute as to how and when an effluent limit for residual chlorine should be incorporated into the SPDES permits. The ALJ proposed that an effluent limit for total residual chlorine could be determined in the context of the hearing about the dry weather flow measurement issue. He further directed that the results of a chlorine die-off study be distributed as soon as possible, with the expectation that the results of that study would be materially helpful in establishing an effluent limit for total residual chlorine.

The ALJ also directed that permit conditions be added so that the City will be required to install double flow monitoring systems at all of its plants. Presently, not all of the City's plants have double flow monitoring. The City has agreed in principle to installing double flow monitoring equipment.

Other than the above two issues (dry weather flow calculation method, and effluent limit for total residual chlorine), the ALJ found no issues for adjudication. In making that determination he rejected a number of issues proposed for adjudication by two intervenors, Riverkeeper, Inc. and the Interstate Sanitation Commission.Other intervenors in this proceeding are Environmental Defense Fund, New York Coastal Fishermen's Association, Natural Resources Defense Council and Connecticut Coastal Fishermen's Association.

The Parties' Appeals

Riverkeeper, Inc. ("Riverkeeper"), successor to intervenor Hudson River Fishermen's Association,As set forth in an October 27, 1997 letter from Riverkeeper's counsel, the Hudson River Fishermen's Association was merged with Riverkeeper Fund in 1992 to form Riverkeeper, Inc. has appealed, pursuant to 6 NYCRR 624.8(d)(2)(i), from the ALJ's determination to exclude from adjudication its proposed "whole effluent toxicity" issue.

The ISC appeals from the ALJ's determination to exclude the "flow measurement" and "plant capacity" issues from adjudication, on the ground that the issues are neither substantive or significant as specified in the Department's rules. ISC also joins in the Riverkeeper's appeal.

In responsive papers, the City and Department Staff each oppose Intervenors' appeals on the above issues. Moreover, they each contend that the Commissioner should reject the ALJ's determination to adjudicate the method for calculating dry weather flow, and the effluent standard for total residual chlorine.


In this Interim Decision, I deny the appeal of ISC. I grant the appeal of Riverkeeper, Inc. on the issue of dilution water to be used in the whole effluent toxicity test procedure and continue this proceeding with respect to that issue. I add that this remand is without prejudice to prompt commencement of review of the City's existing SPDES permits, and their appropriate modification, following established procedures for public notice, comment, and opportunity for hearing. The EBPS modification procedure is not to be deferred because of this remand. Any whole effluent toxicity permit terms and conditions developed as a result of this remand will be incorporated into the modified permits. The parties are encouraged to cooperate in this matter.

The ALJ's recommendations that he adjudicate the method for calculating dry weather flow and the effluent standard for total residual chlorine are rejected.

Having outlined the background of this matter and its current status above, I will now address the issues before me in this appeal. To the extent that they are not inconsistent with this decision, the ALJ's rulings are adopted and made a part hereof.

I. Flow Measurement and Plant Capacity

ISC's appeal on flow measurement and plant capacity is addressed to an array of policy, engineering, design, and operational questions. As stated by ISC, these are:

  1. Total flow vs. dry weather flow;
  2. Design criteria used to determine plant capacity;
  3. Flow verification;
  4. Capacity assurance program;
  5. Treatment of flow captured during wet weather; and
  6. Maximizing combined sewer overflow flowage to the treatment plants.

Each of these points has been raised repeatedly by ISC since at least 1990. Each has been considered by the Department and the City. The Department's consideration of ISC's points has been thorough, as the following discussion based on the record amply shows.See especially Staff's May 20, 1997 letter to the ALJ in response to the April 9 and 11 letters of the Riverkeeper and ISC. All parties have aired their points of view. ISC has not come forward with controverted facts that require a fact-finding hearing. Resolution of these items is a matter for the Department's judgment. The following discussion outlines the rationale for my decision with respect to the ISC's six sub-points under the general rubrics of flow measurement and plant capacity.

1. Total Flow vs. Dry Weather Flow - Since at least 1990, the ISC has urged that the City's SPDES permits should require measurement and reporting of total flow instead of dry weather flow, as the existing permit requires. However, the record shows that dry weather flow was adopted by Staff as the most practical alternative means for measurement and reporting for the City's complex combined sewer system.

Pursuant to 40 CFR Part 122.45(b)(1) and 6 NYCRR Part 754.1, effluent limits in the SPDES permits are to be based on design flow. The current SPDES permits are consistent with these requirements. There is no federal regulation requiring flow limits in SPDES permits. Whether to place any flow limits in the permits is left up to the states. DEC exercises its best professional judgment to develop flow limits for publicly owned treatment works (POTWS) on combined sewer systems to be consistent with the combined sewer overflow (CSO) policy objectives.

