1 Site Visit Report Williams Station 2242 Bush y Par

k Road Goose Creek, SC 29445 February 9, 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 (CWI S) technologies in use at ty pical 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 b etter understand cooling water use and specific issues or technologies that can affect 316(b) compliance. Williams Station (Williams) was selected for a site visit due to its use of a partiall y recirculating cooling water system. 2.0 Facility Description Wi lliams is located on a

pproximately 470 acre s . 1 It began operation in 1973 and has 78 employ ees. It withdraws cooling water from the Back River Reservoir2 and discharges 450

- 500 MGD to the tidal Cooper River under NPDES permit number SC0003883 which was r enewed on June 1, 2009. At the time of the site visit, the permit had expired; Williams had submitted p ermit renewals , but permit reissuance was still in progress. Williams is owned by GENCO, a wholl y owned subsidiary

of SCANA. The facilit y is operated by South Carolina Electric & Gas Company

. 3.0 Electricity Generation and Transmission Williams has a single 650 MW coal

- fired generating unit. It was originall y designed to use #6 fuel oil, but the plant converted in 1984 to utilize coal. Williams is a bas eload unit operating at around 80 to 85 percent availability

. Currently , Williams uses eastern bituminous coal, but has the capabilit y to import coal from South America

. 3 The plant has two routine maintenance outages each

1 Facility representatives estimated that the si te was about 40% developed; 20% of the site was in use by the plant itself and another 20% of the area is covered by the treatment ponds. 2 Downstream of the point of withdrawal, the Back River has been dammed, creating a freshwater reservoir. 3 Williams a dded a barge loading facility to receive coal from South America. Domestic coal is received by rail only.2 ye ar (spring and fall) that ty p icall y last one week. About every three ye ars, Williams has an 8

- 10 week outage for turbine overhaul. The facility

also has two 25MW gas turbines onsite for peaking power and to provide startup capabilities. There is not sufficient distribution infrastr ucture for the facility

to change to natural gas as its base fuel. 4.0 Cooling Water System and Intake Structure Williams withdraws from the Back River Reservoir via a 1000 foot long canal. Where the canal reaches the highway at the facility

entrance, water passes underneath the road via concrete culverts. Additionally , a surface boom upstream of the culverts removes floating debris and vegetation. After passing under the roadway , the canal “day lights” for another 500 feet before reaching the CWIS. Williams has a single CWI S with a common trash rack and six bay s ; e ach pair of bay s has two coarse mesh (3/8” square mesh) fiberglass traveling screen s and one pump . The facilit y occasionally experiences a heavy

debris load from uprooted aquatic vegetation that becomes impinged on the trash rack; the materials are removed from the trash rack b y a claw s ys tem and deposited adjacent to the intake structure and eventuall y disposed of onsite. During a screen cleaning cy cle, one screen rotates continuously for 30 mi nutes, followed by subsequent individual screens . 4 M aterials and fish impinged on the traveling screens are also deposited in a trash bin at the CWIS; there is no fish return

. In1984, Williams added a 5 mm debris filter downstream of the traveling scre ens ( and prior to the condens e rs ) for additional debris removal. 5 The intake pump s are rated at 375,000 gallons per minute (gpm) , giving a design flow of 533 million gallons per day (mgd) and a through

- screen velocity of approximately 0 .72 feet per second ( fps )

. The delta T for Williams’ cooling water sy stem is 20°F. Williams does not use biocides at its CWI S. 5.0 Impingement and Entrainment Information In 1977, Williams conducted a 31 6 ( a ) and 316 ( b ) study with a biological focus on impingement. The 316(a ) study was revised in 198 9 ( following the conversion to coal in 1984 ) and again in 1994. More recentl y (2005

- 2006), the facility conducted a 316(b) stud y to explore impingement rates; the study was conducted in response to the expected requirements of th e now - suspended 2004 rule

