ARCHIVED REPORTS XR0011083 - Laserfiche WebLink

Home Browse Search

' Cytological Tedvda lxc Page 3 Groundwater Monitoring Report ' Project No 724 2 February 13, 2606 ' that the earlier measurements were biased due to the spatial orientation of fewer wells The rose diagram included in Figure 5B shows that the intermediate aquifer gradients at this site ' have had a consistent easterly (northeast to southeast) direction The rose diagram included in Figure 5C shows that the deep aquifer gradient has been to the east to southeast for the sounding events following the installation of four additional deep wells in December 2003 ' Vertical Groundwater Gradients Under vertical groundwater flow conditions, the water level in a monitoring well is a function ' of the length of the well screen and its depth or vertical position in the aquifer As with horizontal flow conditions, the diameter of the well or piezometer is immaterial ' The following procedure is used to calculate the vertical groundwater gradient • Determine vertical distance between the two measuring devices by the distance from the mid -point between the top and bottom seal of the deep well (MW -104, MW --106, MW - 107) and the mrd -point between the groundwater elevation and the bottom seal in the shallow well (MW -4, MW -6, MW -7) ' • Measure the head in both wells used in the calculations • If the lateral distance between the well pair is greater than a few feet, then calculations must be made to correct the down -gradient piezometric head to account for the sloping M water table between the wells The calculation considers the slope of the water table and the distance in a dawn -gradient direction between the two wells used in the calculations ' Figures 2 through 4 show the location of the well pairs used for calculating vertical groundwater gradient in this report MW-4/MW-104, MW-6/MW-106, and MW-7/MW-107 Tables 1, 2 & 3 include Summaries of Water Level and Gradients Slope and Bearing for the ' three aquifer horizons and Table 4 shows the calculated vertical gradients The information used in the calculations is shown below ' Vertical gradient calculation formulas are as follows * vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] vertical head [(head of deep well) - (head of shallow + correction) = vertical head] ' • vertical gradient [(vertical head) / (vertical distance) = vertical gradient] ' For the November 23, 2005 event, the vertical gradient for all three well pairs was negative (downward) The site has a varying trend of negative and positive gradients in these wells The MW -4/104 well is generally negative, the MW -6/106 well pair is typically positive and ' the MW -7/107 well pair has a history of mostly positive gradients It is noted that the vertical distance to the deep well screen in the MW-4/MW-104 well pair is double that observed in the other two well pairs, which may have an influence over the vertical gradient direction