Specific notice to IUs of requirements and enforceability. This notice, provided through POTW sewer use ordinances or individual or general control mechanisms, should make clear which users are subject to the BMPs, and what affected users must do to comply with their requirements.   Installation of treatment. POTWs should provide criteria or specifications that the equipment must satisfy. For example, a requirement for use of oil/ water separators at auto repair facilities could include sizing or design criteria. EPA cautions POTWs to avoid endorsing the use of specific brands or vendors.   Requirements for or prohibitions on certain practices, activities or discharges. POTWs should include specific requirements or prohibitions where necessary to ensure that the use of such BMPs is protective. An example would be a prohibition on discharges of tetrachloroethene from dry cleaning facilities.   Requirements for operation and maintenance ( O& M) of treatment units. POTWs should spell out their O& M expectations to ensure that treatment systems continue to perform as designed and installed. For example, restaurants could be required to have grease interceptors cleaned out at a specified frequency.   Timeframes associated with key activities. POTWs should provide timeframes for when management practices must be implemented, or when required treatment must be installed and fully operational. Other milestones should be added to the schedule where necessary to facilitate the oversight of BMP implementation.   Compliance certification, reporting and records retention. Establishing specific procedures for such requirements will enable POTWs to verify whether required equipment has been installed, or whether required maintenance has been performed at the specified frequency.   Provision for re opening or revoking the BMP conditions. POTWs should include language in the sewer use ordinance and/ or facility control mechanisms that the authorization to use BMPs can be revoked when the POTW determines that the user has not complied with applicable BMPs, or where the POTW determines that it is easier to determine compliance with a numeric limit.   Other requirements as determined by the POTW.

What local legal authority changes will be necessary? POTWs wishing to establish BMPs instead of or in addition to numeric local limits will need to evaluate their sewer use ordinances to ensure they provide adequate authority to require compliance with BMPs by affected users. Further, BMP requirements such as those discussed above, and which IUs they cover, should be specified in POTW sewer use ordinances and/ or Industrial User control mechanisms. In most cases, the initial adoption of a BMP will be a substantial modification subject to the provisions of 40 CFR 403.18( b) where it replaces a different form of local limits, and where it is considered to involve a modification that relaxes local limits. This is discussed in more detail in Section VI. 38 How will compliance and significant noncompliance be determined? Concerns were expressed regarding the ability of Control and Approval Authorities to determine whether a user is in compliance with BMPs. In EPA's view, BMPs that set specific requirements, similar to the common elements presented above, ( i. e., requirements or prohibitions on practices, activities or discharges; requirements for installation, operation and maintenance of treatment units; timeframes for key activities; reporting and records retention; certification and reporting of compliance, etc.) will aid POTWs and Approval Authorities in their compliance determinations. Once these requirements are established for one or more facilities in a sector, an IU's compliance status should be able to be verified through a combination of self reporting and verification inspections. Where a facility subject to BMPs has not satisfied the requirements in the sewer use ordinance or control mechanism, the POTW would need to use its enforcement response plan ( ERP) to determine the appropriate response, and relevant significant noncompliance criteria to assess whether the facility is in significant noncompliance. For example, a facility that fails to install required treatment equipment within a specified timeframe would generally be viewed as being in significant noncompliance 90 days after the schedule date. See 40 CFR 403.8( f)( 2)( vii)( E). Likewise, a facility would be in significant noncompliance if it failed to submit a compliance certification within 45 daysfrom the due date. See 40 CFR 403.8( f)( 2)( vii)( F). POTWs adopting BMPs as local limits, or that have categorical industrial users whose categorical standards include BMPs, should evaluate their ERPs to ensure that they reflect the need to enforce against non numeric requirements.

D. Slug Control Plans ( 40 CFR 403.8( f)( 1)( iii)( B)( 6) and 403.8( f)( 2)( vi))

Today's final rule addresses the requirement that POTWs evaluate the need for a slug control plan for SIUs every two years. The rule will provide POTWs with the flexibility to determine how frequently to evaluate the need for such plans, based on local conditions. At the same time, the new rule specifies that an evaluation must be undertaken for each SIU once within a specified timeframe. Today's rule also clarifies that an actual slug control plan ( e. g., the physical document itself) is not the POTW's only option for controlling facilities with a higher potential for slug discharges. The regulation states that the POTW may choose to require that the SIU take specific, preventative actions instead of requiring the development of a slug control plan. Regardless of the requirements imposed by the POTW, today's rule will require that where actions to control slug discharges are determined to be necessary, the SIU's control mechanism must include provisions addressing those requirements .

These revisions do not alter current requirements regarding annual monitoring and inspections of SIUs. POTWs are still required to conduct their annual facility inspections and effluent monitoring for each of their SIUs. The revisions also do not change the POTW's requirement to prevent disruptions caused by slug discharges. EPA expects that, as an integral part of its ongoing oversight of all SIU facilities, the POTW will consider whether adequate measures are in place to avoid slug discharges. The POTW is authorized to use its own discretion in determining the timing, level of detail, and commitment of resources necessary to ensure the facility has adequate measures in place to prevent slug discharges. POTWs may still require the 39 SIU to develop a slug control plan or take specified preventative measures to prevent slug discharges whenever the facility's slug prevention measures are judged to be inadequate.

Today's rule does not impose any new requirements on industrial users. SIUs remain subject to current requirements to eliminate or mitigate the effects of a slug discharge. These actions may include constructing physical containment facilities as well as implementing sound management practices to prevent slug discharges.

1. What were the rules in place prior to today's rulemaking?

A slug discharge is defined as "  any discharge of a non routine, episodic nature, including but not limited to an accidental spill or non customary batch discharge" ( 40 CFR 403.8( f)( 2)( v)). The regulations also require POTWs to ensure that industrial users have policies and procedures in place to prevent or mitigate the effects of slug discharges. Section 40 CFR 403.8( f)( 2)( v), prior to today's rulemaking, required POTWs to "  evaluate, at least once every two years, whether each such Significant Industrial User needs a plan to control slug discharges." The function of such a plan is to ensure that an SIU has a planning and implementation tool to prevent interference at a POTW treatment facility by a non routine or accidental discharge. The minimum elements required in a slug control plan are ( 1) a description of discharge practices, ( 2) a description of all stored chemicals at the facility, ( 3) procedures for immediately notifying the POTW of the slug discharge and providing written follow up notification, and ( 4) a variety of procedures ( e. g., inspection and maintenance of chemical storage areas) for preventing adverse impacts from any accidental spills ( 40 CFR 403.8( f)( 2)( vu)( A) to ( D)).

The requirement for a once every two years review of the need for a slug control plan was part of the Domestic Sewage Study rulemaking ( 55 FR 30082, July 24, 1990). In the preamble discussion to that rulemaking, EPA explained the need for POTWs to implement slug control programs. As part of the discussion, EPA referenced the guidance manual, Control of Slug Loadings to POTWs ( EPA 21W 4001, February 1991, see http:// www. epa. gov/ npdes/ pubs/ owm021. pdf ), which was then under preparation. This manual provides detailed guidance for POTWs to evaluate whether SIUs need to develop slug control plans. It also provides guidance for SIUs in developing those slug control plans. In addition, the manual recognizes that POTWs need to determine whether existing on site conditions may impact their treatment works, while industries are in the best position to solve problems relative to their physical plants or production processes. Part 403 only requires that, where found to be necessary, a POTW must require an SIU to develop a plan or impose some specified control actions to prevent slug discharges.

2. What changes did EPA propose?

The proposed rule suggested eliminating the requirement that POTWs evaluate the need for a slug control plan for each SIU every two years. Instead, EPA proposed giving POTWs the flexibility to review the need for slug control plans or other actions as part of their ongoing 40 oversight of industrial users. The proposal would have added language to clarify that requiring an actual slug control plan is one of several options the POTW has at its disposal for controlling facilities with a higher potential for slug discharges. The proposed rule would have clarified that a POTW could choose to require that the SIU take certain specified preventative actions to control the slug discharge potential, instead of developing a slug control plan. In addition, to ensure that slug controls are enforceable to the same extent as other standards and requirements, the proposal would have added language to require that, where a slug control plan or other action is found to be necessary, appropriate requirements would be placed in the industrial user's control mechanism.

3. What changes is EPA finalizing in today's rule?

In today's final rule, consistent with the proposal, EPA removes the required minimum frequency for conducting POTW evaluations for the need for slug control plans or other control actions. The final rule also formalizes the requirement for SIUs to address slug discharges by requiring that the POTW include language in the user's control mechanism to control slug discharges, if it determines that a slug control plan or other action is necessary. These rule revisions appear in 40 CFR 403.8( f)( 1)( iii)( F) and 403.8( f)( 2)( vi).

What significant changes were made to the proposed rule?

Today's rule makes the following changes to the proposed rule:

Minimum evaluation frequency: Today's rule specifies that POTWs must evaluate at least once the SIU's need for a slug control plan or other action to control slug discharges. See 40 CFR 403.8( f)( 2)( vi). While the POTW may choose how frequently to assess slug related concerns, it is EPA's view that it is important to impose a minimum frequency of one time per SIU to ensure that each SIU receives at least one thorough evaluation. The provision specifies that this evaluation must have occurred within one year of the effective date of today's rule for SIUs identified as significant ( yet never evaluated for the need for a slug control plan) prior to the rule's effective date. Also, SIUs identified as significant after the effective date of the rule must be evaluated for the need for a slug control plan within one year of being identified as significant.

Notification of significant facility change: EPA also adds a requirement that SIUs must notify the POTW immediately of any changes at their facilities which may affect the potential for a slug discharge. This requirement is especially relevant in the case of those users for which the POTW has determined, from some prior assessment, that a slug control plan or other action is unnecessary. However, EPA emphasizes that this requirement affects all SIUs, even those that already have slug control plans or other measures in place. See 40 CFR 403.8( f)( 2)( vi). This provision places an affirmative duty on such users to provide the POTW with updated information on the potential slug risks that are posed by industrial process changes. This provision is consistent with, but differs from the existing notification of changed discharge in 40 CFR 403.12( j), which focuses on advance notice of change in the volume or character of pollutants in 41 the discharge itself.

4. Summary of Major Comments and EPA Response The following summarizes the major comments received and EPA's response.

Should POTWs be required to conduct annual inspections of SIUs to determine the adequacy of slug control plans? One commenter supported the proposed rule change, but recommended adding language to require the POTW to verify during an inspection that a slug control plan, if required, is adequate. EPA agrees with the commenter that the POTW should be assessing the adequacy of existing slug control plans during its annual inspection of SIUs. However, EPA has not included a specific requirement in the regulation to this effect since existing inspection and sampling guidance already recommends that POTWs assess the adequacy of slug control plans during the POTW's annual inspection.

EPA emphasizes that today's final rule does not alter the POTW's requirements to conduct annual inspections of its SIUs, nor has EPA changed its recommendations about how to assess slug related issues at each facility. According to EPA's Industrial User Inspection & Sampling Manual for POTWs ( 1994) ( http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf), POTW inspectors should ask SIU staff if they are familiar with slug control procedures, and request that a copy of the slug control plan be provided for an assessment of its adequacy. EPA's guidance document Control of Slug Loadings to POTWs ( 1991) ( http:// www. epa. gov/ npdes/ pubs/ owm021. pdf) recommends that inspectors verify compliance with slug control requirements and plans ( see p. 2 44). In addition, EPA's slug loading guidance indicates that   the inspector should ascertain the industrial user's status with regard to compliance with the Plan, report any deficiencies observed in the industrial user's current Plan, and suggest alternatives or modifications" ( see p. 2 44).

