Notes from Site Visit at Dominion Resources’ Clover Power Station 

on October 24, 2008 

EPA conducted a site visit at Dominion Resources’ and Old Dominion Electric Cooperatives’ 

Clover Power Station (Clover) located in Clover, VA on Friday, October 24, 2008 to learn about 

the operations at the plant, specifically the FGD wastewater handling system. Table 1, located at 

the end of this memorandum, identifies the site visit participants. The presentation that the 

Clover personnel gave during the site visit is provided as an attachment to this memorandum. 

Also included as attachments to this memorandum are a flow diagram of the gas cleaning 

system, an overall plant wastewater flow diagram, process flow diagrams for the FGD systems, a 

diagram of the baghouse operation, and a diagram of the plant’s surface water outfall plan. 

This memorandum describes the information collected during the site visit and the pre-site visit 

phone call, which was held on October 1, 2008. 

Plant Overview 

 Clover operates two generating units at the power plant, which is a baseload plant 

with a net generating capacity of 860 MW. The table below contains some general 

information for each generating unit. A process flow diagram of the basic gas 

cleaning system arrangement is included as an attachment to this memorandum. 

Unit 

Installation 

Date 

Net 

Capacity 

(MW) 

Particulate 

Control NOx Control SO2 Control 

1 1995 430 (net) Baghouses SNCR 

installed 2003 

Wet FGD in original 

design (1995) 

2 1996 430 (net) Baghouses SNCR 

installed 2003 

Wet FGD in original 

design (1996) 

 Clover burns eastern bituminous coal in both generating units. Most of the coal 

used at Clover comes from mines in Virginia, but some is delivered from 

Kentucky. Clover consumes approximately 90 rail cars per day of coal. 

 Clover personnel stated that the sulfur content of the coal typically ranges from 

1.0 to 1.3 percent sulfur. Clover personnel stated that the limit for the coal burned 

in the boilers is 1.7 percent sulfur on a per shipment basis and 1.3 percent sulfur 

on an annual basis. 

 Clover personnel provided data from an analysis of the coal burned in the boilers 

in July of 2004 that showed the chlorine content of the coal ranged from 0.03 to 

0.1 percent chlorine on a dry weight basis. 

 Clover operates SNCRs on both generating units. The SNCR process consists of 

injecting urea directly into the boiler. Prior to injection, Clover adds dry urea to 

water to make an aqueous solution of urea. Clover stated that they may switch 

from receiving dry urea to receiving aqueous urea. Clover that costs are the 
Page 2 

driving factor for making the change because, at times, it is more cost effective to 

purchase aqueous urea instead of dry urea. 

 Clover only injects the urea during a portion of the ozone season (i.e., the SNCRs 

are not operated the entire ozone season). Clover operates the SNCR to meet 

emission limits or system targets. Additionally, Clover may operate the SNCR 

when the cost emissions credits make the operation cost effective. Clover stated 

that the SNCR process achieves approximately 25 percent reduction of NOx. 

 Both generating units have baghouses, which achieve approximately 99.9 percent 

removal of fly ash and other particulates. 

 Clover personnel stated that the plant uses oil in the boilers primarily during start 

up. Clover additionally uses oil for stabilization while the boilers are operating at 

a low load. Oil is used for flame stabilization while taking coal mills in and out of 

service typically at loads of 400 MW or less. 

 The baghouses must be bypassed during start-up while burning oil. Clover is 

allowed, by permit, 30 minutes to place the baghouse into service once the first 

coal feed commences. 

 Clover uses the Roanoke River as the source for the power plant’s water. Clover 

withdraws water from the Roanoke River and pumps it to the raw water storage 

pond, which has a capacity of 310 million gallons. Clover maintains the raw 

water storage pond at capacity to ensure that the plant will have a water source if 

the river level decreases. Clover stated that the raw water storage pond has 

enough capacity to keep the plant running for approximately 22 days. An overall 

process flow diagram is included as an attachment to this memorandum. 

 Clover treats the water from the raw water storage pond using clarifiers. Most of 

the clarified water is transferred to the cooling tower as makeup water for the 9-10 

MGD that evaporates. The remainder of the clarified water is transferred to a 

demineralizer/reverse osmosis system for further purification and use as boiler 

make up or service water. 

