Site Visit Report

Union Carbide—St. Charles Operations (SCO)

355 State Highway 3142

Hahnville, LA 70057

January 13, 2010

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 facilities, including the sitespecific 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. Dow’s St. Charles Operations (SCO) facility was selected for 

a site visit because it utilizes cooling water in manufacturing a wide variety of 

basic and specialty chemical products.

2.0 Facility Description

SCO is located on a 2000 acre site on the shore of the Mississippi River near 

Hahnville, LA.

1

 The facility began operations in 19662and employs 

approximately 1100 personnel, plus as many as 1000 contractors. The facility’s 

NPDES permit (NPDES permit number LA0000191) expired June 30, 2009 and 

has been administratively continued as the facility submitted its permit application 

and is awaiting a renewed permit. 

3.0 Manufacturing Information

Dow SCO is an integrated petrochemical plant3 with 23 operating units that 

produce primarily intermediate chemical products. These products end up in a 

variety of consumer goods such as plastics, insecticides, films and fabrics, 

antifreeze and brake fluid, paints and adhesives, pharmaceuticals, personal care 

products , and cleaning agents. According to the company’s website, the facility

is capable of producing over 10 billion pounds of chemical product per year.

 

1 At approximately river mile 128. A second, related facility (referred to as Eastbank) is located on a 40 

acre parcel across the river in Norco.

2 The facility was originally owned and operated by Union Carbide, which was acquired as a wholly-owned 

subsidiary of TDCC in 2001.

3 The term “integrated” refers to the interdependence of the operating units; raw products are brought onsite 

and then developed into intermediate and products in subsequent process units. In addition, the facility 

produces its own water and power.
The site is arranged in a series of complexes (e.g., hydrocarbons complex, oxide 

complex) that may contain multiple plants. This site is also home to four other 

companies: Air Liquide, Air Products, Praxxair, and Western.

4

4.0 Cooling Water System and Intake Structure

SCO’s CWIS is located along the shoreline of the Mississippi River5near a 

receiving pier. Seven inlet pipes6each lead to an inlet bay (each with one single 

speed intake pump), where a coarse mesh (3/8” mesh, ~48% porosity) traveling 

screen removes debris and aquatic organisms. Each screen bank is 10 ft wide and 

36 feet in height. Screens are typically rotated twice per day by a high pressure

wash and discharge to a common trough, which empties into a pit that drains back 

into the river. Facility representatives stated that the screens are refurbished 

approximately every 5 years. The through-screen intake velocity is 2 feet per 

second (fps) at average water level of 20.5 ft and 4.6 fps at low water level of 

around 9 ft.

The design intake flow (DIF) of the CWIS is 907 million gallons per day (mgd). 

The average intake flow (AIF) is 773 mgd, which has remained relatively 

constant for the previous 4-5 years.7

The CWIS provides cooling and process water to a system of internal canals that 

transport water throughout the facility. As many as twenty plants withdraw from 

the canal, use the water (or distribute it to other process units), and discharge to a 

similar series of return canals that connect to a discharge pumping station. This 

station is the primary outfall for the facility and pumps effluent back to the 

Mississippi River.

The facility’s fire suppression system withdraws from the cooling water canals.

Facility representatives stated that sedimentation is not a significant problem at 

this site. Occasionally, dredging is required at the discharge point, but operators 

adjusted the discharge velocity to correct the settling problem.

The facility uses quaternary amine as a biofouling agent to treat for clams.

The CWIS also provides cooling water for Air Liquide and Praxair facilities.

 

4 Air Liquide and Praxair were previously part of the Union Carbide facility, but were sold off.

5 The mean annual flow of the Mississippi River at the site (river mile 128) is approximately 465,000 cfs 

(300,000 mgd) with an average width of approximately 3,000 feet and with a navigable channel of at least 

45 feet depth.

6 The intake pipes project approximately 200 feet offshore to bring in cooler water and less debris beneath 

the water’s surface and withdraw from a depth of approximately 20 feet. The pipes have bar racks to 

prevent large debris from entering. A bulkhead on the upstream side (comprised of pilings and barges) 

protects the intake from large debris. 

7 When the river’s water level is elevated, the facility can operate the intakes without turning on the pumps; 

the water flows into the CWIS and intake canal via gravity.
5.0 Flow Diagram

A general flow diagram is provided in Attachment C. Facility representatives 

stated that 98.9% of the water withdrawn is for once-through cooling. The 

remaining water is clarified and then used for cooling tower makeup (0.4%, ~3 

mgd) and other process uses (0.7%, ~5 mgd).

There are five pump stations throughout the plant that feed 20 of the plant units. 

Canal water is returned via 8 pumps at a rate of 720,000 gpm. 

6.0 Electricity Generation and Transmission

SCO operates two cogeneration power plants (i.e., produces both power and 

steam). Both were built in 1995, use once-through cooling, and use natural gas 

and plant-produced fuel gas (a by-product of production). The electric generating 

capacity is a total of 240MW and the steam generating capacity is a total of 80 

MW. 

Facility representatives also noted that SCO’s steam generation is heavily 

integrated into the facility, as any change in steam production ripples through and 

affects production at multiple process units. Integrated chemical facilities 

(especially those with basic process units) are often good candidates for 

cogeneration power plants. In fact, Dow has previously built “package” plants 

with a chlorine unit, a caustic unit, and a power plant.

