Document ID: EPA-HQ-OW-2008-0667-0596
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-04-20T04:00Z

Site Visit Report

      Valero -- Delaware City Refinery
      2000 Wrangle Hill Road
      Delaware City, DE 09706
      July 15, 2009

1.0	Background and Objectives

      The Environmental Protection Agency (EPA) is in the process of developing 316(b) cooling water intake structure requirements that reflect the best technology available (BTA) for minimizing adverse environmental impact for all existing power plants and manufacturing facilities.  As part of this process, EPA staff is visiting electric generators and manufacturers to better understand the cooling water intake structure (CWIS) technologies in use at typical facilities, including the site-specific characteristics of each facility and how these affect the selection and performance of CWIS technologies.  EPA is also visiting facilities to better understand cooling water use and specific issues or technologies that can affect 316(b) compliance.  Valero's Delaware City Refinery was selected for a site visit because it utilizes cooling water in its petroleum refining processes and in electricity generation.[,]

2.0	Facility Description

      Valero's Delaware City Refinery is located on approximately 5,000 acres along the Delaware River south of Wilmington, DE.  The refinery was built in 1956 and employs approximately 760 Valero personnel.  The facility has two NPDES permits, one for the refinery and the other for a cogeneration power plant (NPDES permit numbers DE0000256 and DE0050601, respectively).  The permits have expired (August 31, 2002 and June 30, 2007, respectively) and are in the process of being renewed.

3.0	Manufacturing Information

      The facility processes heavy, high-sulfur crude oil to produce conventional and reformulated gasoline, low-sulfur and ultra low-sulfur diesel, and home heating oil as well as liquid natural gas and propane.  Crude is received by ship at the facility's dock and offloaded to storage tanks.
      
      Production is approximately 180,000 barrels per day (production was 160,000 barrels per day the day prior to the site visit).  Facility representatives noted that production is at or near historic levels, but that profits are currently much lower than before.
      
      Cooling water usage at the facility includes trim cooling via heat exchangers, overhead condensers on distillation columns, and the firewater system.  Water used for non-contact once-through cooling undergoes little pretreatment and is typically dosed with small amounts of sodium hypochlorite prior to being discharged back to the Delaware River.  Process water and contact cooling water is comprised of a combination of source waters (nine onsite groundwater wells, municipal water systems, and freshwater streams) and undergoes water treatment prior to use. 

4.0	Cooling Water System and Intake Structure

      The Valero Delaware City Refinery operates one CWIS that withdraws from the Delaware River.  The CWIS is located at the end of an intake canal and is approximately (1/2) mile downstream of the main discharge outfall for the refinery and cogeneration plant.  The CWIS is comprised of a concrete structure with a trash rack with nine circulating water pumps and one one-half capacity pump.  The design intake flow (DIF) is 465 million gallons per day (mgd) but the facility is limited by its water use permit with the Delaware River Basin Commission (DRBC) to a maximum withdrawal rate of 452 mgd.  The actual intake flow (AIF) varies throughout the year; in the summer, the facility generally operates all nine pumps.  The facility does not know the through screen velocity.  Each pump has a dedicated 10-foot travelling screen which is rotated and rinsed for 20 minutes three times per day.  The screens are of different mesh sizes and are being replaced at the rate of one per year.  The combined fish and debris return (an open concrete trough) is routed back to the canal outside of the initial trash rack.   Downstream of the screens, there are three bays and two six foot headers.
      
      The refinery's fire suppression system is comprised of a single pump located at the CWIS and a holding tank at the refinery.  The pump operates intermittently to maintain an adequate water level in the tank, but can also directly supply water to the fire suppression system if needed.
      
      This portion of the Delaware River is tidal and brackish in nature.  The canal is dredged twice per year (spring and fall).  Since the Delaware River is tidal in this segment, the facility's intake can entrain warm water from the discharge outfall depending on tidal direction.
      
      The refinery discharges through a 13 MGD water treatment plant and into two holding ponds (aka "guard basins").  These basins provide additional evaporative cooling and also serve as a safety factor in case of catastrophic failures or leaks at the facility.  The power plant effluent discharges just downstream of the basins; the combined effluent cascades down a series of steps (for aeration and cooling) before entering the river.

5.0	Flow Diagram

      Based on information provided in the facility's detailed industry questionnaire and from the site visit, EPA has constructed a water flow diagram.  Virtually all water withdrawn at the refinery and power plant is for non-contact cooling water.  A small amount of pipe washing occurs but generally uses treated freshwater from other sources.  Some contact water is used in other processes and the coker unit uses some quench water, but much of the process water (and any heat produced) at the refinery is recycled.  Contact water is treated at the facility's wastewater treatment plant before discharge.  See Attachment C for the diagram.
      
      As noted above, the DRBC limits the amount of water Valero can withdraw.  In an effort to reduce water withdrawals as it grew and added processes and to recover as much heat as possible, the facility began installing dry and wet cooling systems in the 70s and 90s, respectively.

