## ,··..**,~,t** 

### Exhibil3 

# STATE OF CONNECTICUT DEPARTMENT OF ENVIRONMENTAL PROTECTION

In the matter of The State of Connecticut and Devon ?ower LLC } } } ) ) } } Trading Agreement and Order No. 8181

Whereas, the Commissioner of Environmental Protection ("Commissioner") and Devon Power LLC ("Dpll) agree that it is in the public interest that they work coooeratively to imorove the air auality within the State of Connecticut and that the- use of emission- reduction credit ("E:RC") trading to reduce nitrogen oxide ("NOx") emissions will achieve this result in a timely and cost-effective manner:



### A. At the request and with the agreement of DP, the Commissioner finds the following: 1. DP is an exemot 

### wholesale electric generating company with its orincioal olace of business in Sewickley,**Pennsylvan~a.** 

### On or before uecember 31, 1999 DP 

### will ourchase from The Connecticut Light and ?ower Comoany and then own-one (1) 

### oiece of fuel-burning equioment**("oeaking·un~t")** 

### identified in Table 1 

### of this Trading Agreement and Oraer. This peaking unit is a combustion turbine. 2. On or before December 31( 1999 NRG 

### Devon Ooerations Inc. will ODerate the oeaking unit**identif~ed** 

### in Table 1 

### of this Trading Agreement and Order at OP's facility.
3. 

### Official 

## u.s. Environmental Protection 

### Agency ("EPAu) Reference Method 7E 

### stack testing oerformed on the date indicated in 

### Table 1, resulted in a NOx emission 

### rate set 

### forth in 

### Table 1.

4.

5. Table 1 DP



### - NOx EMISSION RATE AND R.li.CT LIMIT (lbs/MMStu) Peaking :?UEL FLER NO>: ::tACT Stack Stack Test Date of

Unit (lbs/MM3tu) Rate Test Rate Stack Tesc (lbs/MlGtu) Rate (lbs/MY..3tu) (ppmvd) Devon 10 other • ·0.74 0.289 176.5 0.67 10/25/96 oil



### The emission rate for the peaking unit and fuel soecified in Table 1 is in excess of Section 22a-174-22, Table 22-2, oE the Regulations of**Cop~ecticut** 

### State Agencies ("Regulations"), NOx emission rate limits (Reasonably Available Control Technology "RACT"). Pursuant to Section 22a-174-22(b) of the**Re~ulations,** 

### the peaking unit is subject to Sections 22a-174-22(d) througn (k) of the**Re~Jlations,** 

### pertaining to the control of NOx emissions. 5. In accordance with Section 22a-174-22(jl of the Regulations, OP proposes that for the peaking unit identified in Table 1, D? shall use Initials (Printed on

## R~~'&led Paper) 

### Date 

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79 Elm Slree: • Hartford, CT 06106

- 5127 htt?:/Idep.st'le.tl.us An EQu,,1 O"ntnl'''''',u P_-I

......Devon Power LLC Trading Agreement and Order No. 8181

3.



### c. ERC trading when burning nother oil", as that term is defined in Section 22a-174-22 of tne Regulations. 7. Pursuant to the Department of Environmental Protection's "Credit Trading for Sources with Irregular NOx Emissions H policy, with a revisea date of November S, 1997, attached hereto and incoroorated by reference into this Trading Agreement and Order as Exhibit 1, the oeaking unit has Deak daily NOx emissions greater than three times the average daily emissions during the ozone season and is therefore considered a source with irregular NOx emissions. 8. Based on DEP approved stack test data, it has been determined that the oeaking unit's emissions will not meet the aoplicable requirements of**~CT** contained in Section 22a-174-22 of the Regulations. 

### DP proposes to use a Full Load Emission Rate ("FLER") identified in Table 1 lor the purposes of calculating ERCs required.
9. D? intends to continue acquiring approved ERCs as needed. 10. Aoproved ERCs are defined for the ourpose of this Trading Agreement ana Order as those for which the**Comm~ssioner** has provided written**authori~ation** for use in compliance with Section 22a-174-22 of the Regu1aclons.

