Hydroacoustic Report for PIDP Restrike 0 1263

UNDERWATER SOUND PRESSURES ASSOCIATED WITH THE RESTRIKE OF THE PILE IINSTALLATION DEMONSTRATION PROJECT PILES

Measurements Results for the PIDP Restrike - East Span Seismic Safety Project on the SFOBB

Prepared by

James A. Reyff Illingworth & Rodkin, Inc.

Prepared for

State of California Department of Transportation, District 4

Division of Toll Bridge Program 111 Grand Avenue - P.O Box 23660

Oakland, CA 94623-0660

Final Report: July 23, 2003

EXECUTIVE SUMMARY The effectiveness of a two-ring bubble curtain system in reducing underwater sound pressures during marine pile driving was assessed through underwater sound pressure measurements. This was conducted when the three 108m long, 2.4m diameter cast in steel shell piles driven in 2000 as part of the PIDP, were restruck in December of 2002. During the measurements, the bubble curtain system was turned ON and OFF. The restrike involved driving the piles at refusal with the hammer at maximum energy (1,600 to 1,740 kilojoules). This condition is not anticipated during the east span SFOBB new east span construction.

The reduction in sound pressures provided by the bubble curtain system ranged considerably. The direct reduction in sound pressures, which is evaluated by comparing bubble curtain ON and OFF measurements, for Piles 1 and 2 was 6 to 17 dB for peak pressures and 3 to 10 dB for RMS sound pressure levels. Piles 1 and 2 were located next to each other. Reductions at Pile 3, which was in shallower water, were over 20 dB for both peak pressures and RMS sound pressure levels on the north side. However, the reductions on the south side for Pile 3 were much less. Close to Pile 3 on the south side, the reductions were on the order of 5 to 7 dB. Further away at about 450m south, the reductions were only about 2 dB. Uneven bottom topography around Pile 3, which could have compromised the bubble curtain performance near the bay bottom, is suspected to have resulted in the lower reductions to the south. It is important to note that overall sound pressures associated with Pile 3 were lower than those with Piles 1 and 2.

Analysis of individual pile strike impulses indicates that the bubble curtain reduced sound pressures at all measurement positions at frequencies above 1000 Hz. There was a reduction in sound pressures below 500 Hz where the bubble curtain worked particularly well (e.g., 100m north position for Pile 3).

Measurements of peak pressures made at about 100m were consistent with the measurements made during the PIDP in 2000. Those measurements were the basis for predictions of the maximum peak pressures during SFOBB east span construction. With the exception of the 450m south position, predicted peak pressures used in the Biological Opinion were lower than those measured. At 450m south, measured peak pressures were 5 to 8 dB higher than predicted. Conversely, peak pressures at 450m to 500m north were 0 to 6 dB lower than predicted.

RMS sound pressure levels, which are used to define the marine mammal safety zone, did not exceed 190 dB at any of the measurement positions (between 65 and 500m) when the bubble curtain system was operating. Levels of 180 dB RMS did extend out to 450m south for Pile 1, but did not exceed 172 dB at 450m north. With the bubble curtain OFF, the 190 dB RMS sound pressure levels extended out to somewhere between 200m to 300m for Piles 1 and 2 and less than 100m for Pile 3.

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TABLE OF CONTENTS

Executive Summary ..........................................................................................................................................1

Introduction......................................................................................................................................................3

Project description.............................................................................................................................................3

Descriptors used to Describe Underwater Acoustical TRAITs..............................................................................4

Previous Investigations ......................................................................................................................................5

SFOBB PIDP 2000 .......................................................................................................................................5

Hong Kong Aviation Fuel Transfer Facility ....................................................................................................6

Canada Place Cruise Ship Terminal................................................................................................................6

SFOBB Bubble Curtain Design ..........................................................................................................................6

Approach..........................................................................................................................................................7

Measurement Results and Discussion .................................................................................................................8

Peak Sound Pressures and RMS Sound Pressure Levels...................................................................................8

Impulse Analysis.........................................................................................................................................13

Bubble Curtain Performance........................................................................................................................14

Comparison with PIDP Results and Predictions made in the Biological Opinion .............................................15

Marine Mammal Safety Zone.......................................................................................................................17

Conclusions ....................................................................................................................................................17

Table 1 Sound Pressures Measured for Pile 1, reported as dB..............................................................................9

Table 2 Sound Pressures Measured for Pile 2, reported as dB............................................................................11

Table 3 Sound Pressures Measured for Pile 3, reported as dB............................................................................12

Table 4 Comparison of Predicted and Measured Sound Pressures Pile 1..........................................................15



Figure 1 Project Location............................................................................................................................. 3 Figure 2 Location of PIDP Piles................................................................................................................... 4 Figure 3 Menke MHU1700T Hammer.............................................................................................................. 5 Figure 4 Sound Attenuation Devices Used for the 2000 PIDP ............................................................................ 6 Figure 5 PIDP Restrike Bubble Curtain ............................................................................................................ 7

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INTRODUCTION

This report presents results of underwater sound pressure measurements conducted during the restrike of test piles in the San Francisco Bay. These test piles were previously driven in order to develop design information for the replacement of the east span of the San Francisco-Oakland Bay Bridge (SFOBB) and was known as the Pile Installation Demonstration Project or PIDP. The PIDP occurred from late September 2000 through mid-December 2000. These piles were restruck on December 9 and 10, 2002 as part of the PIDP Restrike. Figure 1 is a map showing the location of the new SFOBB East Span and the accompanying project construction limits.. At the request of the Caltrans, underwater sound pressure measurements were conducted to both reaffirm levels measured during the PIDP and measure the sound attenuation provided by a bubble curtain design that will be used for production pile driving on the SFOBB East Span construction project.

Figure 1 Project Location

PROJECT DESCRIPTION The 2000 PIDP involved the installation of three piles into the floor of the San Francisco Bay. The plan sheet shown in Figure 2 shows the location of each pile. The objective of the PIDP was to test and evaluate technical, engineering and environmental factors associated with driving large hollow steel piles approximately 100 meters long (Caltrans 2001). The PIDP involved utilization of two sizes of hammers, three different pile alignment configuration, and two different types of hydroacoustic attenuation systems.

The piles were 108 m (356 ft) long and had an inside diameter of 2.4 meters (8 feet), and an outside diameter of 2.57 m (8.5 ft). The piles were driven in three sections, each approximately 30 meters (108 ft) long. Pile 1 was a vertical pile that had no hydroacoustic attenuation. Pile 2 was a battered pile (driven at an angle) that was angled to the east and included an single ring air bubble curtain. Pile 3 was inserted at a different location and was also battered, but angled to the west. A proprietary fabric barrier system (Gunderboom) was used for Pile 3.

