Dilution and Transport Predictions for Ocean Outfalls

1989 ◽  
Vol 21 (8-9) ◽  
pp. 969-979 ◽  
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Travel Time ◽  
Rio De Janeiro ◽  
Stratified Flows ◽  
Far Field ◽  
Ocean Bottom ◽  
Bacterial Mortality ◽  
Visitation Frequency ◽  
Ocean Outfall

Dilution and transport predictions for an ocean outfall proposed for the Barra da Tijuca, Rio de Janeiro are summarized. The initial characteristics of the wastefield are predicted using the results of recent experiments on submerged wastefield characteristics in stratified flows. Using measured currents and stratifications, it is predicted that the proposed design will result in a wastefield which is always submerged, whose thickness varies from 8.5 to 23.1 m and whose dilution varies from about 200 to well over 2000. The wastefield will often stay near the ocean bottom. Far field transport due to currents is calculated and expressed in terms of spatial “visitation frequency,” the probability of the wastefield visiting any location. It is shown that no effluent reaches shore with a travel time less than 5.5 hours, and computations including oceanic diffusion and bacterial mortality suggest maximum shoreline coliform concentrations of 500 per 100 mℓ, and 98% of the time they will be less than this. For reasons discussed these estimates of shoreline bacteria are conservatively high, and much lower than computed by methods assuming steady onshore currents.

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

The use of Current Data in Ocean Outfall Design

1986 ◽  
Vol 18 (11) ◽  
pp. 111-120 ◽  
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Time Series ◽  
San Francisco ◽  
Coastal Waters ◽  
Puget Sound ◽  
Current Data ◽  
Far Field ◽  
Initial Dilution ◽  
Visitation Frequency ◽  
Time Series Analyses ◽  
Ocean Outfall

Some of the ways in which current meter data can aid in the design of ocean outfalls are discussed. Examples are given, which include time series analyses of currents obtained in Puget Sound, near Alki Point, the prediction of initial dilution of San Francisco, the prediction of far field dilution and transport in Southern California coastal waters, and prediction of the visitation frequency, or transport probability, off Alki Point.

The shape of things to come — Development and testing of a new marine vibrator source

2019 ◽  
Vol 38 (9) ◽  
pp. 680-690 ◽  
Author(s):  
Benoît Teyssandier ◽  
John J. Sallas
Keyword(s):  
Seismic Source ◽  
Test Facility ◽  
Data Sets ◽  
Far Field ◽  
Ocean Bottom ◽  
Air Gun ◽  
Seismic Image ◽  
Field Radiation ◽  
Technical Issues ◽  
To Come

Ten years ago, CGG launched a project to develop a new concept of marine vibrator (MV) technology. We present our work, concluding with the successful acquisition of a seismic image using an ocean-bottom-node 2D survey. The expectation for MV technology is that it could reduce ocean exposure to seismic source sound, enable new acquisition solutions, and improve seismic data quality. After consideration of our objectives in terms of imaging, productivity, acoustic efficiency, and operational risk, we developed two spectrally complementary prototypes to cover the seismic bandwidth. In practice, an array composed of several MV units is needed for images of comparable quality to those produced from air-gun data sets. Because coupling to the water is invariant, MV signals tend to be repeatable. Since far-field pressure is directly proportional to piston volumetric acceleration, the far-field radiation can be well controlled through accurate piston motion control. These features allow us to shape signals to match precisely a desired spectrum while observing equipment constraints. Over the last few years, an intensive validation process was conducted at our dedicated test facility. The MV units were exposed to 2000 hours of in-sea testing with only minor technical issues.

Travel-time residuals of teleseismic P-waves at the Rodriguez Triple Junction in the Indian Ocean using ocean-bottom seismometers

1996 ◽  
Vol 23 (7) ◽  
pp. 713-716 ◽  
Author(s):  
Toshinori Sato ◽  
Kei Katsumata ◽  
Junzo Kasahara ◽  
Naoshi Hirata ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Travel Time ◽  
Triple Junction ◽  
Ocean Bottom ◽  
P Waves ◽  
Ocean Bottom Seismometers ◽  
The Indian Ocean

scholarly journals Future accessibility impacts of transport policy scenarios: equity and sensitivity to travel time thresholds for Bus Rapid Transit expansion in Rio de Janeiro

2018 ◽  
Author(s):  
Rafael Henrique Moreas Pereira
Keyword(s):  
Travel Time ◽  
Low Income ◽  
Rio De Janeiro ◽  
Network Effects ◽  
Boundary Effect ◽  
Income Levels ◽  
Partial Operation ◽  
Time Threshold ◽  
Ex Post ◽  
Policy Scenarios

