NC0028916_Cyanide_20010228

141,
TOWN OF TROY
INCORPORATED 1852
Public Services Dept.
444 N. Main Street
Troy, NC 27371-2799
Phone: [phone]
Fax: [phone]
02/28/01
NCDENR
225 Green Street, Suite 714
Fayetteville, NC 28301
Fax: [phone]
Att: Kitty Cramer
Dear Kitty:
. , D
MAR `f2CI
PPP,
The Town of Troy has determined that the cyanide problem that we had was indeed cyanide. Knowing that the
problem only occurred in the winter months, we went back to NCDOT and asked some more questions
specifically about the salt they put out on the roads. We had found out previously that sometimes a cyanide
compound is used with salt to keep the salt from clumping together.
We found out that the salt that DOT is now using was a shipment that they received in January of last year from
Wilmington. Prior to that they had been using from the same salt stockpile shipped approximately 10 years ago.
We thought it awfully suspicious that the new shipment date coincided exactly with the first occurrence of
cyanide showing up in our pretreatment sampling. We obtained a sample of the salt and had it analyzed. Sure
enough it contained cyanide.
As to how the salt was getting into our collection system, even though no one would admit to it, we believe that
when NCDOT washed out their truck, that they probably opened one of the two manholes in their yard and
washed the salt into the manhole. The one problem though with this is that we were showing cyanide in months
when no salt was put out. But the trend was that the level of cyanide got lower each month. The question was
why? Then while we were doing some tests on the salt in our lab we realized that the salt did not dissolve very
rapidly. We put some salt in a beaker full of water and left it overnight. The next day a good portion.of the salt
was not dissolved. Then the final piece of the pn771e came together. The flow from NCDOT is normally very
low. So if large amounts of salt were washed into the sewer it might take months for the normally small flows to
completely dissolve the salt/cyanide. Only when NCDOT washes out their trucks does a sufficient amount of
water flush out the line. Hence, cyanide salt clumps would persist for one to two months after the actual cyanide
contaminated salt had been used.

r Needless to say, we told NCDOT not to rinse their trucks out anywhere close to our sewer collection system
anymore. We don't know what they will do about their salt/cyanide contamination problem. We just know that it
better not show back up in our pretreatment sample.
We hope this will end the cyanide problem for Troy and will alleviate any more concerns that the region may
have about the problem. If you have any further questions just give me a call.
Sincerely,
E. Gray Walls P.E.
Town Engineer/
Public Services Director