San Diego County Air Pollution Control District Rule 69.4.1

Regulation IV – 11/20/00 -1-

RULE 69.4.1. STATIONARY RECIPROCATING INTERNAL COMBUSTION 

ENGINES - BEST AVAILABLE RETROFIT CONTROL 

TECHNOLOGY (BARCT) (Adopted & Effective 11/15/00)

(a) APPLICABILITY

(1) Except as provided in Section (b), this rule shall apply to stationary internal 

combustion engines with a brake horsepower (bhp) rating of 50 or greater.

(2) An engine subject to this rule and located at a major stationary source of 

oxides of nitrogen (NOx) is also subject to the applicable requirements of Rule 69.4.

(3) An engine subject to this rule shall not be subject to Rule 68.

(b) EXEMPTIONS

(1) This rule shall not apply to the following:

(i) Engines used exclusively in connection with a structure designed for and 

used as a dwelling for not more than four families.

(ii) Engines used exclusively in agricultural operations for the growing of 

crops or the raising of fowl or animals.

(iii) Any engine when operated exclusively within a permitted test cell solely 

for the research, development, or testing of gas turbine engines or their components.

(iv) Any engine when operated exclusively within a permitted test cell solely 

for the research, development, or testing of reciprocating internal combustion 

engines or their components.

(v) Any engine used exclusively in conjunction with military tactical support 

equipment.

(2) The provisions of Subsections (d)(1) through (d)(3), (e)(1), (e)(2), (f)(1), 

(f)(3), (g)(3), (g)(4), (g)(5) and (i)(1) of this rule shall not apply to the following:

(i) Any existing engine which operates less than 200 hours per calendar 

year, as determined by a non-resettable meter that measures elapsed operating time. 

(ii) Any existing emergency standby engine provided that operation of the 

engine for non-emergency purposes does not exceed 52 hours per calendar year. 

Operation for testing or maintenance purposes may be allowed for not more than 

100 hours per year, with written authorization from the Air Pollution Control 

Officer, provided that an owner or operator demonstrates to the satisfaction of the 

Air Pollution Control Officer that such additional operation is necessary.
Regulation IV -2- Rule 69.4.1

(iii) Any existing emergency standby engine at a nuclear power generating 

station subject to the requirements of the Nuclear Regulatory Commission provided 

that operation of the engine for non-emergency purposes does not exceed 200 hours 

per calendar year. 

(3) The provisions of Subsections (e)(1), (e)(2), (f)(1), (g)(3), (g)(4), (g)(5) and 

(i)(1) of this rule shall not apply to:

(i) Any new or replacement emergency standby engine, provided that 

operation of the engine for non-emergency purposes does not exceed 52 hours per 

calendar year. Operation for testing or maintenance purposes may be allowed for 

not more than 100 hours per year, with written authorization from the Air Pollution 

Control Officer, provided that an owner or operator demonstrates to the satisfaction 

of the Air Pollution Control Officer that such additional operation is necessary.

(ii) Any new or replacement engine which operates less than 200 hours per 

calendar year, as determined by a non-resettable meter that measures elapsed 

operating time.

(4) The provisions of Subsections (d)(1) through (d)(3) of this rule shall not apply 

to existing low-use diesel engines equipped with any two of the following: turbocharger, 

aftercooler, or injection timing retard by 4 degrees.

An owner or operator of an engine who is claiming an exemption pursuant to Subsections (b)(2), (b)(3) or (b)(4) shall maintain records in accordance with Subsections 

(g)(1) and (g)(2) of this rule.

(c) DEFINITIONS

For the purposes of this rule, the following definitions shall apply:

(1) "Add-on Control Equipment" means any technology that is used to reduce

emissions from the exhaust gas stream of an engine and is installed downstream of the 

engine.

(2) "Best Available Retrofit Control Technology (BARCT)" means an 

emission limitation that is based on the maximum degree of reduction achievable, taking 

into account environmental, energy, and economic impacts by each class or category of 

source.

(3) "Brake Horsepower Rating, (bhp)" means the maximum continuous brake 

horsepower rating as specified by the engine manufacturer and listed on the engine 

nameplate, if available, regardless of any derating.