Consistent with these objectives, the concept of dry weather flow was developed to accomplish the permit mandate that at least two times design flow be able to be conveyed to and through the wastewater treatment plants. This makes it possible to accomplish the wet weather maximization program (and removal of the major source of contaminants to the estuary) without penalizing the City for exceeding the flow limits based on average design flow in the permits, when the sole cause of the exceedence is enhanced wet weather capture.

DEC applied its best professional judgment in developing SPDES permit limits for flow, which recognize that the City's plants have a peak treatment capacity that is properly used for the treatment of combined sewage, and provide a measure for base flow that is the correct procedure to assess service connections.

In order to ameliorate the skewing effect of wet weather conditions on flow data, a statistical approach is used to record flows during wet weather conditions. If hourly flows exceed a boundary of two standard deviations above the average flow for that hour based on long term measured dry weather flows, the average dry weather flow for that hour is used to calculate the 30-day average flow required by the permit. When the storm event ends, at the hour at which the actual flow dips below the two standard deviations line, the actual flow is again used for reporting purposes.

Also, for purposes of determining whether permit mandated moratoria on service connections are to be imposed, a moving annual average dry weather flow criterion is used. The Department examines the last twelve months of dry weather flow, each time it analyzes whether a moratorium should be imposed on new connections to the system.

Lastly, the City's SPDES permits function as integrated drainage area-wide management tools, whereas the ISC chooses to focus strictly on the treatment plants. The ISC position is not consistent with DEC or EPA combined sewer overflow policies. It would roll back water quality improvements achieved during the 1990s, primarily due to the permit-mandated improvements in wet weather capture, by excising the dry weather flow concept from the City's permit requirements.

2. Design Criteria - The Department advised the City in August 1995 that for all future upgradings, no approvals will be granted unless the primary settling tanks are designed to meet the Ten States Standards. ISC's papers in this appeal admit that this may be a fair compromise. It is a prudent approach in the Department's judgment, and responds to ISC's point that the Ten States Standards should apply to the City.

3. Flow Verification - Pursuant to Department requests, the City has, in recent years, provided two independent means for measuring flow at almost all its plants. The Department Staff has stated that it intends to memorialize this dual measurement requirement in the permit modification process that will commence at the end of this hearing. Dual flow measurement is adequate to monitor flows at the City's plants. A second measurement provides a check on the first one. It also provides a backup, so that a malfunction in one measuring device will not result in a failure to collect flow data.

4. Capacity Assurance - The ISC would like to impose capacity assurance requirements on the City. However, the existing requirement that the City implement and maintain a continuous inflow and infiltration assessment and correction program (I&I Program) whenever dry weather flows exceed 95% of capacity, along with enforcement when the flow limitation itself is exceeded, are adequate in the Department's judgment.

5. Pump-Back - Plans submitted to the Department, as mandated by the CSO/Floatables Consent Order associated with Section III of the SPDES Permits, recommend the construction of up to nine off-line storm water storage/treatment facilities. The permits do not address pump-back of stored water, and should not until the facilities are completed. This is because of the determination of pump-back rates is site specific and sensitive. On the one hand, it is necessary to empty a storage facility as quickly as possible so that its full capacity will be available for the next wet weather event (it rains on the average of every 3.2 days). On the other hand, it is also desirable to avoid overwhelming the regional treatment plant with pumped-back sewage from satellite combined sewer overflow control facilities. In addition, since pump-back is really wet weather flow that has been captured, it should be covered by the dry weather flow concept mentioned above.

Staff should review the individual facility plans and develop SPDES requirements for combined sewer overflow abatement. The objectives of such requirements should be to maximize the capture and treatment of combined sewage from the overflow abatement facilities, as well as the host treatment plant, and be consistent with DEC and EPA policies. These requirements should be implemented in connection with modification of the City's permits in the upcoming permit cycle.

6. Flow Maximization - The 1988 SPDES Permits require the City to be able to convey at least two times design flow to and through all its wastewater treatment facilities that serve districts drained by combined sewers. These requirements were developed in order to reduce the frequency, duration and intensity of combined sewer overflows. The ISC has expressed concern about treatment degradation during wet weather when the City is required to accept flows at twice design levels. It is the Department's judgment that some small degree of degradation is acceptable (however there is no waiver of effluent concentration limits in the permits) based on the understanding that flows generated by smaller storms are completely retained by the collection system. Additionally, overflows generated by larger storms are substantially reduced by flow maximization.

