ML24263A113
| ML24263A113 | |
| Person / Time | |
|---|---|
| Site: | Triso-X |
| Issue date: | 09/19/2024 |
| From: | Triso-X |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML24263A111 | List: |
| References | |
| TX0-REG-LTR-0042 | |
| Download: ML24263A113 (1) | |
Text
Enclosure - Additional Information for the Responses to Hydrology RAI-3 and RAI-4 Page 1 of 2 RAI-3 Volumetric Runoff Rate:
Additional Information for the TRISO-X Response to RAI-3:
The post-developed volumetric values in Table 1 of the 11/8/2023 TRISO-X response to RAI-3 are only for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of a storm, and do not account for the additional volume temporarily retained in the pond. The retained volume will eventually be released later via a valved pipe. The intent of the design is to not overwhelm the sinkhole area by limiting the post-developed volume to be less than the pre-developed volume within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of an event. After the subsequent release by opening the valve, the combined total volume of post-developed flow will exceed the pre-developed volume, which is allowed by state and local regulations.
Evaluating runoff and basin performance on an annual basis is not a regulatory requirement that is specified by the City of Oak Ridge or Tennessee Department of Environment and Conservation (TDEC). The stormwater management system was designed to comply with water quality requirements to manage the first inch of runoff, as well as managing post-developed basin discharges for various events up to a 100-year, 24-hour rainfall event.
License Changes:
None.
Enclosure - Additional Information for the Responses to Hydrology RAI-3 and RAI-4 Page 2 of 2 RAI-4 Hydrology - Runoff Water Quality:
Additional Information for the TRISO-X Response to RAI-4:
Stormwater discharges from all onsite detention basins will be permitted by TDEC under the NPDES Stormwater Multi Sector permitting program for discharges from industrial facilities. As part of the permit program, TDEC will define minimum general site maintenance and housekeeping practices and will establish water quality basin discharge outfall requirements that will consist of numerical limitations. The expected water quality pollutant parameters are total suspended solids, oil and grease, pH, biochemical oxygen demand, chemical oxygen demand, and ammonia as nitrogen, though the TDEC is responsible for selecting the final parameters. TDEC will also select the reporting frequency. This permit will establish and enforce water quality requirements for discharges leaving the site.
License Changes:
Changes to License Chapter 1, Section 1.1.1.3, Hydrology, are shown below in red.
Stormwater discharges from all onsite detention basins are permitted by the state of Tennessee under the NPDES Stormwater Multi Sector permitting program for discharges from industrial facilities. As part of the permit program, the state of Tennessee defines minimum general site maintenance and housekeeping practices and establishes water quality basin discharge outfall requirements for discharges leaving the site.
Stormwater collected during normal operations would contain pollutants typically associated with runoff collected from public streets and parking areas. Small amounts of oil and grease, metals, and other constituents associated with vehicular activity are expected to be carried in runoff from the roads and parking areas within the site. Water quality of stormwater runoff is maintained through the use of detention ponds. Stormwater generated is collected in peripheral ditches and the interior stormwater system before being discharged to the stormwater detention basin. The detention basin is divided into two separate sections, the forebay section and the main detention basin section. The forebay section collects the runoff from the entire permanent site areas and provides storage for a portion of the runoff for water quality treatment that allows sediment and site generated total suspended solids (TSS) to settle at the bottom of the forebay. The main detention basin section receives stormwater overflow from the forebay section and provides additional storage for the remaining stormwater volume to allow for TSS to settle at the bottom of the detention basin section. Treated water effluent is discharged via the valved NW Outlet pipe into an existing drainage swale that traverses at least 400 feet through a vegetated path to an observed sinkhole feature in the adjacent parcel. The intent of the detention basin design is not to overwhelm the sinkhole area by limiting the post-developed volume to less than the pre-developed volume within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of a rainfall event. As such, all constituents within stormwater runoff are expected to be at or below the allowable limits set by TDECthe state of Tennessee. Any stormwater runoff from electrical transformers, mechanical yards and above ground tank containments is collected separately and disposed of after adequate treatment.