### Memorandum

Date: January 2 8 , 2010

To: Brenda Shine, EPA OAQPS

From: Matt Todd, API

cc: Jan Tierney, EPA

API Air Toxics Task Force

Subject: Cooling Tower Monitoring Issues

Identifying Leaking Heat Exchangers in Organic HAP Service

Under §63.654(d) of subpar t CC, when a leak is indicated by the monthly monitoring, sources have 45 days to reduce the leak to below the leak definition. Since the Clean Air Act requires that part 63 rules address HAPs, §63.654(e) of subpart CC provides a procedure for

demonstrati ng that the leak is not from an exchanger in organic HAP service and thus not subject to the repair requirements. It specifies:

(e) If the owner or operator detects a leak when monitoring a cooling tower return line under paragraph (c)(1) of this section, the owner or operator may conduct additional monitoring to identify leaks of total strippable VOC emissions using Modified El Paso Method from each heat exchanger or group of heat exchangers in organic HAP service associated with the heat exchange system for which the leak was detected. If the additional monitoring shows that the total strippable VOC concentration in the stripped air at the heat exchanger exit line for each heat exchanger in organic HAP service is less than 6.2 ppmv for existing sources o r less than 3.1 ppmv for new sources, the heat exchange system is excluded from repair requirements in paragraph (d) of this section.

Thus, the only allowed procedure for demonstrating that a particular leak is not from an exchanger in organic HAP service is to perform modified El Paso monitoring at every individual or group of heat exchangers in organic HAP service associated with that heat exchange system, even including heat exchangers that are on different return lines than the one where the leak was

fo und. This is not how leaking exchangers are identified today and thus does not represent the MACT floor and will result in a great many wasteful El Paso analyses and impose significant costs. Furthermore, this approach would appear to be required even if the source of the leak is identified by other means as not being from a heat exchanger in organic HAP service and would have to be repeated monthly until the non

- HAP leak is repaired.

Typically, when a leak is found sources perform a gas chromatographic analysis of the stripper offgas or of headspace gas collected from a return water sample. This analysis generally narrowsthe potential leak source to a few heat exchangers. While there is always some background level

of chemicals, the fingerprint of th e leaking material almost always stands out because those components are present at many times the background level. Using this information a source can usually identify the leak source with one or just a few confirming El Paso analyses. Since §63.655(i) (4)(i) and (ii) require that sources identify all heat exchangers in organic HAP service in each heat exchange system, it only takes identifying the leaking heat exchanger to determine if the leak is from an exchanger in organic HAP service or not. Thus, sources should be allowed to use whatever means they have to identify the leaking exchanger, confirm that conclusion with an El Paso analysis at the leaking exchanger, and then use their recorded process information to determine if the exchanger is in orga nic HAP service and thus subject to the repair requirements

or not.

Monthly Monitoring

Issue: The new §63.654(c) of Subpart CC requires “ The owner or operator must perform monthly monitoring to identify leaks of total strippable volatile organic compou nd (VOC) from each heat exchange system ...” Does “monthly” mean any time within a calendar month or something else?

Discussion: Neither the preamble or the R esponse to C omments document addresses this issue.

Nor is this issue addressed in the Part 63 Gen eral Provisions. However, there is considerable precedent dealing with this question.

Monthly requirements are prevalent throughout Subpart CC and have always been interpreted as referring to calendar months. For example, the requirement for “weekly” vi sual monitoring and “monthly” Method 21 monitoring of pump seals has always been interpreted to mean that pumps

must be monitored once within each calendar week and month , respectively

.

Th e specific language in Part 63 Subpart s F and H of the HON rule h a ve generally been accepted as the basis for interpreting term s such as monthly under the refining and chemicals rules, unless a subpart specifically specifies a different interpretation . §63.100(k)(9) states:

(9) All terms in this subpart F or subpart G of this part that define a period of time for completion of required tasks (e.g., weekly, monthly, quarterly, annual), unless specified otherwise in the section or subsection that imposes the requirement, refer to the standard calendar periods.

(i) Notwi thstanding time periods specified in this subpart F or subpart G of this part for completion of required tasks, such time periods may be changed by mutual agreement between the owner or operator and the Administrator, as specified in subpart A of this

part (e.g., a period could begin on the compliance date or another date, rather than on the first day of the standard calendar period). For each time period that is changed by agreement, the revised period shall remain in effect until it is changed. A new requ est is not necessary for each recurring period.

(ii) Where the period specified for compliance is a standard calendar period, if the initial compliance date occurs after the beginning of the period, compliance shall berequired according to the schedule s pecified in paragraphs (k)(9)(ii)(A) or (k)(9)(ii)(B)

of this section, as appropriate.

(A) Compliance shall be required before the end of the standard calendar period within which the compliance deadline occurs, if there remain at least 3 days for tasks t hat must be performed weekly, at least 2 weeks for tasks that must be performed monthly, at least 1 month for tasks that must be performed each quarter, or at least 3 months for tasks that must be performed annually; or

(B) In all other cases, compliance shall be required before the end of the first full standard calendar period after the period within which the initial compliance deadline

occurs. (iii) In all instances where a provision of this subpart F or subpart G of this part requires completion of a task during each of multiple successive periods, an owner or operator may perform the required task at any time during the specified period, provided the task is conducted at a reasonable interval after completion of the task during the previous period.

EPA explained the basis for this provision at 61 FR 43702 (August 20, 1996) as follows:

3. Clarification of Compliance Periods

The proposed revisions to subpart F also would add a new paragraph (k)(9) to § 63.100, and a new paragraph (g) to § 63.162 to clarify that when the rule specifies a period of time for completion of required tasks (e.g., weekly, monthly, quarterly, annual), this

refers to standard calendar periods unless it is specified otherwise in the section or paragraph that imposes the requir ement. The current rule does not specify this, and this text is being added to the rule to remove any potential for ambiguity. The new §63.100(k)(9) and § 63.162(g) also provide that time periods may be changed by mutual agreement between the owner or oper ator and the Administrator, as provided in subpart

A of this part. Finally, this new set of provisions also provides that if the rule requires completion of a task during each of multiple successive periods, an owner or operator may perform the required ta sk at any time during the s pecified period, provided the task

is conducted at a reasonable interval after completion of the previous task. When the rule was originally drafted it was assumed that this could be done, but an oversight in drafting language sp ecifying this was omitted from the rule.

It should also be noted that Subpart H of the HON includes essentially the same language at §63.162(g) and that Subpart H is a specified compliance option for equipment leaks under Subpart CC. Therefore, this lang uage already specifically applies to a portion of Subpart CC.

Any other interpretation of the term “monthly” causes major problems because 1) it would be

inconsistent with the MACT floor determination, which was based on monitoring the Heat Exchanger S yst em twelve times per year, as done under Texas rules, not monitoring 13 or more

times as would result from other interpretations, 2) the compliance date for the next monitoring would change after each monitoring, making it difficult for sources and inspecto rs to determine if compliance was timely, and 3) would interfere with efficient scheduling of resources to do the monitoring, because the monitoring would be required at different times each month.R eading the term “monthly” to mean anything other than ca lendar month in this case would also

raise serious questions about due process, since the rulemaking did not provide for notice and comment on any other interpretation than the generally accepted one

, and would raise questions about compliance with all the other provisions in Subpart CC where this term is used (e.g. equipment leaks, wastewater) and where similar terms, such as daily 1 , quarterly and annually are

used.

1 §63.1(a)(10) specifies “ For the purposes of this part, time periods specified in days s hall be measured in calendar days, even if the word “calendar” is absent, unless otherwise specified in an applicable requirement. ”