(4) "Calendar Year" means the same as defined in Rule 2.
Regulation IV -3- Rule 69.4.1

(5) "California Diesel Fuel" means any fuel that is commonly or commercially 

known, sold or represented as diesel fuel No. 1-D or No. 2-D, and which meets the 

requirements specified in Sections 2281 and 2282 of Title 13 of the California Code of 

Regulations. 

(6) "Capacity Factor" means the ratio, expressed as a percentage, of the annual 

fuel consumption to the manufacturer's specified maximum annual fuel consumption or 

manufacturer's specified maximum hourly fuel consumption times 8760 hours, whichever 

is less.

(7) "Certified Engine" means an engine certified to comply with the Tier 1, Tier 

2, or Tier 3 emission standards specified in Section 89.112 of the Code of Federal 

Regulations (40 CFR Part 89) - Control of Emissions of Air Pollution from Non-Road 

Diesel Engines or with the Tier 1, Tier 2, or Tier 3 emission standards specified in Section 

2423 of Title 13 of the California Code of Regulations - California Regulations for New 

1996 and Later Off-Road Compression-Ignition Engines.

(8) "Cyclic Engine" means an engine, such as gantry cranes, having an external 

load which varies by approximately 40 percent or more of rated capacity under normal 

operating conditions during any load cycle.

(9) "Emergency Standby Engine" means an engine used exclusively in emergency situations, except as provided in Subsections (b)(2)(ii), (b)(2)(iii) and (b)(3)(i), to 

drive an electrical generator, an air compressor or a water pump.

(10) "Emergency Situation" means any one of the following:

(i) An unforeseen electrical power failure from the serving utility or of onsite electrical transmission equipment.

(ii) An unforeseen flood or fire, or a life-threatening situation.

(iii) Operation of emergency generators for Federal Aviation Administration 

licensed or military airports for the purpose of providing power in anticipation of a 

power failure due to severe storm activity.

Emergency situation shall not include operation for purposes of supplying power for 

distribution to an electrical grid, operation for training purposes, or other foreseeable events.

(11) "Engine Family" means a group of engines expected to have similar emission 

and other characteristics throughout their useful life as specified in Section 89.116, 40 

CFR 89.

(12) "Engine Tampering" means removing or rendering inoperative any device or 

design element of the engine or its emission control system; or the manufacturing or 

installation of a part or a component which objective is to bypass, defeat, or render 

inoperative a device or design element of the engine or its emission control system.
Regulation IV -4- Rule 69.4.1

(13) "Existing Engine" means an engine which commenced operation in San Diego 

County on or before November 15, 2000.

(14) "Fossil Derived Gaseous Fuel" means gaseous fuel including, but not limited 

to, natural gas, methane, ethane, propane, butane, and gases stored as liquids at high 

pressure such as liquefied petroleum gas, but excluding waste derived gaseous fuel.

(15) "High-use Engine" means an engine operating at a capacity factor of greater 

than 15%.

(16) "Lean-burn Engine" means an engine that is designed to operate with an airto-fuel ratio that is more than 1.1 times the stoichiometric air-to-fuel ratio.

(17) "Load Cycle" means the time interval between consecutive commencement 

of application of external load to an engine.

(18) "Low-use Engine" means an engine operating at a capacity factor of 15% or 

less.

(19) "Military Tactical Support Equipment" means the same as defined in Rule 2.

(20) "New Engine" means an engine which commenced operation in San Diego 

County after November 15, 2000.

(21) "Portable Emission Unit" means the same as defined in Rule 20.1.

(22) "Replacement Engine" means an engine that meets the definition of a 

replacement emission unit in Rule 20.1.

(23) "Rich-Burn Engine" means an engine that is designed to operate with an airto-fuel ratio less than or equal to 1.1 times the stoichiometric air-to-fuel ratio.

(24) "Stationary Internal Combustion Engine" or "Engine" means a spark or 

compression ignited, reciprocating internal combustion engine which is not a portable 

emission unit.

(25) "Stationary Source" means the same as defined in Rule 2.

(26) "Stoichiometric Air-to-Fuel Ratio" means the chemically balanced air-tofuel ratio at which all fuel and all oxygen in the air and fuel mixture are theoretically 

consumed by combustion.

