Étude environnementale portant sur la qualité des sédiments de la portion sud du lac Saint-Pierre utilisée par le Centre d'Essais et d'Expérimentation en Munitions (CEEM) de Nicolet

Abstract

The Department of National Defence (DND) has been operating a Munitions and Experimental Test Centre (METC) in Nicolet since 1952. Inert and explosive shells are tested at this facility. Since the beginning of operations at the site, an estimated half million shells have been fired, of which 300 000 were fired into the lake. A scientific cooperation agreement was negotiated between DND and Environment Canada (DOE) in march 1999 to carry out the sediment characterisation in the southern portion of lake St. Pierre being used by the METC. The goal of this study is to assess the impact of shell firing on the ecosystem of that sector, make recommendations regarding the use of the sector and evaluate the pertinence of restoration. An historical review of firing activities, a scientific review of explosives, a description of the study site and data from the fall 1999 pre-sampling campaign were presented in a previous report. The second phase of the study included 1) a geophysical survey to identify and describe the distribution of shells in the study zone in order to orient sediment sampling operations, and 2) a sampling campaign to assess sediment quality in the sector of lake St. Pierre used by the METC. The geophysical survey (spring and fall 2000) enabled us to identify those sub-sectors where shell and fragment concentrations were highest (hot-spots). Sampling was oriented accordingly. A total of 74 stations were visited in the spring of 2000 and 80 samples were collected and analysed. Analysis of energetic materials has shown no detectable levels (ppb) of these materials in any of the samples. Only one hot-spot shows metal concentrations higher than at the control stations. Nonetheless, those concentrations aren't exceptional in comparison to sediment quality criteria. Differences observed in metal contamination are more probably explained by granulometric differences than the presence of shell fragments. The potential impact of that hot-spot has nevertheless been evaluated on a precautionary basis as the « worst case» scenario. Therefore, the third and conclusive sampling phase included bioassays and a benthic survey in accordance with the Triad approach which was chosen for this study. The observed responses (bioassays and benthos) confirm results from the chemical characterisation phase (phase II). It is evident from these results that, at the time of this study, the projectiles in the sediment had little or no impact on their chemical quality and on the organisms that live in them. The chemical quality of the sediment in the study sector does not pose a risk to the environment at the present time. The conclusions presented in this report reflect the situation in 2000. Considering the potential for projectile degradation, monitoring is recommended at least every 10 years.