Can existing control measures or planning documents substitute for slug control plan requirements at SIU facilities? Several commenters, while supporting the proposal, requested that EPA clarify that existing spill containment procedures or plans may adequately fulfill the pretreatment requirements concerning slug control plans. EPA agrees with the commenter that there will be situations where existing containment and spill planning documents at an industrial user facility describe adequate means for protection against slug discharges. EPA recognizes that a number of existing requirements under other statutes and regulations could serve as components of slug control plans. For example, Spill Prevention, Control, and Countermeasures ( SPCC) plans may address some components of a slug control plan. A POTW could also consult existing Emergency and Hazardous Chemical Inventory reports ( EPCRA Section 312, 40 CFR 370) typically submitted to local fire marshals or other Local Emergency Planning Committee offices for the facility. If an SIU is covered by any of these pre existing plans, the POTW may accept such plans in partial or complete fulfillment of the slug control plan, as long as each element set forth in 40 CFR 403.8( f)( 2)( vi)( A)( D) is addressed in an acceptable manner in some document or collection of documents, and a reference to the need to comply with these procedures is included 42 in the user's control mechanism pursuant to 40 CFR 403.8( f)( 1)( iii)( F). However, EPA notes that many of these pre existing plans have been developed for purposes other than control of slug discharges to POTWs, and the POTW must carefully review the plans to ensure that they meet the requirements of a slug control plan and the needs of the POTW.

In summary, under today's rule, a POTW has the discretion to determine, based on an initial inspection or previous evaluations, that existing procedures and control measures at the facility make the development of a slug control plan unnecessary. The POTW should document this finding as part of its records, and, consistent with existing EPA guidance, should annually assess the adequacy of these existing procedures and control measures as part of its annual inspections. Also, implementation of these procedures or control measures should be included as requirements in the facility's control mechanism.

How should the POTW determine how often to conduct evaluations at individual facilities concerning whether a slug control plan is needed? One commenter pointed out that how frequently a POTW should evaluate the need for a slug control plan may vary for different facilities. The commenter emphasized that at some facilities, conducting such an evaluation once every two years may not be sufficient. Regarding the commenter's concerns about the frequency of slug discharge evaluations, under today's rule, each POTW will need to determine what evaluation frequency is appropriate for its program and/ or for individual facilities. EPA also recommends that POTWs consult with the Agency's guidance document, Control of Slug Loadings to POTWs ( 1991) ( http:// www. epa. gov/ npdes/ pubs/ owm021. pdf), which suggests different ways to prioritize industrial facilities according to slug discharge potential and strategies for assessing the adequacy of existing plans and programs. To ensure that POTWs are provided with sufficient notice of a change in slug discharge potential, EPA has added an additional requirement for SIUs, which are not required to develop a slug control plan, to notify the POTW immediately of any changes at their facilities affecting the need for plans or other actions. EPA believes that placing the affirmative duty on the SIUs to notify the POTW of such changes further reduces the potential for slug discharge in the time between on site inspections.

Although supporting the proposal, several commenters suggested that EPA adopt further criteria for determining when a slug control plan is necessary at an individual facility. Among the suggested criteria were the following: ( 1) slugs from an industrial facility violated the pretreatment requirements or otherwise harmed the POTW; or ( 2) the amount of stored materials, the absence of sufficient secondary containment, and the proximity of drains to the sewer create a significant risk of a harmful slug. EPA agrees with the commenter in general that criteria suggesting when a slug control plan should be developed would assist POTWs in making this decision. On the other hand, EPA decided that it should not develop rigid criteria in its regulation establishing when slug control plans should be required.

EPA emphasizes that a POTW is in the best position to make such determinations and, since such requirements will help ensure continued compliance with its NPDES permit, it is in the interest of the POTW to do so. However, in lieu of providing a list of strict criteria, EPA 43 suggests that POTWs and SIUs consult the guidance document, Control of Slug Loadings to POTWs ( 1991) ( http:// www. epa. gov/ npdes/ pubs/ owm021. pdf), for recommendations on significant factors and types of industries to consider in determining which facilities pose a greater risk of slug discharge, and, therefore, should be required to develop a slug control plan. For instance, the guidance document highlights the following as the most significant factors to consider: quantity and types of materials used or stored at an IU and their potential for causing violation of local limits or the general or specific prohibitions; potential for such materials to enter the sewer system and cause damage ( i. e., whether control measures are in place); and adequacy of existing controls to prevent any potential slug loading ( see p. 2 19). EPA points out, though, that the guidance also clarifies that these evaluations should be conducted on a plant by plant basis and that the list of factors and target industries provides generalizations from which to start. ( see p. 2 7).

In response to the commenter's recommended criteria, EPA agrees that facilities which have had slug discharges, thus violating the pretreatment requirements or otherwise harming the POTW, will need a slug control plan. The slug control plan requirements were adopted to provide POTWs with a mechanism to prevent slug related impacts. EPA is concerned that this criterion may suggest to POTWs that it is sufficient to wait for circumstances to arise ( e. g., an instance of interference at the treatment plant) before addressing the need for a slug control plan at a potentially higher risk facility. EPA does not agree that the only situations where an SIU should be required to develop a slug control plan are those where a violation of the POTW's pretreatment program requirements has occurred. Part of what the POTW must evaluate at each SIU is whether there is the " reasonable potential" for interference or pass through from a slug discharge, thereby necessitating a slug control plan or other preventative action. EPA suggests that waiting for a violation to occur before requiring a slug control plan conflicts with the proactive intent behind 40 CFR 403.8( f)( 2)( vi) and may result in unnecessary interference or pass through occurrences.

EPA does agree that the commenter's second suggested criterion, that the amount of stored materials, the absence of sufficient secondary containment, and the proximity of drains to the sewer create a significant risk of a harmful slug would be appropriate POTW considerations for requiring the development of a slug control plan. These considerations are contemplated in the above referenced guidance. EPA would, however, suggest that a more appropriate application of these criteria would require slug control plans when there is a significant risk of any slug discharge, not just a " harmful slug", as a result of the amount of stored materials, the absence of sufficient secondary containment, and/ or the proximity of drains to the sewer.

How does the rule affect the current practice of evaluating SIUs annually for the adequacy of slug controls? A few commenters were opposed to the proposal because they considered it to be unnecessary. These commenters emphasized the limited burden imposed by the current biannual review requirement and the current practice of conducting annual SIU inspections which focus on, among other things, the adequacy of controls or existing plans for addressing the potential for slug discharges. Another commenter objected to the proposal 44 because of concern that POTWs would no longer dedicate the necessary attention to evaluating SIU facilities for the potential for slug discharges.

The evaluation of slug control procedures and measures is already occurring at POTWs on an annual basis, typically during the inspection of the SIU. This practice is consistent with EPA's guidance document, Industrial User Inspection and Sampling Manual for POTWs ( 1994) ( http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf). EPA's modification of the frequency of the POTW's evaluation of the necessity of slug control plans should not affect the POTW's practice of conducting annual inspections of relevant slug control procedures and measures. The final rule changes do not absolve POTWs from the requirement to prevent disruptions caused by slug discharges. In many instances, operating conditions at an SIU will not have changed significantly since the issuance of its individual control mechanism and the facility will be in compliance with all of its permit conditions. Under these circumstances, the requirement to review and evaluate the need for a slug control plan or other preventative actions could be an unproductive use of resources by the POTW. In addition, today's revision to 40 CFR 403.8( f)( 1)( iii)( F) requires that each POTW evaluate the need for a slug control plan or other action at least one time at every SIU. Following this evaluation, the POTW may determine its own schedule for conducting further evaluations for the need for a plan.

In practical terms, EPA expects POTWs to take the following actions with regard to slug discharges: evaluate all of their SIUs at least once for the need for a slug control plan, conduct follow up evaluations for facilities not required to develop a slug control plans or take other actions as necessary, and inspect each SIU annually to determine the adequacy of and compliance with existing procedures and control measures. While today's revision may reduce the administrative resources currently devoted to biannual reviews for the need for a slug control plan, the POTW's overall level of oversight over slug discharges will not be reduced.

EPA also points out that Approval Authority audits and Pretreatment Compliance Inspections ( PCIs) of POTW pretreatment programs will offer a valuable opportunity to evaluate how today's revisions are being implemented. During these audits or PCIs, the POTW will need to demonstrate that each SIU has been evaluated at least once ( or that there is a plan to conduct such an evaluation within the coming year), and that where a slug control plan or other action was not deemed necessary, a plan to periodically re evaluate the SIU for the need for a plan or other action exists. The POTW may choose a specified frequency level to re evaluate the SIU, or it may choose to re evaluate the facility following a notification of changed discharge pursuant to 40 CFR 403.12( j) or 40 CFR 403.8( f)( 2)( vi). EPA notes that SIUs will now be required to notify the POTW of any changes at their facility that affect the need for a slug control plan or other actions, although POTWs still have the responsibility to ensure that these notifications have been made during the facility inspections. In addition, during the audit or PCI, the Approval Authority should determine whether the POTW is conducting an assessment of the SIU's on site procedures and measures to control for potential slug related discharges.

Does the slug control plan, if required, need to be included in the SIU's control 45 mechanism? One commenter was opposed to what it interpreted as EPA's requirement in 40 CFR 403.8( f)( 1)( iii)( F) to include the entire slug control plan document in the SIU's control mechanism. The commenter further emphasized that the slug control plan should be retained as a separate document, and suggested that the plan be incorporated by reference into the control mechanism requiring compliance with the approved plan.

EPA disagrees with the commenter as far as reading § 403.8( f)( 1)( iii)( F) to require the inclusion of the entire slug control plan in the SIU's control mechanism. Section 403.8( f)( 1)( iii)( F) provides that the control mechanism must include " requirements to control slug discharges." EPA expects that POTWs will include language in the control mechanism that requires control of slug discharges, rather than the terms of a particular SIU's plan. Including the entire slug control plan may prove to be administratively burdensome since changes made to the plan during the term of the control mechanism would potentially require that the control mechanism be modified, or be reopened and reissued.

E. Equivalent Concentration Limits for Flow Based Standards ( 40 CFR 430.6( c)( 5))

Today's amendment to the pretreatment regulations authorizes the use of concentrationbased limits in lieu of flow based mass limits for the facilities in the Organic Chemicals, Plastics, and Synthetic Fibers ( OCPSF) ( 40 CFR 414), Petroleum Refining ( 40 CFR 419), and Pesticide Chemicals ( 40 CFR 455) point source categories. The Control Authority may use the concentration limits listed in the categorical pretreatment standards for these two categories as an alternative to the current requirement to convert those concentration limits to flow based mass limits. Control Authorities establishing concentration based pretreatment standards instead of mass based limits must document that dilution is not being used as a substitute for treatment ( see Parts 403.6( d), 414.111( a), 419, and 455). Additionally, the Control Authority is required to adjust permit limits using the combined wastestream formula in Part 403.6( e) when the wastestream used for demonstrating compliance with the permit limits is mixed with non process wastewater or wastewater from other processes.

1. What are the current rules?

What is a flow based mass limit?

National categorical Pretreatment Standards establish limits on pollutants discharged to POTWs by specific industrial sectors. The standards establish limitations on the amount of pollutants to be discharged by individual dischargers in different ways for different categories. The regulations establishing Pretreatment Standards for new and existing indirect dischargers in the Organic Chemicals, Plastics, and Synthetic Fibers Point Source Category ( OCPSF), for new indirect dischargers in the Petroleum Refining point source category, and for new and existing indirect dischargers in the Pesticide Chemicals point source category currently require limits of certain pollutants to be expressed in terms of mass, based on the promulgated concentrated based standards and the average daily flow rate of the Industrial User's regulated process wastewater 46 ( see Parts 414.111( a), 419.17( b), 419.27( b), 419.37( b), 419.47( b), and 419.57( b), 455.26, 455.27). For an OCPSF indirect discharger, pesticide chemicals indirect discharger, or new petroleum refining indirect discharger, the Control Authority develops a mass limit by multiplying the applicable pollutant concentration that EPA promulgated in the effluent guidelines ( expressed in terms of mass of pollutant per volume of discharge) by the average daily flow rate of the Industrial User's regulated process wastewater ( expressed in terms of volume per day). The result is a permit limit on the mass of pollutants per day ( see July 9, 1993; 58 FR 36890).

The average daily flow rate should be based upon a reasonable measure of the Industrial User's average daily flow for at least a 30 day period ( see § 403.6( e)( 1)). Additionally, EPA " strongly urges the Control Authority to develop an appropriate process wastewater flow for use in computing the mass effluent or internal plant limitations based on water conservation practices," ( see July 9, 1993; 58 FR 36890). Finally, a permit may be modified during its term, either at the request of the permittee ( or another interested party) or on EPA's initiative, to increase or decrease the flow basis in response to a significant change in production ( 40 CFR 124.5, 122.62). A change in production could be an " alteration" of the permitted activity or " new information" that would provide the basis for a permit modification ( 40 CFR 122.62( a)( 1),( 2)) ( see July 9, 1993; 58 FR 36891).

