Tetra Tech, Inc.

10306 Eaton Place, Suite 340 Fairfax, VA 22030 phone 703
- 385
- 6000 fax 703
- 385
- 6007 TO : Paul Shriner, EPA FROM : John Sunda (SAIC) and Kelly Meadows DATE: March 23, 2011 SUBJECT: 316(b) Existing Facility Cost Tool For the 2004 Phase II rule , EPA developed a application of a number of different intake technologies and upgrades to individual facility intakes. Various intake attributes, such as t flow rate, existing control technologies, expected performance standards, and other parameters , were used to determine an appropriate compliance technology

. use does vary

b y typ e of facility , the typ es of intake structures and intake t not different between Phase II and Phase III facilities. same compliance technologies used in Phase II were appropriate for Phase III For the Phase III Rule , EPA developed a cost tool that incorpo equations and cost development methodology tool was a spreadsheet program that created intake compliance costs. The use of this program makes multiple cost cal transparent, and reproducible. appropriate technologies based on compliance requirements various EPA rule options

. The scope of facilities subject to the proposed existing facility rule includes both Phase II and Phase III facilities. Since Phase III already included power generating facilities , the facilities. EPA further updated and corrections , methodology changes development of the existing facility rule, EPA evaluated a number of diffe compliance options for both impingement mortality and entrainment mortality reduction. 

### MEMORANDUM

10306 Eaton Place, Suite 340

Paul Shriner, EPA John Sunda (SAIC) and Kelly Meadows March 23, 2011 316(b) Existing Facility Cost Tool

EPA developed a compliance cost methodology based on the application of a number of different intake technologies and upgrades to individual

Various intake attributes, such as t he intake ty pe, location, size, flow rate, existing control technologies, expected performance standards, and other

were used to determine an appropriate compliance technology

. While water does vary b y typ e of facility , the typ es of intake structures and intake t echnologies are not different between Phase II and Phase III facilities. EPA subsequently concluded the same compliance technologies used in Phase II were appropriate for Phase III

EPA developed a cost tool that incorpo rated the Phase II and cost development methodology for each compliance technology

. tool was a spreadsheet program that created intake

- specific or facility

- specific

The use of this program makes multiple cost cal culations rapid and reproducible. The cost tool also included algorithms that helped select appropriate technologies based on compliance requirements , known site conditions
The scope of facilities subject to the proposed existing facility rule includes both Phase II

Since Phase III already included existing manufacturing and , the cost tool was already designed for use wit h both kinds of further updated and modified the Phase III cost tool to incorporate methodology changes , and additional compliance options. During the development of the existing facility rule, EPA evaluated a number of diffe rent compliance options for both impingement mortality and entrainment mortality reduction. based on the application of a number of different intake technologies and upgrades to individual he intake ty

pe, location, size, design flow rate, existing control technologies, expected performance standards, and other While water echnologies are concluded the same compliance technologies used in Phase II were appropriate for Phase III facilities

. Phase II cost for each compliance technology

. The cost

specific culations rapid , The cost tool also included algorithms that helped select known site conditions , and
The scope of facilities subject to the proposed existing facility rule includes both Phase II existing manufacturing and

h both kinds of cost tool to incorporate compliance options. During the

rent compliance options for both impingement mortality and entrainment mortality reduction.- 2

-

As such, the technology

selection component has been modified several times in order to model different approaches with respect to compliance requirements and technology capabilities

. Some m ethodology changes were made as well and are discussed in detail in Chapter 8 of the T echnical D evelopment D ocument (TDD)

. A major modification to the compliance technology selection process resulted from the re - evaluation of the e ntrainment reduction capabilities of the suite of technologies. The result was that EPA’s compliance assumptions do not rely upon any of the intake technologies as the means to comply with entrainment mortality reductions. Entrainment reduction c ompl iance costs are instead based on closed

- cycle cooling and were developed using a separate methodology

. 1 As a result, the current version of the cost tool was utilized to derive costs for compliance with IM reduction requirements onl y . Also , certain input values (e.g., “Capacity Utilization, “River Proportional Flow”) that were use d in the previous rulemaking efforts as criteria for specifying compliance requirements were not used in this effort. In addition, due to revisions to the technology selection p rocess , certain input values are not used in the active algorithms and are no longer functional, but have been retained in the current version of the cost tool. These are identified on the user input sheet and in the description below. The tool accepts s ite

- specific intake data, executes the cost derivation methodology and anal ys is and then outputs a set of costs for use in compliance option evaluation. The intake

