Here is my issue:
I was recently tasked with conducting field permeability tests inside cased/partially cased boreholes at a site with low permeability (glacial till) deposits and a deep groundwater table to aid in appropriately sizing a proposed stormwater infiltration chamber. All of the references I have come across to calculate the horizontal and vertical coefficients of permeability based on variable (falling) head tests are with respect to infiltrating into saturated (i.e. below the groundwater table) soils. However, in my case, the groundwater table is located at great depths below the proposed base of the infiltration system, and I am 100% certain that I was infiltrating into unsaturated soils. A summary of my testing procedure is as follows:
1. Advance boring to a depth of 14 ft. (proposed depth of chamber base) using driven steel casing and rotary drilling methods
2. After the casing was "washed" out, we filled the casing with 2 ft. of filter sand and lifted the casing up 1.5 ft. (leaving 6 inches of sand inside the casing, and 1.5 ft. of sand below the casing)
3. Fill the casing with clean water to the top (reference point) and measure the head drop at specific time intervals
Am I overthinking this? Is is simply a k = Q/A scenario? Any and all advice is much appreciated.
I was recently tasked with conducting field permeability tests inside cased/partially cased boreholes at a site with low permeability (glacial till) deposits and a deep groundwater table to aid in appropriately sizing a proposed stormwater infiltration chamber. All of the references I have come across to calculate the horizontal and vertical coefficients of permeability based on variable (falling) head tests are with respect to infiltrating into saturated (i.e. below the groundwater table) soils. However, in my case, the groundwater table is located at great depths below the proposed base of the infiltration system, and I am 100% certain that I was infiltrating into unsaturated soils. A summary of my testing procedure is as follows:
1. Advance boring to a depth of 14 ft. (proposed depth of chamber base) using driven steel casing and rotary drilling methods
2. After the casing was "washed" out, we filled the casing with 2 ft. of filter sand and lifted the casing up 1.5 ft. (leaving 6 inches of sand inside the casing, and 1.5 ft. of sand below the casing)
3. Fill the casing with clean water to the top (reference point) and measure the head drop at specific time intervals
Am I overthinking this? Is is simply a k = Q/A scenario? Any and all advice is much appreciated.