Why was the mass limit approach developed?

Effluent guidelines may be specified in a number of ways including production normalized ( mass pollutant/ production unit) and concentration based limitations ( mass pollutant/ volume of wastewater). These two types of effluent guidelines limits can be converted to a mass based standard by using a reasonable measure of the Industrial User's actual long term daily production ( for production normalized limitations) or the Industrial User's actual long term average daily flow rate ( for concentration based limitations). EPA prefers setting production normalized limitations, where feasible, since production normalized limitations can require flow reduction and reduces any potential for the substitution of dilution for treatment. Specifically, production normalized limitations are calculated from production normalized flows ( volume of wastewater/ production unit) and incorporate wastewater flow reductions representing Best Available Technology Economically Achievable ( BAT) ( technology basis for Pretreatment Standards for Existing Sources, or PSES) or New Source Performance Standards ( technology basis for Pretreatment Standards for New Sources, or PSNS).

EPA has established concentration based standards when production and achievable wastewater flow cannot be correlated nationally. EPA explained how to determine mass limits for such standards in the preamble to the proposed Organic Chemicals, Plastics, and Synthetic Fibers ( OCPSF) regulation ( see March 21, 1983; 48 FR 11828) and in the supporting Technical Development Document ( EPA 440 1 83 009 b, February 1983, Page IX 2). A mass limit is developed from the concentration based standard by multiplying the promulgated pretreatment standard ( expressed as a concentration) by the Industrial User's actual long term average daily flow rate. This approach re enforces the requirements of the combined wastestream formula ( see 47 § 403.6( e)) to minimize the potential for dilution of process wastewaters by non process wastewater. The combined wastestream formula of Section 403.6( e) applies to indirect dischargers where process wastewater is mixed prior to treatment with wastewater other than that generated by the regulated process.

The combined wastestream formula was amended on May 17, 1984 to provide the Control Authority with the discretion to change the designation of boiler blowdown streams and noncontact cooling water streams from " dilution" to " unregulated" streams. The individual industrial user must show that these " dilution" streams do contain pollutants and treatment will reduce the discharge of these pollutants. The streams could then be designated as " unregulated" wastestreams since no national standards exist for these streams. This usually results in the development of a less stringent alternative limitation than if these same streams remained defined as dilution streams ( OCPSF comments response document: Outline Code: CA03   85, Comment # 6).

What are the problems with mass limits based on flow?

Flow based mass limits can, however, be difficult for the Control Authority to implement. To develop a flow based mass limit, the Control Authority must determine the average daily flow rate of the Industrial User's regulated process wastewater and then multiply that value by the appropriate promulgated concentration standard. This may be difficult in situations where the facility has highly variable production that leads to flows that often vary week to week or day to day. This is especially true for smaller facilities where: ( 1) the average daily flow rate of the Industrial User's regulated process wastewater may be infrequent or low and difficult to monitor; and ( 2) production tends to be more variable as the installation of equipment to provide flow equalization may not be practical.

In addition, testing for compliance with the flow based mass limit requires having accurate information on the flow from all regulated processes at the time the sample is taken. Testing for compliance with a concentration limit only requires taking the wastewater sample and comparing the sampled concentration to the limit. In particular, since promulgation of the OCPSF pretreatment standards, there have been difficulties in getting Control Authorities and OCPSF facilities to correctly calculate flow based mass limits, and to provide necessary data to determine compliance with the standards. Deficiencies in permits and control mechanisms have in the past hindered enforcement actions against these facilities. Enforcing mass based standards also becomes more complicated because there is an additional factor in the formula to calculate massbased limits. In order to measure compliance, both flow and concentration of the pollutant needs to be accurate and verified in order to produce legally enforceable mass based results.

May alternative limits be developed for flow based categorical standards?

Currently, 40 CFR 403.6( c) allows Control Authorities to apply an equivalent concentration limit in addition to a current mass limit to implement a Pretreatment Standard. 48 However, the regulations do not allow equivalent concentration limits in lieu of mass limits when the Pretreatment Standard requires a mass limit to be calculated from the promulgated concentration based standards and the average daily flow rate of the Industrial User's regulated process wastewater.

2. What changes did EPA propose?

EPA proposed to allow Control Authorities to use promulgated concentration based limits instead of flow based mass limits in establishing limits for industrial users in the OCPSF, Petroleum Refining, and Pesticide Chemicals point source categories. EPA proposed that the Control Authority would be allowed to apply such equivalent concentration limits only if the flow from the facility is so variable that the development of mass limits is impractical. EPA stipulated that 40 CFR 403.6( d) would continue to prohibit facilities from increasing flow in order to meet their concentration limits through dilution.

3. What changes is EPA finalizing in today's final rule?

The final rule allows Control Authorities to use concentration based limits instead of flowbased mass limits for new and existing indirect dischargers in the OCPSF point source category, new indirect dischargers in the Petroleum Refining point source category, and new and existing indirect dischargers in the Pesticide Chemicals point source category. EPA is not limiting the Control Authority's authority to develop concentration limits to circumstances in which the Control Authority determines that the facility's flow is A so variable as to make mass limits impracticable.@ EPA notes that Section 40 CFR 403.6( d) will continue to prohibit facilities from increasing flow in order to meet their concentration limits through dilution. As with other concentration limits, the Control Authority should be certain that dilution is not occurring and that the discharge represents regulated process wastewater flows. The concentration may need to be adjusted using the combined wastestream formula in 40 CFR 403.6( e) if the wastestream is mixed with non process wastewater or wastewater from other processes.

New 40 CFR 403.6( c)( 5), applicable only to facilities in the OCPSF, Petroleum Refining, and Pesticide Chemicals point source categories, requires Control Authorities to document that dilution is not being substituted for treatment. To verify that equivalent concentration limits are not subsequently being met through use of dilution flows, Control Authorities should note that 40 CFR 403.12( e)( 1) requires categorical Industrial Users to provide information regarding maximum and average daily flows in their periodic reports, and enables them to require more detailed flow data as necessary. Using this authority, EPA recommends that Control Authorities consider specifying appropriate flow monitoring requirements and including evaluation of flow data in the review of periodic reports for Industrial Users subject to equivalent concentration standards. This will enable Control Authorities to determine if there have been changes in flows that may indicate dilution, such as increases in process, non process or overall flows, especially those not accompanied by production increases. 49 When are the equivalent concentration limits effective?

EPA notes that flow based mass standards, like all national categorical Pretreatment Standards, are self implementing for new and existing indirect dischargers in the OCPSF point source category and for new indirect dischargers in the Petroleum Refining point source category. Facilities to which these standards are applicable must comply with the flow based mass standards unless a permit or other control mechanism is issued by the Control Authority which establishes equivalent concentration limits under 40 CFR 403.6( c)( 5). Where the Control Authority has not issued a control mechanism that establishes categorical concentration based limits or has not correctly transcribed such limits into the facility's control mechanism, the Industrial User must comply with the default flow based mass limits as established in the applicable categorical Pretreatment Standard.

EPA notes that for the Pesticide Chemicals point source category, the applicable concentration based limits are self implementing. Where the Control Authority has not issued a control mechanism that correctly establishes flow based mass limits as required, the Industrial User must comply with the default concentration based limits as established in the categorical Pretreatment Standard.

EPA emphasizes that for facilities in the OCPSF, Petroleum Refining, and Pesticide Chemicals point source categories, where the Control Authority has properly authorized the use of an equivalent concentration limit and has incorporated that limit into the Industrial User's control mechanism, the concentration limit could replace the mass limit. The Control Authority may also determine that both the flow based mass limit as well as the concentration based limit are applicable and when incorporated into the issued control mechanism, the Industrial User would have to comply with both limits. As with other equivalent concentration limits, as currently provided in 40 CFR 403.6( c), the equivalent limits being authorized under today's final rule are Pretreatment Standards for the purposes of Sec. 307( d) of the Clean Water Act and are federally enforceable.

4. Summary of Major Comments and EPA Response A majority of the commenters supported the proposed rule as written, and most of the remaining commenters stated qualified support. Only one commenter opposed the proposal. The following section summarizes the most significant comments received and EPA's response.

Is Approval Authority review required of an industrial user= s proposed concentration limit prior to Control Authority approval? A total of 22 commenters disagreed that it would be appropriate to require Approval Authority review of an industrial user's proposed concentration limit prior to Control Authority approval. The primary reasoning stated was that such a requirement is not necessary and would create additional burden. 50 EPA notes that this provision is intended to allow the permit limit to be expressed in alternate units. It is not anticipated that this revision will change the Control Authority= s enabling legislation to issue and enforce a control mechanism. As such, EPA does not consider this provision to be a modification of a POTW Pretreatment Program under 40 CFR 403.18, and, therefore, finds that a POTW's use of this provision is not subject to the specified approval procedures in this section. The new equivalent limit is subject to review as part of routine Approval Authority oversight activities, such as a Pretreatment Compliance Inspection or a Control Authority audit. In accordance with current regulations, industrial user control mechanisms and information necessary for determining permit limitations and compliance must be publicly available.

Is this provision limited to highly variable flows? Numerous commenters addressed the question of whether this provision should only be applied to highly variable flows as well as how to define the term A highly variable flow.@ A total of 12 commenters stated that the rule should not be limited to only highly variable flows. Many mentioned the existence of factors in addition to highly variable flows that make implementation of flow based mass limits impractical, such as the cost of obtaining accurate samples or the difficulty of sampling at facilities with very low flows. Ten commenters suggested that the Control Authority have the ability to define A highly variable flows@ on a case by case basis since the basis for such a determination is highly site specific and can vary from seasonal variations in flow to hourly variations in flow. Ten commenters thought that a 20 percent deviation from average flow is an adequate measure for A highly variable flow,@ while five commenters requested that EPA not specify a definition for A highly variable flow@ in the regulations.

EPA acknowledges that the there are numerous factors, many which are site specific, involved in determining that a facility has " highly variable flow( s)", and agrees that it would be difficult to establish a clear cut definition of " highly variable flow" that would apply to all facilities. To be consistent with the goals of providing flexibility in the Pretreatment Streamlining rule, and to support the Control Authority's discretion on this site specific issue, EPA has decided to allow Control Authorities to determine when the acceptable circumstances exist to allow the use of concentration limits.

Is this provision consistent with the Clean Water Act? The commenter that opposed this provision stated that EPA lacks the authority to create a variance or an alternative implementation mechanism and therefore will violate sections 307 and 402 of the Clean Water Act. The commenter also questioned the need for this proposed change, suggested that it will interfere with ongoing enforcement of the categorical standards and the statutory deadlines for achieving them, and suggested that the record does not demonstrate that this proposed change will protect POTWs and the environment.

EPA is promulgating the changes to its pretreatment regulations in part under section 307( b) of the Clean Water Act. Section 307( b) clearly authorizes EPA from time to time to revise pretreatment standards as A control technology, processes, operating methods or other 51 alternatives change.@ Therefore, today= s action is not in violation of section 307( b) to the extent this provision amends the pretreatment standards for the OCPSF, the Petroleum Refining, and the Pesticide Chemicals Point Source Categories. As EPA has explained, the amendments to the regulations will facilitate both user's compliance and POTW oversight. EPA notes that compliance evaluation and enforcement will be more straightforward and less burdensome with new equivalent concentration limits.

Moreover, the current regulations prohibit introduction of pollutants that will adversely affect POTW operations and receiving waters quality. Currently, 40 CFR 403.5 requires approved pretreatment programs and POTWs receiving pollutants from industrial users with potential to pass through or interfere with the POTWs' operations to develop and implement local limits to protect the POTW operations and prevent pass through and interference. Consequently, the use of concentration limits in lieu of mass limits would not be authorized if it resulted in a violation of local limits approved under 40 CFR 403.5. Furthermore, this provision may be implemented only following determination of its feasibility by Control Authorities, and not unilaterally by industrial users. Control Authorities' local limits will continue to ensure protection of the POTW operations and its receiving environment.