- specific data and cost information used by EPA is generall y handled as confidential busines s information (CBI) , but EPA has made available this cost tool (without the facility

- specific input data) so that the cost methodology is transparent. To provide for greater flexibility in use, an input variable has been added to allow users to select compliance technology modules under consideration and obtain separate costs for each. This allows potentiall y regulated facilities to use the cost tool to predict EPA’s compliance cost estimates for various alternatives. The development of the cost technology modules is described in Chapter 1 of the Final Phase II Rule Technical Development Document (DCN 6

- 0004 , FDMS ID EPA

- HQ

OW

- 2002

- 0049

- 1462 )

. The initial development of the cost tool is described in detail in Chapter 5, Section 2 of the Phase III Technical Development Document (DCN 9

- 0004, FDMS ID EPA

- HQ

- OW

- 2004

- 0002

- 1543 )

. Additional modifications to the c ost development methodology are described in Chapter 8 of the Technical Development Document for this existing facility proposed rule. The cost tool will compute compliance costs for the individual cost modules developed under Phase II plus several combin ations listed in Table 1 below:

Table 1. Module Technology Description Module # Description 1 Replace Traveling Screen with Ristroph Screen and Add Fish Handling and Return System 2 Replace Traveling Screen with Fine Mesh Ristroph Screen and Add Fish Handling and Return System 2a Add Fine Mesh Screen Overlays Only 3 Add New Larger I ntake Structure with Double Entry, Single Exit Traveling Screen with Fish Handling and Return

1 See the TDD for a description of the EPRI tool for developing retrofit cooling tower costs.- 3

- 4 Add Passive Fine Mesh Wedgewire Screens (1.75 mm mesh) at Shoreline 5 Add Fish Barrier Net 6 Add Aquatic Filter Barrier (Gunderboom) 7 Relocate I

ntake to Submerged Offshore with Passive Wedgewire Screen (1.75 mm mesh) 8 Add Velocity Cap at I nlet 9 Add Passive Fine Mesh Wedgewire Screen (1.75 mm mesh) at I nlet of Offshore Submerged 10.0 Combination of Module 2 and Module 5 10.1 Combination of Module 2a & Module 5 10.2 Combination of Module 3 & Module 5 10.3 Combination of Module 1 & Module 5 10.4 Combination of Module 1 & Module 8 11 Add Double

- Entry, Single

- Exit Traveling Screen with Fish Handling and Return 12 0.75 mm Passive Fine Mesh Wedgewire Screen at Shoreline (For Estuary & Ocean only) 13 0.75 mm Passive Fine Mesh Wedgewire Screen at I nlet of Offshore Submerged (For Estuary & Ocean only) 14 Relocate Intake to Submerged Offshore with 0.75 mm Passive Wedgewire Screen (For Estuary & Ocean only)

The Cost Tool Structure The cost tool program makes use of basic database retrieval functions and logical statements to mirror the costing methodology hierarc hy

used b y EPA for development of the existing facility

technology

costs to compl y with impingement mortality reduction requirements. The cost model described here modifies the cost tool to Version 6.1 which calculates the costs the Agency developed and c onsidered for the proposed existing facility rule. The cost tool combines the varied analy ses and data presented in the TDD into an automated decision tree that ultimately assigns a te chnology

cost to each facility

. In the “User Inputs” sheet of the cost tool, the user supplies data at the facility level, or the user may

choose to input information at the intake level where multiple intakes at a single facility

have different features that might affect which technolog y modules are feasible for each intake. Once the “user inputs” have been entered, and as long as the “Qualified Impingement?” box is left blank, the cost tool will apply EPA’s decision tree for assigning site

- specific cost modules for IM reduction compliance; see Exhibit 8

- 1 in Chapter 8 of the TDD for a schematic of this decision tree. Finall y, the costing methodology

is performed through a combination of calculations and functions (that is, an algorithm). This work is mostly carried out in the sheet ti tled “Calc. and Data” and is supplemented by

a few logical functions and data retrieval in the “Output” sheet. The cost outputs include capital costs, incremental O&M c osts, and downtime (in weeks). The data fields requested in the “User Inputs” sheet (s ee Figure 1 below ) come from questions in the 2000 industry technical questionnaires sent to facilities plus a few basic observations about the intake, such as a judgment about the degree of debris loading at the intake: “high” or “low.” The program repro duces the methodology the Agency utilized to develop final costing decisions to determine which technology would best suit a particular intake.- 4

