Low-Flow Groundwater Sampling

Low-Flow Groundwater Sampling Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software June 2008 Overview This document provides a description of low-flow sampling techniques, a summary of federal low-flow guidance documents, and outlines the operation of a TROLL 9500 instrument using Flow-Sense software. What is low-flow groundwater sampling? Low-flow groundwater sampling is an increasingly accepted method of collecting groundwater samples with a strict set of guidelines to ensure consistent sample representation and quality. Groundwater is extracted from the well at a very low rate (<500 ml/min) so that drawdown of the water level is minimized. Water samples from the more hydrogeologically conductive areas of the aquifer around the well screen are monitored with water quality instruments for stability to indicate the change from stagnant well water to representative formation water. After the water quality parameters stabilize, a sample of formation water can be taken with a minimal amount of geochemical disruption to the sample. Why use low-flow groundwater sampling methods and a TROLL 9500 instrument? Meet sampling plan or scope of work requirements. Improve sample quality. Improve sample representativeness. Reduce wastewater created by large volumes of sample purging. Reduce field time by setting up sampling events with Flow-Sense software in the office. Reduce field time with automated data collection and stabilization of water quality parameters. Eliminate errors created by manual field recording and manual data transcription. Create more detailed sampling summaries, records, and reports. Save time and money with quick and easy digital report formats. Produce professional reports that can be inserted directly into your project deliverables. Provide a complete calibration history of the sampling event to ensure sample validation. Create a digital sampling record that can be easily replicated by other technicians. Save time and money by digitally organizing sampling events.

Low-flow federal guidance summary The following points summarize federal guidelines that dictate the requirements of a low-flow groundwater sampling event. Summary 1. Low-flow refers to the velocity that is imparted during pumping to the formation pore water adjacent to the well screen, not necessarily the flow rate of water discharged by the pump. 2. Low-flow purging can be used on any well capable of being pumped at a constant rate of 1.0 L/min or less without continual drawdown of the water level in the well. 3. A typical flow rate from a pump during low-flow purging is approximately 0.1 to 0.5 L/min. 4. Continuous discharge pumps with variable flow rates are preferred (Grundfos, Fultz, Nomad, Keck, Proactive). Cyclic discharge is also acceptable (bladder pumps). Dedicated pumps are preferred. Grab sampling devices such as bailers, Kemmerer samplers, and inertial-lift devices cannot be used. Peristaltic pumps are discouraged because of loss of VOCs, degassing, and ph and oxidation reduction potential (ORP) changes. 5. You must have a water level indicator for initial readings and drawdown monitoring with accuracy (±0.01 ft. /3 mm). 6. Flow cells are preferred for monitoring, especially for dissolved oxygen (DO) and ORP readings, which will be altered if exposed to atmosphere. 7. Calibration of multi-parameter equipment is required once a day, with periodic checks. 8. The pump should be placed at the mid-point of the submerged well screen. 9. Drawdown in any well should not exceed 0.1 m/0.33 ft./4 in. or 25% of the distance from the top of the well screen to the pump intake. 10. Stabilization parameters: a. ph: ±0.2 ph units b. Conductivity: ±3% of reading c. DO: ±10% of reading or 0.2 mg/l, whichever is greater d. ORP: ±20 mv e. Turbidity: ±10% of the prior reading or ±1.0 NTU, whichever is greater (not always required) 11. Flow cell sample rate measurement frequency should be based on the time required to completely evacuate one volume of the flow cell, associated tubing and pump volume. 12. Stabilization is reached when three consecutive readings meet the stabilization criterion listed above when sampled at the established rate. 13. Field reporting requirements: a. Equipment calibration report b. Site specific data (project name, site, well number, well depth, well diameter, screen length, casing type, pump type, tubing type) c. Initial water level d. Pump placement/type (relative to well screen and static water level) e. Final pumping rate f. Final stabilized drawdown g. Water quality measurements (date, time, temperature, ph, ORP, conductivity, DO, turbidity) Required field equipment Graduated cylinder Overflow 5-gallon buckets (2) Pump and tubing Sample jars TROLL 9500 low-flow sampling system Visqueen and other PPE Water level indicator Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 2

TROLL 9500 instrument connection and calibration 1. Connect to the TROLL 9500. Open Win-Situ 4. 2. The Connection Wizard will start. Choose a Direct connection to One device. 3. Choose Com 1 for a serial port connection. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 3

4. Choose a Baud Rate of 19200. 5. Choose a name for your connection or use the default ( COM1-19200). Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 4

6. The software should automatically connect to the device and list available parameters. 5 7. 8. Check your battery capacity and confirm that at least 50% of battery capacity remains. If you want to change batteries, insert two new D cell batteries now. Synchronize the TROLL 9500 clock with the clock on your computer. Make sure the computer clock is accurate. Click Edit. 5 Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 5

9. Select Clock. Click Next >. 10. Select Synchronize With Computer Clock. Click Finish. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 6

11. To calibrate, highlight Parameters. Click Quick Cal. 12. Choose the parameters to calibrate. Click Next >. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 7

13. Fill the Cal Cup with Quick Cal solution. Click Run. Wait for ph, conductivity, and DO to automatically stabilize. (It may take a few minutes.) 14. Choose Use Vented Cable for your barometric channel. Click OK. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 8