. The Commissioner, in accordance with the provisions of this Trading Agreement and Order, and pursuant to Section 22a-174-22 (j) of the**~egulations** hereby allows-DP to comply with Section 22a-174-22 of the Regulations through use of ERC trading referenced in Section Al herein, to acnieve the nitrogen oxide**emissio~** reduction required by**Sect~on** 22a-174- 22(d) (2) of the**~egulations.** With the agreement of DP, the Commissioner, acting under Connecticut General Statutes Sections 22a-5, 22a-171, 22a-174, 22a-176, and 22a-177, orders DP as follows: 1. Upon issuance of this Trading Agreement and Order 

### OF shall comoly during operation of the**peak~ng** unit with the**FLE~ sho~~**  in Taole 1 above. 2. On and after the date which 

### DP purchases the peaking unit identified in Table 1 of this Trading Agreement and Order, D? shall have in its possession sufficient approved ERCs to meet aoplicable**~~CT** requirements and the requirements of this Traalng Agreement and Order. 3. On and after the date which DF Du=chases the peaking**~~it** identified in Table 1 of this Trading Agreement and Order, DF shall, on a daily basis, document and recora tne amounts of all fuel used by the**peak~ng** unit each day and the**nu~ber** of SRCs used for the ozone season lfrom May 

## + througn September 30 of each year) and non-ozone season (the**rema~nder O~**  the year)

. 4. On and after the date which DP purchases the peaking**lli~it** identified in Table 1 of this Trading Agreement and Order, pursuant to Section 22a-174-22(jl of the**Regulat~ons,** DP shall acquire from The. Connecticut Light and Power Comoany sufficient approved non-ozone season ERCs in order to meet apolicable RACT reqUirements and the requirements of this Trading Agreement and Order for the operation of the peaking unit identified 

### in Table 1 of this Trading Agreement and Order during the month of December, 1999. 5. Except as provided in paragraph C.4. of this Trading Agreement and Order( on and after the dace which DP ourchases the peaking unit ident2fied in Table 1 of this Trading**~areement** and Order,**pursua~t** to Section 22a-174-22(j) of che**Regulat~onsl** DP shall**ac~ire** Irom The Connecticut Light and Power Company**suff~cient** approved ozone and nonozone season ERCs in order to meet apolicable**~~tT** requirements and the**requiremen~s** of this Trading Agreement and Order for**t~e** following month's**operat~on.** 

### Initials -2- Date 

## '\2/20,/0,0..

### Devon Power LLC Trading Agreement and Order No. 8181

d. 6. In accordance with Exhibit 1 of this Trading Agreement and Order, ozone season ERCs for use during the ozone season shall be purchased by DP prior to the beginning of the ozone season. 7. On and after the date which DF purchases the Deaking unit identified in Table 1 of this Trading Agreement and Order, DP shall maintain and orovide the records required by paragraph C.3. of this Trading Aqreement and Order in accordance wich the following and Sectlon 22a174-4 of the Regulations, and shall:

a. Have in its possession sufficient approved ERCs for the current day! based on the following calculatlons (described also in Exnlbit 1); At all times (mass calculation): ERCs (in tons) = 

### f«(FLER in lbs/MMBtu)

- (0.95 x NOx**?~CT** 

### in lbs/MM3tu) x (actual fuel use in lbs/MM3tu)] + 

### 2000 pounds/ton During the ozone season only (peak day calculation) : the maximum actual excess NOx emissions (in Ibs) on any of the days projected by the Commissioner to be**~moderate** 

### to unnealthLul,n**~up~ealthful,n** 

### or**~very** 

### unhealthful,H divided by 3 and then divided by 13 (with the result in**ton~)** 

### : ERCs (in tons) 

## = [(Maximum excess NOx in lbs) + 

### 3] + 

### [13 lbs!day!ton) ; 

### b. At a**min~mum,** 

### adjust**up~ards ~y**  

### 100% the ERCs required if**~RCs** 

### are not In 

### D?'s possesslon prlor to use;
c. As described in Exhibit 1 of this Trading Agreement and Order, to the extent that ERCs used to offset on a oeak day basis during the ozone season exceed the**to~al** 

### mass excess**em~ssions** 

### remaining ERCs may be used in the non-ozone season in the same or subsequent years until May 1, 2003; Document and record daily fuel use, excess NOx emissions and, during the ozone season, the ozone classification as forecasted by 

### the Commissioner on the previous day;

e.

f. 

### No later than March Ie 

### 2000, 2001, 2002, 2003 and 2004, include with its 

### annual**emiss~ons** 

### renort to the Commissioner, ERCs used (calculated as described in section C.7.a. above), by ozone and non-ozone seasons, for the previous calendar year; Retain the records and supporting documentation as described in this section for a minimum of five years, commencing on the date such records are created;
g. 