 Clover transfers its cooling tower blowdown to the holding pond. Cooling tower 

blowdown accounts for approximately 90 to 95 percent of the flow to the holding 

pond. The holding pond also receives water from the following sources: sewage 

treatment plant, oil/water separator, plant drains, boiler blowdown, and 

neutralization basin. 

 Some of the effluent from the holding pond is reused in the FGD scrubber as 

make up water. The remainder of the effluent from the holding pond is 

discharged to the Roanoke River. 

 Clover operates a combined coal and limestone pile runoff pond. This pond 

collects runoff from the coal storage area as well as the limestone pile and 

scrubber sludge storage area. The pond discharges directly to the Roanoke River; 
Page 3 

however, Clover can transfer the pond’s contents to the emergency sludge storage 

ponds if necessary for reuse in the scrubber system. 

 Clover occasionally adds sodium hydroxide to the coal and limestone pile runoff 

pond and pumps the water from one end of the pond to the other end to neutralize 

the pH in the pond. In addition, Clover may add bags of soda ash to the inlet of 

the pond if there is an excessive amount of rainfall. Clover stated that the pH in 

the pond on the Monday prior to the visit (October 20, 2008) was 2.57 S.U. 

 Clover operates a neutralization basin which receives wastewaters from chemical 

cleaning operations, reverse osmosis reject, and demineralizer regeneration 

wastes. The wastewater from the neutralization basin is typically transferred to 

the emergency sludge storage ponds but can be discharged to the holding pond if 

desired. Acid or caustic can be added to the neutralization basin prior to 

discharge if necessary. 

 Clover operates two emergency sludge storage ponds. The ponds are used to 

store solids in the case of an emergency such as a scrubber failure, in which case, 

the scrubber contents could be transferred to the emergency sludge storage ponds. 

Clover stated that they can use the ponds to allow for additional settling/treatment 

of the coal/limestone pile runoff, if needed. Additionally, Clover transfers the 

waste from the neutralization basin to the ponds. Clover uses the water from the 

emergency storage ponds as make up for the FGD scrubber process. There is 

approximately 1 mgd evaporative loss from the FGD system, and additional water 

is removed from the system along with the gypsum sent to landfill. 

 The Clover plant is located on 1,800 acres of land, 500 acres of which are 

managed wetlands. 

 Clover employs approximately 140 workers. 

FGD System 

 Clover operates limestone forced oxidation wet FGD scrubbers on both 

generating units. Each generating unit has three individual absorber vessels, two 

that are in operation and one spare. Each of the FGD scrubber systems were 

installed at the time the generating units were initially built, 1995 for Unit 1 and 

1996 for Unit 2. Process flow diagrams for the Unit 1 and 2 FGD systems are 

included as attachments to this memorandum. 

 Clover uses ball mills to crush the limestone to the correct size for use in the 

limestone slurry. Clover uses approximately 7,500 tons of limestone each month. 

 The limestone slurry from the ball mills is approximately 50 to 55 weight percent 

solids and is transferred to hydroclones to remove the limestone particles that are 

too large, which are transferred back to the ball mill for additional processing. 

The overflow from the hydroclones is transferred to the limestone slurry storage 

tank and is approximately 30 to 35 weight percent solids. 
Page 4 

 Clover has had foaming issues in the scrubbers; therefore, Clover continuously 

adds a defoaming agent to the discharge pipe of the limestone slurry storage tank 

that feeds the reaction tanks of the FGD scrubbers. 

 Each of the scrubbers at Clover has four spray levels, each operated by a separate 

recirculation pump. However, Clover typically only operates six or seven of the 

spray levels for each generating unit at one time (i.e., three spray levels in each of 

the two operating absorber vessels, or three spray levels in one absorber vessel 

and four spray levels in the other absorber vessel). Clover occasionally rotates 

which spray levels are used within the various absorber vessels. 

 The Clover FGD scrubbers typically achieve an average of approximately 96 

percent removal of sulfur dioxide from the flue gas. Clover’s permit limit 

requires a 94 percent removal. Clover adds adipic acid to the scrubbers daily to 

improve the efficiency of the system. Clover personnel stated that the contractor 

that installed the FGD scrubber system used adipic acid during the testing phase 

of the system and it worked well. Therefore, Clover chose to continue using 

adipic acid in the system. 

