Evaluating Local Impacts of a Utility SCR Retrofit Project

1. Evaluating Local Impacts of a Utility SCR Retrofit Project Steven Klafka, PE, DEE Wingra Engineering, S.C. A&WMA Conference 2002 Wingra Engineering, S.C.

2. Introduction • Wisconsin adopted SIP for new 1-hour ozone air quality standard • Required NOx reductions at utilities in southeastern Wisconsin Wingra Engineering, S.C.

3. Pleasant Prairie Power Plant • WEPCo operates the Pleasant Prairie Power Plant in southeastern Wisconsin. • Two 600 megawatt coal-fired boilers. • To comply with new NOx limitations, WEPCo proposed SCR retrofit of one boiler. • SCR system would use anhydrous ammonia as the reagent. • Proposal included ammonia storage tanks, and equipment for rail and truck deliveries. Wingra Engineering, S.C.

4. Pleasant Prairie Power Plant Wingra Engineering, S.C.

5. Review by State Agencies • Public Service Commission • Department of Natural Resources • Department of Commerce • Village of Pleasant Prairie Wingra Engineering, S.C.

6. Village Permit Application • Application for conditional use permit. • Description of SCR system. • Three 30,000 gallon storage tanks. • Rail and truck delivery. • Risk Management Plan (RMP). • Off-site consequence analysis. Wingra Engineering, S.C.

7. Worst-case Release Scenario • Based on USEPA RMP Comp Model • USEPA Assumptions • Rail tank car contents lossed in 10 minutes • Toxic endpoint is distance to 200 ppm • Model Results • Toxic endpoint predicted to be 6.9 miles • Affected population of 124,568 people Wingra Engineering, S.C.

8. Area of Worst-Case Scenario Wingra Engineering, S.C.

9. Alternative Release Scenario • More realistic accident scenario. • Assumed fracture in loading line from rail car. • Based on USEPA RMP Comp Model. • Toxic endpoint predicted to be 0.3 miles. • Affected population • 13 residences • 100 WEPCo employees • 200 employees at nearby businesses • Public Safety Dispatch Center and Police Department Wingra Engineering, S.C.

10. Area of Alternate Scenario Wingra Engineering, S.C.

11. Issues Considered by Village • More realistic evaluation of risk. • Comparison with existing storage sites. • Identification of potential accidents. • Anhydrous ammonia accident history. • Availability of alternative reagents. Wingra Engineering, S.C.

12. More Realistic Evaluation of Risk • ALOHA model • Tool of local emergency planning coordinators. • Allows changes in release rate, meteorology, and toxic endpoint. • Worst-case and alternative SCR release scenarios repeated using ALOHA model. Wingra Engineering, S.C.

13. RMP Comp and ALOHA Models Wingra Engineering, S.C.

14. Comparison with Existing Sites • 11 existing anhydrous ammonia storage sites in Kenosha County. • Proposed SCR storage is twice current largest site. • Proposed SCR storage and two existing sites potentially affect > 100,000 people based on worst-case release. Wingra Engineering, S.C.

15. Evaluation of Potential Accidents • RMP includes Process Hazard Analysis • Identifies potential accidents, releases, frequency, and mitigation methods. Wingra Engineering, S.C.

16. PHA Results • Accidents Likely to Once per Year • e.g. improper closure of after unloading railcar • Maximum release 10 lbs • Accidents Likely to Occur Once Every 1-4 Years • e.g. truck valves are opened too quickly • Maximum release 10 lbs • Accidents Likely to Occur Once Every 20-75 years • e.g. railcar derails • Maximum release 148,500 lbs Wingra Engineering, S.C.

17. NRC Ammonia Accidents • Releases > 100 pounds reported toNational Response Center (NRC) • Since 1992, five anhydrous NH4 spills. • Since 1993, nine aqueous NH4 spills. • Since 1990, 118 unspecified NH4 spills. Wingra Engineering, S.C.

18. RMP Ammonia Accidents • 15,436 RMP filed with USEPA • 7,540 anhydrous storage sites • 656 reported anhydrous NH4 releases • No industry breakdown for NH4 releases • Of 1,911 releases, 6 attributed to fossil fuel generation facilities. Wingra Engineering, S.C.

19. Alternative SCR Reagents • Aqueous Ammonia and Urea • EPRI reports157 SCR installations in US • Of the 79 site reporting the reagent: • Anhydrous Ammonia -- 63% • Urea -- 25% • Aqueous Ammonia -- 11% Wingra Engineering, S.C.

20. Anhydrous vs Aqueous Ammonia • Anhydrous Ammonia • Stored as compressed liquid • Immediately evaporates during release • Proposed due to widespread use and low cost • Aqueous Ammonia • Stored as liquid • Atmospheric temperature and pressure • Upon release, forms liquid pool then evaporates • Eliminated by WEPCo due to higher costs Wingra Engineering, S.C.

21. Increase Cost of Aqueous Ammonia • Aqueous has higher reagent costs, requires a larger tank farm, more frequent deliveries. • Estimated cost increase for aqueous ammonia is $740,000 per year. • Cost increase to WEPCo customers is $ 0.00007 per kw-hr or 0.1% (Unit 2). Wingra Engineering, S.C.

22. Anhydrous vs Aqueous Release • ALOHA use to estimate distance to end point. • USEPA Evaporation Calculator for aqueous. Wingra Engineering, S.C.

23. Village Response to SCR Project • Anhydrous ammonia reagent posed a significant risk to local population. • Compromised emergency response capability due to proximity of Public Safety Dispatch Center and Police Department. • Informed WEPCo that Conditional Use Permit would not be issued to the SCR project unless a less hazardous reagent than anhydrous ammonia were used. Wingra Engineering, S.C.

24. Influence of September 11th • September 11th terrorist attacks occurred during review of SCR project. • Increased awareness of vulnerability due to hazardous materials storage. • Provided additional incentive to identify a less hazardous reagent. Wingra Engineering, S.C.

25. WEPCo Response to Village • Prior to the public hearing on Condition Use Permit, WEPCo informed the Village it would agree to use an alternative to anhydrous ammonia such as aqueous ammonia. Wingra Engineering, S.C.

26. Conclusions • Use of anhydrous ammonia as an SCR reagent poses risk to a local population due accidental releases. • After September 11th, there is greater awareness of public vulnerability due to the storage of hazardous materials. • Alternative reagents such as aqueous ammonia are more expensive but result in lower potential risk. Wingra Engineering, S.C.