15. Take the TROLL 9500 instrument and invert it so that the sensors point up. Unscrew the black end cap above the sensors. Empty out enough Quick Cal solution so that the DO sensor membrane is exposed to air. Replace the black cap, but leave the hole in the threads open to the atmosphere. Click Run. 16. When the calibration is complete, the software will automatically generate digital calibration reports and save them on your hard drive. Click Yes to view them. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 9

17. The calibration report is generated with the following data: 18. The TROLL 9500 instrument will reset. The Win-Situ 4 dashboard will reappear. Highlight the Flow-Sense Wizard. Click Start. 9500 Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 10

19. Click Verify Units to make sure you are collecting data in the units desired for your project and reporting requirements. Highlight each parameter and select the units you want. Click OK. 20. The Flow-Sense software will open. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 11

21. Collect all the well sampling logs, sheets and information from previous sampling events. Enter all the sampling project information in the Flow-Sense Wizard sequence. First enter the project and site information. Click Next >. 22. Enter well information. Click Next >. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 12

23. Enter pump information. Click Next >. 24. Enter pumping rate and drawdown information. Click Next>. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 13

25. Select channels and enter the stabilization criteria. This information should be in your sampling plan, but are listed below for reference. You can enter the American Society for Testing and Materials (ASTM) or USEPA ranges here. To use a percentage instead of a range, enter a range and a percentage, and the program will default to the percentage. Click on Notes to see or record any information on the sampling event. Turbidity is not listed in this example, but the turbidity stabilization range should be ±1.0 NTU or 10%. Do not click Start until the flow and drawdown values have stabilized. When the values are stable, click Start. 26. Click < Back at any time to change your settings. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 14

27. After the stabilization sequence begins, the information shown in the following screens is being collected. The left column records the latest water quality parameter reading. The right column lists the stabilization targets. The center column lists the current value. 28. The software needs at least three water quality parameter readings to run a 3-point running average and to calculate the stabilization values. For the sample set (A, B, C), [(Max-Min)/A] X 100 = Running Average. 29. This screen also includes the start time of the sampling event, the number of water quality readings collected so far, the total elapsed sampling time, and time left until the next readings are recorded. 30. When all the values in the center column are less than the corresponding values in the right column, stabilization has occurred. Click Accept and collect the groundwater sample. Click Graph to present the stabilization readings graphically. The graph depicts movement away from complete stabilization. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 15

31. After accepting the stabilization values, a Low Flow Notes window will appear. Enter any extra information about the sampling event here. The 32. Save As screen will appear, and the sampling event will be saved automatically (by project, site, well ID, and date). Rename the file as desired. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 16

33. The data file is automatically logged under the Flow-Sense data folder on the Win-Situ 4 software, in alphabetical or chronological order. 34. To print the groundwater data collection record for a specific well and date, simply highlight the appropriate sampling event. Click File, Export To Excel. 35. The data is converted into Excel, but In-Situ Inc. has developed a formatted template that will organize all your data into an integrated data sheet. Just right click on the data spreadsheet tab in the lower left corner of the screen and click Insert. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 17

36. A window will that displays available Excel templates. Double-click the InSituLowFlow template to create the data sheet. You may have to locate the file InSituLowFlow.xlt in the templates directory located in the Win Situ 4 software installation directory. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 18

37. A formatted data sheet is created. It can be pasted or loaded into any sampling report and customized with your company s logo. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 19

38. Open the Flow-Sense data folder and highlight the desired well to sample the well again on another date. All the site data entered for this sampling event will be available for future use. Click Start From Template. References 1. ASTM Guideline D6771-02. July 2002. Standard Practice for Low-Flow Purging and Sampling for Wells and Devices Used for Ground-Water Quality Investigations. 2. Puls, R. W. and M.J. Barcelona. April 1996. Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures. U.S. Environmental Protection Agency, Office of Research and Development. Publication: EPA/540/S-95/504. http://www.epa.gov/ahaazvuc/download/issue/lwflw2a.pdf 3. U.S. Environmental Protection Agency, Region 1. 30 July 1996. Low Stress (low flow) Purging and Sampling Procedure for the Collection of Ground Water Samples from Monitoring Wells. SOP #: GW 0001. http://www.epa. gov/region1/measure/well/lowflow8.pdf 4. Yeskis, D. and B. Zavala. May 2002. Ground-Water Sampling Guidelines for Superfund and RCRA Project Managers. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response. Publication: EPA 542-S-02-001. http://www.epa.gov/tio/tsp/download/gw_sampling_guide.pdf These guidelines are federal and regional suggestions. Review with your local regulator. For more information contact In-Situ Inc. 221 East Lincoln Avenue Fort Collins, CO 80524 1-800-446-7488 (toll-free in U.S. & Canada 1-970-498-1500 (international & domestic) Internet: www.in-situ.com In-Situ, the In-Situ logo, and are trademarks or registered trademarks of In-Situ Inc. 2008, In-Situ Inc., Fort Collins, CO USA. Teflon is a registered trademark of E.I. du Pont de Nemours and Company USA and other countries. Excel is a registered trademark of Microsoft Corporation. Using In-Situ Inc. TROLL 9500 Water Quality Instrument and Flow-Sense Software Page 20