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Site Visit Report 

Possum Point Power Station 

 19000 Possum Point Road 

 Dumfries, VA 22026 

March 10, 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 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. Possum Point Power Station was selected for a site visit due 

to its proximity to EPA Headquarters, its use of combined cycle, and its use of 

partial closed-cycle cooling. 

2.0 Facility Description 

Possum Point is located on a 640 acre site in Dumfries, Virginia. Most of the 

developed area of the site is on a peninsula at the confluence of the Potomac 

River (a tidal river) and Quantico Creek. The facility began operations in 1948 

and employs roughly 110 people. 

Possum Point is owned and operated by Dominion Virginia Power (Dominion). 

The facility’s NPDES permit (VA0002071) is due to expire May 31, 2009.1

3.0 Electricity Generation and Transmission 

Possum Point consists of four active generating units with a total generating 

capacity of 1740 MW (gross summer capacity). Units 3 and 4 (100 MW and 225 

MW, respectively) are 1950s-era units that were converted from coal to natural 

gas in 2003.2

 Unit 5 (840 MW) was added in 1972 and uses #6 fuel oil. Unit 6 

(575 MW) was built in 2003 and is a combined cycle gas combustion turbine with 

a heat recovery steam generator (HRSG).3

 Six small oil-fired (#2) combustion 

 

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 Prior to a recent court ruling, Maryland also claimed jurisdiction to regulate discharges to the Potomac 

River and NPDES permits were jointly issued. The ruling gave sole authority to the state of Virginia; 

going forward, Possum Point’s permit will be issued by only Virginia. 

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 Units 1 and 2 are retired in place. 

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 Unit 6 also has the capability to use #2 fuel oil, but rarely uses it; since startup, Unit 6 has used oil for 

only approximately 250 hours, including startup and testing activities. 
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turbines provide additional peak generating capacity at 72 MW (gross summer 

capacity). 

Units 3, 4 and 5 operate as peaking units, with a capacity utilization rate (CUR) of 

15-20%. Unit 6 is approaching becoming a baseload unit, with a CUR of 75-

80%; in the past, it typically cycled off at night, but has been running 

continuously in recent months. Facility representatives also noted that Possum 

Point is an important part of grid reliability and voltage support in the area. 

Natural gas (mostly from the Cove Point liquefied natural gas [LNG] facility in 

Maryland) is provided via new 14-mile pipeline constructed to supply the new 

Unit 6. There is no natural gas storage onsite. Fuel oil arrives via boat at an 

onsite dock and is stored in tanks. 

The transmission system is owned by Dominion but is operated by a different 

business unit. 

4.0 Cooling Water System and Intake Structure 

Possum Point has two CWISs on the Potomac River; one for Units 3 and 4 and a 

second for Unit 6. Units 3 and 4 employ once-through cooling and have a design 

intake flow (DIF) of 224 million gallons per day (mgd) and an actual intake flow 

(AIF) of 207 mgd. Units 5 and 6 were each constructed with mechanical draft 

cooling towers.4

 Unit 5 withdraws makeup water from the discharge for Unit 3 

and has an AIF of 12-28 mgd.5 Unit 6 withdraws makeup water from the former 

CWIS for Units 1 and 2, with an AIF of 6-14 mgd; raw water is sent through a 

treatment process before being fed to the tower.6

Each CWIS is a shoreline intake structure with a bar rack and standard (i.e., 3/8” 

coarse mesh) traveling screens, as well as a floating boom to divert debris. A 

debris trough returns debris and impinged organisms to the river just downstream 

 

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 Unit 5 and 6 cooling towers employ drift eliminators, but do not use plume or noise abatement. Unit 5 

has two- eleven (11) cell cooling towers of an older less efficient splash bar tower fill design. The tower 

fill was replaced in with Marley’s Optibar (more efficient design of polypropylene material) and partial 

replacement of broken or missing drift eliminators. The Unit 5 towers operate at 2 or less cycles of 

concentration when Unit 5 is generating power and do not currently employ chemical treatment. Biocides 

for maintaining condenser and equipment cooler cleanliness may need to be added in the future. Unit 6 has 

one-ten (10) cell cooling tower of a modern design that uses high efficiency honeycomb type fill. The fill 

is more prone to fouling or plugging so cleaner makeup water is provided and chemical treatment is 

employed consisting of an acid sulfuric acid for scale control and a biocide sodium hypochlorite (bleach) 

for organics control. The Unit 6 tower operates at 4 or less cycles of concentration. 

