Cholla Station

Cholla Station

Location: Joseph City, Ariz.

Client: Arizona Public Service

Completion Date: 2009

Burns & McDonnell, in a joint venture called Cholla Environmental Partners (CEP) that included Zachry Construction Co., was the engineer-procure-construct (EPC) contractor for this turnkey emission control project. It included complete engineering, procurement, construction, startup and commissioning.

  • Preliminary engineering
  • Construction management
  • Detailed engineering
  • Procurement
  • Construction
  • Startup
  • Commissioning

The Cholla project included the replacement of a hot-side electrostatic precipitator (ESP) with a low-pressure, high-volume fabric filter (FF) and an ash handling system replacement compatible with the FF conversion. This project involved the retrofit of the existing Unit 4 ESP (abandoned as part of the Unit 4 air quality control system project) into the new Unit 3 FF. The work included all necessary design, demolition, procurement, construction, erection, controls, and auxiliary support equipment for a complete multi-compartment FF system and ash handling.

In addition, CEP retrofited a new wet lime flue gas desulfurization (FGD) system. The wet FGD is capable of 94 percent sulfur dioxide (SO2) removal and 99 percent availability. The wet FGD system retrofit also included lime storage and delivery systems, bleed slurry removal systems, new induced draft (ID) fans and ductwork. In addition, the existing stack is modified for full wet stack operation.

Burns & McDonnell performed mechanical, electrical, structural and foundation design as well as instrumentation and controls. The controls engineering consisted of integrating a new distributed control system (DCS) for the FGD with the existing plant DCS.

This project required significant coordination and effort among the EPC joint venture partners and with the owner because substantial ductwork tie-ins were completed during scheduled outages. This project was a fast-paced, highly coordinated effort that required teamwork, persistence and a willingness to work together to ultimately make Arizonal Public Service successful and achieve a high level of environmental stewardship and provide value to the customers it serves.