INTAKE DEBRIS SCREEN 

POSTIMPINGEMENTSURVIVAL 

EVALUATION STU,DY 

ROSETON GENERATING STATION 

1990 

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EnvironmentalScience 8c Engineering Consult 

One Blue Hill Haza 0 PearlRiver, New York 11 
CHAPTER3 

SITE DESCRIPTION AND DESCRIPTION OF DUAL-FLOW TRAVELING SCREENS 

3.1 ROSETON GENERATING STATION INTAKE 

ne Roseton Generating Station (Figure 3-1) is located on the west bank of the Hudson 

River approximately 106 km (66 mi) north of the Battery and 6 km (3.7 mi) north of the 

Newburgh-Beacon Bridge. Units 1and 2 were placed in commercial service on 31 December 

and 14 September 1974, respectively. The Roseton plant is a fossil-fueled steam electric 

generating station; its two independent units have a total maximum net generating capacity 

of 1200 MWe. Steam is cooled by a once-through cooling system that uses Hudson River 

water withdrawn from the river at a shoreline intake structure. The intake consistsof four 

cooling-water pumps with a combined rated capacity of 2426-2 m3/min (1462 ft3/s), six 

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conventional vertical traveling screens equipped with 9.5-mm (0.38-in,) square mesh, two dual- >-- i *. 

flow traveling screens equipped with 3.2-mm x 12.7-mm (0.13-in. x 0.5-in.) woven bar mesh, 

and 10 vertical trash rack arrays with 76.2-mm (3.0-in.) spacing (center to center). Heated 

effluent is discharged to the river through a single submerged discharge pipe with a multiport 

diffuser. 

In greater detail, the Roseton Generating Station has a shoreline intake structure measuring 

46.6 m (153 ft) across the face and 12.2 m (40ft) on each end (Figure 3-2). There are 12 

portals on the front face of the intake structure and two each on the north and south ends 

(Figure 3-2). Each portal is 6.5 m (21.3 ft) high; width varies with location: the 10 directly 

in front of a trash rack are 3.1 m (10.2 ft) wide; the other six, located on the corners, are 2.8 

m (9.2 ft) wide. The bottoms of the portals are flush with the base of the intake structure 

at elevation -7.9 m (-26 ft)- The intake deck is at elevation 3.1 m (10 ft), and there is a 1.2-m 

(44) wall completely surrounding the structure. Normal low water is at elevation -0.37 m 

(-1.2 ft), which equates to a water depth of 7.6 m (24.8 ft). At extreme low water only a few 

centimeters of water would be above the intake (portal) openings. The entire upper 

perimeter of the intake structure over the portal area consists of a skimmer wall that extends 

to a depth of 1.7 m (5.4ft) below extreme low water. The wall prevents large floating debris 

3-1 

Lawler, Matusky Sr Skelly Engineers 

5 
and ice from entering the intake structure and clogging the trash racks. Bar racks are located 

between the intake portals and the traveling screens to prevent large debris from entering the 

traveling screen approach (Figures 3-3 and 3-41, There are 10 bar racks: eight on the Front 

of the intake and one on each end. Ekb is 11.1 m (36.5 Et) high and 3-1 m (10.2 ft) wide. 

The individual bar rack openings are 6-7cm (2.6 in.) wide. The total open area of each bar 

rack is approxkatefy 28.0 m2 (302 ft2); however, with the water height at mean sea ievel the 

actual open area for water to flow through each bar rack is approximately 20.0 m2 (215�t*) 

There are eight intake traveling debris screens used to prevent fsh and smaIL debris from 

entering the pump chambers; six are conventional vertical-rotating, single-entry, band-type 

Screens mounted to face the waterway (Figure 3-3), and two doub~ee-entryisingle-t, dualBow, band-type screens mounted perpendicular to the waterway. 

Each conventional vertical traveling screen is 12-8m (42 Et) in height and 3.0 m (9.7 ft) in 

width. The continuous screens have a rotating drum 1.2 m (4ft) in diameter on each end. 

The actual screen mesh has a diameter of 3.1-mm (0.12 in.) and a 9.5-133111(038-in.) square 

opening. The screen mesh material is polyvinyl chloride (PVC) with a reported efficiency 

rating of0.47. Assuming a single face exposure foreach screen of 24.2 m2 (260.0 �t2)at mean 

sea level and the reported screen mesh ef6ciency of 0.47, the open area OF each screen is 

approximately 11.4 m2(122.2 43')- The screen mechanism consists of the screen, the drive 

train, the Front wash spray cleaning system and a disposal trough For return of screenwashings 

to the Hudson River. The maximum washwater volume from the single spray header for each 

screen is 0.98 m3/m;n (260 gpm). The screens move at a rate of 3.1 m (IO Et) per minute, 

making one complete revolution every 8.9 rnin. The drive mechanisms of the screens were 

upgraded to permit continuous screen operation over extended time periods. 

