Occurrence
of Radon in Florida’s Public Water Supplies
Executive Summary:
Background
The
U.S. Congress specified in the Safe Drinking Water
Amendments of 1996 that the U.S. Environmental Protection
Agency (USEPA) shall propose a national primary drinking
water regulation for radon by August 1999 and finalize
the regulation by August 2000. The future radon
regulation may have a significant impact on public water
systems (PWSs) in Florida. To estimate the impact, the
Florida Department of Environmental Protection’s
Drinking Water Section conducted a statewide study of
radon occurrence in raw ground water used, and finished
ground water produced, by PWSs.
Study
Objective
The
primary objective of the Department’s radon occurrence
study was to estimate the following:
- radon
levels in raw ground water used by Florida’s PWSs;
and
- the
percentage of Florida’s PWSs that would exceed
various possible maximum contaminant levels (MCLs) or
alternative maximum contaminant levels (AMCLs) that
could be established by the USEPA in its national
primary drinking water regulation for radon.
Study
Approach
To
accomplish the above objective, the Department’s radon
occurrence study was designed as follows:
- to
include sampling for radon at a portion of
Florida’s community water systems (CWSs) using
ground water and at a portion of Florida’s
non-transient non-community water systems (NTNCWSs)
using ground water (at the time the study was
designed, it was anticipated that the USEPA’s
drinking water regulation for radon would apply to
CWSs using ground water and NTNCWSs using ground
water);
- to
include sampling for radon in raw ground water;
- to
include sampling for radon in finished ground water
if the water system treatment plant selected for
sampling was using a treatment process other than
just chemical addition;
- to
limit sampling to one raw water sample set for each
water system selected for sampling and, where
applicable, one finished water sample set for each
water system selected for sampling; and
- to
accomplish sampling of raw ground water as near the
source of water (i.e., the well) as possible and
sampling of finished ground water downstream of all
treatment processes.
From
May 1999 to August 1999, 341 PWSs (213 CWSs and 128
NTNCWSs) were sampled for radon. Raw ground water samples
were collected at all 341 of the sampled systems.
Finished ground water samples were taken at 127 of the
341 sampled systems. However, for the remaining 214
systems, where the sampled water treatment plants were
using just chemical addition treatment, it was assumed
that the concentration of radon in finished water would
be the same as the concentration of radon in raw ground
water.
Conclusions
The
USEPA proposed a national primary drinking water
regulation for radon after the Department completed the
sampling phase of its radon occurrence study. The
proposed regulation would apply only to CWSs using ground
water, would set an MCL for radon at 300 picocuries
(pCi/L), and would set an AMCL for radon at 4,000 pCi/L.
Based
upon the results of its radon occurrence study, the
Department formulated the following conclusions
concerning Florida’s CWSs and a radon MCL or AMCL of
300 pCi/L or 4,000 pCi/L, respectively:
- The
mean or average concentration of radon in raw ground
water used by Florida’s CWSs is 664 + 141 pCi/L,
and it is estimated that 57 + 6 percent of
Florida’s CWSs using ground water have a radon
concentration greater than 300 pCi/L in their raw
ground water.
- An
estimated 44 + 6 percent of Florida’s CWSs using
ground water would exceed an MCL of 300 pCi/L for
radon, but no more than two percent of these systems
would exceed an AMCL of 4,000 pCi/L for radon.
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Occurrence
of Radon in Florida's Public Water Supplies (724K)
