ML090540558

Memorandum - Synopsis of Long Term Monitoring Plan Bases

ML090540558
Person / Time
Site:	Indian Point
Issue date:	01/25/2008
From:	Barvenik M GZA GeoEnvironmental
To:	Donahue P Entergy Nuclear Northeast, NRC Region 1
References
Download: ML090540558 (9)

Text

MEMORANDUM TO: Mr. Patrick Donahue - Entergy Nuclear Northeast FROM: Matthew Barvenik - GZA REVIEWED BY: Michael Powers - GZA DATE: January 25, 2008 RE: Memorandum - Synopsis of Long Term Monitoring Plan Bases As requested, the following provides a synopsis of the bases' which underpin the Long Term Monitoring Plan (LTMP) currently being implemented at the Indian Point Energy center (IPEC)

Site. These bases were derived from the Conceptual Site Model (CSM) 2 which was developed and refined during over two years of comprehensive hydrogeologic investigations completed at the Site, and as described in the Final Report3. During the progress of the investigations4, Entergy also conducted regular and frequent meetings where GZA presented existing data and exchanged concepts with representatives of the United States Nuclear Regulatory Commission New York (NRC), the United States Geological Survey (USGS), and the New York State Department of Two Pennsylvania Plaza Environmental Conservation (NYSDEC). This interchange of concepts, as well as information Suite 1860 NewYork, NY 10121 garnered during stakeholder and public meetings, was used to help set the course of the then Phone: 212-594-8140 ongoing investigations. Based on the outcome of these investigations and the resulting CSM, Fax: 212-279-8180 GZA has formulated and recommended to Entergy a LTMP design, which Entergy has adopted.

Connecticut 27 Naek Road The overall LTMP design was formulated to satisfy four primary objectives:

Vernon, CT 06066 Phone: 860-875-7655 Fax: 860-872-2416 1. Monitor groundwater to both detect and characterize current and potential future off-Site Massachusetts groundwater contaminant migration to the Hudson River from abnonnal radionuclide One Edgewater Duive releases of liquid effluents, so as to allow computation of potential radiation dose to the Norwood, MA 02062 Phone: 781-278-3700 public; Fax: 781-278-5701 2. Monitor groundwater along the southem property boundary to confirm that contaminated groundwater is not migrating off of the property in that direction; 1It is noted that the sampling installations referenced herein are a compilation of the LTMP as well as the 80-1 0/Effluents Programs.

2 GZA used the Observational Method (see Section 2.0 of the Final Report) to guide our investigations, identify and fill data gaps, assess the reasonableness of findings, and develop parameters controlling contaminant transport, and ultimately to formulate the CSM. This is inherently an iterative process and, as studies progressed, the CSM was refined to better fit observed conditions.

With completion of the investigations, the CSM was consistent with both the Site-specific project data and published data for the area (see Section 3.0 of the Final Report).

3 Final Hydrogeologic Investigation Report, GZA GeoEnvironmental, Inc; January 7, 2008 4 The investigations included approximately 60 shallow and deep, overburden and bedrock, single and multi-level instrument installations, as well as footing drain and man hole sampling points, which encompass approximately 150 individual sampling intervals. A subset of this overall monitoring installation network, as summarized on Figure LTMP 1, is used to provide the data for the LTMP. The level of redundancy designed into the LTM network anticipates and allows for the loss of a number of monitoring zones without significant impact to the adequacy of the monitoring system.

Indian Point Energy Center January 25, 2008 File No. 17869.10 Page 2

3. Monitor groundwater proximate to Systems, Structures and Components (SSCs) which exhibit a credible probability of resulting in a visually undetected release of radionuclides to the subsurface carrying an activity level of significance; and

4. Monitor the groundwater plumes identified on-Site to demonstrate overall reductions in total activity over time as is consistent with the requirements of Monitored Natural Attenuation (MNA)5 , the selected remediation for the IPEC Site.

These objectives are consistent with and fully encompass the guidance provided in the NEI Groundwater Protection Initiative.

To address objectives 1) and 2) above, groundwater monitoring installations have specifically been installed, and are currently being monitored, to both detect and characterize current and potential future off-Site groundwater contaminant migration to the river, both directly and through the Discharge Canal 6 . Additional installations have also been installed specifically for monitoring of the southern Site property boundary7 .

The IPEC Site was subdivided into six individual groundwater flow zones, with each including a separate shallow and deep flow zone. The instrument installations specifically targeted to monitor these individual zones, and the associated discharge pathways to -the Hudson River, are outlined in the attached Dose Computation Monitoring Installation Matrix. As shown on Figure LTMP-1 (included herewith), the multi-level sampling network is concentrated in the Unit 2 and Unit 1 areas given that this is where contaminant concentrations are by far the highests.

To address objective 3) above, monitoring installations have also been installed downgradient 9 of, and in close proximity to, both identified and potential critical Structures, Systems and Components (SSCs). The specific monitoring installations which target locations where identified and credible potential future sources of leakage might exist' 0 are outlined on the attached PotentialSource Monitoring InstallationMatrix. These installations, in concert with specific footing drain monitoring, provide earlier detection of potential future leaks associated with the power generating units than would be possible with boundary wells alone.