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Figure 2 Location of PIDP Piles

The objectives of the PIDP Pile Restrike Project were to conduct a geotechnical evaluation of pile stability and to demonstrate the effectiveness of a bubble curtain system that was designed to provide protection to fisheries resources in San Francisco Bay. For the Restrike, a Menke hydraulic hammer, MHU1700T, with a capacity of 1,700 kilo joules or kJ was used at or near full capacity (Figure 3). The geotechnical evaluation was intended to demonstrate the limits of pile "takeup" over time verify that the pile elements of the foundation would be strong enough to support the construction loadings that are anticipated while the footing is still relatively young (Woods personal communications). The criteria for stability are 670 strikes or 250 millimeters (approximately 1 ft). A secondary objective was to evaluate a bubble curtain system that was improved over the single-ring system used during the 2000 PIDP. This two-ring bubble curtain discharged considerably more air than the 2000 PIDP bubble curtain system and was fitted much more tightly around the pile than either the single-ring bubble curtain or the fabric barrier system.

DESCRIPTORS USED TO DESCRIBE UNDERWATER ACOUSTICAL TRAITS Several descriptors are used to characterize underwater noise. Two common descriptors are the instantaneous peak sound pressure and the root-mean-square sound pressure level averaged over the impulse, which is sometimes referred to as the sound pressure level (SPL) or root-mean-square (RMS) level. The peak pressure is the instantaneous absolute maximum pressure observed during each pulse and can be presented as a pressure (e.g., Pa) or decibel (dB) referred to some standard pressure like 1 Pa. The majority of literature uses peak sound pressures to evaluate injuries to fish. The SPL or RMS level is the square root of the energy divided by the duration of an individual acoustical disturbance (e.g., pile strike). This level, presented in dB re 1 Pa, is equivalent to the mean square pressure level of the pulse. It has been used by NOAA Fisheries (formerly National Marine Fisheries Service) in criteria for judging impacts to marine mammals from underwater impulse-type sounds1. Except where otherwise noted, sound levels reported in this discussion are expressed in dB re 1 Pa. In this report, peak sound pressures are referred to as peak levels and the SPL or RMS pressure level during the impulse is referred to as the RMS level.

1 The RMS (impulse) level is the criterion used by NOAA Fisheries. Underwater sound measurements from the San Francisco-Oakland Bay Bridge Pile Driving Demonstration Project (PIDP) indicated that 90 percent of the acoustic energy for most pile-driving impulses occurred over a 50 to 100msec period with the energy concentrated in the first 30 to 50msec. Analysis of underwater data gathered during the PIDP demonstrated that the acoustic signal measured using the standard impulse exponential-time-weighting correlated well with the RMS level measured over the duration of the pulse.

Pile 1

Pile 2

Pile 3

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It is important to note that sound pressures measured in air are typically described as decibels referenced to a pressure of 20 Pa, rather than 1 Pa, which is used to describe underwater sounds. The use of 20 Pa in air is a matter of convenience, since 1 dB re 20Pa is the human threshold of hearing in carefully controlled laboratory conditions. Because the acoustical impedance is much greater in water, sound intensity and propagation are very different. Underwater and airborne sound pressures are not comparable.

Figure 3 Menke MHU1700T Hammer

PREVIOUS INVESTIGATIONS

SFOBB PIDP 2000

To assess the environmental and technical factors involved in driving the very large piles proposed for the San Francisco-Oakland Bay Bridge East Span Project, a Pile Installation Demonstration Project (PIDP) was undertaken in late 2000 in which three eight-foot diameter steel pipe pilings were driven into the San Francisco Bay (Illingworth and Rodkin 2001). The underwater sound measurements were not comprehensive, but important data came from measurements at hydrophone depths of 1 and 6 m, without a sound attenuation system in place. Using a pile -driver energy of 900 kJ, peak pressures of 207 dB re: 1 Pa at a distance of 103 m and 191 dB at distance of 358 m were measured. Levels were always lowest near the surface (1-meter depth). A spreading loss formula was derived, which corrected for hammer size and measured excess attenuation and yielded approximately 30 dB loss per tenfold increase in distance (Greene 2001). Applying the spreading-loss model for received levels and accounting for an almost doubling of hammer energy (from 900 to 1,700 kj), the corresponding equation for 1,700 kJ is:

RLpeak = 238.9 - 29.6 log(R/10) (adapted from Greene 2001)

Where RL is the peak received level in dB re 1 Pa and R is the distance from the pile in meters for values of R between 100 and 360 meters.

During the PIDP project, measurements were taken at Pile 2 which had a simple unconfined air bubble curtain system (see Figure 4). There was no bubble curtain ON/OFF test, so the effectiveness of the system could not be directly measured. Comparison of measurements between Pile 1 and Pile 2 indicated about 0 to 2 dB attenuation from the system. Fairly strong currents that swept the bubbles away from the pile were suspected to limit the ABC system performance. A Gunderboom System was used for Pile 3 (see Figure 4). This system, which is able to confine bubbles close to the pile, was found to reduce sound pressures by about 5 to 10 dB.

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Figure 4 Sound Attenuation Devices Used for the 2000 PIDP

Air bubble ring used for Pile 2 Proprietary fabric air bubble curtain (Gunderboom) used for Pile 3

Hong Kong Aviation Fuel Transfer Facility Underwater sound measurements were conducted for the Hong Kong Airport Fuel Transfer Facility project to evaluate the performance of an underwater bubble curtain (Wursig 1999). An air bubble ring with a diameter of 50 m was placed around the pile-driving operation. With the bubbles, the RMS sound pressure level was reduced by 3 to 5dB. The greatest sound reduction provided by the bubble curtain was from 400 to 6400 Hz. The contractor did not measure peak pressures.

Canada Place Cruise Ship Terminal At the Canada Place Cruise Ship Terminal in Vancouver, B.C., open-ended steel pipe piles 36 inches in diameter with 0.75-inch wall thickness were driven, as were 24-inch diameter closed-ended steel pipe piles with 0.75-inch wall thickness (Longmuir and Lively 2001). An air bubble curtain was developed to protect fish. It was kept as close to the pile as practical, allowing for battered (slanted) piles to be driven. The authors stated that a proper bubble curtain can reduce underwater sound overpressures from pile driving by at least 85 percent (16.5 dB) and that their bubble curtain in Vancouver reduced underwater overpressures during pile driving from more than 22 psi to less than 3 psi (a reduction of more than 17 dB). They referred to the Canada Department of Fisheries and Oceans criterion for fish safety of not exceeding an explosion blast peak pressure of 14.5 psi (220 dB re: 1 Pa). The Canada Department of Fisheries and Oceans standard for fish safety is based on mortalities immediately after the explosion. The Vancouver study found that, perhaps due to the repetitive nature of pile driving, the peak pressure should be less than 4.5 psi (210 dB re: 1 Pa) to protect small fish.

