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OMYA Inc.
61Main Street
Proctor, Vermont 05765
802 459 3311

April 5, 2000

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 conversations and/or voice mail messages to you on March 16, 20, 21 and 31, the plant visit by Environmental Enforcement Officer Gary Urich on March 17, and my telephone conversation with hirn on March 23, all regarding the unintentional discharge of process water from OMYA's Verpol plant. The following information reiterates the information previously supplied verbally and is intended to satisfy the written non-compliance notification requirements of the permit:

a. The Event/Cause: The incident involved the discharge of 'white water', containing suspended calcium carbonate solids, leaving the Verpol plant site at the same point as the permitted combined stormwater (#1-0843) and process water (#3-0395) discharge systems into the unnamed tributary of Smith Pond, continuing to Otter Creek.

On February 22, 2000 a portion of the berm making up part of a flotation wastewater solids settling basin failed, allowing flotation wastewater to flood the adjacent 'dogleg' portion of the quarry used for settling solids from railcar and plant floor wash water. To reduce the water level in the dogleg area to a functional level, some of the excess water was pumped over to the OMYA East plant quarry for temporary storage until it could be recycled back into the plant process water system. The failed berm was repaired, but unfortunately failed again on March 2, again flooding the dogleg quarry, and again requiring additional water to be pumped over to the OMYA East quarry over the course of several days for temporary storage.

On March 8 OMYA employees first discovered white water escaping from the East plant quarry and surfacing at the base of a rock fill slope between the quarry and the Verpol plant's finished product slurry storage tank complex which is at a lower elevation. At that tirne, as much water as possible was already being returned from the East plant quarry to the Verpol process, and installation of a larger pump to speed the process was under way. The escaping white water followed a course of ditches and culverts paralleling a dirt road on the east side of the Verpol site used by construction contractors to access their parking area. Ultimately it flowed into the wet area on OMYA property which also receives the flow from the site's stormwater detention basin just prior to leaving the site via the culvert under Whipple Hollow Road. The plant engineer was notified of the loss of East quarry water and was instructed to takes steps to remedy the problem.

Unfortunately I made the incorrect assumption that the problem could be remedied quickly, when in fact the only solution was to draw down the level in the East plant quarry below the level where the water was escaping. Also unfortunately, due to our internal miscommunication, neither the plant engineer nor I notified your office of the situation, and the plant engineer didn't inform the plant manager of the water loss. It wasn't until March 16 that the plant manager learned of the problem and he notified me of its ongoing nature. At that time I immediately called you to inform you of the situation.

b. The suspended solids in the discharge water consist of finely ground calcium carbonate particles. A sample of the discharge was taken at the point it leaves the site at approximately 1:00 p.m. on March 16 and found to have the following characteristics: pH: 7.9, TSS: 73.7 mg/1, Turbidity: 183.0 NTU. At about 1:30 p.m. on the same day, the unnamed tributary of Smith Pond was sampled at the culvert where it passes under Fire Hill Road, approximately several hundred feet downstream of where the discharge enters the tributary. That sample was found to have the following characteristics: pH: 7.8, TSS: 4.7 mg/l, Turbidity: 5.9 NTU. No upstream 'background' sample was taken from the tributary at that time.

Another sample of the discharge was taken at the point it leaves the site at approximately 1:00 p.m. on March 20 and found to have the following characteristics: pH: 7.9, TSS: 8.9 mg/l, Turbidity: 12.9 NTU. At about 1:30 p.m. on the same day the tributary was sampled again at the same location as the first sample. That sample was found to have the following characteristics: pH: 7.8, TSS: 1.9 mg/l, Turbidity: 2.0 NTU. No upstream 'background' sample was taken at that time.

A third sample of the discharge was taken at the point it leaves the site at approximately 1:00 p.m. on March 24 and found to have the following characteristics: pH: 7.9, TSS: 3.1 mg/l, Turbidity: 3.9 NTU. At about 1:30 p.m. on the same day the unnamed tributary was sampled at a location just upstream of where the discharge enters the tributary. That 'background' sample was found to have the following characteristics: pH: 7.8, TSS: 3.9 mg/1, Turbidity: 1.6 NTU.

Due to the spring time of year, volumetric flow in the tributary during each sampling period w as relatively high. Visual observation along several hundred feet of its length found no deposition or sedimentation, as would be expected due to the fineness of the calcium carbonate particles and the stream velocity. Visual observation of the west end of Smith Pond where the tributary empties into it found no evidence of settled calcium carbonate solids, although a very slight greenish hue, characteristic of water containing dissolved and suspended calcium carbonate and attributable to calcite's refractive properties, could be seen in Smith Pond. Considering the TSS and Turbidity levels measured in the unnamed tributary, and considering that finely ground calcium carbonate is applied directly 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 aquatic biota of the unnamed tributary, Smith Pond, or Otter Creek.

c. The period of non-compliance is estimated to have begun on or about March 4, after excess water was pumped over from the Verpol dogleg quarry over the course of several days beginning on March 2 (although the non-compliance was not actually discovered until March 8). Based on the March 20 and 24 sampling results, non-compliance with current permitted effluent limits continued until approximately March 19 for TSS and March 21 for Turbidity. (We must note that the NPDES permit renewal application filed with the Agency in December, 1998. which has not yet been acted upon, requested higher effluent limits based on the classification of the receiving water. If granted as requested, the period of non-compliance would have been shorter.)

d. The steps taken to reduce and eliminate the non-complying discharge are described as part of (a) above. In summary, corrective actions included repair of the failed berm which resulted in the flooding of the dogleg portion of the quarry, and the lowering of the OMYA East quarry level as rapidly as possible by pumping the excess water back into the Verpol system at the fastest rate allowed by process limitations.

e. With the second berm repair, an evaluation determined that additional measures should be taken to prevent future failures. Poured concrete was used to better secure the outlet culvert to a receiving manhole where the failure was believed to have originated.

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

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