. During the study , the facility

impinged 5 2 taxa including 44 species of fish. Blueback

4 Facility representatives stated that they previously replaced traveling screens every 3 years due to heavy use, but have recently switched to fiber glass materials and a less frequent screenwash regimen. 5 Facility representatives noted that the debris filter would very likely lead to zero through

- plant entrainment survival, if such a measure w ere included in the revised rule.3 herring and hog choker comprise d 68 percent of the abundance and the top 8 species represent ed more than 90 percent of the total aquatic lif e. Shellfish were observed in very

small abundance. No major diurnal variation or seasonality was observed. Using information collected in this study, Williams estimated its annual calculation baseline to be 57 ,000 organisms, with an approximately 1 ord er of magnitude variation y ear to y ear due primarily to cold shock events ( primarily affecting the shad species). Facility representatives noted that most of the impinged organisms were young - of

- the

- year , indicating that biologically productive years coul d lead to higher impingement rates at the CWI S. Williams has not conducted an y entrainment studies. 6 6.0 Cooling Tower Feasibility The plant originally

had a 14 cell cooling tower that was destroy ed in 1989 by hurricane Hugo. The rebuilt (1990) cooling tow er has 15 cells. Under normal operations, the facility

employ s once - through cooling and uses the cooling tower as a “helper” tower to reduce the amount of heat discharged to the Cooper River

. 7 However, for approximately 4 day s per ye ar, state resource ag encies appl y herbicides to the aquatic vegetation in the Back River R eservoir as part of routine maintenance. During this period, Williams operates its cooling towers as a closed

- cy cle sy stem to increase the residence time of the herbicide within the rese rvoir. 8 , 9 The facility

loses between 50 and 150 MW of electricity generation when operating as closed

- cy cle , depending on variables such as ambient temperature, river temperature and relative humidity

. 10 Depending on seasonal temperatures, the facility

is capable of operating as a closed

- cy cle s ys tem more often, but does not do so in order to maintain the flow to the Cooper River and to av o id the energy

penalt y associated with operating the towers. A ccording to facility

representatives , the existing tower s are reaching the end of their useful lifetime. Facilit y representatives stated that Williams has available land to construct a dditional cooling tower s (enough to enable operations as a fully closed

- cy cle sy stem) , however i t has not considered doing so

.

6 The facility noted that none of SCEG’s plants w ould have been subject to entrainment requirements under the now

- suspended 2004 Phase II 316(b) regulation. 7 Under normal operations (i.e., once

- through with helper towers), only 67% of the cooling water passes through the helper tow ers. The other portion of the flow is directly discharged to the river. 8 Once

- through flows at Williams are the primary driver for flow exiting the Back River reservoir. The next nearest natural channel to the Cooper River is several miles upstream. 9 The discharge from the cooling towers is not directly tied into the condenser

— in closed

- cy cle mode, water is returned to intake canal, adjacent to the CWIS. 10 The facility does not have enough cooling tower capacity to operate at 100% of its generating c apacity while using a closed

- cycle system. Instead, the facility operates only 2 of its 3 intake pumps.4

7.0 Debris Handling As discussed in Section 4.0 above, Williams occasionally experiences high loadings of vegetation. 8.0 Repowering/Future Uses Williams does not have curre nt plans to repower or upgrade. 9.0 Cooling Ponds Williams does not have cooling pon ds. 10.0 Ownership Williams Station is owned by GENCO, a wholl y owned subsidiary of SCANA. The facility

is operated by

South Carolina Electric & Gas Company . Its transmission sy stem is owned by South Carolina Electric & Gas Compan y . 11.0 316(a) 316(a) permi t requirements for thermal discharges were originall y developed when the facility

was a fuel oil facility and was updated to reflect coal operations. The state ha s requesting the 316(a) anal ys is be updated and reviewed to reflect current environmental con ditions and a verification study is in progr ess . Current thermal limits are set at a 17.5 °F differential and a 104 °F maximum discharge temperature. To meet these thermal limits, Williams has had to throttle back power production an average of once per ye ar. 11 12.0 Ash Handling Williams does not have an ash pond. Ash is sent to a cement compan y or landfill. 13.0 Air Emissions Controls At the time of the site visit, Williams wa s adding a wet flue gas desulfurization (FGD) unit ; it was completed in October 2009. R esulting waste is sent to a low volume sedimentation pond, identified as “Pond C.” FGD water is discharged; no recy cle or reuse loop is planned at this time. No additional neutralization is intended for FGD wastewater prior to discharge at this time.