 Clover operates the FGD scrubbers at a pH of 5.4 to 5.5. The scrubber operates 

with a constant solids concentration of 13 weight percent. The chlorides 

concentration in each of the scrubbers ranges from 20,000 to 40,000 ppm. The 

FGD system piping is either constructed of stainless steel or is rubber lined to 

prevent corrosion. 

 The blowdown from the scrubbers is controlled by the level in the scrubbers and 

is essentially continuous. The blowdown is not controlled by a pump, but rather, 

by gravity. A small pipe is located at the bottom of the reaction tank which 

extends from the scrubber, turns upward, and extends approximately 25 feet along 

the outside of the scrubber vessel. The pipe then angles downward and is directed 

to the nearby waste slurry sump. This configuration causes a blowdown from the 

scrubber at all times when the level in the scrubber is above the top point of the 

blowdown pipe. 

 The blowdown in the waste slurry sump is pumped to the thickener feed tanks, 

which also receives water from the holding pond and filtrate from the vacuum 

filters. The water from the holding pond is make-up water for the FGD scrubber 

system, which is treated in thickeners prior to being sent to the system. Clover 

operates two thickeners in parallel, each with a capacity of two million gallons. 

 The overflow from the thickeners is transferred to the reclaim tank. From the 

reclaim tank, the water is used in the limestone preparation process, used for 

conditioning the fly ash/FGD solids prior to disposal, or returned directly to the 

scrubber. 

 The underflow from the thickeners, which is approximately 35 weight percent 

solids, is pumped to the filter feed tanks. From the filter feed tanks, the thickener 

underflow is sent to the vacuum drum filters that dewater the solids. The FGD 

solids from the vacuum drum filters, which are primarily gypsum, contain 15 to 
Page 5 

18 percent moisture and are conveyed to a pug mill where they are mixed with 

dry fly ash and water. 

 

 The filtrate from the vacuum drum filter is transferred to the waste treatment area 

sump then to either the thickeners or to the emergency sludge storage ponds. 

 Clover has the capability of processing just fly ash, just FGD solids, or a 

combination of the two in the pug mills. Typically, fly ash and gypsum are 

processed together. If just fly ash is being processed, Clover adds water from the 

reclaim tanks to the pug mill to bring the fly ash to 20 percent moisture. If just 

FGD solids are being processed, Clover may add water from the reclaim tanks to 

the pug mill if necessary to bring the moisture content to 20 percent. Clover 

stated that the additional water is needed to achieve the correct compaction of the 

material in the landfill. 

 Clover personnel stated that they have the capability to add lime to the pug mill, 

but have never done so because it is not necessary to aid in proper stabilization of 

the material in the landfill. 

 Clover personnel stated that when they start processing the solids in the pug mill, 

they typically start with just fly ash and water, and then they slowly add the FGD 

solids to the mixture. From the pug mill, the processed solids are conveyed 

outside to the stack out area. 

 Clover personnel stated that they typically operate the vacuum drum filters and 

the pug mill during the night shift. Clover fills up the filter feed tanks and the fly 

ash silos during the day shift and then processes the materials during the night 

shift. In the morning, the solids that were sent to the stack out area are trucked to 

the landfill. 

 Clover personnel stated that the gypsum produced is not marketable partially 

because of the chlorides level present in the gypsum. Clover personnel also stated 

that because of the location of the plant, the transportation costs for hauling the 

gypsum would be greater than sales from the gypsum. 

Ash Handling and Wastewater Treatment 

 Clover operates a dry bottom ash handling system, specifically a submerged 

bottom ash scraper/conveyor. At the bottom of each boiler is a collection trough 

that contains a water bath. The holding pond provides water for the water bath. 

The bottom ash generated in the boiler is collected in the trough and Clover 

operates a drag chain that moves across the trough and drags the ash out of the 

boiler. At the end of the boiler, the conveyor chain reaches an incline which acts 

to dewater the bottom ash by gravity draining the water as the ash moves upward. 