F. Use of Grab and Composite Samples ( 40 CFR 403.12( b), ( d), ( e), ( g), and ( h))

This section discusses: 1) the application of minimum required grab samples for pH, cyanide, total phenols, oil and grease, sulfide, and volatile organics to the periodic compliance reports; 2) when a time proportional sample may be used instead of a flow proportional sample; 3) when multiple grab samples may be composited prior to analysis; 4) whether four grab samples are required whenever grab sampling is appropriate; and 5) the sampling of facilities that discharge less than 24 hours per day. Other issues raised by commenters are also discussed.

1. What are the existing rules?

What are " grab samples"?

A grab sample is "... a sample which is taken from a wastestream without regard to the flow of the wastestream and over a period of time not to exceed 15 minutes" ( Industrial User Inspection and Sampling Manual for POTWs, EPA 831/ B 94 001, April 1994, http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf). Grab samples of volatile organic compounds ( VOCs) must be collected almost instantaneously ( i. e., less than 30 seconds of elapsed time) and properly preserved ( Comparison of Volatile Organic Analysis Compositing Procedures, EPA 821/ R 95 035, September 1995). An analysis of an individual grab sample provides a measurement of pollutant concentrations in the wastewater at a particular point in time. Grab samples are usually collected manually, but can be obtained with a mechanical sampler.

Grab samples are required in order to accurately analyze those pollutant parameters that may be affected by biological, chemical, or physical interactions and/ or exhibit marked physical 52 and compositional changes within a short time after collection. Grab samples should be used when: 1) wastewater characteristics are relatively constant; 2) parameters to be analyzed are likely to be affected by the compositing process, such as the procedures used for oil and grease; 3) composite sampling is infeasible or the compositing process is liable to introduce artifacts of sampling; and 4) the parameters to be analyzed are likely to change with storage. In particular, accurate determination of pH, temperature, total phenols, oil and grease, sulfide, volatile organic compounds, and cyanide requires properly collecting and carefully preserving grab samples.

What are composite samples?

A composite sample is formed by mixing discrete samples or " aliquots." For a " flow proportional" composite sample, each individual aliquot is collected after the passage of a defined volume of discharge ( e. g., every 2,000 gallons). For a " time proportional" composite sample, the aliquots are collected after the passage of a defined period of time ( e. g., once every two hours), regardless of the volume or variability of the rate of flow during that period. Flow proportional compositing is usually preferred when effluent flow volume varies appreciably over time. The number of discrete samples necessary for a composite sample to be representative of the discharge depends upon the variability of the pollutant concentration and the flow.

Automatically collected composite samples are usually preferred to collecting grab samples and then manually compositing the grabs into a single sample. Possible handling errors made during the compositing process could yield a sample that is not truly representative of the discharge. However, composite samples can be prepared from manually collected grab samples if each grab contains a fixed volume that is retrieved at intervals that correspond to the periods of wastewater discharge or time of the facility= s operation.

When may the requirement for flow proportional composite samples be waived?

The regulations in effect prior to today's rule allowed Control Authorities to waive the requirement for flow proportional compositing of samples for baseline monitoring reports and 90 day compliance reports in limited circumstances. These regulations allowed the Control Authority to accept sample data that are obtained from time proportional composite sampling or a minimum of four grab samples if flow proportional sampling is infeasible ( e. g., the facility cannot accurately measure flow) and the industrial user demonstrated that these alternative sampling techniques will provide a representative sample of the effluent ( 40 CFR 403.12( b)( 5)( iii)). The section on periodic compliance reports was silent on the subject of grab and flow proportional sampling.

2. What changes did EPA propose?

EPA proposed to clarify the sampling requirements in 40 CFR 403.12 in the following ways: 53 Do the sampling requirements apply to periodic reports on continued compliance? EPA proposed to extend the requirements of 40 CFR 403.12( b)( 5)( iii), which were explicitly applicable to the baseline monitoring reports and 90 day reports required by 40 CFR 403.12( b) and ( d), to the periodic reports required in 40 CFR 403.12( e) and ( h). These changes would be accomplished by consolidating the new requirements for all of the reports in 40 CFR 403.12( g). Redundant sections would be removed.

Is a minimum frequency required for grab samples? EPA proposed that for periodic monitoring reports, a minimum of four grab samples would not need to be taken in all instances to measure pH, cyanide, total phenols, oil and grease, sulfides, and volatile organic compounds. Instead, Control Authorities would have the flexibility to determine the appropriate number of grab samples required for periodic compliance reports. For new facilities, the industrial user would still be required to take a minimum of four grab samples to measure pH, cyanide, total phenols, oil and grease, sulfide, and volatile organic compounds to meet baseline monitoring and 90 day compliance report requirements. For existing facilities, where historical sampling data are available, the Control Authority may authorize a lower minimum.

When and what type of grab samples can be manually composited? EPA proposed to explicitly state that compositing of certain types of grab samples prior to their analysis would be permitted.

When can time proportional or grab samples be used in lieu of flow proportional composite samples? EPA proposed that Control Authorities may authorize time proportional or grab sampling in lieu of flow proportional sampling as long as the samples are representative of the discharge.

What are the sampling requirements for those facilities that do not discharge continuously? EPA proposed language intended to clarify that, although a " 24 hour composite sample" must be taken within a 24 hour period, the sample should only be collected during that portion of the 24 hour period that the industrial user is discharging from the regulated process and/ or from the treatment unit.

3. What changes are being finalized by EPA in today= s rule?

EPA is finalizing language intended to clarify the sampling requirements in 40 CFR 403.12. Specific changes to the regulations, as well as pertinent details related to their implementation, are discussed below.

Do the sampling requirements apply to periodic compliance reports? Today's rule finalizes the extension of sampling requirements, which previously were only explicitly applicable to the baseline monitoring reports and 90 day reports required by 40 CFR 403.12( b) and ( d), to the periodic reports required in 40 CFR 403.12( e) and ( h). These changes are accomplished by 54 consolidating the new requirements for all of the reports in 40 CFR 403.12( g). Redundant sections are removed.

Is a minimum frequency required for grab samples? The final regulatory changes eliminate the requirement that a minimum of four grab samples be taken in all instances to measure pH, cyanide, total phenols, oil and grease, sulfides, and volatile organic compounds. Control Authorities will have the flexibility to determine the appropriate minimum number of grab samples industrial users are required to take. The Control Authorities will be responsible for documenting the site specific circumstances in the industrial user= s file. New facilities and facilities that make changes or install new treatment are still required to take a minimum of four grab samples to measure pH, cyanide, total phenols, oil and grease, sulfide and volatile organic compounds to meet baseline monitoring and 90 day compliance report requirements. For facilities where historical sampling data are available, the Control Authority may authorize a lower minimum number of grab samples.

There are some cases where a single grab sample can be reasonably expected to be representative of a discharge. Appendix V to the EPA guidance ( Industrial User Inspection and Sampling Manual for POTWs, EPA 831/ B 94 001, April 1994, http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf) lists cases where a single grab sample may appropriately be substituted for a single composite sample, including small batch discharges. For example, a homogeneous batch discharge is consistent with existing guidance on the appropriate use of a single grab sample.

When and what type of grab samples can be manually composited? Today= s final rule clarifies that multiple grab samples for cyanide, total phenols, sulfide, oil and grease, and volatile organic compounds collected during a 24 hour period may be composited prior to analysis. Control Authorities also will be allowed to authorize manually composited grab samples for other parameters that are unaffected by compositing procedures. Using protocols ( including appropriate preservation) specified in 40 CFR Part 136 and appropriate EPA guidance, EPA clarifies in the rule that multiple grab samples collected during a 24 hour period may be composited prior to the analysis as follows: for cyanide, total phenols, and sulfides, the samples may be composited in the laboratory or in the field; for volatile organics and oil and grease, the samples may be composited in the laboratory.

It is important that a composite sample provides an accurate representation of the pollutant in the wastewater. The composite sample should provide analytical results that are comparable to averaged results of the individual grab samples taken over a specific time interval. In all cases where a series of grab samples is manually composited, those parameters that have preservation requirements in 40 CFR Part 136 must be properly preserved and/ or stored at the time of collection as required by the specific analytical method employed prior to compositing. In addition, EPA wishes to reaffirm that some pollutants are not amenable to the compositing process. For example, total residual chlorine, pH, and temperature samples cannot be " composited" under any circumstances because the results would be changed by the compositing 55 process. Today's final rule does not allow Control Authorities to authorize composite samples for these parameters.

Although analytical procedures for compositing oil and grease samples have been developed, the general consensus among laboratory experts is that current techniques do not provide consistently reliable results. However, continuing advances in analytical technology may provide methodologies that will make accurate compositing of oil and grease samples technically less cumbersome and more cost effective in the future. Under today's rule, the Control Authority has the flexibility to allow industrial users to submit data from composited oil and grease samples as long as the samples were composited in the laboratory and the sampling and analytical procedures used are sanctioned by EPA in 40 CFR Part 136.

EPA guidance ( Industrial User Inspection and Sampling Manual for POTWs, EPA 831/ B 94 001, April 1994, http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf) describes procedures for manually compositing individual grab samples that will provide accurate results. The reader should also consult the regulations in 40 CFR Part 136 to identify the accepted analytical protocols for specific classes of compounds or individual parameters. A separate guidance manual ( Comparison of Volatile Organic Analysis Compositing Procedures, EPA 821/ R 95 035, 1995, http:// www. epa. gov/ clariton/ clhtml/ pubtitleOW. html) discusses procedures for accurate compositing of volatile organic compounds.

When can time proportional or grab samples be used in lieu of flow proportional composite samples?

Today= s final rule will allow Control Authorities to waive the requirement that industrial users collect flow proportional samples. The regulation no longer requires Control Authorities to require the industrial user to demonstrate that flow proportional samples are " infeasible." The alternate sampling ( time proportional composite samples or grab samples) must still be representative of the discharge and would need to be documented by the Control Authority in the industrial user= s records.

If the Control Authority doubts the equivalency of the two sampling methodologies ( time proportional versus flow proportional samples), because of highly variable flow or other complicating factors, it still may require the industrial user to demonstrate that the time proportional or grab samples are representative of the discharge prior to allowing the industrial user to submit such samples. Where time proportional composite sampling or grab sampling is authorized by the Control Authority, the samples must be representative of the discharge and the decision to allow the alternative sampling must be documented in the individual industrial user records for that facility. Documentation should include the use of statistical analysis of grab and composite data sets. See for example, the March 2, 1989, Office of Water Regulations and Standards ( OWRS) Memorandum to Region 9 describing the results of a statistical analysis of sampling data from a single industrial facility. [ http:// www. epa. gov/ region09/ water/ pretreatment/ program_ impl. html] These sampling data 56 included both individual grab and flow proportional composite sampling obtained during different, non overlapping time periods. After reviewing the data, OWRS concluded that the composite and grab sample data sets displayed similar patterns for lead, copper, and total metals. In fact, the analyses did not find any statistically significant difference in the concentration values measured between the grab and composited data. Furthermore, additional statistical tests of the two data sets indicated that the means and variances for each pollutant were similar. Control Authorities must ensure that compliance samples are taken with sufficient care to produce evidence admissible in enforcement proceedings or in judicial actions as required by the section modified today at 40 CFR 403.8( f)( 2)( vii).

What are the sampling requirements for those facilities that do not discharge continuously?

As will be discussed below in the response to comments section, the final rule does not include the sentence in the proposed rule that read, " For those industrial user discharges subject to categorical pretreatment standards that do not operate on a 24 hour per day schedule, the samples must be collected at equally spaced intervals during the period that process wastewater is being discharged." EPA interprets a " day" to be a 24 hour period which does not have to occur within a calendar day. This interpretation is consistent with the definition of " daily discharge" in the NPDES regulations at 40 CFR 122.2. Daily discharge means the " discharge of a pollutant" measured during a calendar day or any 24 hour period that reasonably represents the calendar day for purposes of sampling. During parts of the day when there is no discharge of process wastewater, standing water should not be disproportionately sampled and analyzed as it would not be representative of the discharge from the facility. As always, the Control Authority must prescribe a sampling protocol that produces representative results. The selected protocol should take into consideration all of the operation conditions and the physical configuration of the industrial user facility.