SFOBB BUBBLE CURTAIN DESIGN Following the PIDP, Caltrans consulted with experts on bubble curtains and effects of underwater sound pressures on Fish (Greene 2001, Hastings 2001). A review of literature and consultation with experts indicated that a properly designed bubble curtain could provide about 10 dB of sound attenuation. As a result, Caltrans included a two-stage bubble curtain in the specifications for the construction project and so a version of this bubble curtain was used for the PIDP restrike. The bubble curtain was designed and constructed by the contractor KFM, Joint Venture (Woods personal communications). The bubble curtain frame supported two rings of perforated pipes that encircled the pile. One ring of perforated pipes ran along the bottom of the frame. The second ring of pipes was 5 meters above the bottom ring. Air was supplied by six 45,326 liter-per-minute (1,600 cubic-foot-per-minute) compressors. During a demonstration on December 4th, the bubbles raised the water level about a foot above sea level, and rendered the entire area above the bubble curtain frame a froth of white foam. A matrix of pressure sensor hoses was linked to the air delivery pipes, manifolds and perforated pipes to determine the pressure at various points in the system. The objectives were to produce a bubble flux density of at least 3 cubic meters per minute per linear meters of pipeline in each concentric ring (32 cubic feet per minute per linear foot) and

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to completely surround the pile at all times and in all current conditions with bubbles (NMFS 2002). The bubble curtain system is shown in Figure 5.

Figure 5 PIDP Restrike Bubble Curtain

Air bubble curtain system with compressors in background. Air bubble curtain system in operation during the PIDP Restrike

APPROACH The measurement program was designed to quantify the effectiveness of the bubble curtain system in reducing underwater sound pressure levels and characterize both attenuated and unattenuated sound pressures for each of the three PIDP piles. This required sound measurements with the system working (ON) and when it was not operational (OFF).

Prior to measurements, plans were developed to measure at 5 different positions. One position was made at about 60m from the pile on the barge, and four positions were both 100m and about 450m north and south of the pile. At the four distant positions (100m and ~450m), measurements were made 2m below the water surface and about 2m above the bottom. A depth of about 8m was made from the barge (60m distance position). Buoys were set at the approximate 100m and 450m positions; however, exact positions varied due to the influence of tidal currents.

Measurements at the fixed ~100m and ~450m positions were made using G.R.A.S. CT10 hydrophones with PCB in-line charge amplifiers (Model 422E13) and PCB Multi Gain Signal Conditioners (Model 480M122). The signals were fed into Larson Davis Model 820 Integrating Sound Level Meters (Type 1) and Sony Model TCD-D100 Digital Audio Data Recorders (DAT).

At the ~60-meter position from the barge, a PCB Type ICP Pressure Transducer was used to acquire the acoustic signals. The transducer was connected to both a Larson Davis Model 820 Integrating Sound Level Meter (Type 1) and a Sony Model TCD-D100 DAT through the PCB multi gain signal conditioner. The pressure transducer was used at this position, instead of a hydrophone system, since peak pressure signals from the unattenuated piles were predicted to exceed the hydrophone system limitations. The multi-gain signal conditioner provides the ability to add gain or boost the signal so that measurements are made within the dynamic range of the instruments used to analyze the signals.

The peak pressures and SPLs or RMS levels were measured, either live or subsequently from DAT recordings using the SLM. The RMS sound pressure levels were measured with the SLM using the standard impulse exponential-time -weighting (35 msec rise time) function of the Larson Davis Model 820 SLM. Additional subsequent analyses of the acoustical impulses were performed using a Larson Davis Model 2900 Real Time Analyzer. The real time analyzer provides narrow-band frequency and waveform analysis.

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The measurement systems were calibrated prior to use in the field with a G.R.A.S. Type 42AA Pistonphone and hydrophone coupler. The systems calibration status was checked during post calibrations at the end of the measurement event. All systems were found to be within 0.5 dB of the calibration levels. Pre- and post-measurement recordings of calibration tones were made on all DAT tapes.

MEASUREMENT RESULTS AND DISCUSSION Underwater sound measurements were made on December 9, when two PIDP piles (Piles 1 and 2) and on December 10, 2003 when one PIDP pile (Pile 3) were driven as part of the SFOBB PIDP Restrike. The Menke 1700 kj hammer was used at nearly full energy. Data summaries and graphical representations of measured data are provided in Appendix A. Hammer and bubble curtain data are provided in Appendix B.

Much of the data collected at the deeper sensor 450 to 500m north of the piles could not be used due to contamination. These measurements were made from a motorized boat that was holding position near a buoy. The boat movement caused noise on the deeper hydrophone, and therefore, that data was discarded. Measurements made at the shallow level (2m deep) from the barge had to also be discarded. Unattenuated levels were quite low at this position, indicating that there were obstructions from the barge affecting the sound attenuation.

Peak Sound Pressures and RMS Sound Pressure Levels Pile 1 The pile was driven by the Menke 1,700 kJ hammer in single blow mode instead of stroke sequence mode because of technical concerns for safe hammer operation. Hammering was in the more regular stroke mode for the other piles. Hammering started at 10:36 with the bubble curtain in operation at full capacity. Hammering stopped 21 minutes later at 10:57. At 11:03 hammering started again but with the bubble curtain off and continued for about 18 minutes with a number of brief interruptions in driving activity. Hammer energy was mostly above 1,600 kj and the blow count was about 30 blows per minute. Tidal currents were almost non-existent, but observations of floating buoys at the measurements positions indicated a light north to south current (flood). This pile driving operation was carried out in a driving rain storm. A history of pile strikes measured from the DB General (65m from the pile) is shown in Figure 6.

PILE 1, from Barge at 65m History of Pile Stikes at the Deeper Sensor

160

170

180

190

200

210

220

10:3

0

10:3

4

10:3

8

10:4

2

10:4

6

10:5

0

10:5

4

10:5

8

11:0

2

11:0

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11:1

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11:1

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11:1

8

11:2

2

11:2

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11:3

0

Time

Sou

nd P

ress

ure

(dB

)

Peak

RMS

Figure 6 Time History - Pile 1

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The time history of the strikes shown in Figure 6 shows a large variation in the amplitude of sound pressures, particularly peak pressures from strike to strike. This is possibly due to the large variation of hammer energy used since the hammer was operating in manual mode. Information provided on the bubble curtain operation is inconclusive to identify any operational problems that the bubble curtain may have experienced. There were flow meters that failed during the bubble curtain operation, but this does not mean that the curtain did not operate as designed. The pile was completely surrounded by bubbles at the surface during bubble curtain operation. Table 1 shows the sound pressure levels in terms of peak pressure and RMS sound pressure levels for both the Bubbles ON and Bubbles OFF condition. Time periods that best represent a particular condition for the pile and each bubble curtain operation mode were selected.

Peak pressures varied considerably based on direction. Peak pressures measured at 65m were similar to those measured at 100m north. At 450m north, pressures were about 10 dB lower than 450m south with or without the bubble curtain (the bubble curtain reduced pressures by 8-10 dB at both positions). Peak pressures with the bubble curtain ON were about 5 dB lower 100m south than at 100m north. Without the bubble curtain, peak pressures were similar at both positions.