(27) "Uncontrolled NOx Emissions" means NOx emissions from an engine 

before application of add-on control equipment.

(28) "Volatile Organic Compound (VOC)" means the same as defined in Rule 2.
Regulation IV -5- Rule 69.4.1

(29) "Waste Derived Gaseous Fuel" means gaseous fuel including, but not 

limited to, digester gas and landfill gas, but excluding fossil derived gaseous fuel.

(d) STANDARDS

(1) A person shall not operate a stationary internal combustion engine subject to 

this rule unless: 

(i) Uncontrolled NOx emissions from the following engines are reduced 

with add-on control equipment by not less than the following:

Weight Percent

Engine Category

Reduction

Rich-burn engines using fossil derived gaseous fuel or gasoline 96

Lean-burn engines using fossil derived gaseous fuel 90

Engines using exclusively waste derived gaseous fuel 90

Engines using diesel or kerosene fuel 90

or

(ii) The emissions of NOx, in parts per million by volume (ppmv), calculated 

as nitrogen dioxide at 15% oxygen on a dry basis, or in grams of NOx per brake 

horsepower-hour, as indicated, are not greater than the following:

Engine Category Concentration of NOx

Rich-burn engines using fossil derived gaseous fuel or

gasoline 25 ppmv

Rich-burn engines using exclusively waste derived 

gaseous fuel 50 ppmv

Lean-burn engines using gaseous fuel 65 ppmv

Existing low-use engines using diesel or kerosene fuel 9.0 g/bhp-hr or 700 ppmv

Existing cyclic engines using diesel or kerosene fuel 9.0 g/bhp-hr or 700 ppmv

High-use engines using diesel or kerosene fuel 6.9 g/bhp-hr or 535 ppmv

New or replacement low-use engines using diesel or 

kerosene fuel 6.9 g/bhp-hr or 535 ppmv

New or replacement cyclic engines using diesel or 

kerosene fuel 6.9 g/bhp-hr or 535 ppmv

(2) For all engines subject to Subsection (d)(1) of this rule, emissions of carbon 

monoxide (CO), calculated at 15% oxygen on a dry basis, shall not exceed 4,500 ppmv.

(3) For all rich-burn engines subject to Subsection (d)(1) of this rule, emissions of 

VOC, calculated as methane at 15% oxygen on a dry basis, shall not exceed 250 ppmv.
Regulation IV -6- Rule 69.4.1

(4) Any engine subject to this rule and operating on diesel fuel shall use only 

California Diesel Fuel. 

(e) MONITORING REQUIREMENTS

(1) An owner or operator of an engine without add-on control equipment, except 

engines specified in Subsections (b)(2) or (b)(3), shall monitor the operating parameters 

recommended by the engine manufacturer and any additional operating parameters 

identified by the Air Pollution Control Officer. Such operating parameters may include, 

but are not limited to:

(i) engine air-to-fuel ratio;

(ii) engine inlet manifold temperature and pressure; and

(iii) oxygen content of the exhaust gas.

Where the Air Pollution Control Officer determines that it is not feasible to monitor 

operating parameters of an engine or such monitoring may not be indicative of air 

contaminant emissions, the requirements of this subsection may be waived provided that 

periodic inspection and maintenance are conducted as specified in Section (f).

(2) An owner or operator of an engine with add-on control equipment shall install, 

operate and maintain in calibration, devices that continuously monitor the operational 

characteristics of the engine and any NOx emission reduction system as determined 

necessary to ensure compliance by the Air Pollution Control Officer. Such operational 

characteristics may include, but are not limited to:

(i) engine air-to-fuel ratio;

(ii) temperature of exhaust gas at the inlet and outlet of the add-on control 

equipment; 

(iii) oxygen content of exhaust gas at the inlet and outlet of the add-on 

control equipment; and

(iv) flow rate of NOx reducing agent added to the engine exhaust gas.

