Midwest Independent Mailing Address: Overn ight Deliveries: ww w.midwestiso.org Transmission System Operator, Inc. P. O. Box 4202 701 City Center Drive 317-249-5400 Carmel, IN 46082-4202 Carmel, IN 46032 Arthur W. Iler

Assistant General Counsel

Direct Dial: 317-249-5497 E-mail: ailer@midwestiso.org

September 8, 2010

EPA Docket Center (6102T) 1200 Pennsylvania Ave., NW. Washington, DC 20460

Re: Docket ID No. EPA-HQ-OAR-2010-0295

Dear Sir/Madam,

The Midwest Independent Transmission System Operator, Inc. (“Midwest ISO”) is a fully integrated regional transmission organiza tion (“RTO”) whose operati onal area consists of parts of 13 states and the province of Manito ba. The non-profit Midwest ISO administers a common wholesale tariff to assure industry cons umers of unbiased regional grid management and open access to the transmission facilities und er Midwest ISO's functi onal supervision. The Midwest ISO appreciates the opportunity to co mment on the amendments to its regulations governing the operation of stati onary internal com bustion engines that the Environmental Protection Agency (“EPA”) proposed on June 8, 2010, in part, because the proposed amendments are in apparent c onflict with section 69. 3.5 of the Midwest ISO’s Federal Energy Regulatory Commission (“FERC”) approved Op en Access Transmission and Energy and Operating Reserves Markets Tariff (“Tariff”).

Currently, the Midwest ISO has almost 10,000 MW of Load Modifying Resources. Of that 10,000 MW, over 5,000 MW of such Resour ces are from behind-the-meter generation, including many internal combustion engines. The proposed amendments to Section 60.4243 d (4) of the EPA’s regulations would, among ot her conditions, impose a maximum 15-hour per year limit on the operation of a stationary inte rnal combustion engines as part of a demand response program of an RTO (such as the Midwest ISO) during emergency conditions. Furthermore, the proposed amendment would provide that the 15 hours per year of demand response operation would be counted as part of the 50 hours of operation per year provided for “non-emergency situations”.

The Midwest ISO’s Tariff, which has been a pproved by the FERC, provides that entities may qualify resources (which ofte n include internal combustion engines) as Demand Resources to provide generating capacity to the Midw est ISO Region during emergency conditions. Subsections 69.3.5(iv) and (v) of the Tariff, provi de, in part, that in order for a resource to qualify as a capacity resource, the resource must be capable of being operated (during Emergency conditions where the re liability of the electric grid needs to be maintained) a

minimum of at least five times for at least f our continuous hours per event during the Summer Season during any Planning Year (J une 1st through May 31st of the following calendar year).Docket ID No. EPA-HQ-OAR-2010-0295 September 8, 2010 Page 2

Thus, internal combustion engines that seek to be qualified as Demand Resources within the Midwest ISO Region must be capab le of being operated for a total of at least 20 hours per Planning Year. Other RTOs have similar ope rational requirements for emergency capacity

resources.

In order to allow customers to meet th e minimum requirements for qualifying these resources as capacity resources under the Tariff, the Midwest ISO is requesting that the emergency usage time being proposed in the ame ndments to Section 60.4243 (d) (4) be modified consistent with the Demand Response qualific ation requirements developed by RTOs and approved by the FERC. Such modification to the subject proposed amendment would: (1)

increase the total number of hours that an emer gency internal combustion engine could operate during a year from 15 to at least 20 hours; and (2 ) clarify that such operations would be counted as emergency, rather than non-emergency opera tions. Although the Midwest ISO understands the potential environmental concerns associat ed with these resources, the Midwest ISO respectfully requests that the EPA also rec ognize the importance of ba lancing environmental concerns with the need to maintain electric gr id system reliability during emergency conditions by using appropriate and consiste nt reliability standards for em ergency stationary internal combustion engines.

Thank you for the opportunity to provide these co mments. Please feel free to contact me if you have any further questions regardi ng the comments outlined in this letter.

Sincerely,

/s/ Arthur W. Iler

Arthur W. Iler

Assistant General Counsel