At 65m, the shallow water measurement appeared to be shielded by the barge or some other underwater obstruction; therefore, those data were discarded. While peak pressures differed by only 1 dB with and without the bubble curtain, tape recordings indicated that the impulses with the bubbles sounded different than without the bubbles.

In summary, RMS sound pressure levels were about 3 to 7 dB lower with the bubble curtain ON, while peak pressures were reduced by 6 to 12 dB. Changes in waveforms and frequency spectra are discussed later in this report.

Table 1 Sound Pressures Measured for Pile 1, reported as dB

Peak Pressures Positions Measured Distance and General Direction from the Pile

Time Period

Bubble Curtain

Condition South ~460m

South 100m

North 65m

North 100m

North 195m

North ~450m

Water Depth = 10m 10m 9m 10m 10m 8m 10:46:30 10:52:29 am

ON Up = 194 Dn = 196

Dn = 199

Up = 201 Dn = 201

10:56:00 10:57:29 am

ON Up = 185 Dn = 189

Dn = 194

Up = 175 Dn = --

11:04:00 11:07:59 am

OFF Up = 205 Dn = 206

Dn = 204

Up = 209 Dn = 207

Up = 182 Dn = --

11:20:00 11:20:59 am

OFF Up = 194 Dn = 198

Dn = 208

Up = 194 Dn = --

Estimated Reduction Up = 9 Dn = 9

Up = 11 Dn = 10

Dn = ~9

Up = 8 Dn = 6

Up = 7 Dn = --

RMS Sound Pressure Levels

Positions Measured Distance and General Direction from the Pile

Time Period

Bubble Curtain


South 100m

North 65m

North 100m

North 195m

North ~450m

10:46:30 10:52:29 am

ON Up = 183 Dn = 185

Dn = 186

Up = 188 Dn = 189

10:56:00 10:57:29 am

ON Up = 175 Dn = 178

Dn = 182

Up = 162 Dn = --

11:04:00 11:07:59 am

OFF Up = 190 Dn = 192

Dn = 189

Up = 192 Dn = 194

Up = 168 Dn = --

11:20:00 11:20:59 am

OFF Up = 183 Dn = 185

Dn = 193

Up = 181 Dn = --

Up = 171 Dn = --

Estimated Reduction Up = 7 Dn = 7

Dn = ~7

Up = 4 Dn = 5

Up = 8 Dn = --

Note: Up = upper portion of water column or about 2m below the water surface Dn = lower portion of water column or about 2-3m above bottom.

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Pile 2

The DB General barge was moved into position north of Pile 2 and stabilized with spud piles and anchor lines. The bubble curtain frame was lowered into the water around the pile and secured in place on the bottom. The hammer was placed on the pile about 13:18. Pile driving started at 13:55 with the bubble curtain on and continued for 14 minutes stopping at 14:09. Hammering started again at 14:20 and continued for 7 minutes without the bubble curtain OFF. The Menke hammer was in automatic mode for most of the drive. After about 13:53, the hammer energy was consistently above 1,500 kj and the blow count was about 30 blows per minute. Due to the shorter driving period with the bubble curtain OFF, all

measurements could not be completed (i.e., at distances of 450m south and 200m north). Heavy rain occurred during most of the driving period. A history of pile strikes measured from the DB General (60m from the pile) is shown in Figure 7.

The history plot of sound pressures shown in Figure 7 indicates that sound pressures were more consistent than Pile 1. Table 2 presents sound pressures in terms of peak pressure and RMS sound pressure levels for both the Bubbles ON and Bubbles OFF condition. Time periods that best represent a particular condition for the pile and each bubble curtain operation mode were selected. There was a light north to south current.

Peak pressures were more consistent during the driving of Pile 2 than they were for Pile 1. All measurement positions indicated at least 10 dB reduction in peak pressures with the bubble curtain ON, except for the 100m north station at 2m below the water surface. An explanation for this anomaly cannot be made, except that the tape recording for that position sounds much louder with the bubbles OFF. In summary, peak pressures were reduced by 9 to 17 dB and RMS sound pressure levels were reduced by about 6 to 10 dB. At the 450m north position, the reduction was 11-15 dB for peak pressures and 7-10 dB for RMS sound pressure levels.


160

170

180

190

200

210

220

13:4

8

13:5

2

13:5

6

14:0

0

14:0

4

14:0

8

14:1

2

14:1

6

14:2

0

14:2

4

14:2

8Time

So

un

d P

ress

ure

(dB

)

Peak

RMS


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Time Period

Bubble Curtain


South 100m

North 60m

North 100m

North 195m

North ~450m

Water Depth = 10m 11m 10m 11m 11m 9m 13:54:00 13:57:29

ON Up = 194 Dn = 197

Dn = 197

Up = 200 Dn = 196

Up = 175 Dn = 179

14:02:00 14:06:59

ON Up = 190 Dn = 191

Dn = 198

Up = 180 Dn = 184

Up = 176 Dn = 180

14:20:00 14:23:59

OFF Up = 211 Dn = 208

Dn = 208

Up = 201 Dn = 205

Up = 190 Dn = 190

Estimated Reduction Up = -- Dn = --

Up = 17 Dn = 11

Dn = 11

Up = 1* Dn = 9

Up = -- Dn = --

Up = 15 Dn = 11

RMS Sound Pressure Levels Positions Measured Distance and General Direction from the Pile

Time Period

Bubble Curtain


South 100m

North 60m

North 100m

North 195m

North ~450m

Water Depth = 10m 11m 10m 11m 11m 9m 13:54:00 13:57:29

ON Up = 183 Dn = 185

Dn = 186

Up = 187 Dn = 184

Up = 164 Dn = 170

14:02:00 14:06:59

ON Up = 180 Dn = 180

Dn = 187

Up = Dn = 172

Up = 166 Dn = 171

14:20:00 14:23:59

OFF Up = 194 Dn = 195

Dn = 192

Up = 189 Dn = 193

Up = 174 Dn = 177

Estimated Reduction Up = -- Dn = --

Up = 11 Dn = 10

Dn = 6

Up = 2* Dn = 9

Up = -- Dn = --

Up = 10 Dn = 7

* The levels measured at 100m north at the UP position (2m below the surface) are suspect.

Pile 3 The DB General barge was moved into position north of pile No. 3 and was ready for driving on the morning of December 10, 2002. Hammering started at 10:02 and continued for 37 minutes with stops to adjust the air delivery system and strain gages. Hammering restarted at 10:52 and continued until 11:07 without the bubble curtain in operation. Hammer energy was consistently above 1,600 kj and the blow count was about 30 blows per minute. A history of pile strikes measured from the DB General (60m from the pile) is shown in Figure 8. Three different conditions were tested with this pile: (1) bubble curtain system ON with manifold pressure of 70 to 80 pounds per square inch (psi), (2) bubble curtain system ON with manifold pressure reduced to 50 psi, and (3) bubble curtain system OFF. These three periods are indicated as ON+, ON-, and OFF. Time periods that best represent a particular condition for the pile and each bubble curtain operation mode were selected. Pile driving was suspended between each measurement period. There was a light south to north or ebb current observed, although the predictions indicated a light flood current. A history of pile strikes measured from the DB General (60m from the pile) is shown in Figure 8.

