the maximum losses to porous formations would reduce the barite discharge to 
800,000 1b. Danenberger suggested that the most likely range of barite 
discharge is between 1 million and 1.5 million lb. We will assume the mid 
value of this range, 1,250,000 1b, for the total barite discharged to the 
ocean while drilling this well. 
The net mass of barite added by drilling within the 6 km circle at the 
time of cruise 5 represents 25 percent of the total amount discharged 
(270,000/(1,250,000*(0.85))(100). The factor 0.85 represents the fraction of 
pure BaSQ, contained in mined barite. 
In our evaluation of the rate at which barite decreases within the site- 
specific survey, we have considered only the area between the 0.5 and 2 kn 
ring. This choice includes 20 of the 29 stations and avoids the area of the 
outer two rings where half of the total area is controlled by as few as four 
stations. We have also excluded the actual drill site, where large within- 
station variability was measured. Another advantage in considering this 
smaller area is that data on Ba in the fine fraction are available from most 
of these 20 stations, which permits an additional rate calculation. The 
changes in inventory of Ba as BaSO, in the 0.5-2 km area are shown in figure 
19. 
For cruise 5, we assigned a value of 1 to the net barite inventory 
(total barite-background barite) for the 0.5 to 2 km area and calculated the 
net barite for each successive cruise relative to cruise 5. A semi-log plot 
of the data appears to have two relatively straight line segments (fig. 20), 
which approximates the mathematical model for radioactive decay for two 
isotopes having different half-lives. If one uses this model and least 
squares regression to describe the removal of barite from the surface 
sediments, the initial “half-life” or half-time of barite within this area of 
the site-specific survey is 0.34 years (cruises 5, 6, and 8, r=-.99). 
60 
