§  75.16 Special provisions for monitoring emissions from common, by-pass, and multiple stacks for SO2 emissions and heat input determinations.

(a) Phase I common stack procedures. Prior to January 1, 2000, the following procedures shall be used when more than one unit utilize a common stack:

(1) Only Phase I units or only Phase II units using common stack. When a Phase I unit uses a common stack with one or more other Phase I units, but no other units, or when a Phase II unit uses a common stack with one or more Phase II units, but no other units, the owner or operator shall either:

(i) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct to the common stack from each affected unit; or

(ii) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the common stack; and

(A) Combine emissions for the affected units for recordkeeping and compliance purposes; or

(B) Provide information satisfactory to the Administrator on methods for apportioning SO2 mass emissions measured in the common stack to each of the affected units. The designated representative shall provide the information to the Administrator through a petition submitted under §  75.66. The Administrator may approve such substitute methods for apportioning SO2 mass emissions measured in a common stack whenever the method ensures complete and accurate accounting of all emissions regulated under this part.

(2) Phase I unit using common stack with non-Phase I unit(s). When one or more Phase I units uses a common stack with one or more Phase II or nonaffected units, the owner or operator shall either:

(i) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct to the common stack from each affected unit; or

(ii) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the common stack; and

(A) Designate any Phase II unit(s) as a substitution or compensating unit(s) in accordance with part 72 of this chapter and any nonaffected unit(s) as opt-in units in accordance with part 74 of this chapter and combine emissions for recordkeeping and compliance purposes; or

(B) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct from each Phase II or nonaffected unit; calculate SO2 mass emissions from the Phase I units as the difference between SO2 mass emissions measured in the common stack and SO2 mass emissions measured in the ducts of the Phase II and nonaffected units; record and report the calculated SO2 mass emissions from the Phase I units, not to be reported as an hourly average value less than zero; and combine emissions for the Phase I units for compliance purposes; or

(C) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct from each Phase I or nonaffected unit; calculate SO2 mass emissions from the Phase II units as the difference between SO2 mass emissions measured in the common stack and SO2 mass emissions measured in the ducts of the Phase I and nonaffected units, not to be reported as an hourly average value less than zero; and combine emissions for the Phase II units for recordkeeping and compliance purposes; or

(D) Record the combined emissions from all units as the combined SO2 mass emissions for the Phase I units for recordkeeping and compliance purposes; or

(E) Provide information satisfactory to the Administrator on methods for apportioning SO2 mass emissions measured in the common stack to each of the units using the common stack. The designated representative shall provide the information to the Administrator through a petition submitted under §  75.66. The Administrator may approve such substitute methods for apportioning SO2 mass emissions measured in a common stack whenever the method ensures complete and accurate accounting of all emissions regulated under this part.

(3) Phase II unit using common stack with non-affected unit(s). When one or more Phase II units uses a common stack with one or more nonaffected units, the owner or operator shall follow the procedures in paragraph (b)(2) of this section.

(b) Phase II common stack procedures. On or after January 1, 2000, the following procedures shall be used when more than one unit uses a common stack:

(1) Unit utilizing common stack with other affected unit(s). When a Phase I or Phase II affected unit utilizes a common stack with one or more other Phase I or Phase II affected units, but no nonaffected units, the owner or operator shall either:

(i) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct to the common stack from each affected unit; or

(ii) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the common stack; and

(A) Combine emissions for the affected units for recordkeeping and compliance purposes; or

(B) Provide information satisfactory to the Administrator on methods for apportioning SO2 mass emissions measured in the common stack to each of the Phase I and Phase II affected units. The designated representative shall provide the information to the Administrator through a petition submitted under §  75.66. The Administrator may approve such substitute methods for apportioning SO2 mass emissions measured in a common stack whenever the method ensures complete and accurate accounting of all emissions regulated under this part.

(2) Unit utilizing common stack with nonaffected unit(s). When one or more Phase I or Phase II affected units utilizes a common stack with one or more nonaffected units, the owner or operator shall either:

(i) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct to the common stack from each Phase I and Phase II unit; or

(ii) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the common stack; and

(A) Designate the nonaffected units as opt-in units in accordance with part 74 of this chapter and combine emissions for recordkeeping and compliance purposes; or

(B) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in the duct from each nonaffected unit; determine SO2 mass emissions from the affected units as the difference between SO2 mass emissions measured in the common stack and SO2 mass emissions measured in the ducts of the nonaffected units, not to be reported as an hourly average value less than zero; combine emissions for the Phase I and Phase II affected units for recordkeeping and compliance purposes; and calculate and report SO2 mass emissions from the Phase I and Phase II affected units, pursuant to an approach approved by the Administrator, such that these emissions are not underestimated; or

(C) Record the combined emissions from all units as the combined SO2 mass emissions for the Phase I and Phase II affected units for recordkeeping and compliance purposes; or

(D) Petition through the designated representative and provide information satisfactory to the Administrator on methods for apportioning SO2 mass emissions measured in the common stack to each of the units using the common stack and on reporting the SO2 mass emissions. The Administrator may approve such demonstrated substitute methods for apportioning and reporting SO2 mass emissions measured in a common stack whenever the demonstration ensures that there is a complete and accurate accounting of all emissions regulated under this part and, in particular, that the emissions from any affected unit are not underestimated.