### Maintain documentation to attest to the fact that 3RCs·used during the ozone season were generated during**~he** 

### ozone season. The ozone season**~s** 

### from May 1 through Seotewber 30 in any calendar year. Generatbr certificatlon 01 this fact shall be sufficient; and h. Provide the records specified above to the Commissioner within thirty (30) days of receipt of a written request from the Commissioner. 8. Pursuant to the intent of Section 22a-174-22a(fl (4) of the Regulations, DP may, for a budget source, use allowances acauired pursuant to the orovisions of Section 22a-174-22a of the Regulations to comply with subsection {el of Section 22a-174-22 of the aegulations pursuant to the provisions of subsection (j) of Section 22a-174-22 of ehe Regulations as long as D? remains an owner of that budget source, for pUrPoses of this Trading Agreement and Order. Any allowance used for compliance with**subsect~on** 

### (e) of Section 22a-174-22 of the



### , Initials

# ~~- -3- 

### Date 

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,Devon Po-wer LLC Trading Agreement and Order No. 8181

9.

10.

11.

12.

13. Regulations shall be subject to all restrictions and/or requirements applicable to ERCs**conta~ned** in this Trading Agreement and Order ana/or Section 22a-174-22a of the Regulations. The terms and conditions established by this Trading Agreement and Order shall become effective on the date DP purchases the peaking unit identified in Table 1 of this Trading Agreement and Order, and upon issuance of this Trading Agreement and Order. No later than May I, 2003, DP shall comply -with the requirements of Section 22a-174-22 (d) (.2) of the**Regulat~ons.** HO'",ever, after full Drogram revie-w of this and other Trading Agreements and Orders and, if aetermined to be aDorooriate, the Commissioner may grant a -written extension of this TradIng Agreement and Order.**8efiU,it~ons.** As used in this order, "Commissioner" means the**omm~SS10ner** of Environmental Protection or an agent of the Commissioner. "Other oil# means a fuel that is**li~uid** at standard conditions and is not residua-l oil. "Residual oil' means any fuel oil of No.4, No.5, or No. 6**~rades,** as defined by Commercial Standard C.S. 12-48. "Ozone season
.means the period from May 1 through Seotember 30 in any given calendar year. "Issuance# means the date this Trading Agreement and Order is deposited in the u.s. Mail or the date it is personally delivered, whichever is earlier. Ngtification of noncQIDoliance. In the event that DP becomes a-ware t at**~t** did not or may not comply, or did not or may not comply on time, with any requirement of Eh1s Trading Agreement and Order or of any document**requ~red herelli~der,**  DP shall bi telephone immediately notify the Bureau of Air Management and sha I take all reasonable steps to ensure that any noncompliance or delay is avoided or, if unavoidable, is minimized to the greatest extent possible. DP shall also notify the Commissioner in writing within ten days of becoming aware of the noncomoliance or potential noncompliance stating the date, time, and duration of the noncompliance,-the reasons for the noncomoliance or delay and all activit1es which DP and its agents, employees and representatives took to avoid or repair the results of the noncompliance and orevent the noncomoliance, and propose! for the review and written approval of the Commissioner( dates by wh1ch comoliance will be acnieved. DP shall comply**w~th** any dates which may be aporoved in writing by the Commissioner. Notificacion by DP shall not excuse noncompliance or delay and the Commissioner's aporoval of ani compliance daces proposed shail not excuse noncompliance-or delay un ess specifically so stated by the Commissioner in writing. Nothing herein shall negate DP's obligation to comply with Section 22a-174-7 of the Regulations. To the extent that the orovisions of Section 22a174-7 are inconsistent -with the provisions oI this Trading Agreement and Order, the more stringent of-the provisions in the Trading Agreement and Order or Section 22a-174-7 shall control. Certification of QQ§uments.**.~"Y** document, including but not limited to any**not~ce, wh~c.**  is required to be submitted to the Commissioner under this Trading Agreement and order shall be signed by the resPonsible corporate officer of DP or a duly authorized representative of such officer, 'as those terms are defined in Section 22a-430-3 (b) (2) of the Regulations and by the individual or individuals resoonsible for actualiy preparing such document! each of whom shall examine and be familiar with the information subm1tted in the document and all attachments thereto! and shall make inquiry of those individuals resEonsible for**obtain~ng** the information·to determine that the intormation is true, accurate, and complete, and each of whom shall certify in writing as follows: "I have personally examined and am familiar with the information submittea in this document and all attachments thereto, and I certify that based on reasonable investigation, including my inquiry of those individuals responsible for**obta~ning** the information, the submitted information is true, accurate and complete to the best of my knowledge and belief. I understand that any false statement made in the 

### Initials -4- 

### DateDevon Power LLC Trading Agreement and Order No. 8181

14

.

