U of C Geology and Geophysics Research Project

Waterline supported a U of C Department of Geology and Geophysics Research Project to determine the recharge potential of a low impact development system in Okotoks

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Waterline was pleased to support Glenn Hall and Edwin Cey of the University of Calgary, with their research pertaining to the effectiveness of a Low Impact Development System (bioretention system) installed in the Town of Okotoks Alberta adjacent to the Sheep River.

The bioretention system comprises a series of engineered, interconnected, vegetated depressions composed of loam, mulch and compost. The depressions (bioswales) are situated directly above an alluvial, gravel and sand aquifer adjacent to the Sheep River. Storm water runoff from adjacent parking lots is diverted towards the bioswales and allows for the stormwater to infiltrate instead of directly entering the Sheep River via Okotoks’ stormwater infrastructure as a stormwater flood event. Several two-inch groundwater monitoring wells were installed at various locations near the bioswale to measure the water table’s response to precipitation and runoff inputs.

Alluvial aquifers, such as the one beneath the project area, are generally characterized by high hydraulic conductivity material, which can pose challenges for completing hydraulic response tests on 2” monitoring wells. Slug tests completed by the U of C produced hydraulic conductivity (K) values that did not match K values estimates obtained via back-calculation of a groundwater mounding solution, thus, a different style of hydraulic response test was needed. Ed and Glenn reached out to Waterline to help them design a short-term, high-flow aquifer test utilizing the existing two-inch PVC monitoring wells.

In June of 2020, Waterline hydrogeologists and students of the U of C mobilized to the research site to complete short-term hydraulic response follow-up tests to the initial slug tests. The follow-up testing used a gas-powered centrifugal pump (trash pump) to provide sufficient groundwater level change for analysis. This method provided sufficient groundwater level displacement to allow the U of C to estimate the hydraulic conductivity of the alluvial aquifer using the Theis (1935) and Cooper-Jacob (1946) aquifer analysis methods. Analysis of the aquifer tests yielded hydraulic conductivities on the order of 10-3 m/s, which is consistent with values reported in texts for coarse-grained (sand and gravel) unconsolidated sediments and correlates to water balance calculations completed previously by the U of C.

The unconventional aquifer test method proved effective in displacing the water table sufficiently to calculate meaningful hydraulic conductivity values and enabled the researchers to refine their conceptual, analytical and numerical models used to evaluate the recharge potential related to the Low Impact Development installation. Waterline was pleased to partner with the University of Calgary to support their ongoing research efforts.