What significant changes were made to the proposed rule?

EPA did not make significant changes to the proposed rule. The changes made from the proposal to the final rule include minor wording changes, a clarification to compositing methods, the reinstatement of a sentence that was removed in the proposal, and the removal of a sentence from the proposal.

The changes ( other than minor wording changes intended to provide clarification) are as follows:

The following sentence, which had been deleted in the proposal, is returned to the regulations: " The Control Authority shall require that frequency of monitoring necessary to assess and assure compliance by Industrial Users with applicable Pretreatment Standards and Requirements." This sentence had been taken out in the proposed rule. However, because the sentence adds clarity, EPA has decided to retain it. The rationale is discussed in the response to comments section below. 57 The following sentences at 40 C. F. R. 403.12 ( g)( 3) were removed from the regulations: " For those industrial user discharges subject to categorical pretreatment standards that do not operate on a 24 hour per day schedule, the samples must be collected at equally spaced intervals during the period that process wastewater is being discharged. Multiple grab samples for cyanide and volatile organic compounds that are collected during a 24 hour period may be composited in the laboratory prior to analysis using protocols specified in 40 CFR Part 136 and appropriate EPA guidance." The rationale is discussed in the response to comments section below.

For parameters that require grab sampling, EPA explicitly states which parameters may be composited in the field and the laboratory and which parameters may only be composited in the laboratory. This addition further clarifies the issue of compositing for samples that require collection by grab methods in order to preserve sample integrity.

4. Summary of Major Comments and EPA Response Commenters were generally supportive of the sampling changes that EPA proposed. Some of the comments requested further clarification of issues. The following section summarizes EPA's response to these comments.

Will the final rule on compositing increase workload for sampling personnel? A commenter stated that manually compositing cyanide and volatile organics samples should be avoided for sample integrity and workload increase.

Regardless of whether multiple grab samples are individually analyzed or composited, samples must be properly preserved. Therefore, any workload change will likely occur at the laboratory, and increased workload for compositing the sample would be offset by decreased workload for analysis. EPA further clarifies in the final rule which parameters currently may be composited in the laboratory and which ones may be composited in the field. Under the current EPA approved methods, oil and grease, and volatile organics may only be composited in the laboratory. Whether samples are composited in the lab or the field, sample integrity must be preserved, including preserving each grab sample in accordance with 40 CFR Part 136.

May industrial users determine the appropriate sampling flexibility without Control Authority approval? Industrial users commented that EPA should give more flexibility to industrial users to determine what sampling schemes are appropriate for their facility. EPA disagrees. Control Authorities are responsible for ensuring that compliance samples are taken with sufficient care to produce evidence admissible in enforcement proceedings or in judicial actions as required by 40 CFR 403.8( f)( 2)( vii) and for ensuring compliance by IUs with Pretreatment Standards and Requirements. To the extent that sampling is representative of the discharge, the Control Authorities will be able to determine the appropriate sampling flexibility. The Control Authorities retain the responsibility for documenting site specific circumstances and 58 allowing alternate sampling by including the alternate sampling in the industrial user control mechanisms.

May Control Authorities determine the appropriate number of grab samples for baseline monitoring and 90 day compliance reports? EPA requested comment on whether Control Authorities should be allowed the flexibility to determine the appropriate number of grab samples required to meet baseline monitoring and 90 day compliance report requirements for facilities without historical sampling data. Commenters supported the proposal to eliminate the requirement that a minimum of four grab samples be taken to measure pH, cyanide, total phenols, oil and grease, sulfides, and volatile organic compounds. Commenters stated that Control Authorities should be given flexibility to determine the appropriate number of grab samples required to meet reporting requirements, but did not provide concrete reasons as to how this would ensure that the sampling was representative of the discharge.

EPA stresses that the flexibility should only be provided to the extent that the sampling is representative. The Control Authority will be responsible for documenting site specific circumstances and allowing alternate sampling in the industrial user control mechanisms. Baseline Monitoring Reports ( BMRs) will likely provide the first samples for a parameter, and 90 day compliance reports will provide samples after any treatment has been added. Therefore, it is likely that at a minimum this data will be needed in order to document that alternative sampling is representative. Because it is unlikely that a Control Authority could properly document that sampling is representative without data from BMRs and 90 day compliance reports, EPA retains the requirement for a minimum of four grab samples for BMRs and 90 day compliance reports in order to document potential future sampling decisions for new facilities. For existing facilities where there is historic data representative of the current discharge, Control Authorities may authorize a lower minimum number of grab samples for pH, cyanide, total phenols, oil and grease, sulfides, and volatile organic compounds. Of course, where there has been a change to existing facilities, for example, the addition of treatment, historic data that does not represent the current discharge would not be able to be used to justify a lower minimum of grab samples.

As stated previously, Control Authorities must ensure that compliance samples are taken with sufficient care to produce evidence admissible in enforcement proceedings or in judicial actions as required by 40 CFR 403.8( f)( 2)( vii). To further strengthen this point, the following sentence, which the proposed rule would have deleted, is retained in 40 CFR 403.12( g)( 3): " The Control Authority shall require that frequency of monitoring necessary to assess and assure compliance by Industrial Users with applicable Pretreatment Standards and Requirement." Sampling and analysis techniques must yield analytical data that is representative of the discharge. The Control Authority will still need to document how alternate sampling techniques are representative of the discharge, and may require that more than four grab samples be taken and separately analyzed to ensure that sampling is representative. Where the Control Authority cannot verify that previous techniques were representative, such data will not support the use of this alternative practice. In those cases, Control Authorities may need to take side by side samples and/ or perform a statistical analysis to show that there is not a statistically significant 59 difference in the concentration values measured between individual grab and flow proportional composite sampling obtained during different, non overlapping time periods.

Will EPA define " representative" sampling in the rule? Commenters noted that the rules repetitively use the concept of A representative@ samples, but do not precisely define what the samples are supposed to represent. In the proposed rule preamble ( 64 FR 39582, July 22, 1999), EPA indicated that it would not offer a comprehensive definition of what constitutes a A representative sample@ or specific guidance. EPA is not defining A representative sample@ in the final rule. Guidance on the subject may be found in Industrial User Inspection and Sampling Manual for POTWs ( EPA, 1994, http:// www. epa. gov/ npdes/ pubs/ owm0025. pdf).

Sampling methods to yield a representative sample may vary depending on the site specific situations of an individual discharger and the parameter that must be analyzed. Issues for the Control Authority to consider and document in prescribing sampling protocols include: ( 1) the appropriate sampling period ( e. g., 24 hours or during the period of discharge); ( 2) use of flow proportional versus time proportional methods; ( 3) use of grab samples versus composite samples; ( 4) use of grab samples for pH monitoring; ( 5) use of grab samples for degradable and volatile parameters; ( 6) allowing manual compositing of samples when the methodology is approved by EPA ; and ( 7) applying the criteria to instantaneous, daily maximum, and monthly average limits.

Is EPA providing further clarifying language for collection of samples during process wastewater discharges in the final rule? A commenter asked EPA to clarify whether a sample taken during a 24 hour period must be taken during a calendar day, or whether a sample may be taken over the course of two days. For example, if a facility discharges 24 hours per day, must the sample be taken from midnight to midnight, or may it be taken for other twenty four hour periods ( e. g., noon to noon)?

EPA interprets a " day" to be a 24 hour period and does not require that it occur within a calendar day. This is consistent with the definition for A daily discharge@ in the NPDES regulations at 40 CFR 122.2. Daily discharge means the A discharge of a pollutant@ measured during a calendar day or any 24 hour period that reasonably represents the calendar day for purposes of sampling. For pollutants with limitations expressed in units of mass, the A daily discharge@ is calculated as the total mass of the pollutant discharged over the day. For pollutants with limitations expressed in other units of measurement, the A daily discharge@ is calculated as the average measurement of the pollutant over the day. This is existing policy and was not proposed to be included in the rule, and therefore has not been added to the final rule. EPA recognizes that Control Authorities may define a more specific sampling period.

Another commenter asked for EPA to clarify whether a sample may be taken over the course of two calendar days in other circumstances. For example, if a facility discharges from 7: 00 AM to 7: 00 PM, must a sample be taken from 7: 00 AM to 7: 00 PM, or may a sample be taken from noon on one day to noon on the next day so long as only regulated wastewater is 60 sampled? In the example provided, the sampling for compliance would need to be representative of the categorical process discharge, and would need to account for other factors such as ensuring that stagnant water is not sampled if the facility is not discharging, and that process wastewater is not being discharged during the 7: 00 PM to 7: 00 AM period ( for instance in an overtime situation). Where a sampler is placed from noon to noon, and wastewater samples ( with volume proportionate to discharge) are only collected during the discharge period ( e. g., there is not a process wastewater discharge, and no samples are collected from 7: 00 PM to 7: 00 AM), and the samples are properly preserved, then it is likely that the sample would be appropriate for use to determine compliance during a 24 hour period. Since this example addresses a site specific situation, EPA is not inclined to revise the rule to address one particular set of circumstances. While other industries may have similar situations, the Control Authorities will need to consider all of the site specific circumstances in detailing the sampling requirements for the facility in the individual industrial user= s control mechanism.

A commenter expressed concern with the proposed language pertaining to required sampling periods. The section originally clearly pertained only to sampling required for reporting under subsections 40 CFR 403.12( b), ( d) and ( e), of all categorical streams. As revised in the proposal, the requirements also apply to reports required under subsection ( h) as well as to all other non categorical waste streams. The commenter stated that the discussion in the preamble to the proposed rule seemed to indicate these very specific requirements only apply to categorically regulated wastestreams. However, the commenter indicated that this intent was not adequately stated in the regulation itself.

The commenter went on to state, " Local limits are developed based on total daily average influent loadings and total daily flows from all sources tributary to the receiving treatment plant. Many IUs, particularly larger ones, will have wastewater flows, from sources such as cooling systems, boilers, etc that continue throughout the 24 hour day, as well as flows from maintenance and clean up activities that often occur during non process periods. In some cases, continuing composite sampling during these ` off process' periods may, in fact, reduce the daily average concentration of a pollutant. In other cases, pollutant discharges during maintenance or clean up activities, may contribute higher levels of pollutants than during normal processing periods. In either case, to determine compliance with local limits, it seems sampling should be conducted throughout the period of discharge, regardless of whether or not ` process' operations are occurring the entire time."

In response, EPA removed the sentence from the proposed rule that read, " For those industrial user discharges subject to categorical pretreatment standards that do not operate on a 24 hour per day schedule, the samples must be collected at equally spaced intervals during the period that process wastewater is being discharged." It would be too complicated to try to address all local limits variations in this section of the regulation, and as indicated by the commenter, the proposed language did not clarify the issue.

G. Significant Noncompliance Criteria ( 40 CFR 403.8( f)( 2)( viii)) 61 1. What were the rules in effect prior to today's rule?

How is " Significant Noncompliance" ( SNC) currently defined?

40 CFR 403.8( f)( 2)( vii) defines " Significant Noncompliance" ( SNC), as it applies to industrial users to include violations that meet one or more of eight criteria. The criteria are: ( 1) chronic violations of discharge limits ( where 66 percent or more of all measurements taken during a six month period exceed the daily maximum limit or the average limit for the same pollutant parameter); ( 2) technical review criteria ( TRC) violations ( where 33 percent or more of all measurements for each pollutant parameter taken during a six month period equal or exceed the product of the daily maximum limit or the average limit multiplied by the applicable TRC ( TRC equals 1.4 for BOD, TSS, fats, oil and grease and 1.2 for all other pollutants except pH)); ( 3) any other violation of a pretreatment effluent limit that the Control Authority determines has caused, alone or in combination with other discharges, interference or pass through; ( 4) any discharge of a pollutant that has caused imminent endangerment to human health, welfare or to the environment or has resulted in the POTW= s exercise of its emergency authority to halt or prevent such a discharge; ( 5) failure to meet, within 90 days after the schedule date, a compliance schedule milestone contained in a local control mechanism or enforcement order for certain activities; ( 6) failure to provide required reports within 30 days after the due date; ( 7) failure to accurately report noncompliance; and ( 8) any other violation or group of violations which the Control Authority determines will adversely affect the operation or implementation of the local Pretreatment Program.