It should be noted that both DEC's Division of Water Technical and Operational Guidance Series (T.O.G.S.) 1.6.3/CSO Control Strategy and EPA's National CSO Control Policy (Nine Minimum Control Measures) require maximization of flow to the treatment plants during wet weather. ISC's position on this issue appears to be counter to State and EPA Guidance. Furthermore, pursuant to DEC's CSO Control Strategy and EPA's Policy, the City is expected to be capturing and treating more combined sewage at the wastewater treatment plants.

II. The ALJ's Determination to Adjudicate Issues on the Dry Weather Flows Calculation and Effluent Standard for Total Chlorine Residual

Based on the above discussion of total vs. dry weather flow, the method for calculating dry weather flow has been set forth. The facts are undisputed. The ISC contends that the method is inappropriate. I disagree. Based on my review of the record, the dry weather flow calculation is technically sound and may continue to be used, subject to rational alteration from time to time as Staff may agree upon. No issue for adjudication has been raised.

As to the allowable chlorine residual in the effluent, Staff is directed to move forward with establishing appropriate limitations, in accordance with the EBPS modification procedure.

III. Whole Effluent Toxicity

Riverkeeper appeals from the ALJ's ruling that denied an adjudicatory hearing to determine standards for whole effluent toxicity testing at the City's plants; specifically, Riverkeeper's appeal contends that the selection of an appropriate dilution water for use in the City's whole effluent toxicity testing procedures is a substantive and significant issue.

The gist of Riverkeeper's appeal is that the whole effluent testing procedure in effect, as approved by the Department, employs synthetic dilution water, not actual river water. Riverkeeper argues that "since the East and Hudson Rivers waters into which the City's effluent will be discharged are polluted, the City's use of purified tap water for dilution will tell little about the real-life peril faced by aquatic organisms which come into contact with the City's effluent." Riverkeeper argues further that: "Because the toxicity testing performed by the permittee must determine the effect of adding toxic discharges to already contaminated receiving water, actual receiving water must be used for dilution purposes."

In essence, the Riverkeeper asserts that whole effluent toxicity testing protocols should use ambient river water for dilution in order to look at potential synergistic effects of effluent and ambient water on marine organisms. Thus, the outcome of the Riverkeeper's proposed issue depends on the purpose of the whole effluent toxicity test, what information the test seeks to obtain, and whether it is practical to use ambient river water for dilution.

A whole effluent toxicity measurement is made by placing groups of test organisms in undiluted effluent, in 50% diluted effluent, in 25% diluted effluent, in 12.5% diluted effluent and 6.25% diluted effluent. Observations are then made as to how well the test organisms survive as compared to a control group. If the observer is seeking information about the toxicity of the effluent itself, to use synthetic dilution water may be acceptable. If on the other hand contaminated river water is used as a dilutant, the test may tell the observer something about the synergistic effects of the effluent and the contaminated water; but the effectiveness of the sewage treatment process may be obscured.

The record is unclear as to the objective of the whole effluent toxicity test procedure as it is currently done, and as to the practicality of using ambient river water in lieu of synthetic dilution water. I conclude that this matter should be remanded for clarification, I direct the Staff to confer with the City, the Riverkeeper, and other interested parties, as to the most effective means of resolving this matter and to report to ALJ O'Connell within 30 days of the date of this decision. I suggest that alternatives may be preferable to adjudicatory hearings. For example, the parties may be able to agree that whole effluent toxicity tests should be performed using both synthetic and ambient water, for purposes of comparison. They may agree on the purpose of the test. Other alternative agreements may be possible. If no agreement can be reached, the ALJ will hold a hearing.

IV. Permit Renewal

While granting the Riverkeeper's appeal on whole effluent toxicity, I direct that this limited remand should not delay or result in deferral of any aspect of the periodic five year SPDES permit cycle applicable to the City's sewage treatment plants. In 1996, the permits issued in 1988 were administratively renewed without prejudice to this proceeding. It is now time for them to be reviewed, reconsidered and re-issued with such modifications as may be appropriate. This process will employ the Department's usual procedure for both technical review and public notice and comment, and opportunity for hearing. Staff is encouraged to solicit the City and the public, including the parties hereto for their preferences for terms and conditions of the City's renewed SPDES permits, and to move forward with the permit modification process. I anticipate that the parties to this remand proceeding will participate in the permit modification process, and will work together constructively to incorporate the outcome of this remand into the renewed SPDES permits for the City.


For the foregoing reasons, ISC's appeals are denied, and Riverkeeper's appeal is granted. This matter is remanded to ALJ O'Connell for further proceedings consistent with this decision.

For the New York State Department of Environmental Conservation

By: Erin Crotty
Deputy Commissioner for Water Quality and Environmental Remediation
April 16, 1998
Albany, New York

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