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Site Visit Report 

Harllee Branch Steam Electric Generating Plant 

 1100 Milledgeville Road 

 Milledgeville, GA 31061 

February 11, 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. Harllee Branch (Branch) was selected for a site visit due to 

its use of a retrofitted helper cooling tower. 

2.0 Facility Description 

Branch is located on Lake Sinclair, which is formed by the confluence of the 

Oconee and Little Rivers in central Georgia. It was built in 1965 on a site of 

approximately 3100 acres and employs approximately 250 people. Branch is 

owned by Georgia Power and operates under NPDES permit GA0026051 (due to 

expire February 28, 2010). 

3.0 Electricity Generation and Transmission 

Branch operates four generating units with a total generating capacity of 1540 

megawatts. The coal-fired units use eastern bituminous coal from Appalachia.1

 

Branch operates as a baseload generator2

 and each unit typically has outages of 1-

2 weeks every 18 months. Georgia Power also owns the switchyard and 

transmission equipment. 

4.0 Cooling Water System and Intake Structure 

Branch is located on a short peninsula in Lake Sinclair and is bounded by the 

Little River portion of the lake to the south and a small inlet formed by 

Beaverdam Creek to the north.3

 The two cooling water intake structures (CWISs) 

for Branch are located at the end of a 400 foot intake canal on the southern side of 

 

1

 Coal trains arrive daily, bringing approximately 70-80 cars of coal. 

2

 The facility operates all the time, but frequently reduces its generating load at night. 

3

 See Section 11.0 of this report for more information on Beaverdam Creek. 
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the facility and withdraw from Lake Sinclair.4 The CWIS for Units 1 and 2 

consists of 3 coarse mesh traveling screens; the CWIS for Units 3 and 4 has 4 

coarse mesh traveling screens. Both CWISs also have trash racks. Debris and 

fish removed from the screen are washed back into the intake canal.5

 The design 

through-screen velocity is between 1.1 and 1.3 feet per second, depending on lake 

level. 

Branch uses once-through cooling and discharges to Beaverdam Creek. Each 

generating unit has 2 circulating pumps, which are located at the condensers. The 

total design intake flow (DIF) is 1152 million gallons per day (mgd). 6 Actual 

intake flow (AIF) is typically at the design capacity. 

5.0 Impingement and Entrainment Information 

Branch completed one year of impingement sampling under the requirements of 

the now-suspended Phase II rule. These results have not yet been submitted to the 

state. The study found that the hydraulic zone of influence for the CWIS 

extended outside the mouth of the intake canal. 

The facility was evaluating two technology alternatives to comply with the nowsuspended rule: 

 Aquatic filter barrier at entrance of the intake canal (Gunderboom): 

Ultimately determined would not be feasible, due to the expected high 

operations and maintenance (O&M) costs and high levels of nutrients in 

Lake Sinclair from local dairy farms (leading to high biofouling growth 

rates). 

 Expanded intake structure: There is no space at the existing CWIS for 

expansion or addition of screens. The facility designed a new intake 

structure that would be upstream of the current CWIS in the intake canal. 

The CWIS would be rebuilt with a “saw tooth” appearance to provide for 

more screen surface area, therefore reducing the design intake velocity to 

0.5 fps. The location of a fish return for this design was problematic, as 

the distance to the return location would have been significant. Initial cost 

 

4

 One CWIS serves Units 1 and 2, the other Units 3 and 4. 

5

 Facility representatives noted that problems with re-impingement of debris or fish are rare; when 

problems do occur, maintenance workers collect the material and deposit into the landfill. 

6

 All four units operate at about the same load and withdraw their full design flows. Under rare 

circumstances where an extended period of low generation is expected, a unit may reduce its intake flow by 

simply using one pump. 
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estimates were $40 million.7 This alternative was also unlikely to be 

implemented, as the costs outweighed the expected benefits.8

Facility representatives also stated that Georgia wildlife officials conducted a fish 

population study of Lake Sinclair and estimated over 40 million fish resided in the 

lake. 

6.0 Cooling Tower Feasibility 

In the 1980s, Lake Sinclair experienced some fish kills due to drought conditions, 

leading to a consent order and requirements to address thermal discharges.9

 The 

facility quickly ruled out closed-cycle cooling due to the difficulty of tie-in with 

the condenser and the configuration of the site (the peninsula is bounded by water 

on two sides, a roadway on a third, and is confined by the coal pile and rail line to 

the west).10

Instead, Branch installed a helper cooling tower in 2002 at a cost of $36 million; 

these helper towers are able to remove approximately half of the heat load from 

the facility. The helper tower array consists of 32 50-foot tall fiberglass 

mechanical draft cooling towers (arranged as 16 100 ft x 50 ft towers back to 

back) located to the northwest of the generating units. The towers are grouped 

into 4 groups with each grouping capable of being served by any of the four 

circulating pumps. The towers employ drift eliminators11 but do not include any 

design considerations for noise or plume abatement. Each tower uses a 200 

horsepower single speed fan. 

