EPA On-line Tools for Site Assessment Calculation

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Three Point Gradient Calculator

Planning the next phase of the investigation; delineation of the dissolved contaminant plumes, will require us to know the groundwater flow direction. After installing at least three monitoring wells and determining their relative elevation, we can use the three-point calculator to quickly give us both the direction and gradient of groundwater flow while in the field.

To use the three point gradient calculator, it is best to select three wells, which are widely separated and not aligned in any single direction. Let's try wells W1, W2 and W7. The well coordinates in map scale, using the lower left hand corner of the map as the origin (O,0), and the field measured groundwater elevation (casing elevation - depth to water)for these locations is as follows:

"Well Coordinates and Heads"

Well ID	X-coordinate (ft)	Y-coordinate (ft)	head (ft)
W1	190	163	90.24
W2	138	153	90.27
W7	217	43	90.01

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Contact Jim Weaver to ask a technical question on this material.