# INTAKE DEBRIS 

# SCREEN POSTIMPINGEMENTSURVIVAL EVALUATION STU,DY ROSETON GENERATING STATION 

# 1990 

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## December 1991

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### Environmental

### Science8c 

### Engineering Consult OneBlue Hill Haza 0 

### Pearl River, New 

### York 11

### CHAPTER3 SITE DESCRIPTIONAND 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 1 and 2 were placed in commercialservice on31December 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 Steam is cooled by a once-through cooling system that uses Hudson River water withdrawn from the river at a shoreline intake structure.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 consists of four cooling-water pumps with a combined rated capacity 

### of 2426-2 m3/min (1462 ft3/s), six f&c t5 d 4

~ conventional vertical travelingscreensequippedwith

### 9.5-mm (0.38-in,) squaremesh, 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 10vertical 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 consistsof a skimmerwall that extends to a depth of 1.7 m 

### (5.4ft) below extreme lowwater. Thewall prevents large floating debris 3- 1 Lawler, Matusky Sr 

### Skelly Engineers 

## 5and ice fromentering theintake structureand clogging the trash racks. Bar racks arelocated between the intake portals and thetravelingscreens 

### to prevent large 

### debris fromenteringthe 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. 

### Ekbis 11.1 m 

### (36.5 Et) 

### high 

### and 3-1

### m (10.2 ft) 

### wide. The individual bar rack 

### openings are 6-7

### cm (2.6 

### in.) wide. The total open area 

### of each bar rack is approxkatefy

### 28.0m2 (302 

### ft2); however, with thewater height at mean sea ievel the actual open area for water to flow through eachbar 

### 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 singleface 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, theFront

### wash spray cleaning system and 

### adisposal

### trough 

### For returnof screenwashings to the Hudson 

### River. 

### Themaximumwashwater volumefrom thesingle 

### sprayheader foreach 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 accommodatea fish escapepassageway, 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 hnttrash 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 

### Engin1TABLE 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 travelingscreens 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. Thenarrower 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-m 

### x 1.2-m (1.5-ft 

### x 4.0-ft) and is fitted with 1.6-mm (0.063 

### - -in.) diameter stainlesssteel Smooth-Texwovenwire mesh having 3-2-rnm

### x 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 anefficiencyrating (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 

### Engineerseliminates vortices in the trough that buffet and stress the captured organisms (Fletcher 1990). The screenmesh is ofEset 18"from the vertical, which facilitates organisms falingoff the mesh into the lip trough. The dual-flow screens areequippedwith 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 eachunit. Thelow-pressureorganismremoval systemlocated 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 sprayingacrossthe face 

### ofthe 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 

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

### psi) The low-pressure spray systemwashes material into a trough onthe 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, especiallyat the most southern screen (20). During the second week 

### of October a curved piece of fiberglasswas fitted across the distal end 

### of the 

### ffih trough 

### of the southern screen to minimize dead spacewhere debris had been accumulating,and additional flow

### was added to help wash out the screened material. Theadditional flowwas 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 troughjust 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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