-

If multiple sets of intake/plant data are to be run, the input data can be entered on separate lines in the “Ma cro Input” worksheet. Then if the “AutoInput” macro is run, the corresponding output data is copied into the “Macro Output” worksheet. For individual computations, data can be entered directly into the “User Inputs” worksheet and the calculated costs can be read directl y from the “Output” worksheet. Figure 1 presents a screen shot of the “User Inputs” page. Figure 1 Screenshot of User Inputs Sheet

Cost Tool Inputs This section describes the inputs to the Cost Tool (see Figure 1), and defines the default values used. The default value s are used when input values are left blank. Modifications User Inputs -- At The Intake Level Facility I nformation T ables/Keys
Facility Type = ( 3 = Manuf act urer, 2 =Power Generat

ion) (Required Field) Cooling Sy st

em Type = ( 1 = Full Recirculat ion, 2 = Cooling Ponds, 0 = All Ot hers) Int

ake Locat ion / Description 1 = Shoreline Int

ake (f lush, recessed) State A bbreviation = (Required Field) 2 = Int ake Canal 3 = Embaym

ent, Bay, or Cove Wa terbody T

ype = (1=Ocean, 2=Est uary, 3=Great

Lake, 4=Fresh River, 5=Lake/Res.) 4 = Subm erged Of fsh ore Int ake 5 = Near-shore subm

erged int ake FuelType = (1 = Nuclear, 0 = Non-Nuclear) 6 = Shoreline Subm erged Int ake Capacit y Ut ilizat ion (1996-99) = % (No Longer in use) Im pingment T ech nologies In-place 0 = None of

t hose list ed Intake Location / Description (choose f rom Descript ion t able at right ) (Required Field) 1 = Traveling Screens
Dist ance Of fsh ore f or Subm erged Inlet f

t (use f or subm erged of fsh ore t echnologies) Dam , Leaky Dike, 3 = Barrier Net Canal Lengt

h = f

t (if canal is present

bet ween m out h and screens) 4 = Fish Div ersion or Avoidance (Louvers, Acoust ics, et c.) 5 = W edgewire Screens Navi gat ion / W at erbody Use (1 = boat /barge navigat

ion near int ake, No longer in use ) Th rough Screen Velocity Fl ow Basis 1 = Ex isting Equipm

ent Design Int ake Flow Mean I ntake W ater

Depth = f

t 2 = New Design Int ake Flow 3 = Av erage Int

ake Flow Int ake W ell Dept h = f

t In-place Tech EPA "Qualif ied" f or Im pingment Reduct

ions Riv er Proport

ional Flow = (No Longer in use) 0 = none 1 = Fish Handling and Ret

urn Syst ems & Rist roph Traveling Screens or Existing Equipm

ent Design I ntake Flow = gpm (Required Field) Passiv e Int akes (v elocit

y cap, t -s cr eens, porous dam

s, et c.) 2 = Through screen velocit

y of .5 f ps or less only New Design Int

ake Flow = gpm (Use only if

new t echnology will use dif

fe rent design f low) Entrainment Tech nologies In-place Av erage I ntake Flow = gpm (Required Field) 0 = None of t hose list ed 1 = Traveling Screens w/ Fine Mesh Ex isting T hrough Screen Vel ocit y = fp s (def

ault s will be used if

lef t blank) 2 = Far Of fsh ore Int ake 3 = Passiv e Screens w/ Fine Mesh Through Screen Velocit

y Fl ow Basis = ( Choose f rom Through Screen Velocit

y Fl ow Basis list

at right In-place Tech EPA "Qualif ied" f or EntrainmentReduct

ions Wa te r Type = (1 = m arine, 0 = f resh) Fi ne Mesh Screens (passive or t ravel ing screens) Far Of fsh ore Int ake w/ Passive Int

ake at Inlet Debris Loading = (1 = high, 0 = norm al) Recent ENR Construction Cost I ndeces Im pingement T

ech I n-Place = (choose f rom Im pingm ent Tech list at right ) Year Inde x 2002 (Def ault ) 6538 Qu alified I mp ingem

ent? = (1 or 2 = Qualif ied, 0 = none; see im

pingem ent reduct ion t able t o right ) 2003 6694 2004 7115 Ent rainm ent Tech In-Place = (choose f rom Ent rainm ent Tech list at right - No Longer in use) 2005 7446 2006 7751 Qualif ied Ent rainm ent ? = (1 = Qualif ied, 0 = none; No longer in use ) 2007 7966 2008 (Oct ober) 8623 avg annual generat

ion '96 - '99 = (MW h, report ed dat a, excluding out

liers, EG only ) 2009 (February) 8533
Se lected T

echnology Module = (Technology Module will be select ed f or you if lef t blank) Regional Cost