The history plot of sound pressures shown in Figure 8 indicates that sound pressures were consistent, much like Pile 2. The Menke hammer was in automatic mode for most of the drive. Table 3 presents the sound pressure levels in terms of peak pressure and RMS sound pressure levels for both the bubble curtain ON and OFF. Time periods that best represent a particular condition for the pile and each bubble curtain operation mode were selected. There was a light north to south current..

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Sound pressures associated with this pile were lower than either Pile 1 or Pile 2, probably due to the shallower water. Some large reductions in peak pressure still occurred on the north side. Reductions were over 20 dB close to the pile on the north side. On the south side, reductions were about 5 to 7 dB. Although there was little measured reduction at the 450m south location, levels were 185 dB or lower with the bubble curtain system ON. At ~470m north, levels with the bubble curtain system ON were too low to measure accurately. It is estimated that peak pressures were less than 170 dB with the bubble curtain ON and less than 180 dB with the system OFF.

Sound pressures were measured with the bubble curtain air delivery pressure at two settings, as indicated by ON+ and ON-. Results indicate that there was little difference between the settings. In fact all measurements were within 2 dB of each setting and some levels were even lower with the reduced delivery pressure.


160

170

180

190

200

210

220

10:0

2

10:0

6

10:1

0

10:1

4

10:1

8

10:2

2

10:2

6

10:3

0

10:3

4

10:3

8

10:4

2

10:4

6

10:4

9

10:5

3

10:5

7

11:0

1

11:0

5

Time

So

un

d P

ress

ure

(d

B)

Peak

RMS

Data from 1st part of drive not collected at barge


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Time Period

Bubble Curtain


South 100m

North 60m

North 100m

North 200m

North ~470m

Water Depth = 5m 5m 6m 4m 4m 4+m 10:04:30 10:55:59

ON+ Up = 193 Dn = 192

Up = 179 Dn = 179

Up =

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conditions between the location of Pile 1 and 2 and the location of Pile3. At Pile 3, sound pressures were much lower even without the bubble curtain ON. In fact, the bubble curtain OFF condition resulted in similar, but slightly higher, peak pressures as the bubble curtain ON conditions at Piles 1 and 2. However, the shape of the waveform is much different in terms of rapid pressure rise/fall t imes.

Pile 1 The pressure time traces show similar patterns of rapid rise and fall of pressures during the first 0 to 15 msec of the acoustical event when the bubbles were OFF. With bubbles ON, much of that fluctuation was reduced. Frequency spectra for the bubbles OFF condition are similar at 100m north and south, where most energy is contained below 1000 Hz. With bubbles ON, sound pressures were reduced from 500 Hz and above with the greatest reductions above 1000 Hz. The bubble curtain was more effective at reducing sound pressures at 100m south. The bubble curtain provided about 11 dB of reduction at the south position and about 6 dB at the north position.

Pile 2 While the magnitude of sound pressure was greater for 100m south, there were more substantial fluctuations at the 100m north position with the bubble curtain OFF. This appears to be evident in the low frequency spectrum (i.e., below 500Hz).With bubbles ON, acoustic energy above 1000 Hz was attenuated by 10 to 30 dB, especially at the 100m north position. At the 100m north position, bubbles ON appeared to reduce sound pressures by 5 dB at the lower frequencies. The resultant frequency spectra at 100m north and south were similar with the bubbles ON, while showing some considerable differences at the lower frequencies without the bubbles. Overall, the bubble curtain provided about 10 dB of attenuation at these positions for this pile.

Pile 3 The unattenuated piles at 100m north and south for Pile 3 showed some similar characteristics as the attenuated conditions for Piles 1 and 2. As a result, the bubbles OFF sound pressures for this pile were similar to those of Piles 1 and 2 when the bubbles were ON. When bubbles were OFF at Pile 3, sound pressures were reduced further by 5 to 7 dB at 100m south and 15 to 20 dB at 100m north. At 100m south, most reductions occurred above 1000 Hz. At 100m north, reductions of 5 to 10 dB occurred around 200 Hz and reductions of 30 dB occurred between 1000 and 1500 Hz. This was in addition to the 20 to over 30 dB reduction above 1500 Hz. The sound pressure amplitude was reduced to a fraction of the amplitude when the bubbles were OFF.

Bubble Curtain Performance The bubble curtain performance was directly measured by making sound pressure measurements with the system ON and with it OFF. The system performance varied considerably from location to location as a result of differences in measurement positions and pile conditions. All piles were driven at refusal using full or nearly full hammer energy.

When evaluating ON/OFF conditions for Pile 1, the reductions between ON and OFF conditions were 6 to 10 dB for deep sensor positions and 6 to 12 dB lower for the shallow sensor positions, excluding the measurements from the barge, where the shallow sensor was suspected to be shielded by underwater obstructions. The reductions in RMS sound pressure levels was generally 2 to 4 dB less than peak pressures (i.e., 2 to 7 dB reduction). At 100m, reductions were 4 to 7 dB greater to the south. Reductions at 450m were similar between north and south, except that levels with the bubble curtain ON or OFF were 10 dB lower to the north than to the south. This indicates that there is excess attenuation of about 10 dB at 450m north.

The location of Pile 2 was next to Pile 1 so measurement positions changed very little. Reductions measured for Pile 2 were on the order of 9 to 17 dB for peak pressures and 6 to 11 dB in RMS sound pressure levels. The one exception was the shallow sensor at 100m north where the measured reduction was only 1 to 2 dB. Again, the bubble curtain appeared to be more effective 100m south than at 100m north. While OFF measurements could not be made for 450m south, the ON measurements indicate that reductions were greater at 450m north. The ON pressures at 450m north were 15 dB lower than they were at 450m meters south.

Pile 3 was at a different location than Piles 1 and 2. Overall sound pressures with the bubble curtain OFF were about 5 to 12 dB lower than they were for Piles 1 or 2. The bottom topography at this pile was rough, where it is likely that there was a gap of about 5 to 7 feet in the southwest and west directions. This would limit the effectiveness of the bubble curtain due to flanking of sound underneath in the southwest and westerly directions. Towards the north, the measured reductions were 11 to 25 dB in peak pressures and 14 to 21 dB in RMS pressures (RMS levels could not be measured at 450m north). In the southerly direction, the reductions were 2 to 8 dB in peak pressures and 1 to 5 dB in RMS sound pressure levels. The

15

differences in attenuation from the bubble curtain in these directions is indicative of a leak in the south side, probably due to the uneven bottom terrain. It should be noted that the sound pressures in the south with the bubble curtain ON were 10 to 15 dB lower than OFF conditions for Piles 1 and 2.