To address objective 4) above, monitoring installations have been strategically placed to monitor the behavior of the plumes identified on the Site (see Figure LTMP- I). Because of the nature and age of the releases; groundwater contaminant migration rates, and interdictions by Entergy to eliminate/control releases, the groundwater contaminant plumes have reached their maximum 5The selection of MNA as the remediation for the Site is more fully discussed in Section 11.0 of the Final Report.

6 The methods used to monitor and compute the magnitude of radiological release to the river, and justification for their selection, are more fully discussed in Section 6.0 of the Final Report.

7 Selection of appropriate installations to monitor the southern property boundary in light of groundwater elevation transients are more fldly discussed in Section 6.6 of the Final Report.

8 The monitoring installations located downgradient of Unit 3 are judged sufficient for monitoring and computations in this area given the low contaminant concentrations measured, even in the typically more contaminated shallow flow regime.

9 Groundwater flow contours are provided on Figure LTP.-1, attached herewith, to demonstrate the groundwater flow 0athway relationships between the potential source and the monitoring installation locations.

The identification of contaminant sources and release mechanisms on the Site is more fully discussed in Section 8.0 of the Final Report.

Indian Point Energy Center January 25, 2008 File No_ 17869_ 10 Page 3 spatial extent and should now decrease over time". The specific instrument installations which target the monitoring of these ,plumes are summarized on the attached Plume Attenuation Monitoring Installation Matrix. This monitoring is intended to verify that reductions are occurring in an anticipated manner.

Groundwater testing is performed quarterly on the majority of the LTMP installations, with G.

some sampled semi-annually and the rest remaining on standby to provide added detail, if required. The sampling frequencies, targeted analysis suites, radionuclide analyses MDCs, and investigation trigger levels and associated action procedures are provided in the Radiological Ground Water Monitoring Procedures12. During long term monitoring, GZA anticipates that contaminant concentrations in individual monitoring wells will fluctuate over time (increasing at times as well as decreasing, as potentially related to precipitation events), and that a future short term increase in concentrations does not, in and of itself, indicate a new leak. In addition, it is also expected that some areas within the plumes~will exhibit faster decay rates than others. Both behaviors are commonly observed throughout the industry with groundwater contamination sampling and analyses, and therefore, conclusions pursuant to plume behavior and the potential for new leaks must be evaluated in the context of all of the Site-wide monitoring data. Overall, however, GZA believes that the continuing monitoring will demonstrate decreasing long term trends in groundwater contaminant concentrations over time given the source interdictions completed by Entergy.

We appreciate the opportunity to be of service to you. Should you have any questions or comments, please feel free to.contact me (781) 278-3805.

Very truly yours, GZA GEOENVIRONMENTAL, INC.

Matthew J. Barvenik, LSP Michael Powers, PE Senior Principal Consultant/Reviewer Attachments: Figure LTMP -1 Potential Dose Computation Monitoring Installation Matrix Potential Source Monitoring Installation Matrix Plume Attenuation Monitoring Installation Matrix.

The temporal and spatial behavior of the plumes identified on the IPEC site are more fully discussed in Section 9.0 of the Final Report.

12 Radiological Ground Water Monitoring Program; IPEC Site Management Manual; IP-SMM CY- 110; January 11, 2008.

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'Additional Long Term Monitoring Plan information isprovided inthe Hydrogeologic, Site Investigation Report; GZA GecEnvironmental, Inc.;

January 7. 2008.

2Itisnoted that the sampling installations referenced herein are a compilation of the LTMP as well as the 80-10/lEffluents Programs.

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Potential Source Monitoring Installation Matrix Potential Source Monitoring Installation Matrix NOTES:

Potential Sources are Systems, Structures or Components which exhibit a credible probability of resulting in a visually undetected release of radionuclides to the subsurface with an activity of significance.

Additional Long Term Monitoring Plan information is provided in the Hydrogeologic Site Investigation Report; GZA GeoEnvironmental.

Inc.; January 7, 2008.

Primary Monitoring Installations are those generally closest to a potential source and most likely to-initially detect a release. 4 Secondary Monitoring Installations are those that are located futher down or cross gradient from a potential source.

Itis noted that the sampling installations referenced herein are a compilation of the LTMP as well as the 80-1 0/Effluents Programs.

Plume Attenuation Monitoring Installation Matrix

'Direct Groundwater Flow designates that portion of the Unit 2 Tritium release that enters the groundwater below the IP2-SFP and then n*avesdowngradient to the West Unsaturated zone flow designates those portions of the Trttium release that first migrate above the water table along fracture orientations in directions other than that of the groundwater flow prior to entering the groundwater, with migration along groundwater flow oaths, thereafter.

3Additional Long Term Monitoring Plan information is provided in the Hydrogeologic Site Investigation Report; GZA GeoEnvironmental, Inc.; January 7, 2008.

4 It is noted that the sampling Installations referenced herein are a compilation of the LTMP as well as the 80-10/Effluents Programs.