AMSA Regulatory Alert (RA 02-1)
To: Members & Affiliates, Wet Weather Issues and Legal Affairs Committees
From: National Office
Date: January 14, 2002
Subject: EPA’s DRAFT WET WEATHER GUIDANCE ON EMERGENCY OVERFLOW STRUCTURES,
PEAK EXCESS FLOW TREATMENT FACILITIES, AND BLENDING
Reference: RA 02-1
Attachments: Draft Wet Weather Guidance (PDF
~25 KB) and AMSA's Comments on EPA Draft Blending Policy
(PDF ~390 KB)
On December 21, 2001, the U.S. Environmental Protection Agency's (EPA's) Office of Water (OW) released draft guidance addressing several critical wet weather issues for Regional and state review. The draft guidance, titled NPDES Requirements for Municipal Wastewater Treatment During Wet Weather Conditions (see Attachment A), advises states and EPA Regions on how to address the following issues in a wastewater treatment plant's National Pollutant Discharge Elimination System (NPDES) permit:
This Regulatory Alert provides an overview of the draft guidance's key provisions.
AMSA has been anticipating the release of certain portions of this draft guidance for several weeks. The National Office has worked closely with Agency staff on the blending and PEFTF issues, and has actively encouraged Assistant Administrator Tracy Mehan to issue a final blending policy as soon as possible. AMSA understands that this document is on the fast track to be finalized, even though the Agency is not indicating yet when a final guidance should be expected. Although OW is actively seeking comments from the Regions and states on the draft guidance (these comments are due to EPA by January 21), it is not inviting outside comments. However, earlier last week, AMSA sent comments to EPA on the blending provisions (see Attachment B), and the National Office plans to meet with OW staff to detail additional issues and concerns regarding the PEFTF and emergency overflow structure provisions.
AMSA encourages you to review this document and to inform us of any issues or concerns you have with these draft provisions. Please forward any comments to Greg Schaner at gschaner@amsa-cleanwater.org, or call with questions at 202/296-9836. The draft guidance will be discussed in detail at AMSA's Wet Weather Issues Committee meeting on February 5 in Orlando, FL in connection with the Association's Winter Conference.
Discharges from Emergency Overflow Structures
The draft guidance first discusses how NPDES permits should address emergency overflow
structures located within separate sanitary sewer collection systems. Typically installed
at pumping stations, these structures are designed to release flow during power outages or
other emergency conditions. EPA clarifies that the draft provisions are applicable to
separate sanitary systems, and that overflow structures within combined sewers will
continue to be addressed by the National CSO Policy. Because this guidance
applies exclusively to separate sewer systems, it serves to highlight some key Agency
positions with regard to what AMSA considers to be "uncontrollable" sanitary
sewer overflows (SSOs).
EPA considers emergency overflow structures to be part of the larger POTW. For NPDES purposes, this means that these structures must be identified in the permit and that applicable effluent limits or prohibited releases must be incorporated. More specifically, EPA states that "permits addressing discharges from such an outfall must either prohibit the discharge or contain technology-based effluent limitations based upon secondary treatment or, to the extent that the discharge is at a level that will cause, have reasonable potential to cause, or contribute to an excursion of water quality standards, any more stringent water quality based effluent limitations, in numeric and/or narrative form" (page 2). AMSA is concerned that these requirements are potentially unworkable in most wet weather scenarios.
Discharges from an emergency overflow structure are also subject to the "bypass" provisions of the permit regulations (40 CFR 122.41(m)). The bypass provision prohibits bypasses except in limited circumstances where the bypass is for essential maintenance and does not cause effluent limitations to be exceeded. A discharge from an emergency overflow structure that causes a permit violation may be excused if the permittee can demonstrate that certain criteria are met. One of the more controversial criteria for authorizing a bypass is the requirement that there be "no feasible alternatives" to the bypass. EPA indicates in the draft guidance that in order to satisfy the "no feasible alternatives" criterion, "adequate back-up equipment should be installed in the exercise of reasonable engineering judgment to prevent a bypass" (page 3). EPA also suggests the use of the U.S. v. City of Toledo (63 F.Supp. 2d 834, N.D. Ohio 1999) analysis in determining whether the discharge meets the "no feasible alternative" criterion. For discharges caused by inadequate capacity, the City of Toledo court held the permittee responsible for failing to undertake additional construction to correct existing capacity problems prior to the discharge. Because remedial actions to correct capacity deficiencies are by necessity long-term projects, most, if not all, facilities will have significant work remaining at any one time. By holding permittees to a standard that requires them to have completed capacity upgrades or collection system improvements at the time of an emergency overflow, AMSA is seriously concerned that the City of Toledo interpretation will render the bypass provision essentially impossible to meet.
