DEQ-CFW_00004421

The DVV{l,4PS Groundwater Planning Unit has investigated our existing groundwater quality databases
and publications in order to provide estimates of approximated groundwater quality hardness values for
12 NPDES permitted facilities that discharge treated groundwater to surface water bodies. The
groundwater quality data that was utilized for this investigation consisted of historical ambient
monitoring wells, DVV{lgroundwater quality research stations, and data from private water supply vve||s
obtained by local county health departments. In addition, | obtained some groundwater hardness data
from reports published by N[DENR for certain parts of the state. | used best professional judgment to
estimate the hardness values based on the geology assumed to be present at the sites using the 1985
"Geologic Map of North Caro|ina" The results of this analysis are shown on the attached table, which
also includes information on the source of the data used to provide the hardness estimate for each
permitted site. All hardness estimated values are reported in milligrams per liter.
The data from the table provides an indication of the degree of variability associated with groundwater
hardness. Groundwater hardness is a highly variable parameter, and is a function of rock type, depth,
and groundwater flow. Groundwater hardness may also vary over time, although temporal variations
are much less pronounced than spatial variations based on hydrogeologic conditions. Therefore, please
be aware that these estimates are not very reliable for any particular well or site. They are gross
generalizations and estimates that are obtained from highly variable data. | do think that they are
suitable for the purpose ofestimating for a Fiscal Note calculation, but the best solution to this question
would betoobtain hardness data from each respective system.
OEQ-CFVV_00004421