Document ID: EPA-HQ-OW-2008-0667-3645
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2014-08-15T04:00Z

MEMORANDUM

Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
phone	703-385-6000
fax	703-385-6007

TO:			Paul Shriner and Lisa Biddle, EPA
FROM:		John Sunda, Tetra Tech
DATE: 		June 21, 2012

SUBJECT:		Review of EPA Estimates for Traveling Screen Capital Costs

This memo provides a comparison of reported capital costs for replacement of traveling screens against estimated costs developed with the EPA cost technology modules that are incorporated into the cost tool.  During EPA's 2009 visits to several power plants in EPA Region VII, EPA obtained reported total capital costs for the entire replacement of traveling screens at intakes at the Cooper nuclear power plant and the Labadie coal-fired power plant. Both plants withdraw water from the Missouri River, which carries a high amount of sand and sediment resulting in a high degree of wear and tear on the traveling screens.  In the case of Cooper, the installation involved the conversion from single-entry single-exit (through flow) traveling screens to double-entry single-exit (dual flow) traveling screens. This conversion was performed to help reduce the frequency of condenser backwash and cleaning maintenance that resulted from excessive debris carryover on the through flow traveling screens.  The construction company that designed, built and delivered the dual flow traveling screens stated in a scope of work that "these screens were the first travelling screens designed to both minimize the owners' downtime, and also have the ability to minimize damage to both juvenile and adult fish" (Rand Construction 2006).  EPA did not actually visit this site and it is not clear to what extent these screens include Ristroph-type features but it is apparent from the description that some features may be included. The new traveling screens at Labadie did not include Ristroph features but the purchased screens were described as being designed to allow for an easy retrofit to incorporate Ristroph modifications.

In order to compare the costs of these projects to the EPA estimates, an estimate of the relative costs of conventional and modified Ristroph screens is required. A traveling screen vendor was contacted and reported that the increase in cost between a conventional traveling screen and a modified Ristroph traveling screen of the same dimensions and mesh size would be around 24% to 26% for screens where the spray wash and debris return on the original screen are on the downstream (descending) side of the screen. The increase would be around 30% for a screen with the original debris return on the upstream (ascending) side due to the need for a taller screen (Gathright 2012). Approximately 30% to 45% of existing traveling screens have the debris return on the upstream side.

Most facilities do not account for traveling screen O&M costs separately, so data for an O&M cost comparison is not available.  Table 1 below summarizes pertinent intake design and cost data provided for the Labadie and Cooper facilities.

                                    Table 1
             Intake Design and Cost Data Provided by Each Facility
                                     Plant
                               Design Flow (gpm)
                               Number of Screens
                               Screen Width (ft)
                                  Screen Type
                                 Capital Cost
                                  Labadie, MO
                                    856,250
                                       8
                                      10
                    3/8 inch Through-flow Traveling Screen
                                  $2,800,000
                              Cooper Nuclear, NE
                                    669,444
                                       9
                                      10
                      3/8 inch Dual Flow Traveling Screen
                                  $6,000,000
gpm  -  gallons per minute
ft  -  feet

In order to estimate comparable total capital costs using the EPA cost methodology, the total screen width and screen well depth must be estimated.  Screen well depth was not provided but at two other plants visited by EPA on the Missouri River (North Omaha and Nebraska City), traveling screen design schematics were provided that indicated the screen well depths at these two plants ranged from 46 feet (ft) to 49 ft and screen widths were 10 ft.  Thus, the 50 ft screen well depth option in EPA's cost methodology is a good fit for comparable cost estimation. For the Cooper facility, 3/8 inch mesh dual flow traveling screens replaced existing through-flow screens, which is comparable to the technology in Cost Module 11.  The Labadie plant reported they installed 3/8 inch standard through-flow traveling screens, which is comparable to the technology in Cost Module 1. 

As documented in the TDD for the final rule, a review of the cost data suggests that the proposal cost estimates for traveling screens may represent easier retrofit situations and that in some situations there may be additional costs such as electrical/instrumentation and instances where modification to the screen house and other infrastructure may be necessary. Based on the data provided here and best professional judgement (BPJ), EPA concluded that a 20% increase in the traveling screen component would provide a cost estimate that is more reflective of the wider range of costs represented by the example provided here. As described in the final TDD EPA also increased the cost estimate for the fish return components by 100%. Table 2 presents a comparison of the screen replacement costs reported by the facilities to the EPA capital cost estimates for the proposed and final rules.

                                    Table 2
Comparison of Reported Cost of Traveling Screen Replacement to Comparable EPA Cost Module Capital Cost Estimate and Cost Module Design Basis
                                     Plant
                 Reported Screen Replace-ment Capital Cost[1]
                                       
              EPA Estimated Capital Cost Estimate (2009 Dollars)
                          EPA Cost Estimate Basis[2]
                                       
                                       
                                   Proposal
                                   Final[3]
                                 Type of Plant
                                  Cost Module
                            Total Screen Width (ft)
                              Regional Factor[4]
                                  Labadie, MO
                                  $2,800,000
                                  $3,300,000
                                  $4,100,000
                                  Non-nuclear
                                       1
                                      80
                                     1.054
                              Cooper Nuclear, NE
                                  $6,000,000
                                  $6,300,000
                                  $7,900,000
                                    Nuclear
                                      11
                                      90
                                     0.847
1 Costs do not include fish return, added spray water pumps, or certain Ristroph features.
[2] Screen well depth is assumed to be 50 ft and costs are adjusted to February 2009 Dollars. 
3 Traveling screen upgrade capital cost estimates were increased from proposal including a 20% increase for the screens and a 100% increase for the fish return components. 
4 Regional cost factors that account for regional variations from the national average in construction and materials costs were developed from ENR data for Phase II. 

The EPA proposed rule capital cost estimates were very close in value to the reported estimates but the EPA costs included the full suite of modified Ristroph features plus the fish return spray pumps piping and fish return flume. This, along with several public comments to the proposed rule stating that Ristroph traveling screen costs were underestimated, prompted a re-evaluation of traveling screen costs and the final rule revisions.

The EPA final rule cost estimates are 30% higher for the Cooper Nuclear plant where there are indications that some Ristroph features may already be present. Thus, this extra 30% should be sufficient to cover the spray water pumps and fish return trough not included in the reported facility costs.  

The EPA final rule cost estimates for the Labadie plant are 46% higher than the reported facility cost for screen replacement. Therefore, the EPA cost estimate is clearly sufficient to include the cost of the estimated 24% to 30% for Ristroph features plus additional money to cover the spray water pumps and fish return flume. As indicated in the site visit report for Labadie, facility personnel estimated that an upgrade of the existing screens to modified Ristroph traveling screens would have cost $4 million which is nearly equal to the revised final rule estimate (DCN 10-6532).

These examples confirm that the BPJ adjustment factors of 20% for traveling screens and 100% for fish returns used to revise the capital cost estimates for traveling screens used in the final rule are representative of reported facility costs.

References

Rand Construction Co. Dual Flow Conversion. Cooper Nuclear Station. Brownsville, NE. Scope of Work. Completed January 2006. Accessed May 24, 2012 website: http://www.randsc.com/industrial_dual.html#

Gathright, Trent, Ovivo. Telephone Contact Report with John Sunda, Tetra Tech. Regarding relative capital costs of conventional and modified Ristroph traveling screens. May 24, 2012. DCN 12-6653.

Site Visit Report. Labadie Power Plant. DCN 10-6532.

Site Description Report. Cooper Nuclear Power Plant. DCN 10-6522.