The accessibility impacts of transport projects ex-post implementation are generally evaluated using cumulative opportunity measures based on a single travel time threshold. Fewer studies have explored how accessibility appraisal of transport plans can be used to evaluate policy scenarios and their impacts for different social groups or examined whether the results of project appraisals are sensitive to the time threshold of choice. This paper analyzes how different scenarios of full and partial implementation of the TransBrasil BRT project in Rio de Janeiro (Brazil) will likely impact the number of jobs accessible to the population of different income levels. The analysis is conducted under various travel time thresholds of 30, 60, 90 and 120 minutes to test whether the results are sensitive to the boundary effect of the modifiable temporal unit problem (MTUP). Compared to a partial operation scenario, the full implementation of TransBrasil that extends this corridor into the city center would lead to higher accessibility gains due to network effects of connecting this BRT to other transport modes. Nonetheless, the size of the accessibility impacts of the proposed BRT as well as its distribution across income classes would significantly change depending on the time threshold chosen for the accessibility analysis. Considering cut-off times of 30 or 60 minutes, both scenarios of TransBrasil would lead to higher accessibility impacts in general and particularly for low-income groups, moving Rio towards a more equitable transportation system. However, under longer thresholds of 90 and 120 minutes, an evaluation of this project would find much smaller accessibility gains more evenly distributed by income levels. The paper highlights how time threshold choice in cumulative opportunity measures can have important but overlooked implications for policy evaluation and it calls for further research on the MTUP in future transport and mobility studies.

An Example of How Bad Public Relations Can Defeat a Good Water Pollution Control Project

1992 ◽  
Vol 25 (9) ◽  
pp. 261-267
Author(s):  
E. R. de Britto ◽  
S. A. S. Almeida ◽  
F. B. Gonçalves
Keyword(s):  
Public Relations ◽  
Pollution Control ◽  
Rio De Janeiro ◽  
Public Information ◽  
Government Agency ◽  
Mutual Understanding ◽  
Information Program ◽  
Public Work ◽  
Elective Period ◽  
Ocean Outfall

Cedae, a Rio de Janeiro Government Agency, carefully planned and designed an ocean outfall to be built in Barra da Tijuca, one of the most valuable and beautiful dwelling regions of Rio de Janeiro. Due to the non-implementation of a public enlightening campaign, Cedae had to face radical community opposition to the outfall construction, fronted by very active persons, interested in personal promotion in a political elective period. The authors concluded that it is indispensable for any planned public work to put an action in enlightening public information program, based on fact and mutual understanding, to inform the community to be served about the various technical, economical and social questions involved and as to the facilities to be built.

scholarly journals Precise aftershock distribution of the 2019 Yamagata-oki earthquake using newly developed simple anchored-buoy ocean bottom seismometers and land seismic stations

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Masanao Shinohara ◽  
Shin’ichi Sakai ◽  
Tomomi Okada ◽  
Hiroshi Sato ◽  
Yusuke Yamashita ◽  
...  
Keyword(s):  
Shallow Water ◽  
Travel Time ◽  
Focal Mechanism ◽  
Water Depth ◽  
Source Area ◽  
Focal Mechanisms ◽  
Reverse Fault ◽  
Ocean Bottom ◽  
Fault Type ◽  
Ocean Bottom Seismometers

AbstractAn earthquake with a magnitude of 6.7 occurred in the Japan Sea off Yamagata on June 18, 2019. The mainshock had a source mechanism of reverse-fault type with a compression axis of WNW–ESE direction. Since the source area is positioned in a marine area, seafloor seismic observation is indispensable for obtaining the precise distribution of the aftershocks. The source area has a water depth of less than 100 m, and fishing activity is high. It is difficult to perform aftershock observation using ordinary free-fall pop-up type ocean bottom seismometers (OBSs). We developed a simple anchored-buoy type OBS for shallow water depths and performed the seafloor observation using this. The seafloor seismic unit had three-component seismometers and a hydrophone. Two orthogonal tiltmeters and an azimuth meter monitored the attitude of the package. For seismic observation at shallow water depth, we concluded that an anchored-buoy system would have the advantage of avoiding accidents. Our anchored-buoy OBS was based on a system used in fisheries. We deployed three anchored-buoy OBSs in the source region where the water depth was approximately 80 m on July 5, 2019, and two of the OBSs were recovered on July 13, 2019. Temporary land seismic stations with a three-component seismometer were also installed. The arrival times of P- and S-waves were read from the records of the OBSs and land stations, and we located hypocenters with correction for travel time. A preliminary location was performed using absolute travel time and final hypocenters were obtained using the double-difference method. The aftershocks were distributed at a depth range of 2.5 km to 10 km and along a plane dipping to the southeast. The plane formed by the aftershocks is consistent with the focal mechanism of the mainshock. The activity region of the aftershocks was positioned in the upper part of the upper crust. Focal mechanisms were estimated using the polarity of the first arrivals. Although many aftershocks had a reverse-fault focal mechanism similar to the focal solution of the mainshock, normal-fault type and strike–slip fault type focal mechanisms were also estimated. Graphical Abstract

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