Fact or = ( 1.0 = Nat ional Av erage - Leave blank f or def ault st at e average)
ENR Const

ruct ion Cost Index = ( Inf

lat ion Index f or desired cost

year - see t

able at right ) Compliance Screen Mesh (mm) = (Select f rom 9.5, 2.0, 1.0, 0.5 - def ault = 2.0))
Scr een Velocity f

or Module 3 (fps) = (default is 1.0 fps) Maximum Acceptable Screen Velocity (f ps ) = (Us ed to dertermine if existing technology must be replaced) 2 = Passiv e Int ake (Velocit

y Cap)- 5

-

to the previous Phase III version of the cost tool include the addition of the following input variables:

 New Design Intake Flow (gpm)
 ENR Construction Cost Index
 Compliance Screen Mesh (mm)
 Screen Velocity

for Module 3 (fps)
 M aximum Acceptable Screen Velocity (fps) The input variables in the current cost tool are described b elow: Facility Type: This input value was added to allow for proper selection of default input values to the cost tool for different ty pes of facilities (“3” = Manufacturer ; “2” = Power G eneration). Facility

typ e is a required input variable in the cost tool. Cooling System Type: Used to identify whether the cooling s ys tem is once

- through or recirculating. In the current version of the tool, this input is not used in the active algorithms since intakes must meet impingement reduction requirements regardless of cooling type. State Abbreviation: The two letter state abbreviation is used to identify the state where the intakes are located. The state is used to assign state

- specific capital cost factors developed for the Phase III Rule. The state also is used to identify whether zebra mussels are a potential problem at a facility, requiring the use of more costl y CuNi alloys in wedgewire screen s. Waterbody Type: The numeric values 1 through 5 represent the waterbody typ e for each intake’s location. These values are “1” = Ocean, “2” = Estuary , “3” = Great L ake, “4” = Fresh River, “5” = Lake/Reservoir. This input variable affects technology sel ection and certain cost components. Waterbody type is a required input variable in the cost tool. Fuel Type: A value of “1” (one) indicates the intake is part of a nuclear facility and results in additional cost factors applied to both capital and O&M co sts. A value of “0” (zero) indic ates the intake is non

- nuclear. Capacity Utilization Rate (CUR): In the current version of the tool, this input is not used in the active algorithms. This percentage value reflects the ratio between the average annual net generation of power b y the facility (in MWh) and the total net capability of the facility to generate power (in MW), multiplied by the number of hours during a ye ar. Intake Location : The numeric values 1 through 6 represent the location and description for each intake. These values are “1” = shoreline intake (flushed, recessed), “2” = intake canal, “3” = embay

ment, bank, or cove, “4” = submerged offshore intake, “5” = near

shore sub merged intake, “6” = shoreline submerged intake. This input variable affects technology

selection and certain cost components such as costs for longer fish returns. Intake Location/Description is a required input variable in the cost tool.- 6

-

Distance Offs hore for Submerged Intakes: Submerged offshore intake distance affects construction and civil costs as well as O&M costs, and is a critical parameter for relocating intakes and adding wedgewire screens to existing offshore intakes. The default distance of submerged offshore intakes is the median of all reported values from Phase II facilities by

waterb ody

ty pe as follows in Table 2: Table 2. Default Values for Distance Offshore for Submerged Intakes Waterbody Code Distance Offshore (Meters) Ocean 1 500 Estuaries/Tidal Rivers 2 125 Great Lakes 3 500 Rivers and Streams 4 125 Lakes/Reservoirs 5 125 Canal Length: This variable is used to determine the length of the fish return system. The default value for the constructed canal length is the median of all reported values from Phase II facilities as follows in Table 3:

Table 3. Default Values for Canal Length Waterbody Code Canal Length (Ft) Ocean 1 3,370 Estuaries/Tidal Rivers 2 1,650 Great Lakes 3 1,460 Rivers and Streams 4 690 Lakes/Reservoirs 5 800 Navigation/Waterbody Use: In the current version of the tool, this input is not used in the active algorithms. A value of “1” indicates the intake is located where boat/barge navigation near the intake is a consideration when making any modifications to the intake. A value of “0” (zero) indicates navigation does not occur in the vicinity of the intake.
Mean Intake Water Depth : This value is used for estimating total existing screen width and selecting compliance technologies. Default values are shown in Table 4 below:

