45 



than seen at the other reference areas in September, which averaged 1.09 cm at SOUTH 

 and 1.00 cm at SW-REF. Physical effects primarily caused surface roughness, although 

 some replicates did indicate biogenic activity or were indeterminate. 



3.5.2.2 Benthic Community Assessment 



Stage III or Stage I on III indicators characterized most replicates, even though the 

 Stage III feeding voids lacked oxygenated sediment halos (Appendix C). Because the low 

 water temperature in early March reduces the metabolic rate of benthic organisms, the 

 active voids may have been less oxygenated. The lower metabolic rate also decreases the 

 consumption rate of oxygen in the sediments. The lower biological oxygen demand (BOD) 

 results in greater RPD depths. The RPDs at the potential reference area stations were 

 deep, ranging from 1.83 to 4.63 cm and with an average of 3.04 cm. A few replicates 

 (200N C, 300E A, 300SE A, and 200S C) were exceptions with RPDs less than 1 cm. 

 The total OSI values, with a median of 10, were very high for a WLIS reference area 

 (Figure 3-13, Table 3-4). For comparison, in September 1997 the median OSI value of 

 both SOUTH and SW-REF was 7. 



3.5.3 Sediment Grab Samples 



All sediments collected at random locations in SE-REF with the grab sampler shared 

 similar characteristics with little variation (Figure 3-1 1). Black, silty clay overlain with a 

 thin (0.2 to 1.0 cm) olive-grey, oxidized layer was observed at each station in the potential 

 reference area. REMOTS® photo 200SW C (Figure 3-12) is representative of the 

 appearance of the grab samples. It is not known how much of the surface, oxidized layer, as 

 visible in lOONW D (Figure 3-12), was resuspended as the sampling device was lowered to 

 the seafloor, immediately prior to sample extraction. The samples were retrieved and 

 brought on deck for description and sub-sampling. The sediments had a fine, pudding-like 

 texture and sulfidic odor. Small shell fragments and Mulinia shells covered the surface. A 

 7-cm polychaete was found in Grab 8, and a worm was observed in Grab 1. 



3.5.3.1 Grain Size Results 



The ten WLIS reference grab sample grain size data had consistent sand and fine- 

 grained fractions (Table 3-5). Most of the samples had silt (26 to 49%) and fine sand (26 

 to 41 %) as the primary component, with the general classification either a silty fine sand, 

 or sandy silt. One sample (GR-9) was dominated by clay (45%), with nearly equivalent 

 concentrations of silt (26%) and fine sand (28%). Other than GR-9, clay varied from 16 to 

 28% in the samples. The sand fraction in all of the samples was dominated by fine sand. 



Monitoring Cruise at the WLIS Disposal Site, September 1997 and March 1998 



