| Summary: | Stormwater runoff from log yards in different BC regions can affect aquatic habitats to varying
degrees given differences in weather, water quality and tree species. The objective of this thesis
was to compare runoff quality and total runoff loadings from a coastal and interior log yard.
Chemical analyses, toxicity tests and treatments were conducted. Data were compared to criteria,
statistically compared between sites and assessed for seasonal trends. Export coefficients (ECs)
were compared between sites. Relationships between toxicological and chemical variables were
explored statistically.
Runoff toxicity was similar between sites and fairly low. LC50s for 48-hour Ceriodaphnia dubia
tests ranged from 32.95 to > 100 and 58.70 to > 100 for coastal and interior runoff, respectively.
Microtox ®.5 minute EC50s ranged from 27.12 to > 100 for coastal runoff and 22.22 to > 100
for interior runoff. Several metals and dehydroabietic acid (DHA) exceeded criteria in runoff
from both sites. Biochemical oxygen demand, alkalinity, pH and metals were significantly higher
(p < 0.05) at the interior site. Sodium and conductivity were higher at the coastal site. No
seasonal differences in runoff quality were observed. Therefore, acute effects would occur during
periods of high runoff, during autumn at the coastal site and late winter at the interior site. The
unpaved interior site generated less runoff per square meter due to ground infiltration. ECs were
comparable to the paved coastal site. Exceptions to this include tannins and lignin (11 fold higher
at the coastal site) and DHA (9 fold higher at the interior site). C. dubia toxicity was partially
associated with TSS for both sites. Tannins and lignins were correlated (r² =0.91) with C. dubia
toxicity for coastal runoff. Tannin and lignin concentrations ranged from 45 to 263 mg/L and 43
to 75 mg/L in coastal and interior samples, respectively.
Since results suggest that TSS is partially responsible for toxicity, and since contaminants are
often bound to TSS, source control and treatment options for TSS should be implemented.
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