The bottom ash is then dumped onto another conveyor which transports the 

bottom ash outside and dumps it onto a storage area. Any water that drains off 

the bottom ash in the storage area is collected in a sump and transferred back to 

the boiler bottom ash collection trough or to the FGD absorbers. Clover 

personnel stated that the consumptive water use for the bottom ash system is low. 
Page 6 

The solids that accumulate in the sump are removed via a jet pump back to the 

bottom ash pit. The bulk of the water that accumulates in this sump is transferred 

to the scrubber system and is re-used as reclaim water or can be sent to the 

emergency sludge storage ponds. 

 Clover transports the bottom ash, along with mill rejects/pyrites, by truck to the 

on-site landfill for disposal. Clover estimated that they generate 50,000 tons of 

bottom ash per year. 

 Clover operates a dry fly ash handling system. Clover uses baghouses to remove 

the particulates from the flue gas. The flue gas enters the baghouse compartment 

and is forced upward into the bottom of the bags. The flue gas passes through the 

bags fabric filter, which removes particulates in the gas. The filtered flue gas then 

exits out the top of the baghouse compartment. A diagram presenting the 

operation of the baghouses is included as an attachment to this memorandum. 

 After a few hours of operation, the fly ash collected in the baghouses can generate 

enough back pressure to burst the bags or restrict flow through the bags. 

Therefore, every few hours, Clover reverses the flow in the baghouse 

compartment forcing clean air to travel from the outside of the bags to the inside, 

which causes the dust cake to crack and fall into the hopper below. The fly ash is 

collected at the bottom of the baghouse compartment in a hopper and 

pneumatically transferred to the fly ash silos. Clover stated that the bag cleaning 

process takes approximately 10 minutes for each compartment. 

 The bags used in the baghouse are about 40 feet long. Each of the generating 

units has 32 baghouse compartments and each compartment holds 288 bags, for a 

total of 9,216 bags per generating unit. 

 As discussed in the FGD System section, the fly ash is processed in a pug mill 

with water and FGD solids and then transferred to the on-site landfill for disposal. 

Clover Landfills 

 Clover is currently operating Stage III of the on-site landfill. Stage I and Stage II 

were filled, capped, and closed in 2003. Additionally, Phase 1 of the Stage III 

landfill is filled, capped, and closed. Clover estimates that they have enough onsite landfill space to last for the life of the station. Clover stated that they estimate 

the life of the plant to be 40-50 years and they estimate 55-60 years of landfill 

space. 

The leachate from Stage I and Stage II is piped directly to the Stage III leachate 

collection ponds. Therefore, the stormwater runoff sediment pond located in the 

Stage I and Stage II landfill area contain only stormwater and no leachate. The 

stormwater runoff pond is batch discharged on an as needed basis, based on 

rainfall accumulations, directly to the Black Walnut Creek. 
Page 7 

 Clover operates four concrete leachate collection basins associated with the Stage 

III landfill. These collection basins also receive some stormwater runoff from 

Stage III as well as the leachate from Stage I and Stage II. The leachate collection 

basins are discharged directly to the Roanoke River; however, the discharge is not 

continuous. Clover stated that they typically batch discharge to the river for 

several days each month. Clover monitors the discharge for pH, total suspended 

solids, and flow rate. 

 Clover also operates several stormwater runoff sediment ponds in the Stage III 

landfill area. Like the Stage I and Stage II stormwater runoff sediment pond, the 

Stage III stormwater runoff sediment ponds discharge directly to the Black 

Walnut Creek. 

 Clover also operates five other stormwater runoff drainage areas that are not 

associated with the landfill area and discharge directly to the Black Walnut Creek. 