6.0	Electricity Generation and Transmission
      
      The refinery has a 280 MW cogeneration facility located onsite.  The cogeneration facility was originally designed to use the refinery's petroleum coke production as the fuel source.  In 1998, the power plant was repowered with a combined cycle turbine to increase the generating capacity and now uses gasified petroleum coke as its fuel.  The power plant supplies electricity and steam to the refinery and accounts for approximately 33% of the cooling water needs for the complex (refinery and cogeneration plant).

7.0	Impingement and Entrainment Information

      Impingement and entrainment studies were conducted in the 1990s  -  2000 time period. 

8.0	Cooling Tower Feasibility
      
      Valero has several cooling towers, several of which are process-dependant.  One was constructed for a process that is no longer in operation and is not currently being used.  The cogeneration facility has a 3-cell helper cooling tower which is used approximately 4 months per year to provide supplemental cooling in the warmer summer months.  All of the cooling towers are wooden and many are only operated seasonally.  Typically, the towers using the untreated saline river water have 1.5 cycles of concentration.  An onsite vendor maintains standard antifouling and antiscaling chemical feeds for all the towers.   
      
      The facility has considered retrofitting additional closed-cycle cooling at the site, but has concluded that closed-cycle cooling is not the most appropriate solution.  Facility representatives discussed the limitations of both dry and wet cooling and the difficulties with the use of existing cooling towers at both the refinery and cogeneration plant.  Specifically, they noted that the brackish nature of the Delaware River may influence the metallurgy within the cooling system and limit the cycles of concentration that can be achieved without pretreatment.  They added that the existing wastewater treatment capacity at the refinery might not be able to treat the increased flows that would be generated by closed-cycle cooling systems.  In addition, groundwater or municipal sources are unlikely to be available for makeup water.  Facility representatives also noted that closed-cycle cooling systems are limited by the ambient air temperature and humidity, requiring that the cooling towers be overdesigned to perform in worst case conditions.
      
      Facility personnel also mentioned potential drift or plume from the towers; however, no mention was made of any problems from current towers on-site.  Lastly, facility representatives noted that the refinery had made significant capital investments in improving the metal tubing throughout the facility in an effort to improve process efficiency and reduce the concentration of metals in the effluent; if closed-cycle cooling were installed, the cost-effectiveness of these upgrades may be lost or significantly reduced.

9.0	Future Activities
      
      As part of its discussions with DNREC concerning the renewal of the facility's two NPDES permits, Valero may be required to reduce water usage at the facility.  Facility personnel are also continuing to investigate reusing treated effluent and redistributing the heat load throughout the facility as ways to reduce cooling water requirements.

10.0	Cooling Ponds
	
      There are no recirculating cooling ponds on-site.

11.0	316(a)

      The NPDES permit contains temperature discharge limits including a daily maximum withdrawal volume.  During portions of the summer, the facility has problems meeting the thermal limits, occasionally resulting in a reduction of production capacity.

12.0	Ash Handling

	There is no ash produced onsite.

13.0	Air Emissions Controls

      The facility is currently constructing a scrubber system on the cracking unit and is retrofitting the boilers at the power plant to low NOx burners.  EPA did not collect any further data on air emissions.

13.0	Issues with Debris
      
      The Delaware River carries a high debris load, especially after large storms.  Other than the dredging of the cooling water canal due to silt and sediment buildup, the facility did not identify any problems with handling the debris loading.  Periodic cleaning of the area directly in front of the CWIS (and behind the canal bar rack) also occurs to remove material.

15.0	Additional Information

      The facility considered several intake technology options.  A 2007 fine mesh wedgewire screen feasibility study concluded that a large number of screens would be required and that locating the screens in an area of sufficient depth would be difficult.  Obtaining permits and ongoing maintenance (such as dredging) would also be difficult and expensive.  Other technologies were examined, but were largely not considered due to poor performance in entrainment reduction.
      
      The facility's NPDES permit does not contain any requirements for 316(b).  As noted in Section 4.0, however, the facility does have a maximum permitted flow of 452 mgd.  During portions of the summer, the facility occasionally has to curtail production as it approaches the withdrawal limit.
      
      The facility had a 3-month shutdown earlier this year; this was the first time the entire plant had been closed in its history (nearly 60 years).
      
      A small rail line within the property is owned by Valero, but a second rail line (separating the refinery from the power plant) is not.

Attachments

Attachment A		List of Attendees
Attachment B		Aerial Photo
Attachment C		Flow Balance Diagram

Attachment A--List of Attendees

Paul Shriner, USEPA
Jan Matuszko, USEPA
Steve Geil, Tetra Tech
Kelly Meadows, Tetra Tech
Mike Gudgeon, Valero
Eric Jacobs, Valero
Joe Greenfield, Valero
John Gillespie, Valero
Brian Muldowney, Valero
Mike Seaner, Valero
Bob Wojewodski, Valero

Attachment B--Aerial Photo

Please see DCN 10-6553A accompanying this document.

Attachment C--Flow Balance Diagram