What are the background and purpose of the SNC criteria?

On July 24, 1990, EPA modified 40 CFR 403.8( f)( 2)( vii) to include the existing definition of SNC ( 55 FR 30082). The purpose of this modification was to provide some certainty and consistency among POTWs for publishing their lists of industrial users in noncompliance. EPA modeled the modification after the criteria under the NPDES program used to determine SNC violations for direct dischargers. By making the modifications, EPA also established more parity in tracking violations by direct and indirect dischargers.

What happens when an industrial user facility is in SNC?

POTWs are required to publish annually a list of industrial users in SNC at any time during the previous twelve months. In the previous rules, the POTW was required to publish this list in the largest daily newspaper published in the municipality in which the POTW is located.

The Agency has emphasized that industrial users are liable for any violation of applicable Pretreatment Standards and Requirements, and has strongly encouraged Control Authorities to take some type of enforcement response for each such instance of noncompliance. Supporting this approach, EPA notes that the very underlying premise of the Enforcement Response Plan ( 40 62 CFR 403.8( f)( 5)) is that there be some type of POTW response for each instance of noncompliance. Appropriate types of enforcement responses are addressed in the POTW's Enforcement Response Plan, although EPA guidance recommends that violations rising to the level of SNC be met with some type of formal enforcement action like an enforceable order ( Guidance For Developing Control Authority Enforcement Response Plans, EPA 832 B 89 102, September 1989, see http:// www. epa. gov/ npdes/ pubs/ owm0015. pdf).

2. What changes did EPA propose?

EPA proposed the following modifications to the SNC provision in 1999:

a. Publication EPA proposed to amend 40 CFR 403.8( f)( 2)( vii) to allow publication of the SNC list in any paper of general circulation within the jurisdiction served by the POTW that provides meaningful public notice rather than in the largest daily newspaper published in the municipality as is the currently required.

b. Applicability EPA proposed to amend the SNC criteria to apply only to significant industrial users ( SIUs). Under the existing regulations, SNC can apply to any industrial user.

c. Daily Maximum or Average Limit Violations EPA proposed to amend 40 CFR 403.8( f)( 2)( vii)( A), ( B), and ( C) to include a broader set of violations than just daily maximum and average limits.

d. Other Issues EPA also took comment on several other issues, but did not propose specific changes. These issues include Technical Review Criteria ( TRC), late reports, and rolling quarters.

3. What changes is EPA finalizing in today= s rule?

EPA is finalizing four changes to amend 40 CFR 403.8( f)( 2)( vii).

a. Publication EPA is amending 40 CFR 403.8( f)( 2)( vii) to allow publication of the SNC list in any paper of general circulation that provides meaningful public notice within the jurisdiction served by the POTW. EPA's intent in modifying this requirement is to be consistent with the July 17, 1997 amendments to Part 403 regarding modifying POTW pretreatment programs ( 62 FR 38406). 63 Under the amended 40 CFR 403.11( b)( 1)( i)( B), publication can be in any paper of general circulation within the jurisdiction served by the POTW that provides public notice. It is EPA's view that this new performance standard for publishing SNC violations properly balances the need to give the POTW the flexibility to choose an appropriate newspaper within its community, with the need to ensure effective public notice and deterrence of " bad actors."

b. Applicability EPA is amending the SNC criteria so that SNC will apply only to SIUs and to those industrial users that have caused pass through or interference, have a discharge that resulted in the POTW= s exercise of its emergency authority to halt or prevent such a discharge, have caused imminent endangerment to human health, welfare, or the environment, or have otherwise adversely affected the POTW= s ability to operate its pretreatment program. This approach is consistent with the NPDES SNC policy which only applies to major dischargers. See A Revision of NPDES Significant Noncompliance ( SNC) Criteria to Address Violations of Non Monthly Average Limits,@ memorandum from Steven A. Herman, Assistant Administrator for the Office of Enforcement and Compliance Assurance, September 21, 1995. Additionally, EPA emphasizes that the SNC criteria apply not only to SIUs, but also to IUs that impact the POTW. These modifications should cut down on administrative burdens and allow better resource targeting. These modifications ensure the POTW= s ability to address all potentially problematic users adequately. The Agency wants to make it clear that this change is focused only on the POTW= s publication and reporting requirements. EPA fully expects POTWs to take appropriate enforcement actions against any industrial user that violates a pretreatment standard or requirement. POTWs still have the option of publishing non significant industrial users with violations that do not fall within one of the above mentioned categories.

c. Daily Maximum or Average Limitations EPA is amending 40 CFR 403.8( f)( 2)( vii)( A) and ( B) to apply to a broader range of violations such as other numeric limits, instantaneous limits, narrative limits, or operational standards to numeric pretreatment standards, and amending 40 CFR 403.8( f)( 2)( vii)( C) to address other pretreatment standards and requirements. This change is important since some local limits may be expressed as instantaneous limits or narrative limits. The revised language addresses other types of requirements like operational standards. The amendment is generally consistent with EPA's revision to its NPDES SNC policy where EPA broadened the criteria to address nonmonthly average limitations. See A Revision of NPDES Significant Noncompliance ( SNC) Criteria to Address Violations of Non Monthly Average Limits,@ memorandum from Steven A. Herman, Assistant Administrator for the Office of Enforcement and Compliance Assurance, September 21, 1995.

d. Late Reports 64 EPA is amending 40 CFR 403.8( f)( 2)( vii)( F) so that SNC applies to reports that are provided more than 45 days after the due date, instead of to reports that are 30 days late. The change applies to required reports such as baseline monitoring reports, 90 day compliance reports, periodic self monitoring reports, and reports on compliance with compliance schedules. EPA is making this change because many Control Authorities and Industrial Users that commented on the late report issue argued that the 30 day timeframe was too restrictive. EPA notes that Industrial Users that submit reports even one day late are in violation.

4. What significant changes were made to the proposed rule?

a. Applicability EPA modified the proposal by adding to the scope of SNC those IUs that cause pass through or interference, have a discharge that resulted in the POTW= s exercise of its emergency authority to halt or prevent such a discharge, cause imminent endangerment to human health, welfare, or the environment, or otherwise adversely affect the POTW= s ability to operate its pretreatment program.

b. Daily Maximum or Average Limit Violations In the proposal, EPA proposed to modify the provisions of 40 CFR 403.8( f)( 2)( vii)( A), ( B) and ( C) to address not only violations of daily maximum or longer term average limits, but also a broader range of violations such as other numeric limits, instantaneous limits, narrative limits, or operational standards. EPA has modified the proposal in the following ways:

Chronic violations: EPA has clarified the revised language to more accurately describe the target violations. The term " numeric" was added to clarify that only Standards or Requirements that can be numerically quantified can be examined for possible chronic violations. Also, EPA specifies that chronic violations include violations of both " Standards and Requirements"; the term " Requirements" was not included in the proposal. The inclusion of this term provides the intended broader scope that EPA sought in the proposal. EPA also clarifies that violations of instantaneous limits are also to be considered for chronic violations.

TRC: EPA adopted the same changes for TRC violations that were made for chronic violations.

Any other violations: EPA has modified the proposed rule by including clarifying language on what is meant by a " Pretreatment Standard or Requirement." EPA provides parenthetical examples, including daily maximum, long term average, instantaneous, or narrative standards.

c. Late Reports 65 EPA did not propose any changes to 40 CFR 403.8( f)( 2)( vii)( F), which contains the SNC criterion for late reports. Instead, EPA sought comments on several options for the late report criterion. The options included tying SNC to a pattern of late reporting; applying the SNC criterion to a late report only if the report indicated that a violation of monitoring requirements or numeric limitations had occurred; allowing POTWs to extend " waivers" in some circumstances to Industrial Users that offered a satisfactory reason why reports were late; limiting the types of reports to which the SNC criterion applies; retaining the 30 day late report criterion, but changing the publication requirement as it pertains to late reports; extending the time after which a late report puts an Industrial User in SNC ( e. g., to 45 days or 60 days); or providing the POTW with complete authority for determining when late reports trigger SNC. EPA is amending the criterion so that Industrial Users are in SNC if reports are not provided within 45 days after their due date.

5. Summary of Major Comments and EPA Response a. Publication Most commenters were in favor of making the change that EPA is adopting in today's rule. EPA is amending the regulation to allow publication of the SNC list in any paper of general circulation that provides meaningful public notice within the jurisdiction served by the POTW. One reason given for supporting this change included possible lower costs to the municipality. Other commenters pointed out that the previous use of the largest daily newspaper requirement did not make sense in certain situations. Such examples included that the largest daily newspaper may not always have provided the most effective notice, and the fact that some municipalities may only have a weekly publication and no daily publication.

EPA also sought comment on an appropriate definition for A meaningful public notice@ to ensure some level of consistency across the pretreatment programs. Some commenters provided suggestions for defining A meaningful public notice@ such as linking it to the service area population, the circulation rate of the newspaper, or the official daily newspaper as determined by the control authority. Other commenters stated that the definition of A meaningful public notice@ should be determined by the Control Authority because defining it by service population or circulation rate could be overly burdensome and not necessarily meet the intent of the standard. EPA agrees with the commenters who suggested that defining " meaningful public notice" could be overly burdensome. Therefore, at this time, EPA has decided not to define A meaningful public notice.@

b. Applicability The majority of commenters supported either modifying the application of SNC to SIUs only, or to SIUs and those Industrial Users which caused pass through or interference, had a discharge that resulted in the POTW= s exercise of its emergency authority to halt or prevent such 66 a discharge, caused imminent endangerment to human health, welfare, or the environment, or otherwise adversely affected the POTW= s ability to operate its pretreatment program. Some commenters did not want to limit SNC to apply only to SIUs because not all Industrial Users are properly identified as SIUs. The commentors also noted that all IUs are required to comply with Pretreatment Standards and Requirements, regardless of whether they are designated as SIUs. Several commenters also indicated that changing the SNC definition to apply only to SIUs would force larger users to shoulder the regulatory burden, because this definition would not apply to IUs that could cause the same types of impacts as SIUs. EPA agrees that certain Industrial Users should be published as SNC. By including the application of SNC to SIUs and those IUs which cause the specific problems referenced above, the commenters' concerns should be addressed.

The distinction EPA is making today is not focused on the size of the facility; rather, EPA focuses on those dischargers with the largest potential to impact the system. EPA continues to strongly encourage POTWs to use their existing authority under 40 CFR 403.3( t) to designate any industrial users as significant if they have the reasonable potential to adversely affect the POTW's operation or to violate any Pretreatment Standard or Requirement. This includes considering smaller facilities that have the potential ( either individually or collectively) to impact the system. Furthermore, all industrial users are required to comply with Pretreatment Standards and Requirements, regardless of whether they are designated as SIUs, and EPA expects appropriate enforcement to be taken for each violation by any industrial user.

c. Daily Maximum or Average Limit Violations Commenters were divided on this proposed rule language. One commenter mentioned that the revision would be much more consistent nationally if it were to apply only to numeric effluent limits, excluding local limits. Another commenter indicated that the Control Authorities often are required to make A subjective judgments regarding compliance with narrative standards, instantaneous limits and some general prohibitions,@ and that such a subjective judgment would be an inappropriate basis for an SNC determination. Another commenter indicated that all applicable pretreatment standards are enforced now, and that there would be no discernible benefit to expanding the types of violations that could trigger a SNC determination. Some commenters cited the possible increased burden on the Control Authorities if such additional standards were used to make SNC determinations.

On the other hand, several commenters were supportive of the proposed rule change. Some commenters indicated that the revision would better reflect the fact that industrial users must be in compliance with all applicable pretreatment standards and requirements in order to meet the goals of the national Pretreatment program. Other commenters focused on the fact that interference or pass through could be caused by violations of standards other than categorical pretreatment standards, and therefore they saw a need to expand the SNC criteria.