The helper towers are operated seasonally (May to October) and each cell can be 

controlled individually to meet the cooling needs of the facility; a flow-weighted 

temperature algorithm determines the optimal number of cells needed to meet the 

thermal discharge limits.12 The maximum flow that can pass through the towers 

is 576 mgd, half of the facility’s DIF. 

 

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 Facility representatives expected minimal downtime during construction of this configuration, as they 

would build half of the new CWIS at a time. They also noted that McDonough and Yates (both complete 

closed-cycle retrofits) experienced 6-8 weeks of downtime, during which time the facilities were able to 

perform other maintenance as well. 

8

 Impingement monitoring suggests few organisms are impacted by the CWIS; additionally, many of the 

impinged organisms are moribund shad. 

9

 Branch was the last facility constructed by Georgia Power before the passage of the Clean Water Act. All 

facilities constructed since that time employ closed-cycle cooling. See Section 14.0 for more information. 10 Facility representatives noted that the site was likely selected to minimize the length of condenser piping. 

11 The vendor noted that modern drift eliminator technology reduces drift to approximately 1% of what was 

possible with technologies from 30 years ago. 

12 Typically, when ambient water temperatures reach 90°F, the helper towers begin operating. The facility 

can operate any combination of pumps, towers (with or without fans), and any number of fans to remove 

the appropriate amount of heat. In May and October, the towers operate about 10% of the time. From June 

to September, the towers operate most of the day and at about a 50% load at night. 
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The helper towers are not connected to the power block of the facility and would 

require significant re-piping to serve as part of a closed-cycle cooling system.13 

The re-piping would likely involve significant excavation activities and would 

likely interfere with other elements of the generating units (e.g., precipitators). 

The towers are permitted to use biocides, but have not needed them to date. 

Facility representatives estimate that the cost to construct a second fully 

recirculating cooling tower of similar size (including tie-in with the condenser) 

would be approximately $110 million. 

7.0 Debris Handling 

Branch does not have significant problems with debris loading. However, facility 

representatives did note that seasonal debris loading would likely preclude the use 

of a barrier net or aquatic filter barrier. 

8.0 Repowering/Future Uses 

There are currently no plans to expand generating capacity or make other 

significant operational changes at Branch. 

9.0 Cooling Ponds 

 

There are no cooling ponds onsite. 

10.0 Ownership 

Branch is owned by an investor-owned company, Georgia Power, a Southern 

Company. Plants operated by Southern Company provide approximately 95% of 

the electricity in the state, making them the single largest entity for promoting 

economic development in the state. Georgia Power’s rates are set by the Public 

Service Commission and any large expenditures (such as cooling towers) would 

require approval before being passed along to consumers. 

11.0 316(a) 

Beaverdam Creek is a small sub-watershed of Lake Sinclair. A large portion of 

the watershed is dammed by the ash pond upstream and does not reach the lake. 

As such, there is virtually no flow in the creek except for the facility’s discharge. 

The bridge over the outlet of Beaverdam Creek provides passage for state 

highway 24/441. Much of the bridge is actually a causeway, leaving minimal 

cross-sectional area for discharge flows into Lake Sinclair. 

 

13 Facility representatives stated that Branch serves as a good example of a cooling tower retrofit that 

minimized costs; they added that there have been no problems with the generating units or cooling water 

systems. 
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The once-through discharge for Branch flows into a retention area with a weir that 

empties into Beaverdam Creek. The pool forms the “source waterbody” for the 

helper towers, which discharge at the lake bottom several hundred feet upstream 

of the primary discharge point. The remaining 50% of the once-through flow 

(i.e., that which does not pass through the helper towers) overflows the weir into 

Beaverdam Creek. 

The lake bottom location of the tower discharge creates an artificial thermal 

stratification in Beaverdam Creek. Following approval by the state and 

subsequent litigation from environmental groups, a 316(a) study was conducted to 

verify that the configuration would support a balanced indigenous population 

(BIP). Following a 2-year monitoring study, Branch demonstrated that the 

artificial stratification functioned appropriately, even maintaining stratification as 

it passed through the confined outlet from Beaverdam Creek embayment into 

Lake Sinclair. The study also conducted extensive transect sampling to ensure 

that an appropriate zone of passage was provided for aquatic life.14 Facility 

representatives added that the past 3 years have been periods of high power 

demand and severe drought, but that fish populations have not shown any signs of 

stress. 