Comparison with PIDP Results and Predictions made in the Biological Opinion The restrike involved driving a pile at refusal with the hammer at maximum energy (1,600 to 1,740 kilojoules). This condition was not encountered during acoustical measurements associated with the PIDP in 2000 and is not anticipated during construction. For these reasons, the results obtained during the restrike are not directly comparable to results that were obtained during the PIDP in 2000 or upcoming construction. In addition to the differences discussed above, measurement positions were slightly different.

Pile 1 During the PIDP, a peak pressure of 207 dB was measured about 100m west of the pile when the hammer energy was about 1,000 kilojoules. During the restrike with the bubble curtain OFF, the highest peak pressures were 206 dB southeast and 209 dB northwest. With the bubble curtain ON, peak pressures were 194-201 dB (6 to 14 dB lower). The PIDP measurements for Pile 1 (Illingworth & Rodkin, 2001) were used as a basis for predicting impacts to biological resources (Greene 2001, NOAA 2001). The PIDP Restrike results were lower than predicted for all position except 450m south. At that position, unattenuated pressures were 8 dB higher than predicted. The basis for these predictions was measurements for Pile 1 at 103m west and 358m northwest. At distances of 450m, the predictions were 6 dB to high for 450m north and 8 dB to low for 450m south with unattenuated conditions. Predicted and measured sound pressures for Pile 1 are summarized in Table 4.

Table 4 Comparison of Predicted and Measured Sound Pressures Pile 1

Predicted Sound Pressures with NO Sound Attenuation*

Measured with Bubble Curtain OFF

Measured with Bubble Curtain ON

Position RMS Peak RMS Peak RMS Peak

65m 203 215 193 208 186 199

100m South 197 209 192 206 185 196

100m North 197 209 194 207 189 201

450m South 178 190 185 198 178 189

450m North 178 190 171 184 162 175

* The Biological Opinion (Caltrans 2001) assumed about 10 dB of sound attenuation.

Pile 2 During the PIDP, measurements were only made at about 200m west with a bubble curtain in operation for Pile 2. Peak pressures with the PIDP at 200m were 201 dB and 200 dB with hammer energies of 550 and 1000 kilojoules. During the restrike, peak pressures at 100m were 201, 206, 206, 208, and 211dB. A measurement made with only the bubble curtain ON at almost 200m during the restrike had peak pressures of 180 to 184 dB. For the restrike, Pile 2 appeared to be slightly louder than Pile 1 when comparing sound pressures for the bubble curtain OFF conditions. With the bubble curtain ON during the restrike, peak pressures were 194 to 200 dB at 100m. With the bubble curtain OFF measurements were equal or less than predicted (by 0 to 7 dB). Measurements with the bubble curtain OFF could not be made at 450m south, but would probably have been higher than predicted. With the bubble curtain ON, sound pressures were 1 dB higher than unattenuated predictions at 450m south and 6 dB lower at 450m north. Closer in, pressures were 12 to 17 dB lower than unattenuated predictions (see Table 5).

16






65m 203 215 192 208 187 198

100m South 197 209 195 208 185 197

100m North 197 209 193 205 184 196

450m South 178 190 NA NA 180 191

450m North 178 190 177 190 172 184

* The Biological Opinion (Caltrans 2001) assumed about 10 dB of sound attenuation.

Pile 3 Measurements from the PIDP in 2000 and the restrike indicate that Pile 3 resulted in lower sound pressures than Piles 1 or 2. This was likely caused by the shallow water conditions at Pile 3. At many of the measurement locations, the water was about 50% shallower (e.g., 5m for Pile 3 vs 11m for Piles 1 and 2). Measurements made during the PIDP at about 100m were 193 to 197 dB (with the Gunderboom system not operating) and 189 dB when the Gunderboom was operating and hammer energies were 1600 kilojoules (comparable to the restrike). Measurements during the PIDP restrike at about 100m were 197 to 199 dB with the bubble curtain OFF and 179 to 192 dB with the bubble curtain ON (the south side was 192 dB and the north side was about 179 dB). At 500m north during the PIDP with the Gunderboom ON, peak pressures were about 170 dB. At about 470m north with the bubble curtain ON, peak pressures were less than 170 dB and about 184 dB with the bubble curtain OFF.

At all measurements positions, bubble curtain OFF pressures were less than predicted unattenuated pressures, even at 450m south. At most locations, OFF pressures were about 10 dB lower than predicted. At 450m south, the OFF conditions were only 3 dB less than predicted. When the bubble curtain was ON, sound pressures were 5 to 35 dB lower than unattenuated predictions. With the exception of the 450m south position, all bubble curtain ON sound pressures were 20 to 30 dB lower than unattenuated predictions (see Table 6).






65m 203 215 191 204 170 180

100m South 197 209 186 199 181 192

100m North 197 209 184 198 169 179

200m North 187 199 180 195 168 178

450m South 178 190 175 187 174 185

500m North 176 189 172 184

17

Marine Mammal Safety Zone The marine mammal monitoring safety zone is defined as the area where RMS sound pressure levels are less than 190 dB. Based on the PIDP restrike measurements with the bubble curtain ON, the safety zone extended out to about 100m north for Pile 1 and was less than 100m for Piles 2 and 3. In fact, RMS sound pressures levels of 190 dB or greater were not measured at any of the measurements positions for Piles 2 and 3 when the UABC system was ON. When the bubble curtain was OFF, the limit of the safety zone extended beyond 100m to somewhere between 200 and 300m for piles 1 and 2. For Pile 3 with the bubble curtain OFF, the safety zone did not appear to extend beyond 100m.

CONCLUSIONS The effectiveness of a two-ring bubble curtain system in reducing underwater sound pressures during marine pile driving was assessed through underwater sound pressure measurements. This was conducted when the three 108m long, 2.4m diameter cast in steel shell piles driven in 2000 as part of the PIDP, were restruck in December of 2002. During the measurements, the bubble curtain system was turned ON and OFF. The restrike involved driving the piles at refusal with the hammer at maximum energy (1,600 to 1,740 kilojoules). This condition is not anticipated during the east span SFOBB new east span construction.

The reduction in sound pressures provided by the bubble curtain system ranged considerably. The direct reduction in sound pressures, which is evaluated by comparing bubble curtain ON and OFF measurements, for Piles 1 and 2 was 6 to 17 dB for peak pressures and 3 to 10 dB for RMS sound pressure levels. Piles 1 and 2 were located next to each other. Reductions at Pile 3, which was in shallower water, were over 20 dB for both peak pressures and RMS sound pressure levels on the north side. However, the reductions on the south side for Pile 3 were much less. Close to Pile 3 on the south side, the reductions were on the order of 5 to 7 dB. Further away at about 450m south, the reductions were only about 2 dB. Uneven bottom topography around Pile 3, which could have compromised the bubble curtain performance near the bay bottom, is suspected to have resulted in the lower reductions to the south. It is important to note that overall sound pressures associated with Pile 3 were lower than those with Piles 1 and 2.

