### 316B RULE **TELEPHONE LOG**
Name of Caller: John Sunda, SAI C
Date: October 14 , 2008 Company Name: Eimco ( Brackett Green ) Street Address: 1335 Regents Park Dr., Suite 260 City /State/ZIP: Houston, TX Person Contacted: Trent Gathright Title: Group Product Manager Telephone #: 281

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- 7955 Ext 27 Trent T. Gathright Group Product Manager P&IScreen Products EI MCO Water Technologies 1335 Regents Park Dr., Suite 260 Houston, TX 77058 Tel: 281

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- 7955 Ext. 27 Fax: 281

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- 8225 Mob: 832

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- 7956 Email: trent.gathright@glv.com Web: www.glv.com Called to ask about feasibility of fine mesh screens in high sediment and deb ris waterway s, technical issues, and examples of fine mesh (<2mm) traveling screen installations. He said that it is difficult to nearly impossible to retrofit existing screens with high screen velocities with fine mesh of 0.5 mm especially if there is a high debris or sand loading because of the rapid blinding of the screens. He said the Mississippi and especially the Missouri ( big muddy ) have problems with sand and retrofitting high velocity screens with 0.5 mm mesh would be nearly impossible. Iasked ab out larger mesh sizes and at what point (size) would the problem diminish. He said the problems would be significant when mesh size drops below 1.0 mm and that 2.0 mm and above would present no problem with sand . They have done numerous 1/8 in (3.175 mm) r etrofit installations and screen velocity was not a problem in those cases. Basically , yo u can have fine mesh screens with low velocities like around 0.5 fps and coarse mesh screens with high velocities but you can’t have both fine mesh (0.5mm) and high sc reen velocities if there are any

chances of debris /sand loading being a problem

.Regarding O&M cost issues, one of the biggest O&M cost items associated with fine mesh is the

more frequent need for chain replacement. Factors that contribute to increased rates are more frequent or continuous operation, operating at faster rotation speeds, and higher depth differentials (head loss) across the screen. All of these tend to increase with reductions in mesh size. L abor is the biggest component for chain replace ment. When asked about the relative increase in O&M for high debris/fine mesh screens, he said O&M costs should increase by about 30%. They recommend installing 2 speed screens so speed can be tailored to debris conditions, thus minimizing wear on screens . Ty pical coarse mesh screen speed is 10 fps and fine mesh will be around 15 fps and 30 fps. Their dual flow screens go up to 45 fps since screen panels travel both down and then up between washes. Regarding screen velocities he said that 2.5 fps is prob ably a good cutoff point for acceptable screen velocities if the screen mesh isn’t too small. At higher velocities increased head loss across the screen become an issue.
I talked about the fact that overseas they use fine mesh but probably with lower ve locities and may use closer spaced bar racks. He said they also recommend use of closer spaced bar racks but only if the mesh size is smaller. For example it would make no sense to put 1 inch bar racks in front of 3/8 in mesh screens. Another problem wi th finer mesh is corrosion. They use stainless steel but also can use polyester screens but these are les s strong and more easily damaged. He said that puncture of the screens is not that much of a problem. Regarding ty

pes of debris, with regard to leaves mesh size doesn’t matter since the leaf will collect on the surface regardless. Algae can be a problem with fine mesh because it can form a matt on the surface essentially creating filtering surface that will catch finer particles. Lake Ontario has proble ms with algal blooms and the Mississippi and Missouri rivers can have problems with algae and leaf mats in addition to sand. He will send me additional information regarding their experience later this week via email.