15.

16.

17,

18.

19.

20.

21.

22. submitted information may be punishable 

### as a criminal offense**~~der** Section 22a-175 of the**COrL~eccicut** General Statutes or, in accordance with Section 22a-6 of the Connecticut General Statutes, under Section 53a-157b of the Connecticut General Statutes, and in accordance with any other applicable statute." 

### Final Agreement and**or~er.** This Trading Agreement and Order is the 

### rrnal agreement and or er by and between tne Commissioner and DP with resoect to the matters addressed herein, and shall not be modified without the written agreement of both parties. False statemeRts, Any false statement in any information submitted pursuant to t**~s Trad~ng**  Agreement and Order may be punishable as a criminal offense under Section 22a-175 of the Connecticut General Statutes or, in accordance with Section 22a-6, under Section 53a-157b of the Connecticut General Statutes. Notire 

# §f**tr~nsf;r; li~bilitv**  of 

### PF and**0ah~rs,** Until 

### OP has fully como**~e w~tn** **tn~s** Traolng Agreement andraer, 

### OP shall notify the Commissioner in writing no later than fifteen (15) days after transferring all or any portion of the**facility~** the operations, the site or the business wnich are the subject of cnis Traaing Agreement and Order, or obtaining a new mailing or location address.**JL~y** license transfer shall be conducted**~n** accordance with Section 22a-60 of the Connecticut General Statutes. DP's obligations under this**T~ading** Agreement and Order shall not be**affecte~ ~y** **t~e** passage of**t~tle** to any property to any other person or**mun~clpal~ty. c~~;sS~QnerIS**  PQwers, Nothing in this Trading Agreement and Order**s~!** a:recc the Commissioner's authority to**inst~tute** any oroceeding or take any other action to nrevent or aoate violations**o~** law,**~revent** or abate oollution, recover costs and natural resource aamages, and to impose penalties for violations of law which are**will~ul** or criminally negligent or for which oenalties have not been specifically orovidea in**th~s** Trading Agreement and Order, including but not limited co violations of any oermit issued by the Commissioner, If at any time the Commissioner determines that the actions taken by DP oursuant to this Trading Agreement and Order have not fully achieved comoliance with Section 22a-174-22 of the**~e~lationsl** the Commissioner may institute any oroceeding against DF ana/or requlre DP to undertake further investigation or furtner action. 

# 8

P's**Ob~iOttiO~S** und§T liw. Nothing in this Trading Agreement and rcier s:al re**leve~** or other**obl~gations** under appllcable federal, state and local law, Ayc.ss to**recor~s** and**fa~ilitv.** Pny**repre~entative. of~th~**  gepartment or**~nv~ronmenta** ?rotectlon may enter and**~nsoect** tne**rac~l~ty** and insoect and cooy records within normal business hours without prior notice for the-purposes of monitoring and enforcing the actions required or allowea by this Trading Agreement and Order. 

# SO**effe~t ~n** **r~aRts** of other**per~Qns,** This Trading Agreement and

rder**s~al** nelt er create nor a:rect any rights or persons who or municipalities which are not parties to chis Trading Agreement and Order. No Creation of Property Riopts. This Trading Agreement and Order does noc create any property rlgnts with respect co these ERCs.**~oticB** t9 Commissioner 9f**ch~noes,** Within fifteen (15) days of the

ate? Decomes aware or a c:ange in any information submitted to the**Co~~issioner** under this Trading Agreement and Order, or that any such information was inaccurate or misleading or that any relevant information was omitted c DP shall submit the correcc or omitted information to the**Comm~ssioner.**



### Initials -5-Devon Power LLC Trading Agreement and Order No. 8181
23.**Subm~ss~on** of**d§cumen~s,** Any document required to be submitted to the Comm1ss1oner un er tn1s**Trad~ng** Agreement and Order shall, unless otherwise specified in writing by the Commissioner, be directed to: Mr. David Jawin Deoartment of Environmental Protection Bureau of Air Management Compliance and Field OPerations Division Emissions and Credit Trading Section 79 Elm Street Hartford, Connecticut 06106