 A diagram of the Clover’s surface water outfall plan is included as an attachment 

to this memorandum. 
Page 8 

 Table 1. Site Visit Attendees 

Name Organization (Representing) Telephone E-Tim Hamlet Dominion Resources (434) 454-2150 tim.hamlet@doWilliam Gwynn Dominion Resources (434) 454-2026 william.gwynnKen Roller Dominion Resources (804) 273-3494 kenneth.roller@Oula Shehab Dominion Resources (804) 273-2697 oula.k.shehab-dJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epa.gRon Jordan EPA/Office of Water (202) 566-1003 jordan.ronald@T.J. Finseth ERG (Contractor to EPA) (703) 994-7130 thomas.finseth@
Attachment 

CLOVER PRESENTATION 
Clover Power Statio

Welcome 

to the 
How It All Started

A brief history of the Clover Power Station

♣In 1989, Old Dominion Electric 

Cooperative and Dominion team up to construct Clover Power Station

♣In February 1992 Construction Comm♣Unit #1 began commercial operations 

fall of 1995 and Unit #2 in the spring o1996.
How It All Works

♣ Coal is delivered by train from Virginia min♣ Clover consumes approximately 90 rail cars 

coal per day when the units are at full capac

♣ Fuel oil is used for start-up then we switch t

to heat the water to steam to drive the turbingenerator

♣ Each of our two units produces approximate

Net MW of electricity which is enough to papproximately 100,000 homes.
Keeping It Clean

One of our major concerns is the impact that we 

on the environment

Over $400 million of the $1.2 billion plant costs was 

equipment to ensure that this station maintains comp

its regulatory permits 

Two major pollution control measures used at Clove

baghouses and wet limestone scrubbers

In addition, an SNCR may be used during the ozone s

beyond 
The Baghouse
The Baghouse

♣ The baghouse acts as a filter that removes th

from the flue gas before entering the scrubbsystem

♣ This very efficient process takes 99.9% of th

ash out of the flue gas

♣ The ash is transported to a silo then to the p

where it is mixed with the scrubber byproduwater before being placed in our on-site lan
The Scrubber

♣ The scrubber removes the sulfur dioxide that is pro

as a result of burning coal

♣ This is done by mixing the hot flue gas with a slurr

limestone and water

♣ Our typical removal rate is approximately 96% alth

the permit limit is 94%

♣ Adipic acid is also used to improve removal efficie♣ Forced oxidation air is supplied to all of the vessels 

assist in forming a sulfate product instead of sulfite is easier to dewater

♣ Refer to scrubber process diagram
Selective Non-Catalytic Reduc

• Dry Urea is mad

an aqueous soluand injected into furnace for NOx Reduction.

• Results in an 

approximately 2reduction.
This is the basic overview of the sta
Wastewater Treatment Systems

♣ All oil tank secondary containments and floor drains that hav

potential for receiving oil spills drain through oil/water separa

♣ All bulk chemical tank secondary containments drain to lift st

then to the neutralization basin

♣ All sanitary wastes are routed to the on-site sanitary treatmen

♣ Cooling tower and boiler blowdown, sanitary waste treatmen

oil/water separators and neutralization basin discharge to the pond before release to the Roanoke River.

♣ Limestone storage pile, the coal pile and coal combustion byp

stackout areas drain to the coal/limestone pile runoff pond berelease to the Roanoke River

♣ The landfill wastewater treatment system consists of 4 leacha

collection basins and 7 stormwater runoff sediment ponds. Lepumped to river through a 2.34 mile forcemain and the sedimdischarge to Black Walnut Creek.

♣ 5 stormwater runoff discharges in addition to the 7 landfill po

♣ Refer to wastewater process diagram
Some interesting facts about t

Clover Power Station


The power station withdraws water from the river and p

to the raw water storage pond. From there, it is clarified bulk of which is routed to the cooling towers as make-uapproximately 9-10 MGD they evaporate


The remainder is routed to the water treatment plant for 

purification and used throughout the plant in various syincluding boiler water make-up, service/fire water


The scrubber receives its water needs from the holding 

well as the 2 emergency sludge storage ponds and accouapproximately 1 MGD of evaporative losses through the 
Some other interesting fac

about the Clover Power Stat


The Clover Power Station employs 

approximately 140 workers, is base loadand remains in operation year round


The station is located on 1800 acres of 

of which approximately 500 acres are managed wetlands


We have an on-site landfill with the cu

cell occupying approximately 30 acres.
Tour Reminders

♣Please remain with your tour guide at 

times

♣Feel free to take pictures and ask ques

but please refrain from including emplin photos. 
Attachment 

CLOVER PROCESS FLOW DIAGRAMS