EPA agrees with those commenters who supported an expansion of the range of SNC 67 criteria consistent with the proposed rule, and has added other numeric limits, instantaneous limits, narrative standards, or operational standards as part of the SNC criteria. This approach will give more equal weight to categorical standards, local limits, and other standards as applicable Pretreatment Standards and Requirements. This expansion of SNC criteria would also potentially enhance the Control Authority= s ability to address such violations ( i. e., other numeric limits, instantaneous limits, narrative standards, or operational standards) by placing a higher priority on these violations. EPA believes that such a change would still provide national consistency and be more protective by better ensuring compliance with all applicable Pretreatment Standards and Requirements. Control Authorities are currently expected to address violations of all applicable Pretreatment Standards and Requirements, so that this proposal should not necessarily impose any increased enforcement responsibilities on the Control Authorities. In addition, as the preamble to the proposed rule states ( 64 FR 39593), this approach would be consistent with A EPA= s recent revision to its NPDES SNC policy where EPA broadened the criteria to address non monthly average limit violations.@ See A Revision of NPDES Significant Noncompliance ( SNC) Criteria to Address Violations of Non Monthly Average Limits,@ memorandum from Steven A. Herman, Assistant Administrator for the Office of Enforcement and Compliance Assurance, September 21, 1995.

Under the NPDES SNC policy, when a parameter has both a monthly average and a nonmonthly average limit, a facility is only considered in SNC for the non monthly average if the monthly average is also violated to some degree ( but less than SNC). EPA sought comment on whether such a caveat is also appropriate for the pretreatment regulations. Very few commenters focused on this particular topic. A few commenters indicated that a determination that a particular violation or set of violations constituted SNC should only occur if there was a meaningful violation of the POTW= s NPDES permit limit for that particular parameter. EPA has decided not to modify the regulations for circumstances in which the monthly average is exceeded to include caveats regarding whether it is appropriate to consider non monthly averages ( i. e., daily maximum, instantaneous limits) for SNC determinations.

d. Technical Review Criteria ( TRC)

In the existing regulations, the Technical Review Criteria ( TRC) may be found at 40 CFR 403.8( f)( 2)( vii)( B). As described in the preamble to the proposed rule ( 64 FR 39593), these TRC A... are numeric thresholds used to define a subcategory of SNC... based on the magnitude of an effluent violation. A TRC violation occurs where 33 percent or more of all of the measurements for each pollutant parameter taken during a six month period equal or exceed the product of the daily maximum limit or the average limit multiplied by the applicable TRC.@ TRC is equal to 1.4 times the applicable standard for BOD, TSS, fats, oils and grease; TRC is also equal to 1.2 times the applicable standard for all other pollutants except pH.

As further stated in the preamble to the proposed rule ( 64 FR 39593), EPA was not proposing to amend the TRC. However, EPA did seek comment on this topic, particularly 68 regarding local limits. EPA stated that it was A... interested in suggestions for workable alternatives... that would ensure that the magnitude of a violation...@ continues to be part of the definition of SNC, with the condition that such alternatives A... would not unduly increase the workload on either the Control Authority or the Approval Authority.@ Based on its review of the comments, EPA is not considering any further changes to TRC.

Several commenters expressed a clear preference that TRC not be modified. Several commenters also provided alternative numeric thresholds for TRC. However, there was no consensus among the comments for an alternate threshold and a sufficient justification for the use of such alternative thresholds was not provided. As explained in the preamble to the proposed rule ( 64 FR 39593), the existing regulations are A consistent with the NPDES approach which has generally been accepted over the years as an indicator of a >

significant= level of exceedance which should be reviewed for enforcement purposes.@ Furthermore, as that same preamble stated, A( T) he same considerations apply to the TRC as it is applied to categorical standards in the pretreatment program and may be relevant for local limits.@ In a sense, by keeping the TRC the same for both direct dischargers to surface waters and indirect dischargers to POTWs, the criteria help maintain a A level playing field@ by ensuring that this subcategory of SNC is linked to some nationally consistent designated magnitude above the applicable standard, whether that standard is an NPDES permit effluent limit, a categorical pretreatment standard, or a local limit.

Several commenters, using similar language, stated that A it is incumbent on EPA to develop TRC that are germane to the objectives of the pretreatment program, developed in a manner that lends credence to application of effluent guidelines and local limits, and are technically sound and defensible.@ Just as best achievable technology standards ( BAT) and stream use are factors considered in the development of effluent limits, BAT and protection of the POTW= s operations are factors considered in the establishment of categorical pretreatment standards and local limits respectively. Therefore, if these pretreatment limits are properly derived for their intended purpose, the TRC are simply intended to represent numeric thresholds at magnitudes above these applicable standards such that, above this level, such significant noncompliance should make the authority sufficiently concerned and warrant appropriate action. As such, EPA believes that there is not sufficient reason to try to account only for instances of potential pass through or interference, or to make allowances for the range of treatment plant performance, or to have different TRC for individual pollutant parameters for different POTWs. Such revisions would be contrary to EPA= s intent to keep the regulations simple to understand and implement, and to not unduly increase the workload on the Control Authority or Approval Authority.

Some of the commenters advocated the elimination of the TRC entirely. EPA disagrees with these commenters. As indicated above, EPA believes that a measure of the magnitude of the violation is an appropriate consideration in determining SNC. The preamble to the proposed rule ( 64 FR 39593) stated that EPA was not proposing to amend the TRC, and EPA believes that radical revisions to the TRC are not warranted. 69 One commenter indicated that TRC should only apply if the levels are at least five times the applicable standard. EPA believes that this level is far too high a threshold to serve as a proper deterrent to dischargers and as an adequate indicator of potential compliance problems. EPA emphasizes that POTWs should be concerned about reported results, the adequacy of industrial treatment, and potential impacts on the plant operations or receiving waters at levels which are much less than five times the applicable standard.

Some commenters sought to adjust the TRC by having them only apply to daily maximum limitations. Other commenters suggested that, for TRC and chronic criteria, EPA modify the percentages to 34% and 67% of all measurements taken, respectively, of the number of measurements taken that exceed the applicable standard for the violations to rise to the level of SNC. EPA disagrees with these commenters, because it is not clear how these changes will improve the application of TRC or provide equal if not added environmental protection when compared to the existing TRC criteria.

As stated above and in the preamble to the proposed rule ( 64 FR 39593), EPA did seek comment on the TRC, particularly regarding local limits. No commenters focused on whether TRC may be inappropriate for local limits, based upon a distinction in the derivation, site specific variability and intent of local limits as compared to categorical pretreatment standards. Therefore, EPA did not adopt changes to reflect the use of TRC for local limits.

e. Late Reports The existing regulations require that Industrial Users that submitted reports more than 30 days late be considered in SNC. This is consistent with the NPDES SNC approach for late reports. EPA did not propose any specific changes to this part of the SNC definition, but did solicit comment on possible options or combinations of options to modify this portion of the definition. The options included tying SNC to a pattern of late reporting; applying the SNC criterion to a late report only if the report indicated that a violation of monitoring requirements or numeric limitations had occurred; allowing POTWs to extend " waivers" in some circumstances to Industrial Users that offered a satisfactory reason why reports were late; limiting the types of reports to which the SNC criterion applies; retaining the 30 day late report criterion, but changing the publication requirement as it pertains to late reports; extending the time after which a late report puts an Industrial User in SNC ( e. g., to 45 days or 60 days); or providing POTWs with complete flexibility for determining when late reports trigger SNC.

Comments on this issue were mixed. Many commenters noted that reporting is important in and of itself and it serves a vital role in ensuring adequate implementation and oversight of the pretreatment program. Commenters noted that failure to submit or late submittal of reports impede POTWs from meeting goals of their approved programs. Because of the importance of reporting, a few commenters ( POTWs) argued that EPA should retain the existing SNC criterion 70 for late reports.

However, a majority of commenters asked EPA to modify the SNC criterion for late reports in some way. They noted that reports are sometimes late because of circumstances that are beyond the control of the Industrial Users. Commenters also stated that publication should be reserved to Industrial Users that violate numeric Pretreatment Standards or fail to monitor, rather than for violations that some commenters characterized as " administrative" violations. One commenter also noted that a 30 day criterion may be appropriate for NPDES permittees, but not for the Pretreatment Program because NPDES permittees generally submit reports more frequently than Industrial Users regulated by the Pretreatment Program and because the Pretreatment Program also relies on surveillance by the POTWs. Based on these comments, EPA agrees that modifications to the SNC criterion for late reports are appropriate.

Although most commenters favored modifications to the SNC criterion for late reports, commenters disagreed on how the provision should be modified. Some commenters stated that POTWs should be given complete flexibility in determining whether late reports constitute SNC. Others argued that POTWs should be provided some amount of flexibility, but not total flexibility. EPA believes that the definition of SNC should be consistent throughout the Pretreatment Program. Therefore, the Agency has chosen to establish a consistent SNC criterion for late reports that would avoid the use of different SNC criterion by various POTWs for the same type of reporting violations.

Some commenters suggested that the SNC criterion for late reports should recognize a pattern or late reporting, or should consider the Industrial User's compliance history. For example, some commenters suggested that a late reporters be considered in SNC if 33 percent percent or more of required reports in a specified reporting period are provided more than 30 days late. Another commenter suggested that three monitoring reports submitted more than thirty days late could constitute a history of chronic late reports, and another commenter suggested that failure to submit a completed discharge monitoring report in any two months of any consecutive six month period should trigger SNC. EPA agrees that POTWs should take steps to address Industrial Users that demonstrate a pattern of late reporting. In addition, EPA strongly believes that the SNC criterion for late reports must address reports that are submitted extremely late or that are never submitted, even if the extremely late submittal or failure to submit is a one time occurrence.

Some commenters argued that SNC for late reports should apply only if the report, once submitted, indicates that the Industrial User has violated a numeric Pretreatment Standard or failed to monitor. Others supported a provision in which reports provided more than 30 days late, but less than 45 days, should trigger SNC only if they indicated another violation. EPA believes that this provision might minimize the importance of reporting as a tool for POTWs to implement local Pretreatment Programs. Also, EPA strongly believes that the SNC criterion for late reports must address reports that are submitted extremely late or that are never submitted, even if the 71 extremely late submittal or failure to submit is a one time occurrence and even if the report does not indicate monitoring or effluent violations.

A number of commenters supported extending the number of days until which late reports trigger SNC from 30 days to 45 days. EPA agrees that this change is appropriate and easy to implement. A few commenters suggested the option of extending the period from 30 days to 60 days. EPA believes that this change is not appropriate because most cases of late laboratory reports or other miscommunications can be addressed quickly. EPA also believes that receiving data 60 days late would be more likely to jeopardize POTWs' management of their Pretreatment Programs and have the potential to adversely impact the POTW and its receiving water.

A few commenters suggested EPA apply changes to the SNC criterion for late reports should only apply to periodic self monitoring reports and 90 day self compliance reports. EPA believes that, in order to avoid confusion and ease tracking of late reports, the same criterion should be applied to all reports. One commenter asked that EPA amend the regulations so that SNC for late reports applies to " baseline monitoring reports, 90 day compliance reports, periodic self monitoring reports, or reports on compliance with compliance schedules" ( rather than " baseline monitoring reports, 90 day compliance reports, periodic self monitoring reports, and reports on compliance with compliance schedules"). The commenter was concerned that the provision could be interpreted to imply that Industrial Users must submit both the 90 day compliance reports and the periodic self monitoring reports to avoid being in SNC. The list of reports comprises a list of examples of " compliance reports." EPA does not believe that the commenter's interpretation is valid or that any change is needed to this language.