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 The circulating pumps for Unit 5 operate continuously, even if the unit is not generating; during these 

periods, circulating water is not pumped to the top of the towers and is bypassed directly to the basin and 

returned to the condenser. 

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 The treatment process is clarification for suspended solid removal. The Unit 6 intake also supplies high 

purity demineralized water for boiler makeup at the facility through further processing by sand filtration, 

carbon filtration, reverse osmosis, and electrodeionization (EDI). As such, not all of the water withdrawn 

is for cooling purposes. 
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of the screens. The CWIS serving Unit 6 has two 8-foot traveling screens and one 

dual flow traveling screen. The CWIS for Units 3 and 4 has two 10-foot screens. 

Both CWISs have two circulating pumps per unit (one operating and one backup), 

for a total of 8 pumps. The traveling screens are rotated automatically on a timer 

or based on a head differential across the screen. The design through-screen 

velocity at each CWIS is 1.3 feet per second (fps). 

Facility representatives noted that they will be replacing the traveling screen on 

the former Unit 2 soon. Screen maintenance is performed on an as-needed basis, 

with maintenance typically occurring every few years. Inspections by divers are 

conducted approximately every two years. 

Possum Point is capable of recirculating hot water to its CWISs to address icing, 

but has not needed to do so in several years. The CWIS also has an air aspiration 

device that can create turbulence at the CWIS; in recent years, continuously 

operating the aspirator has been sufficient to control icing. 

5.0 Impingement and Entrainment Information 

The Potomac River is approximately 1.5 miles wide at the facility and up to 60 

feet deep. The river is tidal, but has fairly small changes in depth. As a result of 

the brackish waters, a mix of marine and freshwater species are present. The 

facility is also home to many rare birds that reside in the tidal marshes and 

surrounding areas. 

Possum Point collected impingement samples in 1976 and again in 2005/2006. In 

order to facilitate comparison of the data, Possum Point used the same procedure 

and methodology during both sampling periods. During the sampling periods, 

Possum Point conducted impingement sampling two times a month for a year for 

a total of 24 sampling events. During each 24-hour sampling event, the facility 

ran the screens continuously and collected impingement samples from each screen 

wash for 10 minutes each hour. The facility did not conduct entrainment 

sampling during the 2005/2006 study.7

The table below shows results from the two impingement studies. The facility 

collected 18 common species during the two sampling periods. In both studies, 

more fish were collected at night. The total fish counts are raw numbers; they do 

not reflect an annual estimate of impinged organisms. 

 Sampling Period 

1976 2005/2006 

Number of species collected 24 24 + 2 shellfish1

Primary species White perch 

Gizzard shad 

White perch 

Bluegill 

 

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 In the 2005/2006 study, the study plan assumed that the facility would not meet the 15% CUR threshold 

and would therefore not be subject to entrainment requirements. 
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 Pumpkinseed 

Total number of fish collected 4550 703 

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 The facility did not sample for shellfish during the 1977 sampling period. 

During the 2005/2006 sampling period, Possum Point also conducted ambient 

studies, in which the facility collected 925 fish from 13 species. 

6.0 Cooling Tower Feasibility 

The two largest units at Possum Point already employ closed-cycle cooling (see 

Section 4.0). Facility representatives stated that there are no plans to study 

retrofitting the remaining units to closed-cycle cooling. They added that, due to 

the facility’s location on the peninsula, available space is virtually non-existent. 

Space may be available further inland, but would require an expansion of the 

facility’s fenced perimeter. 

7.0 Debris Handling 

Possum Point does not have significant problems with debris loading. Facility 

representatives did note that there are occasional problems with hydrilla or logs, 

but these events do not significantly affect operations. 

