SHASTA COUNTY AIR QUALITY MANAGEMENT DISTRICT
RULE 3:19 - HEXAVALENT CHROMIUM AIRBORNE TOXIC CONTROL MEASURE FOR COOLING TOWERS
(Added 10-2-90) (Amended 12/23/92)
For the purposes of this rule the following definitions shall apply:
Cooling Tower: Any open water recirculation device that evaporates circulating water to remove heat from
a process, building, or refrigeration device, and puts the heat into the ambient air.
Hexavalent Chromium: A cancer-causing substance existing as part of various inorganic chromate compounds,
for example, sodium dichromate or lead chromate.
Water Treatment Chemicals: Any combination of chemicals added to cooling tower water including tracers,
corrosion inhibitors, anti-scalants, dispersants, biocides.
- Hexavalent Chromium Removal: Effective October 2, 1990, no person shall add any hexavalent chromium- containing
chemicals or any compound that may produce hexavalent chromium to a cooling tower operating in the District.
- Circulating Water Concentration - Wooden Cooling Towers: Effective October 2, 1990, no person shall operate
a wooden cooling tower in the District unless the following requirements are met:
- From October 2, 1990, to March 12, 1991, hexavalent chromium levels in the circulating water are not to exceed
eight (8) milligrams/liter of circulating water.
- After March 12, 1991, hexavalent chromium levels in the circulating water are not to exceed 0.15 milligrams/liter
of circulating water.
- A decrease in hexavalent concentration in the circulating water must be demonstrated each month during a period
of up to six (6) months following the compliance date in order to avoid being cited for a violation of the 0.15
- Circulating Water Concentration -- Non-Wooden Cooling Towers: Effective October 2, 1990, no person shall operate
a non-wooden cooling tower unless the hexavalent chromium levels do not exceed 0.15 milligrams/liter of circulating
- By December 12, 1990, any owner/operator of a cooling tower shall notify the District in writing regarding
the following information about the cooling tower.
Any owner/operator of a newly constructed cooling tower shall provide the District with the following information
at least ninety (90) days before the tower is operated:
- Owner/operator of the tower;
- Location of the tower;
- Cooling tower type and materials of construction;
- Whether hexavalent chromium-based treatment chemicals were ever used in the cooling tower;
- If hexavalent chromium based chemicals were previously used, the date they were discontinued;
- A description of the alternate treatment program chosen, as well as the circulating water monitoring plan.
d. Monitoring - General
- Effective October 2, 1990, any person subject to the requirements of b.2 or b.3 shall test the circulating
water in the cooling tower at least once every six (6) calendar months to determine the concentration of hexavalent
Testing may be discontinued when two consecutive required tests show hexavalent chromium concentrations less than
0.15 milligrams/liter of circulating water.
The District may require testing of the circulating water at any time if the District has reason to believe the
water may contain hexavalent chromium.
- Any person subject to the monitoring requirements in d.1 or e.1 below shall maintain records of the results
of all required tests of circulating water for two (2) years and provide them to the District upon request.
- Monitoring requirements may be waived by the District for any owner/operator of a cooling tower who demonstrates
to the District that the hexavalent chromium based treatment chemical has never been used in the cooling tower
or has not been used for a period of at least one (1) year prior to the appropriate compliance date.
e. Monitoring of Wooden Cooling Towers
- Any person subject to the requirements of b.2(B) shall test the circulating water at least once every calendar
month to determine the concentration of hexavalent chromium.
f. Determination of Hexavalent Chromium Content
- Samples of circulating water shall be analyzed for hexavalent chromium using American Public Health Association
Method 312 B or an equivalent method approved by the District.