Analysis of individual pile strike impulses indicates that the bubble curtain reduced sound pressures at all measurement positions at frequencies above 1000 Hz. There was a reduction in sound pressures below 500 Hz where the bubble curtain worked particularly well (e.g., 100m north position for Pile 3).

Measurements of peak pressures made at about 100m were consistent with the measurements made during the PIDP in 2000. Those measurements were the basis for predictions of the maximum peak pressures during SFOBB east span construction. With the exception of the 450m south position, predicted peak pressures used in the Biological Opinion were lower than those measured. At 450m south, measured peak pressures were 5 to 8 dB higher than predicted. Conversely, peak pressures at 450m to 500m north were 0 to 6 dB lower than predicted.

RMS sound pressure levels, which are used to define the marine mammal safety zone, did not exceed 190 dB at any of the measurement positions (between 65 and 500m) when the bubble curtain system was operating. Levels of 180 dB RMS did extend out to 450m south for Pile 1, but did not exceed 172 dB at 450m north. With the bubble curtain OFF, the 190 dB RMS sound pressure levels extended out to somewhere between 200m to 300m for Piles 1 and 2 and less than 100m for Pile 3.

18

REFERENCES

Greene, C.R., Jr. 2001. Proposed Construction Impact Avoidance and Minimization Measures, Regarding the

interaction between fish and sounds from pile driving while building the new San Francisco-Oakland Bay Bridge. Produced by Greeneridge Sciences and Illingworth & Rodkin, Inc. under contract to the California Department of Transportation, Task Order No. 2, Contract No. 43A0063. September.

Illingworth and Rodkin, Inc. 2001. Noise and Vibration Measurements Associated with the Pile Installation

Demonstration Project for the San Francisco-Oakland Bay Bridge East Span, Final Data Report. Produced by Illingworth & Rodkin, Inc. under contract to the California Department of Transportation, Task Order No. 2, Contract No. 43A0063. June.

Longmuir, C. and T. Lively. 2001. Bubble Curtain Systems for Use During Marine Pile Driving. Produced by

Fraser River Pile & Dredge, Ltd. National Marine Fisheries Service, Southwest Region. Biological Opinion San Francisco-Oakland Bay Bridge

East Span Seismic Safety Project. Ref: 151422-SWR99-SR-190 Reyff, J., P. Donavan, C. R. Greene Jr. 2002. Underwater Sound Levels Associated with Construction of the

Benicia-Martinez Bridge. Produced by Illingworth & Rodkin, Inc. and Greeneridge Sciences under contract to the California Department of Transportation, Task Order No. 18, Contract No. 43A0063. August.

Reyff, J. 2003. Underwater Sound Levels Associated with Seismic Retrofit Construction of the Richmond-San

Rafael Bridge. Produced by Illingworth & Rodkin, Inc under contract to the California Department of Transportation, Task Order No20, Contract No. 43A0063. January.

Wursig, B., C. R. Greene, Jr., T. A. Jefferson. 1999. Development of an Air Bubble Curtain to Reduce

Underwater Noise of Percussive Piling. Marine Mammal Research 49 (2000) 79-93.

19

Appendix A

Data Summary and

Time History of Sound Pressures

22

Pile 1

Pile 1

Pile 3

23

Pile1 12-09-2002

160

170

180

190

200

210

220

10:30 10:34 10:38 10:42 10:46 10:50 10:54 10:58 11:02 11:06 11:10 11:14 11:18

450mdn450up100mSdn100mSup60mdn100mNdn100mNup200mNup450mNup

ON OFF

Pile2 12-09-2002

160

170

180

190

200

210

220

13:54 13:55 13:56 14:02 14:03 14:04 14:05 14:06 14:20 14:21 14:22 14:23

450mdn450up100mSdn100mSup60mdn100mNdn100mNup200mNdn450mNdn450mNup

ON

OFF

ON

Pile3 12-10-2002

160

170

180

190

200

210

220

10:04:30 10:30:57 10:32:57 10:38:24 10:45:36 10:52:48 10:54:48 10:56:48 10:58:48 11:06:15

450mdn450up100mSdn100mSup

60mdn100mNdn100mNup200mNdn200mNup450mNup

ON

OFF

ON ON ON

OFF

25

Appendix B

Summary of Hammer Performance Data and Bubble Curtain Operation

Pile 1

Time: hh:mm:ss

Blow No.

Blows/min Stroke cm

Energy kNm

Activity

10:35:52 Stop key in cabin pushed

11:37:15 Start: single blow mode 11:17:34 Start : stroke sequence mode

11:17:59 19 23.9 86 1623 11:18:22 29 28.2 86 1699 11:18:42 39 29.9 86 1730 11:19:03 49 30.5 86 1730 11:19:23 59 29.7 86 1724 11:19:43 69 28.9 86 1696

C2 reported hammer not on pile

Pile 2

Time: hh:mm:ss

Blow No.

Blows/min Stroke cm

Energy kNm

Activity

13:51:37 Start

13:51:52 12 75.9 38 620 13:52:03 22 67.9 56 903 13:52:04 Stop 13:52:37 Start 13:53:11 32 22.3 86 1545 14:07:37 472 31.1 86 1622 14:07:36 Stop 14:18:42 Start 14:18:59 482 30.6 86 1684 14:25:13 672 29.9 86 1676 14:25:20 Stop 14:26:05 C2 Hammer not on pile

26

Pile 3

Time: hh:mm:ss

Blow No.

Blows/min Stroke

cm

Energy kNm

Activity

10:01:50 Start in stroke sequence mode 10:02:03 14 42.1 40 746 10:02:21 24 28.8 62 1201 10:04:41 93 31 88 1733 10:05:01 103 30.8 88 1736 Stop 10:29:15 116 30.5 86 1746 Start 10:31:29 186 31 86 1713 10:31:48 196 31.1 86 1703 Stop 10:35:07 215 31.1 86 1712 Start 10:38:06 305 30.6 86 1688 Stop 10:43:07 315 30.6 86 1693 Start 10:46:02 405 31.3 86 1698 Stop 10:51:22 416 30.3 86 1703 Start 10:59:05 648 29.3 86 1691 Stop 11:04:20 659 30.2 88 1725 Start 11:05:40 699 29.7 88 1735 Stop

11:07:09 C2 reported hammer not on the pile

27

BUBBLE CURTAIN REPORT

December 9, 2002

PDIP Restrike Data The Bubble Curtain was used as a noise attenuation device during the re-strike of the PDIP piles. During the re-strike the following observations were noted: Pile 1: Two of the four flow meters at the aeration pipe failed during the re-strike. One on meter the top ring and one on the bottom ring. The two remaining meters at times had significant fluctuations in their readouts. The flow meters at the compressors were inaccurate because of wide fluctuations in their readouts. This could have been attributed to the flow characteristics of the distribution manifold. This problem continued throughout the entire project. Pile 2: The flow meters at the aeration pipe were repaired and reliable readings were obtained at pile 2. Reliable readings were also obtained at all but one of the pressure gauges. No readings were taken from the flow meters at the compressor due to the constant fluctuation of the meters. The manifold pressure was held constant at 70 psi. Pile 3: Accurate readings were obtained from the flow meters at the aeration pipe during the pile driving operation. One of the pressure gauges on the bottom ring failed and no readings were obtained from this gauge. No readings were taken from the flow meters at the compressor due to the constant fluctuation of the meters. On this particular pile the manifold pressure was kept at constant intervals of 80, 70 and 50 psi in order to change the flow of air through the system. A higher manifold pressure decreases the flow rate at the aeration pipe and decreasing the manifold pressure increases the flow rate at the aeration pipe. With decreased flow at the aeration pipe the inlet pressure should also be reduced. An increase in flow by decreasing the manifold pressure increases the inlet pressure. The size of the bubble can be determined from the pressure and flow rate. The goal was to determine if bubble size had an influence on attenuating the sound pressure levels.

