378 



in each direction, because symmetric distribution of 

 deposited material is expected initially due to the strong 

 rotary tidal currents in the area. Sampling is also more 

 intensive along the axis parallel to the direction of mean 

 current flow, particularly in the area dovmcurrent from the 

 rig site. 



The array of site-specific stations is divided into 

 "primary," "secondary," and "special" stations. Benthic 

 infauna samples, geology and geochemistry samples, and 

 bottom photographs are collected at all "primary," 

 site-specific stations. Hydrocarbon subsamples are 

 collected and archived. Sampling is conducted at 

 "secondary" stations in a manner similar to the "primary" 

 stations but the samples are analyzed only if data from 

 the "primary" stations suggest that additional analyses 

 would be beneficial. "Special" stations are located at 

 the rig site, two kilometers downcurrent from the rig site, 

 and six kilometers upcurrent from the rig site. Sampling 

 is conducted as described for "primary" stations. 

 The following additional work is conducted at the "special* 

 stations: (1) "dredge/trawl collections" of epifauna for 

 identification of voucher specimens eind einalysis of 

 hydrocarbon and trace metal concentrations in tissues; (2) 

 subsampling and analysis of sediment hydrocarbons from 

 "geology and geochemistry grab samples"; and (3) any 

 additional studies of special interest. In addition, 

 measurements of dissolved oxygen, salinity, and water 

 temperature eU'e made at the drill site. 



All monitoring stations, both long-term, regional and site- 

 specific, are sampled seasonally, until concentrations of 

 drilling fluid components observed during the post-drilling 

 surveys are similar to pre-drilling concentrations. 

 Furthermore, if the benthic community has changed as a result 

 of drilling activities (based on comparisons of pre-drilling 

 and post-drilling samples and/or comparisons of control 

 stations and experimental stations) sampling and analysis 

 will continue until such changes are no longer 

 distinguishable from changes identified as natural variation. 

 Quarterly sampling has been selected to evaluate the 

 magnitude of seasonal changes in the abundance of benthic 

 organisms and concentrations of hydrocarbons and trace metals 

 in the sediment. Analysis of historical benthic samples, 

 which has been funded by BLM/MMS and recently completed, 

 will provide pertinent background seasonal data for several 

 long-term, regional stations. Additional background 

 information, including benthic sampling data, exists from the 

 ELM- funded USGS/WHOI program and the National Marine 

 Fisheries Service Ocean Pulse and MURT programs. 



