Environmental Engineering Reference
In-Depth Information
control point and might have affected the natural groundwater quality at such a location.
The final choice of the control borehole was based on the following considerations:
Figure 9.7. Sampling borehole at
Crowborough farm.
• The site is near the study area and has similar geological conditions, which would be the
basis for similar background pollution characteristics;
• It lies on the opposite bank of an adjacent stream from the study area. This stream acts
as a pressure barrier to groundwater flow from the area beneath the farm.
During the period of study, the area near the control borehole (BH6) was used for
informal agriculture (maize crop) and a new high-density residential suburb was under
construction nearby. BH1 is located at the lowest part of the study area, which collects
the excess hydraulic load from the pasture. It is wet throughout the year, and has not
being used for irrigation; correspondingly it has not being provided with a drainage
system for collection of seepage. BH2 is located within the premises of the treatment
plant near to the unlined ponds and was selected in order to investigate the possible effect
of infiltration of the ponds effluent and the impacts on soils and ground water. BH5 and
BH4 are located at the most frequently irrigated areas, with BH5 being located in the
lowest part of the area, near the protection dike. BH3 represents the impact of the sludge