# ~' Initials

## ~~ -6-

### Devon Pow,=:r LLC Trading**Agreem~nt** 

### and Order No. 8181
DP consents to the issuance of this Trading Agreement and Order without further notice. The undersigned certifies that he/she is fully 

### authorized to enter into this Trading Agreement and Order and to legally bind UP to the terms and 

### conditions of 

### the Trading Agreement and Order.

Devon Power LLC
Signature: Type Name: Type Title: Date: 

### Robert S.**~vaos** 

### II

12/29/99

Issued as a final consent order of the

## Co~~issioner 

# ,"",,,_..,,, 'M,oH,""" 

# <;;;:'(j/V

. "", / , ) 

# 1/

, fJr.

CITY OF MILFORD LAND**;{ECO~DS ~~!LED**  

### CERTIFIED**~~IL,** 

### RETURN RECEIPT REQUESTED Certified Document

### Exhibit 1 Trading Agreement and OrderNo. 818!

# STATE OF CONNECTICUT DEPARTMENT OF ENVIRONMENTAL PROTECTION

REVISED ll/5/97 

### CreditTrading for Sources with IrregularNOx Emissions

The following outlines the Department's concerns and methodologyfordealing withNOx compliancepursuantto §22a-174-22(j). Regulations ofConnecticutStateAgencies ("Regulations"), emission trailing for "peakers" and othersources thathavepeak emissions that
are substantiallyhigherthan their averagedaily emissions. Forpurposes ofthis protocol, 

### peakingunits are defined as sources with

### peakdailyNOx emissions greaterthan threetimes their averagedailyemissions during theozone season.
Thebasic conceptofthe tradingprogram is that sources with 

### excess NOx emissions (arate that exceeds therate limits in the Regulations) mayobtainNOx emissionreductioncredits ("ERCs") from sources that have**"over~controlled"** theirNOx emissions. Although typical sources can obtain credits on a mass basis (one ton ofERCs to offset one ton ofexcess emissions) with an acceptable environ.JTIental outcome, sources with large variations in emissions from dayto day pose an additional problem for ozone attainmentplamling.

The most common peaking

### units or "peakers" are electricity generating units thatrun during times ofhigh electricityconsumption. Electricity demand is often the highest duringhot, humid days oflbe summerwhen thepotential for ozone [onnation is also high. Peakers frequently have high emission rates. To the extentthat these units produce emissions at exactlythe time when emissions need to bereduced to limitozone fonnation, allowingpeakers to continue to comply with new rate lii-ruts through the use ofERCs on a ton-far-ton basis will exacerbate this effect. On the otherhand, ifitcan be demonstrated that the ERCs being used bypeakers were generated
on a comparable basis (i.e., during days ofhigh ozonepotential), then ton-far-ton use bypeakers would be appropriate.

The full impact oftheNOx emissions from these types offacilities during summeroperation must considertemporal variabilityas well as mass ofexcess emissions. AnyERC trade must considerequivalencyto the NOx reductions that control equipment wouldproduce on an ozone dayonboth a temporal and a mass basis. The protocol below places appropriaterequirements
on peaking units to reflect the greaterimpact ofNOx emitted undl?T this type ofusagepattern. Attachment 1 provides a detailed example ofthis issue.



### NOxEmissionsReduction Credit Use Computation ForPeakers

• Peaking units are onlyconsidered to be a temporal issue for the ozone season months.

• All excess NOx emissions during the winter (non-ozone season) need only be offset

### by ERCs on a mass basis.

• Priorto each ozone season there will be aprospective calculation to determinehow many tons ofERCs mustbe "on hand" during the ozone season. A retrospectivecalculation will detennine how manyERCs were actually aused" during the ozone season.

(Prinled on Recycled Papet) 79 £1m Smel • Ha:l!ord, cr 06106·5127 hllp:lldep. Stilt. Cl.us2

For EReuse during the ozone season:


### 1. Prosoective calculation detennines the number ofERCs thatmustbe provided for the
ozone season. (Beginning in 1996, the ERCs mustbe in place no later than May 1.)