28

LOCATION START TIME PIPE SECTION Pile 1 1030 hrs Top Ring INLET FLOW METER READING @ ARETION PIPE (cfm) Reading # 1 1500 3100 Reading # 2 2600 0 Reading # 3 2740 0 Reading # 4 2100 0 MANIFOLD PRESSURE (psi) INLET PRESSURE (psi) Reading # 1 60 10 0 20 12 Reading # 2 60 20 20 25 25 Reading # 3 68 20 20 25 25 Reading # 4 70 22 22 25 25 COMPRESSOR FLOW @ DISTRIBUTION MANIFOLD (cfm) Reading # 1 Reading not reliable due to constant fluctuation of meters Reading # 2 Reading not reliable due to constant fluctuation of meters Reading # 3 Reading not reliable due to constant fluctuation of meters Reading # 4 Reading not reliable due to constant fluctuation of meters

NOTES:

1. Bubble curtain on for first 400 blows. 2. Bubble curtain off for remaining 270 blows.

LOCATION START TIME PIPE SECTION Pile 1 1030 hrs Bottom Ring INLET FLOW METER READING @ ARETION PIPE (cfm) Reading # 1 3500 3100 Reading # 2 3600 1700 Reading # 3 3470 0 Reading # 4 3390 0 MANIFOLD PRESSURE (psi) INLET PRESSURE (psi) Reading # 1 60 0 0 25 25 Reading # 2 60 0 0 20 20 Reading # 3 68 0 0 22 22 Reading # 4 70 0 0 20 20 COMPRESSOR FLOW @ DISTRIBUTION MANIFOLD (cfm) Reading # 1 Reading not reliable due to constant fluctuation of meters Reading # 2 Reading not reliable due to constant fluctuation of meters Reading # 3 Reading not reliable due to constant fluctuation of meters Reading # 4 Reading not reliable due to constant fluctuation of meters

NOTES:


29


NOTES:



NOTES:


30


NOTES: Manifold Pressure: Pressure regulated at valve on exit side of the manifold. Flow and pressure at aeration pipe are reduced as a result. 1. Bubble curtain on for blows 0 100. LOCATION START TIME PIPE SECTION Pile 3 1000 hrs Bottom Ring INLET FLOW METER READING @ ARETION PIPE (cfm) Reading # 1 2700 2100 Reading # 2 2640 2120 Reading # 3 2640 2110 Reading # 4 2670 2120 MANIFOLD PRESSURE (psi) INLET PRESSURE (psi) Reading # 1 80 13 0 15 15 Reading # 2 80 12 0 14 15 Reading # 3 80 12 0 15 15 Reading # 4 80 12 0 13 12 COMPRESSOR FLOW @ DISTRIBUTION MANIFOLD (cfm) Reading # 1 Reading not reliable due to constant fluctuation of meters Reading # 2 Reading not reliable due to constant fluctuation of meters Reading # 3 Reading not reliable due to constant fluctuation of meters Reading # 4 Reading not reliable due to constant fluctuation of meters

NOTES: Manifold Pressure: Pressure regulated at valve on exit side of the manifold to maintain a constant pressure of 80 psi. Flow and pressure at aeration pipe are reduced as a result. 1. Bubble curtain on for blows 0 100.

31


NOTES: Manifold Pressure: Pressure regulated at valve on exit side of the manifold to maintain a constant pressure of 70 psi. Flow and pressure at aeration pipe show constant readindgs. 1. Bubble curtain on for blows 101 200. LOCATION START TIME PIPE SECTION Pile 3 1030 hrs Bottom Ring INLET FLOW METER READING @ ARETION PIPE (cfm) Reading # 1 3200 2990 Reading # 2 3210 3080 Reading # 3 3180 3060 Reading # 4 3240 3020 MANIFOLD PRESSURE (psi) INLET PRESSURE (psi) Reading # 1 70 18 0 18 20 Reading # 2 70 17 0 17 20 Reading # 3 70 16 0 17 18 Reading # 4 70 18 0 18 20 COMPRESSOR FLOW @ DISTRIBUTION MANIFOLD (cfm) Reading # 1 Reading not reliable due to constant fluctuation of meters Reading # 2 Reading not reliable due to constant fluctuation of meters Reading # 3 Reading not reliable due to constant fluctuation of meters Reading # 4 Reading not reliable due to constant fluctuation of meters

NOTES: Manifold Pressure: Pressure regulated at valve on exit side of the manifold to maintain a constant pressure of 70 psi. Flow and pressure at aeration pipe show constant readindgs. 1. Bubble curtain on for blows 101 200.

32


NOTES:

Manifold Pressure: Pressure regulated at valve on exit side of the manifold to maintain a constant pressure of 50 psi. Flow and pressure at aeration pipe show constant readings. Flow and pressure at the aeration pipes are increased as a result. 1. Bubble curtain on for blows 201 350.


NOTES:

Manifold Pressure: Pressure regulated at valve on exit side of the manifold to maintain a constant pressure of 50 psi. Flow and pressure at aeration pipe show constant readings. Flow and pressure at the aeration pipes are increased as a result. 1. Bubble curtain on for blows 201 350.

33

Depths around PIDP Piles

PIDP Pile Nos. 1 and 2

8 foot radius 20 - 30 foot radius

North 31' North 31'Northwest 33' Northwest 33'West 34' West 35'SouthWest 31' SouthWest 32'South 31' South 32'SouthEast 31' SouthEast 20'East 31' East 30'NorthEast 31' NorthEast 32'

PIDP Pile No. 3

8 foot radius 20 - 30 foot radius

North 24' North 23'Northwest 24' Northwest 27'West 25' West 29'SouthWest 30' SouthWest 26'South 25' South 22.5'SouthEast 20' SouthEast 21'East 20' East 22'NorthEast 21' NorthEast 22'

Hydroacoustic Report for PIDP Restrike 0 1263

Documents

underwater sound pressures

measurements of peak

overall sound pressures

maximum peak pressures

db rms

db lower

rms sound pressure levels

bubble curtain performance