(3) An owner or operator of an engine subject to this rule shall install a nonresettable totalizing fuel meter and/or non-resettable meter that measures elapsed 

operating time as determined appropriate by the Air Pollution Control Officer. 
Regulation IV -7- Rule 69.4.1

(f) INSPECTION AND MAINTENANCE REQUIREMENTS

(1) An owner or operator of an engine subject to this rule, except engines specified 

in Subsections (b)(2) or (b)(3), shall conduct periodic inspections of the engine and any 

add-on control equipment, as applicable, to ensure that the engine and control equipment is 

operated in compliance with the provisions of this rule. Inspections shall be conducted at 

least once every 4000 hours of operation, or every six months, whichever is less.

(2) An owner or operator of an engine subject to this rule shall conduct periodic 

maintenance of the engine and any add-on control equipment, as applicable, as recommended by the engine and control equipment manufacturers or as specified by any other 

maintenance procedure approved in writing by the Air Pollution Control Officer. The 

periodic maintenance shall be conducted at least once each calendar year.

(3) Notwithstanding the frequencies specified in Subsections (f)(1)and (f)(2), the 

Air Pollution Control Officer may require an owner or operator of an engine to conduct 

inspections and/or maintenance of the engine and any associated add-on control equipment more frequently if deemed necessary to assure compliance with this rule.

(g) RECORDKEEPING REQUIREMENTS

(1) An owner or operator of an engine subject to this rule shall keep the following 

records and shall maintain these records on-site for at least the same period of time as the 

engine to which the records apply is located at the site:

(i) engine manufacturer name and model number;

(ii) brake horsepower rating; 

(iii) combustion method (i.e. rich-burn or lean-burn); 

(iv) fuel type; 

(v) California Diesel Fuel certification, if applicable; and

(vi) a manual of recommended maintenance as provided by the engine 

manufacturer, or other maintenance procedure as approved in writing by the Air 

Pollution Control Officer.

Where the information specified in Subsections (g)(1)(i) through (g)(1)(iv) is 

contained in a District Permit to Operate or Certificate of Registration, and is the most 

current information, an additional record of this information shall not be required.

(2) An owner or operator of an engine exempt pursuant to Subsections (b)(2) or 

(b)(3) shall maintain an operating log containing, at a minimum, the following:

(i) dates and times of engine operation. If applicable, indicate whether the 

operation was for non-emergency purposes or during an emergency situation and the 

nature of the emergency, if available;
Regulation IV -8- Rule 69.4.1

(ii) total cumulative hours of operation per calendar year, based on actual 

readings of engine hour or fuel meter; and

(iii) records of periodic engine maintenance, including dates maintenance 

was performed.

The records specified in Subsection (g)(2)(i) are not required if total engine 

operations for any purpose, including emergency situations, do not exceed 52 hours 

in a calendar year.

(3) An owner or operator of an engine subject to this rule, except engines 

specified in Subsections (b)(2) or (b)(3), shall maintain a log containing at a minimum, 

the following: 

(i) records of engine inspection, including dates an inspection was 

performed; and

(ii) records of engine maintenance, including dates maintenance was 

performed and the nature of the maintenance.

(4) An owner or operator of an engine subject to this rule, except engines 

specified in Subsections (b)(2) or (b)(3), shall measure and record at least once each 

calendar month the applicable operating parameters identified pursuant to Subsections 

(e)(1) or (e)(2).

(5) An owner or operator of a low-use engine operating on diesel or kerosene fuel 

and subject to the requirements of Section (d)(1) shall maintain records of total 

cumulative hours of operation or total fuel consumption per calendar year, as applicable.

(6) All records required by Subsections (g)(2) through (g)(5) shall be retained onsite for at least three years and made available to the District upon request.

(h) TEST METHODS

(1) All testing performed to determine compliance with the emission limits of 

Subsections (d)(1), (d)(2) and/or (d)(3), except as provided in Subsection (h)(3), shall be 

conducted in accordance with the following procedures:

(i) Measurement of NOx, CO, carbon dioxide (CO2) and oxygen content of 

exhaust gas shall be determined in accordance with the San Diego County Air 

Pollution Control District Test Method 100, Air Resources Board (ARB) Test 

Method 100 or equivalent Environmental Protection Agency (EPA) Test Method.

