Document ID: EPA-HQ-OW-2008-0667-1286
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-04-20T04:00Z

Site Visit Report

	Brunswick Steam Electric Plant
      Highway 87 North
Southport, NC 27562 
      January 28, 2008

1.0 Background and Objectives

      The Environmental Protection Agency (EPA) is in the process of revising the 316(b) Phase II regulation.  As part of this process, EPA staff is visiting several electric generators 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.  Brunswick Steam Electric Plant (Brunswick) was selected for a site visit due to its use of fine mesh traveling screens with a fish return and its relatively large intake flows. 

2.0 Facility Description

      Brunswick is a two unit nuclear facility in North Carolina 40 miles south of Wilmington. Unit 1 is a 938 MWe General Electric Type 4 boiling water reactor that began operations in September 1976.  Unit 2 is a 937 MWe General Electric Type 4 boiling water reactor that began operations in December 1974. The source waterbody for cooling is tidal water (salinity typically 15 to 30 parts per thousand) obtained from Walden Creek near the Cape Fear River estuary.  The owner Carolina Power & Light (Progress Energy) employs about 900 employees. Brunswick permit number is NC0007064, expired as of November 30, 2006.

3.0 Electricity Generation and Transmission
      
      Total generating capacity is approximately 1580 MW of nuclear fueled power for baseload electricity with a capacity utilization rating of 94.7 percent. Scheduled outages that include refueling occur every year alternating between units 1 and 2.  Outages are usually for 20 to 30 days.  

4.0 Cooling Water Intake Structure

      The Cape Fear River Estuary is an elongated shallow bay with a narrow dredged deep ship's channel. Above the narrow constriction at Sunny Point, the estuary is highly stratified with salt water intrusion along the bottom and freshwater flow out along the surface. Below Sunny Point the estuary is well mixed and characterized by a large ocean exchange rate of about 80 percent of the water over a 12-h period. Brunswick obtains cooling water from the lower reach, with approximately 0.74 percent of the tidal excursion withdrawn by the intake canal.
      Brunswick has vertical turtle bars (bar racks) at the canal entrance. Additional fish diversion structure with 3/8 inch (9.4 mm) screens installed in 1982.  The diversion structure is located near the confluence of the intake canal and Walden Creek. Copper-nickel screen panels are set between reinforced concrete pilings. Mechanical grass rakes keep debris out of the canal. The canal is dredged 18 feet deep with frequency dictated by annual storm events. Design intake flow is 1.9 billion gallons daily, with the actual intake (3-year average) reported as 1.427 billion gallons daily with an intake velocity of 0.98 feet per second.  
      
      A fine mesh and a fish return handling system was installed in 1983. After the 2.7 mile long intake canal, water flows to each generating unit's cooling system consisting of four intake bays and pumps. Originally, vertical traveling screens installed in each bay were fitted with 9.4 mm mesh screens. Eight fine mesh FMC screens were retrofit on the traveling screens to reduce entrainment of larvae. The third fine-mesh screen per unit was installed in 1987. As of a 2000 study, three of the four traveling screens for each unit were fitted with 1 mm fine-mesh screens. Currently, an alternative configuration is being studied where 1 mm fine mesh overlay is installed on 2 of 4 screens creating a 50/50 panel on the two bays. The other two bays have fine mesh screens on all panels.  The traveling screens have two operating speeds, where the higher speed is triggered by a pressure drop across the screens. The screens are visually inspected twice daily. Impinged organisms are washed off the screens into a 1.4-km fiberglass fish return. The organisms are transported to a constructed holding pond that is open to a tributary of Walden Creek, allowing impinged organisms a full return route to the sourcewater.  
      
      December through March flow reduction management is utilized for further protection of larval fin fish. Cooling water flow is reduced from 31.1 cm/unit to 26.1 cm/unit. Normally, all flow is through traveling screens fitted with fine mesh. The cooling water flow for one unit only is allowed to be increased to 34.8 cm during July, August, and September by using a forth intake pump fitted with 9.4-mm mesh screens.

      Seasonal algae has been observed to foul the intake. Biocontrol is conducted by addition of hypochlorite and brome into the service water bays every other hour, and to the salt water pumps twice a day. A silicone coating on the main cooling water system further reduces biofouling. 
      
      The return canal is a 5 mile open canal that is eventually piped under the Intra-Coastal Waterway and remains submerged into the Atlantic Ocean.  The returned warm water is dispersed 200 feet offshore the Oak Island area. Water is returned less than 4 degrees F higher at the ocean. Permit conditions allow for a 2 acre mixing zone, with a 2,000 acre grid monitored for compliance.
      

5.0 Impingement and Entrainment Information

      Brunswick has conducted a representative species approach to population level effects as part of the demonstration to the state that there is no adverse environmental impact; population modeling is not required by the state.  Brunswick has conducted some form of monitoring for more than 30 years. Brunswick staff indicated their data shows that the species composition, seasonality, and abundance of organisms has not changed as a result of operation of the plant.
      
      As early as 1968, baseline studies were designed to collect preliminary biological and environment data prior to simultaneous operation of both units. Initial studies were conducted when plant operations commenced in the 70's. Detailed I&E studies were conducted weekly in the mid-80s. Sampling was conducted 3/day and 3/night over a 24 hour period, with data stratified by the tide conditions. Two nets in the discharge canal are used to collect organisms to show comparative density of entrainment.  Overall abundance was generally found to be lower in the fall.  Brunswick performance data showed 84 percent reductions in entrainment with the fine mesh over regular mesh (9.4 mm).  Impingement mortality reductions ranging from 40 to 92 percent were observed depending on species and mesh configuration.  Currently monitored species of interest include Atlantic menhaden, spot, blue crab, and shrimp.  Other previously monitored species include croaker, flounder, mullet, bay anchovy, and sea trout. Potential impacts to threatened and endangered (T&E) species include short-nosed sturgeon and turtles. 
      
6.0 Additional Information

      The base for a natural draft wet cooling was built, but the tower was not completed due to projected adverse impacts to air. 

List of attendees: Charles Nelson, Thomas Thompson

Attachments:

Please see DCN 10-6559A through Q accompanying this document for photos from the site visit.