11 This has happened several times in 2010 due to unusual atmospheric conditions and equipment being out
- of

- service

.5

14.0 Additional Information Following promulgation of the now

- suspended 2004 Phase II rule, the facility explored various impingement compliance alternative s. 12 These alternatives include placing a barrier net in the intake canal, installing Ristroph trave ling screens with fish return, and the addition of dual entry banks to reduce the intake velocity below 0.5 fps. The facility concluded that a barrier net may be problematic due to the high levels of vegetation that is impinged on the intake screens. The facility

concluded that a fish return and handling s ys tem would not be viable, due to the approximately 3,000 foot distance to the reservoir ; there were also concerns as to whether the location of the return would be sufficiently far enough from the intak e to avoid re

- impingement. Dual entry screens were also eliminated from consideration, as facility representatives stated that the reduction in intake velocity was unlikel y to be sufficient to reach the 0.5 fps threshold. The facility

determined the most cost
- effective solution would be a block net. The facility

also evaluated various scenarios for “multimode” operations of the cooling tower. 13 Facility

representatives concluded that the current configuration for the cooling towers would not permit recir culation back to the intake structure without adding additional pumps. Williams also evaluated reducing the number of pumps in use (from 3 to 2), but found that this would only be feasible during winter, as ambient water temperatures in the summer inhibit heat rejection. The facility also concluded the variable speed pumps would not be especiall y effective in reducing the overall intake flow. The facility

is still considering the use of variable speed controls on pumps for power savings reasons. Facili ty representatives noted that Summer Nuclear Station (another SCANA facility) is proposing to add two new generating units. Both would utilize closed

cy cle cooling due to regulatory restrictions . However, they noted that evaporative consumption via the c ooling towers is a concern. Facilit y representatives stated that the prevailing opinion is that dry cooling would not be effective, as ambient air temperatures in the summer would limit the heat rejection capability of the tower. Additionally , summer is the period of greatest energy demand from consumers. Facilit y representatives described the h yd rologic history of the region. In the 1940s, the Army

Corps of Engineers constructed two shallow reservoirs nearby

12 The facility did not explore entr ainment technologies because it w ould not have been subject to entrainment requirements. The facility did not submit a Comprehensive Demonstration study (CDS) to the state. 13 Multimode refers to operating in various modes of recirculation, depending on th e need to reduce intake flows at a given time. Williams may be capable of operating as fully closed

- cy cle, once

- through with helper tow ers, or simply as once

- through.6 and re

- routed the Santee River into the Coop er River. However, due to problems with siltation and other issues, the Corps diverted the flow back to the Santee River in 1984. As a result, flows in the Cooper River are lower than before. Facilit y representatives noted that there are several neighbo ring industrial sites that depend on the once

- through flow from Williams to maintain low salinity conditions in the Back River Reservoir ; some sites advocate for Williams to pump even when not generating, as this improves the dissolved oxy gen in the Cooper R iver. Facility

representatives added that the once

- through flows also help to prevent salt water intrusion in the City of Charleston’s drinking water supply upriver. Attachments Attachm ent A List of A ttendees Attachment B Aerial Photo s Attachment C Site Visit Photos7

Attachment A -- List of Attendees Paul Shriner, EPA Jan Matuszko, EPA Kelly Meadows, Tetra Tech Stephen Summer, SCANA Services, Corporate Environmental Services Timothy Lucius, SCE&G Milton Quattlebaum, SCANA Services, Corporate Enviro nmental Services Mark Ferguson, SCANA Services, Corporate Environmental Services Terry Cheek, Geos yntec

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Attachment C

— Site Visit Photos Please see the attached materials.