(ii) Measurement of VOC emissions shall be determined in accordance 

with EPA Test Methods 25A and/or 18.
Regulation IV -9- Rule 69.4.1

(iii) NOx, VOC, and CO emission concentrations shall be calculated as an 

average of three subtests. The averaging period to calculate NOx and CO emission 

concentrations and to determine compliance shall be at least 30 minutes and not 

more than 60 minutes unless otherwise specified in writing by the Air Pollution 

Control Officer. 

(2) Specifications for California Diesel Fuel, if not provided by a vendor, shall be 

determined by the test methods specified in Sections 2281 and 2282 of Title 13 of the 

California Code of Regulations.

(3) For an engine operating on diesel or kerosene fuel without add-on control 

equipment and certified by EPA or ARB at an emission rate equal to or below the 

applicable emission rate limits of Section (d), measurements of NOx, CO, CO2, and 

oxygen content of exhaust gas shall be conducted in accordance with a test method 

approved by the District and ARB. Until such test method is approved, such engine shall 

be deemed in compliance with the emission rate limits of Section (d), provided the 

requirements of Subsection (i)(4) are met.

(4) If a portable emission analyzer is used to provide emission data, the analyzer 

shall be calibrated and operated in accordance with a protocol approved in writing by the 

Air Pollution Control Officer.

(i) SOURCE TEST REQUIREMENTS

Except as provided in Subsection (i)(4), source tests shall be conducted according to 

the following:

(1) After initial compliance has been determined, any engine subject to the 

requirements of Subsections (d)(1), (d)(2) and/or (d)(3), except engines specified in 

Subsection (b)(3), shall be source tested at least once every 24 months, unless otherwise 

specified in writing by the Air Pollution Control Officer.

(2) Emissions source testing shall be conducted using the test methods specified in 

Section (h) and a source test protocol approved in writing by the Air Pollution Control 

Officer prior to testing.

(3) Emissions source testing shall be performed at no less than 80 percent of the 

brake horsepower rating. If an owner or operator of an engine demonstrates to the 

satisfaction of the Air Pollution Control Officer that the engine does not operate at these 

conditions, then emissions source testing shall be performed at the highest achievable 

continuous brake horsepower rating, or under the typical duty cycle or operational mode 

of the engine.

(4) Notwithstanding the requirements of Subsection (i)(1), any engine operating 

on diesel or kerosene fuel without add-on control and certified by EPA or ARB at 

emission rates equal to or below the applicable emission rate limits of Section (d) shall 

not require an initial or periodic source test, until an appropriate test method is approved 

by the District and ARB, provided the following requirements are met:
Regulation IV -10- Rule 69.4.1

(i) The engine family has been tested and certified according to an EPA or 

ARB approved procedure, and the certification documents are provided to the 

District.

(ii) The engine family does not participate in the federal ABT program 

specified in 40 CFR 89, Subpart C and adopted by reference by ARB. 

(iii) The engine and its emission control system are maintained as specified in 

Section (f).

(iv) There is no evidence of engine tampering.

(j) COMPLIANCE SCHEDULE

(1) For an engine operating on diesel fuel, comply with the requirements of 

Subsection (d)(4) by May 15, 2001.

(2) The owner or operator of an existing engine subject to the requirements of this 

rule shall meet the following increments of progress:

(i) By May 15, 2001, submit to the Air Pollution Control Officer an 

application to modify conditions on the Permit to Operate or to convert a Certificate 

of Registration to a Permit to Operate, as necessary to comply with the applicable 

requirements of this rule. The application shall include the following information 

for the engine that will be evaluated for compliance with this rule:

(A) The information required by Section (g)(1),

(B) emission rate data and source of such data, and

(C) description of how compliance will be achieved (e.g. retrofit, 

replacement).

(ii) By November 15, 2002, submit to the Air Pollution Control Officer 

documentation which demonstrates that the engine is in compliance with the Section 

(d)(1) through (d)(3) emission limits for NOx, CO and VOC, and all other 

applicable requirements of this rule. 

(3) For a new or replacement engine, including a new or replacement engine 

operating less than 200 hours per calendar year or a new or replacement emergency 

standby engine, comply with all applicable requirements of this rule upon installation and 

startup.