Table 4. Default Values for Mean Intake Water Depth Facility type Code Mean Intake Water Depth (ft) DIF ≥ 50 MGD DIF < 50 MGD Electric Generating 2 15 12 Manufacturing 3 19 16- 7

-

Intake Well Depth : The intake well depth is the distance from the intake deck to the bottom of the screen well, and includes both water depth and distance from the water surface to the deck. The intake well depth is used to select the total height of the required traveling screen. For a given screen width, deeper screens result in higher capital costs. If not entered, then screen well depth is calculated by adding the freeboard depths in the following Table 5 to the mean intake water depth:

Table 5. Default Values for I ntake Well Depth Waterbody Code Assumed Distance from Mean Water Surface to Screen Deck

(ft) Ocean 1 15 Estuaries/Tidal Rivers 2 15 Great Lakes 3 15 Rivers and Streams 4 30 Lakes/Reservoirs 5 20 River Proportional Flow: This input value was used in selecting compliance requirements in previous rulemaking efforts. In the current version of the tool, this input is not used in the active algorithms. A value of “1” (one) indicates the design intake flow is greater than 5 p ercent of the mean annual flow of a freshwater river or stream. A value of “0” (zero) indicates the design intake flow is less than or equal to 5 percent of the mean annual flow of a freshwater river or stream. Existing Equipment Design Intake Flow (DIF) : The DIF is the numerical value assigned during the facility ’s design to the total maximum volume of water withdrawn. Design Intake Flow (DIF) is a required input variable in the cost tool. New Design Intake Flow : This value is intended to represent current maximum intake flow requirements, as opposed to the DIF, which is based on maximum design flow capacities and may

include pumping capacity no longer used or needed. This value is used to develop costs for compl iance technologies that do not involve upgrade or replacement of existing traveling screens (e.g., wedgewire screens, fish barrier nets, new intake, velocity cap). Average Intake Flow (AIF) : This input variable was added to allow for adjustment of the variable portion of the O&M costs to reflect actual equipment operating costs. Average Intake Flow is a required input variable in the cost tool. Existing Through
-

Screen Velocity: This input v ariable is used to estimate the existing screen width as well as for selecting the appropriate compliance technology. The power generation default values shown in Table 6 below are the mean reported values for all electric generators with greater than 50 MGD design intake flow. For manufacturing facilities, the default values are the mean reported values of Phase III Facilities.- 8

- Table 6. Default Values for Existing Through
- Screen Velocity Facility Type Code Screen Velocity (Ft/Sec) DIF ≥ 50 MGD DIF < 50 MGD Electric Generating 2 1.5 0.6 Manufacturing 3 1.2 0.8 Through
- Screen Velocity Flow Basis: This input variable is used to identify the flow basis of the “ Existing Through

- Screen Velocity” and is used in the selection of the proper flow for calculation of existing screen width (“1” = Existing Equipment Design Intake Flow; “2” = New Design Intake Flow; “3” = Average Intake Flow). If left blank, default is Existing Equipment Design Intake F low (“1”). Water Type : A value of “1” indicates the water type is marine. A value of “0” indicates the water type is freshwater. The default is “0.” Debris Loading : This input variable is used to estimate O&M costs for wedgewire screens. A value of “ 1” indicates high levels of debris and trash near the intake. A value of “0” indicates debris is low or negligible. The default is “1.” Impingement Technology In
- Place : This input variable is used to select compliance technologies and baseline O& M costs. A numerical value of 0 through 5 is used to indicate the intake has impingement technologies reported as in

- place by the facility. A value of “1” = Traveling Screens, “2” = Passive Intake (Velocity Cap, Porous Dam, Leaky Dike, etc.), “3” = Barri er Net, and “4” = Fish Diversion or Avoidance (Louvers, Acoustics, etc.). The default is “0” (no controls). Qualified Impingement: This input variable identifies intakes that are already compliant with IM reduction requirements. A value of “1” means th e existing intake is compliant and will receive no costs. A value of “0” or if left blank means IM compliance technology

upgrades are needed. For facilities with traveling screens, this input value indicates whether a fish return mechanism is in

- place. This in turn affects the cost module selected, as well as baseline O&M costs. Qualified Impingement is a required input variable in the cost tool. Entrainment Tech in
-

