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Crisp said the plant staff could have
overfed the calcium thiosulphate in an
effort to make sure there was no
chlorine released into the stream. The
plant’s federal permit to discharge the
water says there should be no more than
17 parts per billion of chlorine
discharged, which translates into none.
“I think we may have applied too much
and that caused the precipitant to form
in the creek.” Other work at the plant
could also have caused the overfeed,
Crisp said. The staff has reduced the
amount of the chemical it uses.
There is no water quality standard for
calcium.
Susan Massengale, the spokesperson for
DWQ, said that if the precipitate, the
white goo, is calcium, it would not pose
a danger. She could not say anything
definite about the deposits until the
tests are completed.
As for the algae, Massengale said it
appears to be typical winter algae that
forms naturally. Crisp said the current
stretch of warm weather could help the
algae grow.
Crisp also said the algae could be
growing because of problems with the
septic tanks in Sheffield Manor. “I know
they’re had problems out there.” About
one-third of the homes there were tied
into city sewer after their septic tanks
failed during Hurricane Fran in 1996.
“The rest are on individual septic tanks
and they may be the source of the
nutrients {which allow the algae to
grow].”
Naujoks was concerned about both the
composition of the white goo on the
stream bed and the formation of algae,
saying algae in the winter could
indicate high nutrient loading.
He also cited a 1997 DWQ memo which
said: “No provision in the [federal]
permit allows the city to discharge
leftover chemicals used in the
processing of drinking water.”ater.”
The stream has been in the news and
investigated for more than a decade
because of reported releases of sludge
and other chemicals from the plant.
In 1996 subdivision residents reported
the creek was bright red and had been so
for at least eight hours. DWQ
investigated and found it had been an
intentional – and illegal – release of
about 753 pounds of a chemical called
Cairox (potassium permanganate) along
with other chemicals that were in a
drying bed. After lengthy negotiations,
the amount of the chemical was reduced
to 63 pounds, and the plant was cited
for that violation of its permit.
In 2002 Channel 5, WRAL-TV, ran several
stories about the creek and its lack of
aquatic life of any kind. DWQ
investigated and found the creek to be
nearly sterile because of high
concentrations of chlorine. The city
installed a system to remove chlorine.
In July 2004 the consultants hired by
the city, Black & Veatch International
Company of Cary, said determining
whether trihalomethanes, polymer and
cyanide were causing the toxicity in the
creek was the top priority. If an
investigation does not show what is
poisoning the creek, the engineers said,
a further evaluation would be necessary.
The plant might have to change how it
treats wastewater generated by the water
production process. Trihalomethanes are
formed during the chlorination process
to produce drinking water. |