To accommodate a fish escape passageway, the conventional vertical traveling screens were 

mounted flush with the shoreline, with the trash racks extending off the shoreline (Figure 

3-2). Thus,fish that pass through the hnt trash racks and approach the traveling screens 

can escape laterally through the trash racks Located at each end of the intake structure. 

3-2 

bwter, Matusky & Skelly Engin1 
TABLE 3-1 

ROSETON COOLINGWATER PUMP FLOW CHARACTERISTICS 

No. OF PUMPS No. OF UNITS 

3.2 DUAL-FLOW SCREEN 

3.21 Description 

COOUNG-WATER FLOW 

m3/min gpm 

825.1 218,000 

1423.2 376,000 

1582.1 418,000 

2123.4 561,000 

2426-2 641,000 

' 

' 

The two dual-flow screens were installed in the existing 1.6-m x 3.1-m (5.3-ft x 10.2-ft) deck 

openings of the two conventional traveling screens they replaced. Each dual-flow screen unit 

shown in Figure 3-6 is 14.9 m (49.0 ft) in height, with screen mesh baskets 1.2 rn (4.0ft) in 

width. The narrower screen baskets are the result of the 90" change in screen orientation and 

the size of the existing deck opening. At mean water level (zero elevation) approximately 

19.3 m2 (208 ft') of screen surface area would be available for filtering cooling water. 

Each screen basket measures 0.46-mx 1.2-m (1.5-ft x 4.0-ft) and is fitted with 1.6-mm (0.063 -

-in.) diameter stainless steel Smooth-Tex woven wire mesh having 3-2-rnmx 12.7-mm (0.13-in. 

x 0.5-in.) openings. The long axis of the screen mesh opening is oriented vertically. The 

Smooth-Tex mesh has an efficiency rating (open space) of 0.61, which yields an open filtering 

area of 11.8 m2 (126.9 ft2) per screen at mean water. The screen baskets are fitted with 

water retaining lip troughs (Figure 3-7), with the leading edge curved inward. The screen 

basket lip trough facilitates fish removal by reducing escapement and reimpingement and 

3-4 

Lawler, Matusky & Skelly Engineers 
eliminates vortices in the trough that buffet and stress the captured organisms (Fletcher 

1990). The screen mesh is ofEset 18"from the vertical, which facilitates organisms faling off 

the mesh into the lip trough. 

The dual-flow screens are equipped with a dual spray wash system (a low-pressure organism 

removal spray, and a high-pressure debris removal spray) located on the descending screen 

basket side of each unit. The low-pressure organism removal system located at the top of the 

unit where the baskets go' over the drive sprocket consists of two pipes with spray nozzles, 

one inside the rotating screen baskets spraying through the mesh and the second external to 

the screen baskets spraying across the face of the screen panel into the lip trough as it passes 

the vertical. The spray discharge for each pipe in the low-pressure spray system is: 

0.265 m3/min (70 gpm) at a line pressure of 3515.5 kg/mz (5 psi) 

0.379 m3/min (100 gpm) at a line pressure of 7031.0 kdm2 (10 psi) 

0 0.478m3/min (125 gpm) at a line pressure of 10546.6 kg/m2 (15 psi) 

The low-pressure spray system washes material into a trough on the north side of the screen 

housing approximately 1.5 m (5.0 ft) above the deck of the intake structure on the east side 

of the unit. 

During the initial phase of the screen evaluation study, vegetation and fish washed from the 

screens by the low-pressure wash system were observed to accumulate in the trough, 

especially at the most southern screen (20). During the second week of October a curved 

piece of fiberglass was fitted across the distal end of the ffih trough of the southern screen 

to minimize dead space where debris had been accumulating, and additional flow was added 

to help wash out the screened material. The additional flow was obtained by tapping into the 

debris wash spray header. 

The high-pressure debris spray system consists of two pipes, both spraying from the inside 

though the screen panels into a trough just above deck elevation. The spray discharge for 

each pipe in the high-pressure debris spray system is: 

3-5 

Lawler, Matusky & Skelly Engii 

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