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To: Members & Affiliates, Wet Weather Issues Committee
From: National Office
Date: February 21, 2001
Subject: EPA’S DRAFT BLENDING POLICY - REQUEST FOR MEMBER COMMENTS/AMSA BLENDING SURVEY RESULTS
Reference: RA 01-3

Action Please By:
Monday, March 19

The U.S. Environmental Protection Agency (EPA) has provided AMSA with an opportunity to review its draft policy on wet weather blending. "Blending" (also referred to as "recombination", "slipstreaming", and "internal bypassing"), is the practice of mixing partially-treated, disinfected wet weather flows with fully treated effluent prior to discharge to meet secondary treatment standards during wet weather events. The January 19 draft document (see ATTACHMENT A), Current Thinking on Peak Flows at POTWs, presents an outline of the Agency's current legal interpretation of blending. AMSA's preliminary analysis of the draft document indicates that this policy interpretation will be helpful for facilities that are designed to blend. In order to assist the National Office in providing appropriate feedback to the Agency, we ask that you review the attached document and provide comments by Monday, March 19. Please send your comments to Greg Schaner by fax at 202/833-4657 or by email at gschaner@amsa-cleanwater.org.

 

Background
Last spring, AMSA and other municipal organizations requested that EPA reconcile the Office of Wastewater Management's (OWM's) position that blending is conditionally authorized with the Office of Enforcement & Compliance Assurance's (OECA's) differing interpretation that all such blending practices constitute an illegal bypass. AMSA wrote the Agency on September 19, 2000 expressing the Association's concern and urging EPA to uphold its long-held recognition of the practice of wet weather blending. In order to assist AMSA in participating in the dialogue with EPA, a survey was conducted in mid-January 2001 to assess the extent of the membership that is designed to blend. A summary of the survey results are included below.

 

Draft Policy Outlines "Principles" for Authorizing Blending
The draft policy document represents the Agency's initial attempt to reconcile the secondary treatment and bypass regulations with current and past POTW blending practices. The document establishes a list of minimum criteria for NPDES permit authorities to use in authorizing such discharges, including the requirement to meet secondary treatment standards, document information on the treatment scheme included in past permit applications, and to use blending only when flows exceed the capacity of storage and treatment units. The document also indicates that those flows which are routed around the biological treatment units and which do not meet the policy's minimum criteria would be considered prohibited bypasses.

EPA also outlines additional considerations for permit writers addressing blending. These considerations include clear and enforceable permit conditions for compliance monitoring, developing information on collection system and treatment facility management during wet weather, assessing potential water quality impacts, and encouraging comprehensive consideration of intended treatment and collection system performance.

EPA's Specific Requests for Comments: In requesting comments from AMSA, EPA is specifically interested in learning about the process that POTWs utilize in sizing and designing their blending facilities. In particular, the Agency requests comment on the specific criteria or methods used by wastewater agencies to determine long-term system design elements. Therefore, AMSA asks that, in addition to commenting on the specific principles contained in the draft policy, each member provide feedback on the following related questions from EPA:

  • Are there standard principles or criteria that can be relied upon to determine when blending is triggered?
  • Are there textbooks that are commonly used to determine the appropriate capacity of the biological units or the size of the equalization tank?
  • Are cost-effectiveness or "knee-of-the-curve" factors considered in long-term design of blending facilities?

If you have any questions about the draft policy, please call Greg Schaner at 202/296-9836 or by email at gschaner@amsa-cleanwater.org.

 

Blending Survey Yields Conclusive Results
AMSA surveyed its membership (refer to ATTACHMENT B for a copy of the survey form) in January via Fax Alert (Fax Alert Special Edition, January 17, 2001) to demonstrate the impact of reinterpreting the policy on blending practices. AMSA received over 120 responses, representing roughly 40% of the membership. Our analysis indicates that reinterpreting the blending policy to constitute all such events as illegal bypasses of the treatment system would significantly impact the membership. The survey found the following:

 

  • 50% of the respondents have plants that are designed and operated to blend peak wet weather flows.
  • Of those agencies which have blending facilities, 30% responded that their plant had been redesigned to blend peak wet weather flows.
  • 30% of those with blending facilities responded that their permit specifically authorized the use of blending and, of the remaining 70% that are not so authorized, 33% included blending information in their previous permit applications.
  • Respondents were asked "If blending was banned from use - what would be the likely outcomes?" Of all those surveyed:

    (1)    46% would potentially experience decreased treatment efficiency and possible exceedance of permit limits;       
    (2)    41% would potentially experience wash out of biomass and solids from the treatment facility;
    (3)    33% would potentially experience bypass of raw sewage before the headworks;
    (4)    30% would potentially experience surcharging in the collection system; and,
    (5)    15% would potentially experience basement flooding.

AMSA will incorporate these results into the Association's comments on the draft blending policy. If you have any questions on the survey results, please contact Greg Schaner at 202/296-9836 or gschaner@amsa-cleanwater.org.

Attachments:

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