Place : This input value was used in selecting compliance requirements in previous rulem aking efforts. In the current version of the tool, this input is not used in the active algorithms. Qualified Entrainment: This input value was used in selecting compliance requirements in previous rulemaking efforts. In the current version of the tool, this input is not used in the active algorithms. Users of the tool can still hardcode a entrainment technology for purposes of cost estimation.- 9

-

Avg Annual G

eneration '96
- '99: This input value was used in estimating power generation downtime costs and “per MWh” costs in previous rulemaking efforts. In the current version of the tool, this input is not used in the active algorithms

. Regional Cost Factor: This input value is used to adjust capital cost estimates to reflect regional labor and material cost considerations. If left blank, a regional cost factor based on the reported state will be used. A value of “1.0” should be entered if a national average value is desired. Screen Velocity for Module 3: This input variable selects the design screen velocity to be used for estimating the size of technology Module 3 (new larger intake), which in turn will affect costs of the new intake. The default value is “1.0” fps. Maximum Acceptable Screen Velocity: This input variable is used for selecting compliance technologies and establishes the maximum existing velocity acceptable for continued use of existing traveling screens. The referenced existing screen velocity is calculated based on the “New Design Intake Flow.” The defau lt value is “2.51” fps. Cost Tool Outputs The cost tool outputs can be found on the “Output” worksheet or in the “Macro Output” worksheet if the macro is used for multiple entries. Many of the values represent interim computations and only

the following are extracted and used in economic impact anal ys es: Assigned Costing Module: This output identifies the selected compliance technology module. Costing Module Service Life: This output identifies the service life of the selected technology

module and is the time period to amortize capital costs or calculate pre sent value of annual O&M costs. Baseline O&M: This output provides the estimated O&M cost of the existing compliance technology

. Gross Module O&M

: This output provides the estimated total O&M of s elected technology

module. Baseline O&M Fixed Factor : This output provides an estimate of the proportion of the baseline O&M costs that are fixed (i.e., do not vary regardless of intake use). Gross Module O&M Fixed Factor : This output provides an estimat e of the proportion of the gross module O&M costs that are fixed (i.e., do not vary regardless of intake use). Compliance Tech Capital: This output provides an estimate of the total capital costs of the selected technology

module.- 10

-

Compliance Net Annual O &M : This output provides the net increase in O&M costs based on the difference between the Gross Module O&M and Baseline O&M. All costs are adjusted using the ENR Construction Cost Index (CCI) value entered as a User Input. The base costs derived for Phase II are in 2002 Dollars (ENR CCI= 6538), which is the default cost basis if no ENR CCIvalue is specified. Cost Tool Limitations The cost tool, with the exception of a few selected combinations, assumes that a single technology

will be sufficient t o meet compliance requirements, while in reality a combination of technologies may be necessary

. Compliance costs for such combinations can be developed b y calculating costs for each intake or for multiple selected technology modules and aggregating the c osts. Care must be taken to avoid double counting baseline O&M costs (i.e., do not sum up net O&M costs). The compliance costs for wedgewire screens were originall y calculated for fine mesh requirements (1.75mm and 0.75mm), which were intended to provide for entrainment reduction in addition to impingement reduction. Use of smaller mesh sizes results in a larger screen area requirement and thus either larger or more screens, which increases the costs compared to coarse mesh. The impingement reduction te chnology requirements do not require screen sizes smaller than 9.5 mm; however, the cost tool modules involving wedgewire screens were not adjusted to account for different mesh sizes. Thus, the estimated screen sizes and costs for wedgewire screens may represent an overestimation of compliance costs if smaller mesh sizes are not required. The purpose of the tool is to generate national level compliance costs. The industry questionnaire database contained only a limited amount of data and so the input opti ons are limited as well. Due to these limitations, the technologies selected by the cost tool may not actuall y be economically or technicall y feasible at the specified intake ; the cost tool is not intended to assess financial conditions or feasibility of a technology

at a site

. Recognizing th ese limitation s , the compliance costs are derived for economic anal ys es using the cost tool , and are considered to represent model facility /intake costs that are representative of additional facilities with similar attributes. These model facility costs are then extrapolated to the entire universe of facilities subject to the proposed rule. For this reason, the user should not necessaril y rely upon the technology selected by the cost tool as being the best fit. Addi tionally , the estimated costs are intended to reflect average conditions and actual costs may differ considerably

depending on local site conditions.