12.0 Ash Handling 

Branch uses a 311 acre ash pond to the northwest of the site to handle its ash 

disposal. The main ash pond replaced several smaller ash ponds; the discharge 

from the main ash pond is now routed through the older ponds for additional 

treatment before being discharged into Lake Sinclair. 

The main ash pond was built in the early to mid-1980s, prior to recommended 

design standards for liners or groundwater monitoring being implemented.15 

However, Georgia does have state requirements for dam safety that apply to the 

main ash pond due to the size of the dam and down-gradient residences. The dam 

is inspected annually by state officials and on a more frequent basis by Georgia 

Power engineers.16

13.0 Air Emissions Controls 

Facility representatives noted that no decision has been reached on emissions 

controls for Branch, but did note that a new landfill is likely to be constructed 

onsite. Scrubbers are being installed at other large plants. Georgia Power is 

currently studying flue gas desulfurization (FGD) wastewater treatment processes. 

 

14 Facility representatives described the zone of passage as being defined as not more than 93°F with not 

less than 3.0 mg/l dissolved oxygen content. 

15 In fact, no Georgia Power facilities have ash ponds with liners. 16 Georgia Power has an internal team of engineers to service the 19 reservoirs operated by the company. 

They conform to Army Corps of Engineers design and inspection standards. 
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14.0 Additional Information 

Facility representatives noted that of the 13 facilities in Georgia owned by 

Georgia Power, 7 employ closed-cycle cooling. The remaining 6 (including 

Branch) use once-through cooling. Facility representatives noted a wide variety 

of results in the impingement monitoring at these sites. For example, Mitchell has 

a small generating unit (not baseload) with a good sweeping flow and low intake 

velocity. Impingement counts were very low. As such, retrofitting to closedcycle cooling would not be a cost-effective solution. In fact, the facility would 

likely close if required to install closed-cycle cooling.17

Georgia Power has an internal team of analysts and engineers that evaluated each 

facility’s CWIS, suggested potential technologies, and calculated approximate 

compliance costs. These engineers tended to focus (at least initially) on solutions 

that would meet the 0.5 fps compliance alternative for impingement mortality, as 

this is often a lower cost alternative. (Several facilities already met this standard 

and one Georgia Power facility would have been required to meet entrainment 

standards under the now-suspended 2004 rule.) 

Facility representatives stated that many of the Georgia Power facilities with 

closed-cycle cooling are located on small rivers. The largest of these facilities is 

located on a river with a 7Q10 of 250 cfs; the second largest on a river with a 

7Q10 of 380 cfs. They noted that they often must remind permitting authorities 

and the public of the differences between total withdrawal rates and consumptive 

(evaporative) losses at these facilities. They also noted that none of these cooling 

towers were installed for 316(b)-related reasons. 

Facility representatives stated that it may be preferable in some circumstances for 

regulations to prescribe a technology, as this provides certainty. Alternatively, the 

maximum amount flexibility possible within the rule would be preferable. 

Facility representatives also stated that they would prefer the rule incorporate a 

minimum threshold for adverse environmental impacts, as some technologies or 

solutions may not be cost-effective. 

Attachments 

Attachment A List of Attendees 

Attachment B Aerial Photos (Google Maps) 

Attachment C Aerial Photo (Side View) 

Attachment D Aerial Photo (12/29/2002) 

Attachment E Site Visit Photos 

 

17 Facility representatives stated that many of Georgia Power’s older facilities are being slowly phased out. 

They are attempting to maintain a good balance of fuel types (coal, natural gas, nuclear) but have not added 

any coal-fired facilities in some time. Georgia Power is also evaluating changing the fuel type for Mitchell 

to waste wood, as there is ample supply of wood products nearby. 
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Attachment A--List of Attendees 

Paul Shriner, EPA Headquarters 

Jan Matuszko, EPA Headquarters 

Karrie-Jo Shell, EPA Region IV 

Kelly Meadows, Tetra Tech 

Bill Evans, Georgia Power 

Donna Hill, Georgia Power 
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 Photo (Side View) 

Please see the attached materials. 

Attachment D—Aerial Photo (12/29/2002) 

Please see the attached materials. [oversize—in hard copy only] 

Attachment E—Site Visit Photos 

Please see the attached materials.