Central Slag Disposal Area (SCU27)

Phase1 - Environmental Site Assessment
Report

5.4.6 Central Slag Disposal Area (SCU27)

The high-mounded slag deposit along the eastern shore of Muggah Creek continues to the north and west of the High Dump (Section 5.4.5). For the purposes of this study, the remaining portion of the slag mound has been divided into two principle areas: Northern (Section 5.4.7) and Central Slag Disposal Areas.

Both consist almost entirely of blast furnace slag mounded to depths of 30 metres, with a relatively thin layer of other industrial wastes placed on top. These waste include blast furnace flue dust, caster slag, coke breeze, refractory waste, and wastewater sludge.

The Central Slag Disposal Area, or SCU 27, has been carved out of the slag mound because of its apparent role as a “buffer” between the suspected environmental issues associated with the High Dump, and the well-documented lack of environmental issues associated with the North Slag Disposal Area where aggregate quarrying has been carried out for many years. SCU 27 also incorporates a buffer zone on the west and north side of the Tank Farm (Figure 5-1).

The results of testing performed by JDAC in 2000/2001 indicate that no soil samples were collected in this area during the JDAC sampling program. Two monitor well locations, MW88-102-A(B), are located within this area. Groundwater from these wells exceeded the Canadian Drinking Water Quality Guideline values for certain heavy metals (sodium, chloride, barium, copper, iron and manganese), EPA 625, PAHs and HCNs.

Petroleum hydrocarbons were detected at levels above the NSDEL Tier 1 guidelines. Sodium and chloride are of course associated with ocean water (Sydney Harbour), and the remainder of the contaminant groups are consistent with those found in the Tar Ponds. It is noted that the groundwater is not used as a source of potable water.

The majority of open space in this area is covered with granular materials. Slopes at certain locations show signs of surface erosion. Overland drainage in the area may present the possibility of siltation and sediment impacts to receiving waters.

Potential Environmental Issues

Potential environmental issues associated with the Central Slag Disposal Area include fill and groundwater contamination associated with industrial waste disposal, including heavy metals, PAHs, and petroleum hydrocarbons. Petroleum impacts may also have resulted from leakage from the Tank Farm area. The potential also exists for coal tar or PCBs contamination to have impacted groundwater and fill due to infiltration from the Tar Ponds. Coal tar-contaminated sediment may also be present beneath the fill in this area.

Blast furnace slag was widely used as a fill material in this area. Various heavy metals are known to be present in blast furnace slag, but often in a highly immobile state. An important part of future environmental testing at this site will be the appropriate evaluation of heavy metal impacts in relations to their environmental risk.