8.0 Repowering/Future Uses 

Possum Point has no current plans for re-powering or upgrades. 

9.0 Cooling Ponds 

 

There are no cooling ponds on site. 

10.0 Ownership 

Possum Point is owned by Virginia Electric and Power Company d/b/a Dominion 

Virginia Power, a subsidiary of Dominion Resources, Inc., an investor-owned 

company. 

11.0 316(a) 

Possum Point has a BTU heat rejection limit with no 316 (a) variance. 

12.0 Ash Handling 

Possum Point no longer burns coal, but still maintains two ash ponds onsite. Pond 

D (or Delta) was constructed in the 1980s and is clay lined. Pond E (Echo) is an 

unlined pond that was built in the 1960s. Pond E was the primary pond for 
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handling wet fly and bottom ash that was sluiced from the facility.8 Pond E 

would overflow into another pond (referred to as the beaver pond) and eventually 

into Quantico Creek. Ash was hydraulically dredged into Pond D for long-term 

storage, which had a projected lifespan of approximately 25 years when Possum 

Point converted to natural gas. Discharges from Pond D, although very rare, were 

controlled and flowed into Pond E. 

Both ash ponds are regulated by the Virginia Department of Environmental 

Quality (DEQ) and are subject to licensing (five year terms) and annual state 

inspections. Dominion also conducts quarterly inspections. 

13.0 Air Emissions Controls 

Possum Point no longer burns coal and has no air emissions control equipment. 

14.0 Additional Information 

With regard to the 2004 316(b) Phase II rule, Possum Point completed its 

biological studies including impingement. The facility did not complete 

technology feasibility evaluations nor did they come to conclusions as to how 

they would have complied with the 2004 rule. However, facility representatives 

indicated they would have considered pursuing reduction credits that were 

achieved by improving generating efficiency and cooling water intake flows.9

 

They thought it was imperative that the new rule offer multiple compliance 

options to allow each facility to accommodate site specific issues. Specifically, 

Dominion Power representatives would like to see rule options that consider 

waterbody type, as man-made reservoirs likely do not merit entrainment 

protection. 

The former coal pile was located at the southern end of the peninsula; coal 

handling equipment remains intact to preserve the facility’s ability to switch fuels 

again if necessary. Remaining coal left after the fuel conversion was stored in the 

ash ponds. This coal is now being re-processed for use at the Chesterfield Power 

Station. 

Attachments 

Attachment A List of Attendees 

Attachment B Aerial Photos 

Attachment C Aerial View of Possum Point Power Station 

Attachment D Possum Point Station Water Flow Diagram 

 

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 Pond E also receives other discharges, such as boiler blowdown and industrial wastewater. 9

 Unit 6 is a combined cycle generating unit—it is more efficient that other generating units. Up to 2/3 less 

cooling water is used since approximately 2/3 of the power generated is from the combustion turbines 

which provide waste heat to generate steam in the HRSGs and do not require the same cooling water 

quantity as a steam turbine. 
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Attachment A--List of Attendees 

Paul Shriner, EPA 

Jan Matuszko, EPA 

Josh Hall, EPA 

Erik Helm, EPA 

Julie Hewitt, EPA 

Richard Witt, EPA OGC 

Shari Goodwin, Tetra Tech 

Kelly Meadows, Tetra Tech 

Peter Sherman, Tetra Tech 

Christine Wong, Tetra Tech 

John Sunda, SAIC 

Bill Bolin, Dominion 

Cathy Taylor, Dominion 

Bill Clancy, Dominion 

Jeff Marcell, Dominion 
Copyrighted page/s removed. Copyrighted 

material is not available in Regulations.gov since 

it may not be reproduced without consent of the 

copyright holder. 

Please contact the EPA Docket Center, Public 

Reading Room to view this document. 

Address: 1301 Constitution Ave, NW 

Room 3334 

Washington, DC 20004 

Telephone: 202-566-1744 

Fax: 202-566-9744 

Email: docket-customerservice@epa.gov
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Attachment C—Aerial View of Possum Point Power Station 

Please see the attached materials. 

Attachment D--Possum Point Station Water Flow Diagram 

Please see the attached materials.