(c) Unit with bypass stack. Whenever any portion of the flue gases from an affected unit can be routed so as to avoid the installed SO2 continuous emission monitoring system and flow monitoring system, the owner or operator shall either:

(1) Install, certify, operate, and maintain an SO2 continuous emission monitoring system or flow monitoring system on the bypass flue, duct, or stack gas stream and calculate SO2 mass emissions for the unit as the sum of the emissions recorded by all required monitoring systems; or

(2) Monitor SO2 mass emissions on the bypass flue, duct, or stack gas stream using the reference methods in §  75.22(b) for SO2 and flow and calculate SO2 mass emissions for the unit as the sum of the emissions recorded by the installed monitoring systems on the main stack and the emissions measured by the reference method monitoring systems; or

(3) Where a Federal, State, or local regulation or permit prohibits operation of the bypass stack or duct or limits operation of the bypass stack or duct to emergency situations resulting from the malfunction of a flue gas desulfurization system record the following values for each hour during which emissions pass through the bypass stack or duct: the maximum potential concentration for SO2 as determined under section 2 of appendix A of this part, and the hourly volumetric flow value that would be substituted for the flow monitor installed on the main stack or flue under the missing data procedures in subpart D of this part if data from the flow monitor installed on the main stack or flue were missing for the hour. Calculate SO2 mass emissions for the unit as the sum of the emissions calculated with the substitute values and the emissions recorded by the SO2 and flow monitoring systems installed on the main stack.

(d) Unit with multiple stacks or ducts. When the flue gases from an affected unit utilize two or more ducts feeding into two or more stacks (that may include flue gases from other affected or nonaffected units), or when the flue gases utilize two or more ducts feeding into a single stack and the owner or operator chooses to monitor in the ducts rather than the stack, the owner or operator shall either:

(1) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in each duct feeding into the stack or stacks and determine SO2 mass emissions from each affected unit as the sum of the SO2 mass emissions recorded for each duct; or

(2) Install, certify, operate, and maintain an SO2 continuous emission monitoring system and flow monitoring system in each stack. Determine SO2 mass emissions from each affected unit as the sum of the SO2 mass emissions recorded for each stack. Notwithstanding the prior sentence, if another unit also exhausts flue gases to one or more of the stacks, the owner or operator shall also comply with the applicable common stack requirements of this section to determine and record SO2 mass emissions from the units using that stack and shall calculate and report SO2 mass emissions from the affected units and stacks, pursuant to an approach approved by the Administrator, such that these emissions are not underestimated.

(e) Heat input. The owner or operator of an affected unit using a common stack, bypass stack, or multiple stacks shall account for heat input according to the following:

(1) The owner or operator of an affected unit using a common stack, bypass stack, or multiple stack with a diluent monitor and a flow monitor on each stack may choose to install monitors to determine the heat input for the affected unit, wherever flow and diluent monitor measurements are used to determine the heat input, using the procedures specified in paragraphs (a) through (d) of this section, except that the term "heat input" shall apply rather than "SO2 mass emissions" or "emissions" and the phrase "a diluent monitor and a flow monitor" shall apply rather than "SO2 continuous emission monitoring system and flow monitoring system." The applicable equation in appendix F to this part shall be used to calculate the heat input from the hourly flow rate, diluent monitor measurements, and (if the equation in appendix F requires a correction for the stack gas moisture content) hourly moisture measurements. Notwithstanding the options for combining heat input in paragraphs (a)(1)(ii), (a)(2)(ii), (b)(1)(ii), and (b)(2)(ii) of this section, the owner or operator of an affected unit with a diluent monitor and a flow monitor installed on a common stack to determine the combined heat input at the common stack shall also determine and report heat input to each individual unit.

(2) In the event that an owner or operator of a unit with a bypass stack does not install and certify a diluent monitor and flow monitoring system in a bypass stack, the owner or operator shall determine total heat input to the unit for each unit operating hour during which the bypass stack is used according to the missing data provisions for heat input under §  75.36 or the procedures for calculating heat input from fuel sampling and analysis in section 5.5 of appendix F of this part.

(3) The owner or operator of an affected unit with a diluent monitor and a flow monitor installed on a common stack to determine heat input at the common stack may choose to apportion the heat input from the common stack to each affected unit utilizing the common stack by using either of the following two methods, provided that all of the units utilizing the common stack are combusting fuel with the same F-factor found in section 3 of appendix F of this part. The heat input may be apportioned either by using the ratio of load (in MWe) for each individual unit to the total load for all units utilizing the common stack or by using the ratio of steam flow (in 1000 lb/hr) for each individual unit to the total steam flow for all units utilizing the common stack. If using either of these apportionment methods, the owner or operator shall apportion according to section 5.6 of appendix F to this part.

(4) Notwithstanding paragraph (e)(1) of this section, any affected unit that is using the procedures in this part to meet the monitoring and reporting requirements of a State or federal NOX mass emission reduction program must also meet the requirements for monitoring heat input in §§  75.71, 75.72 and 75.75.

[60 FR 26522, May 17, 1995, as amended at 61 FR 25582, May 22, 1996; 61 FR 59158, Nov. 20, 1996; 64 FR 28591, May 26, 1999]