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fax 802 459 3428
December 13, 1999

Liz Dickson
Vermont Agency of Natural Resources
Wastewater Management Division
103 South Main Street, Sewing Building
Waterbury, VT 05671-0405

RE: Notification of Non-Compliant Discharge -- Verpol Plant
Discharge Permit Number 3-0395

Dear Ms. Dickson:

In accordance with Part II Condition A.2. of OMYA's current NPDES discharge permit, this written communication follows up my telephone messages to Brian Kookier of your office and Environmental Enforcement Officer Gary Urich on December 8, 1999, and my related telephone conversation with you on December 9, all regarding an accidental, non-compliant water discharge at OMYA's Verpol plant which occurred on December 8. The following information reiterates our conversation and is intended to satisfy the written non-compliance notification requirements of the permit (thank you for granting an extension):

a. The incident involved the discharge of 'white water', containing suspended calcium carbonate solids, via the Verpol plant's permitted combined stormwater (#1-0843) and process water (#3-0395) discharge systems into the unnamed tributary of Smith Pond.

The Event: Arriving at the plant at about 7:00 a.m. on December 8, an employee noticed 'white water' flowing into the plant's stormwater detention basin via a stone-lined ditch which is part of the plant's stormwater collection/conveyance system. The stormwater detention basin's outlet valve was closed, allowing the white water to be retained within the basin. OMYA employees immediately took action to locate the source of the white water and stop its flow into the stormwater basin. The level of the white water in the basin rose but remained below an overflow grate near the top of the basin's berm. At about 10:00 a.m. we became aware that some white water had left the site and was apparent in Smith Pond. A check of the basin's outlet area revealed that, although the level of white water remained below the overflow grate, an indeterminate quantity of white water was being lost into the overflow manhole via a breach in its side near the top. As there was no way to prevent the leakage from exiting the stormwater system via the overflow manhole breach and entering the unnamed tributary, two pumps and tanker trucks were immediately brought to the site to pump out the storm water basin, returning the white water back to the closed-loop system. The leakage of white water from the stormwater basin was stopped at about 5:30 p.m. Contractors continued pumping out the basin until midnight and resumed pumping first thing in the morning, completing the job by late morning.

The Cause: On Monday December 6 the Verpol plant began a week-long shutdown. On December 7 all power and computer systems were taken off line. During the early morning hours of December 8, the computer and power systems were brought back on line. At approximately 5:00 a.m. that morning, plant maintenance staff began routine floor washing within the main plant. This procedure uses white water recycled from a normally closed-loop system. All recycled floor wash water collected in the main plant's sumps is pumped to a settling basin via a pipe which runs through the 'Cascade Mill' building located across a paved area and slightly uphill from the main plant. Within the Cascade Mill building the wash water pipe has an automated drain valve that allows for draining the continuing exterior length during periods of non-use to prevent freezing. During such events, the drained white water is collected in a sump within the Cascade Mill building for later pumping to the closed-loop system. As part of the shutdown, the power source for this drain valve was being rewired. Because this task was not complete when the plant wash water sump pumps were put back into operation, the drain valve did not close and wash water flowed into the Cascade Mill building sump, overflowing it and running into a stormwater catch basin outside the building. After the white water was noticed in the stone-lined ditch as described earlier, the drain valve was manually over-ridden and the flow was stopped.

b. A sample of the discharge was taken at approximately 1:00 p.m. and found to have the following characteristics: pH: 7.9, TSS: 318 mg/1, Turbidity: 804.6 NTU. The suspended solids consisted of finely ground calcium carbonate particles washed from the floor of the plant. Such material does not include any biocides as these are added to finished slurry products upon transfer to storage tanks which are situated apart from the main plant. At about 1:30 p.m. the unnamed stream was visually inspected by Neal Jordan about a hundred yards downstream of the discharge area (there is no discharge point per se, as the discharge flows through a small wetland after leaving OMYA's property and diffusely enters the stream) and again just above where it empties into Smith Pond. Due to the fineness of the calcium carbonate particles and the velocity of the stream flow, no deposition or sedimentation was observed on the stream bed. The stream exhibited a very slight greenish hue, characteristic of water containing dissolved and suspended calcium carbonate and attributable to calcite's refractive properties (the same reason water in marble quarries and the Caribbean is aqua-colored). Stream flow was relatively high due to significant precipitation in the region over the past month and it is believed there were no detrimental impacts on the stream's aquatic biota. In the shallow west end of Smith Pond where the stream empties into it, a slight hint of white (assumed to be settled calcium carbonate solids) could be seen against the dark background of the heavily-organic pond bottom. Considering that finely ground calcium carbonate, including OMYA product, is directly applied to lakes and ponds in various parts of the U.S. to counter the effects of acid precipitation, it is believed there will be no detrimental impacts on the pond's aquatic biota.

c. The period of non-compliance was estimated to have begun sometime after 5:00 a.m. on December 8 and continued until about 5:30 p.m. on the same day.

d. The steps taken to reduce and eliminate the non-complying discharge are described as part of (a) above.

e. As a result of this event, permissive contacts will be installed in the control logic for all sump pumps within the wash water recycle system, preventing their startup if the drain valve in the Cascade Mill building is not closed. The breach in the stormwater retention pond's overflow manhole will not be repaired at this time for several reasons. First, it is near the top of the manhole and doesn't affect the normal function of the stormwater basin, although it does slightly reduce the storage capacity of the basin when the outlet valve is closed in emergency situations such as was just experienced. Second, per the stormwater permit amendment application filed with your Division, OMYA intends to expand and completely reconstruct the basin in the near future as part of a facility expansion. At that time action will be taken to repair or replace the manhole.

If you have questions or require additional information, feel free to call me at (802) 770-7261.

Sincerely,

Neal Jordan
Manager of Environmental & Regulatory Affairs

cc. L. Gaudreau
S. Thompson