October 15, 2009 

Air and Radiation Docket and Information Center 

Environmental Protection Agency 

1200 Pennsylvania Avenue, NW

Washington, DC 20460 

Attn: Melanie King 

Submitted via email to king.melanie@epa.gov 

Re: Docket ID No. EPA-HQ-OAR-2008-0708 

The Bay Area Clean Water Agencies (BACWA) Air Issues and Regulations (AIR) Committee 

appreciates your timely response to our comments in the letter dated 8/19/2009 on the 

proposed national emission standards for hazardous air pollutants (NESHAP) for stationary 

reciprocating internal combustion engines (RICE). 

In response to the questions you asked our committee in your 8/20/2009 email, our 

members have provided the following feedback regarding their facilities’ operation and 

maintenance of their on-site RICE engines. 

You requested any stack test data that our member agencies may have from their engines. 

We have included the Source Test Results for RICE engines conducted and approved by the 

local air district, the Bay Area Air Quality Management District (BAAQMD). Two of our 

member agencies have submitted their facilities’ engine test results for your reference: East 

Bay Municipal Utility District (EBMUD) and San Jose Water Pollution Control Plant 

(WPCP). The test result reports are recent, ranging from 2007 to 2009. Please note that the 

engine size and digester gas percentage vary. All of these engines are cogeneration engines 

which utilize digester gas, a product of the wastewater treatment process, in combination 

with natural gas to fuel the engines and recover heat from the engines for process heating. 

Please see Attachment 1 for the stack test data reports. Also, included in Attachment 1 is the 

testing method used by BAAQMD and cited in the engine test results for your reference, 

Source Test Procedure ST-6. 

The overall average carbon monoxide (CO) emission level from the attached reports, by 

method ST-6 at 15% O2, was about 285 ppm. This average is about 60 percent higher than 

the proposed standard of 177 ppmvd. Therefore, according to the proposed regulation, 

these engines would be subject to emission mitigation measures or have to be replaced. 

In response to your second question regarding our members’ major source status, BACWA 

is comprised of about fifty-five local government agencies of varied jurisdiction sizes 

throughout the San Francisco Bay Area. BACWA members own and operate publicly 

owned treatment works (POTWs) that serve over 5 million people, treating all domestic, 
commercial and a significant amount of industrial wastewater. BACWA members fall into 

both regulatory categories: major and area sources. The two agencies that are submitting 

stack test data, EBMUD and San Jose WPCP, are both major sources of criteria pollutants. 

In response to your third question regarding requiring work practice standards in lieu of an 

emissions limit, we believe that this is a complicated question. Operating and maintaining 

the equipment to improve efficiency may reduce levels of HAPs per engine output 

(mechanical work performed or electricity generated) but may not necessarily result in 

lowest emission concentrations. In addition, operating conditions are sometimes driven by 

the need to simultaneously achieve emission limitations for multiple pollutants. Engine 

owners and operators must adjust operation and maintenance processes to meet CO and 

NOx emission limits. To lower the current CO level, operators would need to raise cylinder 

exhaust temperatures to meet CO limits, but this, in turn, would raise the NOx emissions. 

Achieving compliance for one parameter potentially affects the engine’s ability to meet 

other emission and/or operational requirements. 

The AIR Committee would like to emphasize that our member agencies’ digester gas fueled 

RICE engines meet local air emission and operating requirements and that an annual or 

biannual compliance test would be sufficient to ensure engine compliance. Continuous 

monitoring is not only costly and maintenance intensive, but most importantly does not 

yield dramatically different or more accurate results than a less frequent engine emissions 

test. 

This regulation would potentially discourage the use of valuable and readily available 

alternative fuel sources (e.g. digester gas and landfill gas). Utilities may find purchasing 

power from a utility company and flaring digester gas to be a more economical alternative. 

However, this would have the negative impact of decreasing the number of renewable 

energy co-generation systems that are ubiquitous in wastewater treatment plants. The AIR 

Committee urges the EPA to consider the overall cost compared to net environmental 

benefit of regulating these types of engines, which are already utilizing a form of alternative 

fuel. 

To retrofit or replace existing digester gas-fueled engines would be a heavy financial burden 

on our member agencies, all essential public services. The AIR Committee would like to 

echo the comments of the National Association of Clean Water Agencies (NACWA) that the 

proposed “low emission levels may be an appropriate requirement for new engines, but the 

cost to retrofit existing engines and install emissions controls has not been justified in the 

proposed rule.” Also, these measures would likely cost each utility millions of dollars; in 

addition to the investment to retrofit or replace engines, substantial investment may be 

required in cleaning biogas to reduce siloxane and reduced sulfur concentrations. We would 

support conducting a more detailed cost analysis of the regulation as it affects digester 

engine owners and operators. 

A suggestion the AIR Committee would like to make regarding the implementation of the 

proposed changes to the NESHAP for RICE would be staggered compliance deadlines 

based on facility categories. The AIR Committee requests that EPA consider providing an 

extended compliance schedule for engines combusting renewable biogas to provide time for 

evaluating and implementing cost-effective compliance technologies. This lessens the 

financial impact of these types of regulations on local entities. It also allows for our public 

agencies to form a long-term plan of emission mitigation and to plan ahead and budget for 

the needed funding to implement these measures. 
The Air Committee would welcome an EPA-funded early compliance incentive program 

that would supply grants to agencies that meet certain criteria to help fund equipment 

retrofits or replacement. The projects funded by these grants would provide the needed 

data to assist our member agencies in identifying cost effective compliance approaches 

during these challenging economic times. 

Lastly, the AIR Committee would like to clarify that references made in our previous letter 

to total organic carbon (TOC). TOC is more appropriately used when referring to carbon 

content in an aqueous stream. Instead, we would like the EPA to consider the option to use 

the non-methane hydrocarbons (NMHC) as an alternative surrogate parameter to carbon 

monoxide. The committee proposes giving the owners and operators the option of meeting 

a NMHC limit in lieu of meeting a CO limit. This gives flexibility to an engine’s 

owner/operator while still minimizing HAP emissions. 

Thank you for your consideration of our comments on the proposed NESHAPs for RICE. 

Please contact me at (510) 287-1337 or scheng@ebmud.com if you have any questions about 

the AIR Committee’s comments. 

Sincerely, 

Chair, Air Issues and Regulations Committee