Discharges from Peak Excess Flow Treatment Facilities
Several POTWs around the country have installed wet weather treatment facilities within
their collection systems to provide physical and chemical treatment during peak flow
conditions. AMSA has consistently supported the use of PEFTFs as an effective mechanism
for relieving the collection system of excess wet weather flow, while providing necessary
treatment. The draft guidance considers how NPDES authorities should address discharges
from these facilities.
Due to the intermittent operation of the facility, use of biological treatment is not possible. The draft guidance recognizes that the secondary treatment standards (40 CFR 133) do not specify the type of treatment process that must be used to meet the end-of-pipe effluent limits, nor do they preclude the use of non-biological facilities. The draft guidance also acknowledges that some POTWs achieve secondary treatment requirements using only physical and chemical treatment designs. This recognition is important given the impossibility of using biological treatment components in PEFTFs.
Because treatment plants during wet weather are often treating dilute or less concentrated inflows, the secondary treatment standard's 30-day average 85 percent removal requirement is often extremely difficult to meet. To address this challenge, the regulations (40 CFR 133.103(d)) authorize the permit authority to substitute lower percent removal requirements or a mass loading limit for the 85 percent removal standard. This is important for PEFTFs because if the permittee qualifies for lower percent removal requirements then these adjusted limits may be applied to the PEFTF. In order to qualify, the permittee must first demonstrate, among other things, that the discharge will still meet effluent concentration limits and that the less concentrated influent is not the result of "excessive infiltration and inflow" (I/I). The draft guidance deals primarily with the "excessive I/I" requirement.
The "excessive I/I" requirement is defined in terms of the quantities "economically eliminated" from a sewer system as determined by a cost-effectiveness comparison between the costs for correcting the I/I conditions with the total costs for transportation and treatment of I/I. Significantly, the draft guidance indicates that this cost comparison does not include an examination of the cost of transport and treatment at a PEFTF providing treatment only during wet weather. Rather, the cost comparison is limited to an analysis of the cost of transport and treatment at a continuously operating treatment plant. AMSA believes that this interpretation sets up a flawed analysis which will make it even more difficult to qualify for lower percent removal requirements and make it even less likely that a PEFTF to treat wet weather flows will be authorized.
If a permittee qualifies for an adjustment to the percent removal requirements, and they plan to apply those limits to a PEFTF, the draft guidance would encourage requiring a clear, comprehensive plan to address I/I reduction and to ensure proper operation and maintenance of the system. EPA suggests the use of a capacity, management, operation and maintenance (CMOM) program to address these objectives. The CMOM concept will figure prominently in the proposed SSO rule. In addition, during permit reissuance, EPA suggests that NPDES authorities examine progress made in rehabilitating the collection system and in reducing I/I. If I/I has been reduced noticeably, the percent removal requirements may be adjusted to reflect a stricter standard.
Beyond using PEFTFs within the context of adjusted percent removal requirements, the draft guidance also suggests that these facilities may be approved on an interim basis in an enforcement action. The enforcement vehicle must provide a formal commitment to and schedule for carrying out corrective actions, and a date certain for phasing out the PEFTF. Following the phase-out date, remaining PEFTF discharges may be approved, but only if they meet the bypass requirements. AMSA remains concerned that by imposing a phase-out date on PEFTFs, EPA will severely compromise the potential for using these structures as part of an overall strategy to reduce wet weather overflows.
Blending Designs at POTWs
The draft guidance defines blending as "peak wet weather discharges from POTWs that
consist of effluent routed around biological treatment units blended together with the
effluent from the biological units prior to discharge" (page 5). The intent of the
blending provisions is to provide a list of principles for NPDES authorities to follow in
authorizing blending in permits. The draft guidance essentially incorporates the
provisions of EPA's January 2001 version of the draft blending policy (Current Draft
Thinking on Peak Flows at POTWs). See AMSA's Regulatory Alert RA 01-3 (http://www.amsa-cleanwater.org/private/regalerts/ra01-3.cfm).
Among the list of principles in the draft guidance for authorizing blending is the requirement to meet secondary treatment standards, to document that information on the treatment scheme was included in past permit applications, and to use blending only when flows exceed the capacity of storage and treatment units. The draft guidance also indicates that flows routed around the biological treatment units and not meeting the policy's minimum criteria are prohibited bypasses. EPA also outlines additional considerations for permit writers, including the need to incorporate 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.
AMSA has submitted comments to EPA on its draft blending policy (see Attachment B). The comments are generally supportive of the issuance of the draft blending policy. However, AMSA raises several practical concerns regarding the implication of imposing unnecessary operational limitations on treatment designs that are working well and meeting standards. The letter also provides numerous recommendations on how the language can be clarified. In addition, the comments include a summary of the results of last year's blending survey of AMSA members.
AMSA will keep you apprised of the status of this draft guidance in the coming weeks. Please contact Greg Schaner at 202/296-9836 or gschaner@amsa-cleanwater.org if you should have any questions.
Attachments:
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