ERCs required for the ozone season shall be calculated based on: (a) a mass basis (total anticipated excess NOx emissions overthe ozone season) and (b) apeak-day basis (maximum excess emissions foranyday during the ozone season). Sources will be required to provide credits equal to the greater ofthe amountcalculated on amass or peak-daybasis. The tintingofactual creditprovision will be governed bythe terms ofthe specific trading orderissued forthat source. (a) l\1ass basis: ERCs required \\'ill be equal to the total nwnber oftons ofanticipated
excess NOx emissions overthe entire ozone season, calculated in the same mannerused for other sources using ERCs (i.e., including anydiscounts).
(b) Peak (daily rate) basis: ERCs (in tons) required will be calculated by dividing one·third ofthe maximum daily excess emissions'" (in pounds) by J3 pounds/day/ton:

ERCs required (tons) [(MaximumEstimatedExcess NOx in lbs.) " 3J + [13 Ibs./day/tonJ

·Wheremaximum dailyexcess NOx emissions are the difference between the maximum estimatedhours ofoperationperday atthe full-Ioad-emission-rate and 95% ofthe allowable NOx emissions under Section 22a-174-22(e) ofthe Regulations.

2. Retrospective calculation will determine the actual credit use and the ERC surplus, ifany. Atthe end ofthe ozone season, the calculations required in item 1 above will be repeated using (a) the actual total excess emissions for the ozone season, and (b) t,e maximum actual excess NOx emissions on any ofthe days projected bythe Commissionerto be "moderate to unhealthful', 'unhealthful", or "veryunhealthful". The actual "ERCs required" will be the greaterofthe ERCs calculated on the basis oftotal mass or maximum (peak) day. To the extent thll.tthe number of ERCs used to offsetpeakday emissio,ns exceed the total mass ofexcessNOx'emissions forth.eozone season. the remaining mass value ofsuch ERCs maybe carried forward forusein the winter(nonozone season). AnyunusedERCs maybe carried forward until May 

### 2, 1999, except as maybe limited bythe trading agreement and order, orby regulation.3



### Exhibit 1 ERC Calculation/orPeaking Units

Unless itcan be demonstrated otherwise, ERCs areassumed to be createdbyrelatively small 

### dailyreductions in NOx emissions overthecourseofan entireozone season 

### (153 days). The averagedailyNOx emissions reduction represented byone ton ofcredit is 13 pounds/day calculated as follows: (l ton) x (2000pounds/ton) + 153 days 13 pounds/day/ton
Thus, an ERe (ton) would be equivalentto areduction in NOx emissions of13 pounds/day.
EXA.1\1PLE. Ifa "pea1.'ing" source were to emit oneton ofexcess NOx per daywhen operating, but onlyoperates for five days during theozone season, the owner/operatorofthe source would nominallyneed to obtain five tons ofERCs. However, thoseERCs are likely to have been createdbyrelatively small dailyreductions inNOx emissions overthe course ofan entireozone season (153 days). In this example, assuming apurchase oftive tons ofERCs. that calculates out to a dailvNOx reduction ofapproximately 65 pounds.
(5 tons x 2000pounds/ton) + 153 days 65 pounds/day
Clearly, on anydaythat the "peaking" uriit operates, there is much more excess NOx emissions that will nothavebeen offset, on the order of 1,935 pounds:
(1 ton x 2000 pounds/ton)

- (65 pounds credit) = 1,935 pounds excess NOx emissions

While the total amount ofNOx emitted would be controlled on a seasonal averagebasis, on the "peaking" day there would be apotentiallysignificant increase in NOx emitted, and thus an increase in potential ozone creation. In orderto achieve a commensurate reduction in ozone creation potential forpeakers, an adjustmentin the calculation ofrequired ERCs is needed. One approach would be to require ERCs in aquantitythat would ensure that the daily average reduction represented bythose ERCs would equal the maximum dailyexcessNOx emissions from the peak'ing source on anydaythatitran. 

### On this basis, apeaking.source wiih arnaxL..llum 24-hourexcess NOx emission ofone ton would be required to purchase 153.tons ofERCs.

1 (ton)lday X 153 days/season = 153 tons

This 153 tons ofERCs would be adequate to**"offset~** excess emissions ofone ton perday for as many days as the source operated during aparticularozone season. This has been deemed to be unduly stringent, given some diversityin operation ofthese sources. 

### In light ofthe foregoing, this requirement is adjusted downward bynNo-thirds.