Field Sampling Plan

This section contains the data collection design and activities for the continued groundwater quality assessment of Waste Management Area (WMA) TX-TY. A description of each task is provided.

Additional discussion and background information associated with the tasks are provided in the main body of the plan.

A.1.1 Task Description

The tasks described are a subpart of the Groundwater Performance Assessment Project (groundwater project) managed for the U.S. Department of Energy (DOE) by Pacific Northwest National Laboratory (PNNL). Project management and organizational interfaces and procedures are described in Section A.2.

A.1.1.1 Determine Groundwater Flow Direction

Water Level Measurements. The depth to water will be measured quarterly in all wells at the time of sampling. These measurements are an indicator of conditions in the well at the time of sampling.

However, because these measurements are generally taken over a time period of a few days, they are subject to differential barometric effects due to diurnal and storm-related changes in atmospheric pressure. Therefore, depth-to-water measurements taken at the time of sampling and used to construct water table maps will be corrected for changes in atmospheric pressure if substantial pressure changes occurred over the time period of data collection.

Additionally, depth to water is measured annually in March to construct the annual Hanford Site water-table map. At WMA TX-TY, these March measurements are generally taken in all wells within a few hours time. Thus, the March measurements are not as susceptible to barometric effects as are the quarterly measurements.

A.1.1.2 Well Drilling and Testing

Currently, no new wells are planned for WMA TX-TY. If site conditions change such that new wells are deemed necessary, new wells will be recommended to the well drilling DQO to be prioritized with other Hanford Site well requirements. If new wells will be constructed as a result of the DQO

prioritization, appropriate sampling and analysis activities during drilling, geophysical logging activities, and aquifer testing will be described and documented in a separate sampling and analysis plan for drilling new wells.

A.1.1.3 Quarterly Groundwater Sampling and Analysis

Sampling in the WMA TX-TY well network identified for this assessment is an ongoing activity. A quarterly frequency is required by 40 CFR 265.93(d)(7)(i) by reference of WAC 173-303-400(3) for Resource Conservation and Recovery Act (RCRA)-regulated constituents. This frequency also is adopted for some constituents of interest and groundwater quality indicators. Other constituents of interest are sampled semi-annually or annually. These frequencies are judged to be adequate for assessing the rate and extent of contaminant migration in the groundwater, and contaminant concentrations for the WMA TX-TY based on the time response of previous contaminant occurrences in monitoring wells and a relatively slow groundwater flow rate in the north central part of 200 West Area.

The selection of the constituents to be monitored was discussed in Section 3.4 of the main body of this assessment plan. The wells to be monitored and the monitoring schedule are shown in Table A.1.

A.1.1.4 Special Isotopic Studies

Special isotopic investigations are planned under the scope of the Science and Technology Project and in conjunction with Lawrence Berkeley National Laboratory to try and distinguish the source or sources for contamination downgradient of WMA TX-TY. The WMA TX-TY groundwater assessment will take full advantage of any results from the special isotope studies as is appropriate for the assessment.

The isotopic systems to be investigated include:

• Ruthenium-101, -102, and -104.

• Strontium-87 and strontium-86.

• δ¹⁵N and δ¹⁸O in nitrate.

• Uranium isotopes.

• Stable chromium isotopes.

Several sample sets will be used for these studies. Depth-discrete samples of pumped groundwater from the new well 299-W14-11 were collected for isotopic analyses when the well was drilled.

Supplementing these samples are aliquots of groundwater samples collected during routine, quarterly sampling events between 1999 and 2003. Additional samples can be collected if needed.

A.1.1.7 Project Planning and Direction

This task involves ensuring that tasks are on schedule, that resources and personnel will be available when they are needed, and developing workarounds when schedule conflicts occur. Preparation of the assessment plan (this document), preparation of further assessment work plans that may be necessary to implement individual tasks, and any subsequent revisions of the assessment plan are also included in this task. Attending meetings with stakeholders and the integration project team leads to ensure coordination

A.3

Table A.1. Sampling Schedule for Groundwater Monitoring at Waste Management Area TX-TY

W ell Name Purpose(h) W AC Compliant W ater Level^{(f )}

Chromium (total, filtered) Nitrate (anions) Technetium-99 Tritium Gamma Scan(a) Gross Beta(b) Gross Alpha(c) Metals, filtered (d) Anions(e) Alkalinity pH(f) Specific Conductance(f) Turbidity(f) Temperature(f) Dissolved Oxygen(f) Redox(f) Iodine-1129

Sr-90

(a) Gamma Scan - Analytes include but are not limited to cobalt-60, cesium-137, europium-152, -154.

(b) Gross Beta - Indicator paramenter for strontium-90 and other beta emiters (c) Gross Alpha - Indicator paramenter for uranium isotopes and other alpha emitters

(d) Metals - Analytes include but are not limited to alumium, bismuth, chromium, manganese, sodium, magnesium, potassium, and calcium (e) Anions - Analytes include but are not limited to nitrite, nitrate, chloride, sulfate, and fluoride

(f) Field Measurement

(g) Dash indicates analysis is not performed for the indicated well.

(h) Mid-field wells are wells located downgradient of the downgradient wells and used to determine lateral extent of contamination.

(i) W ater levels are not taken in extraction wells.

Q = Quarterly

SA = Semi-annual

A = Annual

RCRA Constituents of

Concern Constituents of Interest and Supporting Groundwater Quality Constituents

Footnotes

Codes