Facility representatives stated that the power plants are not operated for profit, but 

for facility reliability. SCO can produce its own electricity cheaper than it can 

purchase it from the grid and also has a constant need for both steam and 

electricity.

7.0 Impingement and Entrainment Information

Dow has not conducted any biological studies at the site.

8.0 Cooling Tower Feasibility

SCO utilizes closed-cycle cooling (with mechanical draft cooling towers) at three 

plants, with helper cooling towers (i.e., supplemental cooling along with once 

through cooling) at two other plants. When the facility was originally designed, 

all of the cooling water needs were met with once-through cooling water from the 

canal system. However, as the plant expanded, water needs exceeded the capacity 

of the canal system and newer process units were built with closed-cycle cooling. 

As a result, process units built since the late 1990s (typically in locations further 

from the river) tend to use cooling towers; therefore the DIF has not changed 

because of the additional units. Facility representatives stated that 4% of the 
facility’s heat load is processed through cooling towers; without the cooling 

towers, the facility’s intake flows would be slightly higher.

Facility representatives noted that retrofitting remaining process units to closedcycle cooling would present a number of challenges. First, much of the piping 

used throughout the plant is operating at the upper end of the range for its design 

pressure.

8 Adding cooling towers would require additional pumps and likely 

require widespread replacement of piping throughout the facility. Second,

product reactivity of water in certain process units could make both quality and

safety would be an issue: the increase in pressure could adversely affect some 

process lines that operate at lower pressures, leading to either a lower quality

product, or in some cases, potentially dangerous chemical reactions.9 Third, the 

difference in the cooling water temperature itself could have a negative effect on 

process and product capacity. Anytime the process is condensing water, the 

cooler the better.

For the two cogeneration gas turbines, facility representatives indicated the pump 

station and distribution header would need to be re-engineered. The facility also 

indicated that shell pressure issues may require retrofit of the heat exchangers. 

Facility representatives also discussed the role of cost in selecting the design of a 

cooling system: at a recently constructed facility in Saudi Arabia, the cost of the 

cooling system (approximately $2 billion) was higher than the costs for all other 

environmental infrastructure combined. As such, they noted that cooling system 

retrofits would not simply be an issue of cost and affordability, but could even be 

a barrier to being competitive. 

Facility representatives stated that while individual process lines are periodically 

taken offline for maintenance, the entire facility rarely shuts down. In general, 

there is sufficient redundancy within the facility to prevent widespread downtime; 

for example, boilers can be rotated to continue to provide steam. Each 

cogeneration unit is taken offline once per year and other process units go offline 

as often as twice per year or as infrequently as every 2-3 years.

9.0 Future Activities

SCO representatives were not aware of any plans for significant changes or 

increases in operations.

 

8 Much of the piping is Gifford Hill piping, a reinforced concrete.

9 Changing to cooling towers can cause an increase in the cooling water system pressure which could 

adversely affect some process units. 
10.0 Cooling Ponds

There are no cooling ponds onsite.

11.0 316(a)

The facility has no permit limitations for temperature or 316(a) permit conditions.

12.0 Ash Handling

There are no coal ash wastes generated onsite.

13.0 Air Emissions Controls

EPA did not review air emissions controls.

14.0 Issues with Debris

No significant problems with debris were noted.

15.0 Additional Information

Facility representatives believe that 316(b) should be implemented on a case by

case basis as compliance should be customized to the site specific situation. 

Facility representatives stated that, if forced to meet impingement requirements

through use of a technology, they would consider evaluating installing cylindrical 

wedgewire screens, as these have been successfully implemented at Dow sites in 

West Virginia. They added that there are not many other technologies that would 

be viable candidates at this site other than Ristroph screens. If a cost benefit 

alternative is available for IM requirements, the facility stated they would use this 

alternative. 

The facility has not evaluated entrainment reduction at this facility because it 

believes the costs of such controls would considerably outweigh any benefits. 

However, they noted that they were not aware of any available technologies to 

reduce entrainment at this site. 

The facility also discussed ways in which waste heat recovery could be used to 

give cooling water credits. The difference in waste heat from the base case as 

compared to the heat rejected and recovered could be 10 to 20%. For example, if 

the BTU could be quantified, and the source cooling is known, then the BTU 

could be converted to a quantity of cooling water that would have been needed. 

As a general comment, stand alone plants may have less dependence on fully

integrated site power as opposed to larger integrated manufacturers and utilities 

that generate power for sale.
Attachments

Attachment A List of Attendees

Attachment B Aerial Photos

Attachment C PowerPoint Presentation (January 13, 2010)
Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Kelly Meadows, Tetra Tech

Christine Baldridge, Dow

John Hill, Dow

Tim Finley, Dow

Ed Keough, Dow

Qingzhong Wu, Dow

Sarah Thigpen, Dow

Bryce Chord, Dow

Maria Valdez, Dow (via telephone)

Jim-Bob Williams (via telephone)
Attachment B--Aerial Photo

Please see DCN 10-6556A accompanying this document.

Attachment C--PowerPoint Presentation (January 12, 2010)

Please see DCN 10-6556B accompanying this document.