In considering revisions to the late reporting criterion for SNC, EPA notes that implementation of the Pretreatment Program relies heavily on a self policing and self reporting system. This self reporting is important to enforcement. If a failure to report becomes routine, the entire program can be weakened. EPA expects POTWs to take some level of enforcement action against any Industrial User that provides reports. EPA would also like to emphasize that there is current flexibility in the existing rule to address some of the concerns related to one late report putting an Industrial User in SNC. For example, the Control Authority has some flexibility in setting the due date and can set it to coincide with some other established reporting or billing cycle. Also, in the enforcement response policy the POTW can have an escalation policy, whereby, for example, the Industrial User would receive warning a letter that the report is 5 10 days late past the due date and/ or fines associated with the report before it rises to the level of being in SNC.

f. Rolling Quarters EPA memoranda circa 1991 and 1992 form the basis of EPA= s policy that SNC for IUs should be calculated on a rolling quarter basis. ( September 9, 1991 memorandum from Michael B. Cook, Director of EPA's Office of Wastewater Enforcement and Compliance to Water 72 Management Division Directors, Regions I X and approved pretreatment State coordinators, " Application and Use of the Regulatory Definition of Significant Noncompliance for Industrial Users," http:// www. epa. gov/ npdes/ pubs/ application_ use_ regulatory. pdf, and January 17, 1992 memorandum from Mark B. Charles, Chief of RCRA and Pretreatment Enforcement Section , to the Regional Pretreatment Coordinators, Regions I X, " Determining Industrial User Significant Noncompliance   One Page Summary," http:// www. epa. gov/ npdes/ pubs/ industrial_ user. pdf). The term " rolling quarters", under EPA= s national policy, refers to an approach which requires the Control Authority to evaluate an industrial user= s compliance status at the end of each quarter by using data from the previous six month period. In the regulations, determinations of significant noncompliance are based upon six month periods ( 40 CFR 403.8( f)( 2)( viii)( A) and ( B)).

Many commenters expressed concern regarding the concept of rolling quarters and instead endorsed the adoption of static six month periods that do not overlap. Many commenters were concerned that the use of rolling quarters could result in the need to publish the name of the industrial user in two separate years for SNC for the same violation.

Many commenters who supported the static six month approach voiced concerns that the use of rolling quarters unnecessarily complicated the calculations of SNC and the annual publication of those IUs in SNC, without apparent benefits over the use of static six month periods. They indicated that the concept was complex, difficult to implement and would only result in confusion for the industrial users and increased burden for the control authorities.

Some commenters preferred to begin to A roll@ time periods after a violation occurs, thus giving, as one commenter stated, the possibility to A... allow industrial users to achieve compliance and obtain additional samples@ to verify compliance, all within the given time period. The commenters explained that this could give industrial users an opportunity to demonstrate compliance rather than being listed as being in SNC for violations that were corrected months ago. EPA noted in the preamble to the proposed rule ( 64 FR39594) that while the Agency provided some discussion of the various opinions regarding the use of rolling quarters, EPA did not ultimately propose a specific change regarding rolling quarters national policy, did not seek comment on whether to discontinue EPA= s national policy regarding the use of rolling quarters, and did not propose an alternative approach. It remains EPA= s intention to continue the existing national policy that SNC for industrial users be evaluated on a rolling quarter basis. This approach, which is the same as the one used in the NPDES program for the determination of SNC by direct dischargers, will remain the same.

EPA did seek comment on whether the concept of rolling quarters should be codified in the pretreatment regulations. Some commenters expressed their opposition to such codification, based largely upon their preference to use an alternative to rolling quarters. A few commenters supported codification, indicating that by making the use of the rolling quarters approach mandatory, EPA would help ensure national consistency in its use by Control Authorities. One commenter recommended codification of the due date for the annual publication of industrial 73 users in SNC. After considerable internal discussion and careful deliberation, EPA has decided not to codify rolling quarters in the pretreatment regulations.

In the preamble to the proposed rule ( 64 FR 39594), EPA specifically sought comment on whether the regulations should be revised to allow Control Authorities to waive the second publication ( as described above) A where that second publication is based solely on the violations occurring in the last quarter of the previous pretreatment year.@ Many commenters sought the elimination of this double publication issue through a specific rule change to the publication requirements, particularly if the final rule implements the concept of rolling quarters. Those commenters indicated that such duplicate publications in the newspaper would be unfair to the industrial user which had corrected its compliance problems and would mislead the public regarding the status of such an industrial user.

EPA's 1991 memorandum, cited previously, addressed the issue of possible publication in two different years of an industrial user that is in SNC for the same violation. EPA was clear on the point that double publication is not intended by the use of rolling quarters. It stated that A( I) f a facility has been determined to be in SNC based solely on violations which occurred in the first quarter of the 15 month evaluation period ( i. e., the last quarter of the previous pretreatment year) and the facility has demonstrated consistent compliance in the subsequent four quarters, then the POTW is not required to republish the industrial user ( IU) in the newspaper if the IU was published in the previous year for the same violations.@ EPA does not believe there is a need to revise the regulations on this point.

H. Removal Credits 1. What are the existing rules?

Removal credits are a regulatory mechanism by which industrial users may discharge a pollutant in quantities that exceed what would otherwise be allowed under an applicable categorical pretreatment standard because it has been determined that the POTW to which the industrial user discharges consistently removes the pollutant. The pretreatment regulations define what is meant by the POTW's " consistent removal" at 40 CFR 403.7( b).

Removal credits may be made available for pollutants that are listed in appendix G section I of Part 403 for the sludge use or disposal practice employed by the POTW, when the requirements in 40 CFR Part 503 are met or for pollutants listed in appendix G section II of this part when the concentration for a pollutant in the sewage sludge does not exceed the concentration for the pollutant in appendix G section II. In addition, removal credits may be made available for any pollutant in sewage sludge when the POTW disposes all of its sewage sludge in a municipal solid waste landfill unit that meets the criteria in 40 CFR Part 258.

Where overflows occur prior to the POTW treatment plant at least once per year, the 74 POTW may still claim " consistent removal" of the pollutant, but only if in accordance with 40 CFR 403.7( h): ( 1) the industrial user demonstrates that the Overflow does not occur between it and the POTW Treatment Plant; ( 2) the industrial user provides containment or ceases its process discharge during all circumstances in which an Overflow event is reasonably expected to occur; or ( 3) the " consistent removal" is reduced in accordance with the number of hours in a given year that Overflows occur and the POTW is in compliance with applicable CSO requirements. It is the third criterion ( i. e., relating to reducing the removal credits in correlation to the number of hours a POTW experienced CSOs) that was the subject of the proposal.

2. What changes did EPA propose?

EPA proposed to make industrial users that are upstream of overflows ineligible for removal credits unless it could be established that their discharges would be consistently treated. According to the proposal, if any Overflow point received treatment ( e. g., primary clarification at the outfall) that was demonstrated to provide consistent removal of a percentage of a pollutant, then the POTW responsible for that outfall would be able to apply for removal credit authority for that percentage using the procedures in 40 CFR 403.7( b) for determining consistent removal. However, if no treatment occurs at any Overflow points downstream from an industrial user, that industrial user would not be eligible for a removal credit and would have to comply with the national categorical pretreatment standard. Consistent with that approach, the proposal would have deleted the existing provision in 403.7( h)( 2) which allows removal credits for discharges that are subject to Overflows but reduces the credit by a percentage equal to the percentage of time in a year that the POTW is subject to Overflows.

In addition, references in the regulation to obsolete guidance on construction grants review procedures for developing CSOs control were to be removed by deleting Appendix A as well as discussion of that guidance in 40 CFR 403.7( h)( 2).

3. What changes is EPA finalizing in today's rule?

Today, EPA is amending the removal credits overflow provisions to delete the requirements of obsolete guidance published in 1975, for the construction grants program; existing sections 403.7( h)( 2)( ii) and ( iii) and Appendix A are deleted and replaced with a requirement for the POTW to be in compliance with NPDES permit requirements, orders or decrees affecting impacted overflows.

Today's rule also makes one technical correction in response to comments received. EPA corrects footnote 1 in Appendix G, Table I ( Regulated Pollutants in Part 503 Eligible for a Removal Credit) by including a reference to the use of carbon monoxide. The Part 503 regulations now allow the use of either total hydrocarbon ( THC) or carbon monoxide 75 concentrations to represent organic compounds in exit gas from incinerators. EPA amended Part 503 subpart E ( 59 FR 9095, February 25, 1994) to authorize the demonstration of compliance with the 100 ppm THC operational standard by meeting a 100 ppm CO limit. Therefore, EPA is modifying footnote 1 to reflect the fact that either total hydrocarbon or carbon monoxide, as a surrogate monitoring parameter, may be used.

What significant changes were made to the proposed rule?

EPA is not finalizing the changes contained in the proposed rule regarding overflows, except to delete existing sections 403.7( h)( 2)( ii) and ( iii). These sections are now replaced with a requirement for the POTW to be in compliance with the NPDES permit requirements affecting those Overflows, or any enforcement order or decree affecting those Overflows, issued pursuant to section 402( q)( 1) of the Act.

EPA is amending the removal credits overflow provisions to delete the requirements of obsolete guidance published in 1975 for the construction grants program. Therefore, today's rule leaves in place the existing requirements on the availability of removal credit authority for POTWs with overflows.

4. Summary of major comments and EPA history and actions With the exception described above, EPA did not propose any changes to the removal credit provisions of its General Pretreatment Regulations. A number of commenters asked EPA to consider changes to the regulations to allow greater availability of removal credits for a broader range of pollutants. Some commenters stated that the procedures established in 40 CFR 403.7 that industrial dischargers must follow to get authority for removal credits are unreasonable and extremely difficult to obtain. They recommended revisions to more accurately reflect the total removal by the POTW, and modifications to facilitate the granting of authority when justified. The following discusses the Agency's current thinking on removal credits.

Background Section 307( b) of the Clean Water Act directs EPA to establish categorical Pretreatment Standards in order to prevent interference with POTW operation and pass through of inadequately treated pollutants. Because, in certain instances, POTWs could provide some or all of the treatment of an industrial user's wastewater that would be required pursuant to the Pretreatment Standard, the Act also authorizes a discretionary program for POTWs to grant " removal credits" to their industrial users. The credit, in the form of a less stringent categorical Pretreatment Standard, would allow an industrial user to discharge a greater quantity of a pollutant to the POTW than otherwise authorized if certain requirements are met.

Section 307( b) establishes a three part test that a POTW must meet in order to obtain 76 removal credit authority for a given pollutant. Removal credits may be authorized only if ( 1) the POTW " removes all or any part of such toxic pollutant," ( 2) the POTW's ultimate discharge would " not violate that effluent limitation or standard which would be applicable to that toxic pollutant if it were discharged" directly rather than through a POTW, and ( 3) the POTW's discharge would " not prevent sludge use and disposal by such [ POTW] in accordance with section [ 405]  " ( Sec. 307( b)). Through several rulemakings and court rulings, EPA promulgated and revised its removal credit regulations, which are codified at 40 CFR 403.7.

. The legal and regulatory history of this provision is as follows:

  June 26, 1978: Following promulgation of the Pretreatment Regulations ( 40 CFR Part 403), several actions were brought in federal court challenging various aspects of this regulation ( consolidated in NRDC. et al. v. EPA).   May 31, 1979: EPA entered into an agreement with three of the petitioners ( Chemical Manufacturers Association, the U. S. Brewers Association and the Pacific Legal Foundation), settling most of industry's issues. EPA agreed to propose changes to the June 26, 1978, regulation to reflect the agreements reached in the settlement. Proposed modifications arising out of the settlement agreement included redefinition of " consistent removal" and a revision of removal data sampling procedure.   January 28, 1981: EPA promulgated the General Pretreatment Regulations for Existing and New Source Final Rule ( 46 FR 9404). This rule made it substantially easier for POTWs to grant removal credits and to give larger credits for the same pollutant removals. Industry parties again brought suit, contending that the new rule did not go far enough and was unworkable ( consolidated in National Association of Metal Finishers [ NAMF] et al. v. EPA).   1983: NAMF. v. EPA upheld the 1981 removal credits rule.   1984: EPA revised the rule to provide, but not prescribe, the manner in which the samples used to prove " consistent removal" are to be collected and included the sampling procedures in the appendix as guidance.   April 30, 1986: The U. S. Court of Appeals for the Third Circuit in NRDC v. EPA, 790 F. 2d 289 ( 3rd. Cir. 1986), struck down the removal credits provision on the grounds that EPA cannot, in the absence of CWA section 405 sludge regulations, authorize the granting of removal credits under 307( b)( 1) of the Act. The decision also stated that the 1984 regulatory definition of " consistent removal" failed to implement the requirements of the CWA. The court held that the definition violated a statutory requirement that direct and indirect dischargers be held to the same standards and that EPA's definition of consistent POTW removal, i. e. removal that is achieved only 50% of the time, violates section 307( b)( 1) of the Clean Water Act. The following is a summary of the court's reasoning: