U.S. Department of the Interior USGS Fact Sheet FS 122-98

U.S. Geological Survey November 1998

Technology Transfer Opportunities: Automated Ground-Water Monitoring, A

Proven Technology

Introduction

The U.S. Geological Survey (USGS) has developed and tested

an automated ground-water monitoring system that measures

and records values of selected water-quality properties and

constituents using protocols approved for manual sampling.

Prototypes using the automated process have demonstrated the

ability to increase the quantity and quality of data collected

and have shown the potential for reducing labor and material

costs for ground-water quality data collection. Automated

ground-water monitoring systems can be used to monitor

known or potential contaminant sites, such as near landfills,

underground storage tanks, or other facilities where potential

contaminants are stored, to serve as early warning systems

monitoring ground-water quality near public water-supply

wells, and for ground-water quality research.

About the Invention

The automated monitoring process is designed to: follow

proven ground-water sampling protocols, provide reliable data

indicating ground-water quality, regulate its own performance

through system feedback, and communicate data and system

performance through remote communications. A record of

relatively frequent measurements of water-quality properties

and(or) constituents collected at a monitoring site can indicate

when ground-water quality is changing and can provide a

context for the interpretation of laboratory data from periodic

discrete samples. The process is designed to monitor and

record water-quality properties and constituents in water

pumped from the well or multilevel sampler until purge

criteria have been met. The automated monitoring process

utilizes feedback to monitor the status of the system and to

record and communicate problems if an error is detected. The

ability of the automated system to respond to or initiate

communications allows human operators to check the system

or monitor ground-water quality from a remote site without

costly field visits.

Proven Technology

The U.S. Geological Survey has been operating a series of

prototypes to develop and test the automated ground-water

monitoring technology since 1995. The first prototype

demonstrated that the process was feasible for monitoring in

standard wells. The second prototype demonstrated that the

process was feasible for monitoring several ports of a

multilevel sampler. The third prototype was tested in 1996,

and sufficient quality assurance/quality control data were

collected to demonstrate that the data obtained by the

automated method was equivalent to data obtained by manual

sampling methods using the same protocols.

The fourth and fifth prototypes were designed as technology

demonstration units. Both units were deployed in conjunction

with existing projects at high-profile sites. The fourth

prototype was installed downgradient from an innovative insitu remeidiation technology described as a reactive wall. The

forth prototype was successful in that it recorded substantial

changes in ground-water quality in a short time period (fig. 1),

and it automatically notified the project chief that

measurements had exceeded preestablished ground-water

quality criteria. The fifth prototype was installed at Walden

Pond in Massachusetts at a location that is downgradient of

the State Park’s septic-system leach field. This system has

been successfully documenting the quality of ground water at

this location, information that will be useful in assessing the

septic system as one of the potential sources of nutrients that

may be causing eutrophication of the pond.

Figure 1. Ground-water quality measured by the

automated monitoring process in well SDW 485-0102A,

downgradient of the reactive wall, Cape Cod

Massachusetts.
Advantages Over the State-of-the-Art

Historically, automated ground-water quality monitoring has

been done using passive monitoring devices. These passivemonitoring devices use a data logger to control a water-quality

monitoring probe (or probes) suspended in a well to collect

ambient data at a preset frequency. Passive methods require less

infrastructure, manpower, and maintenance than either our active

automated monitoring process or traditional manual sampling

methods.

Passive monitoring methods, however, have significant

limitations that do not apply to our active system. The size of the

passive monitoring-instrument selected determines the minimum

diameter and screened interval of the well that may be sampled.

It is generally recognized that the composition of water within a

well and in close proximity to the well is probably not

representative of surrounding groundwater quality at a sampling

site. Also, wells that screen more than one zone of a physically

or chemically heterogeneous aquifer can act as conduits for

natural or induced flows between different zones screened by the

wellbore. Therefore, measurements made by passive monitoring

devices emplaced in a well may not represent surrounding

ground-water quality.

Figure 2. Normalized measurements of ground-water

temperature and specific conductance by active and

passive automated monitoring systems in wells SDW-0028

and SDW-0028A respectively.

The USGS did an experiment to compare passive and activeautomated methods in a pair of short-screened wells located

immediately downgradient from a source of ground-water

contamination. Identical probes, which were fully functional,

calibrated and operating within design ranges throughout the

experiment, were used in both the active and passive monitoring

devices. The data obtained from the two methods were

normalized using manual measurements made in each respective

well at the beginning and end of each monitoring period (fig. 2).

Data were normalized for direct comparison to the manual

sampling data and for direct comparison between data from each

well and method. The active system, which pumped and purged

the well once a day, provided data that correlated closely with

the manual sampling data. The passive system, which activated

probes in the adjacent wellbore every two hours, was clearly

affected by natural flows of water in the wellbore from a zone

that was not typical of the average water quality in the screened

interval. This was evidenced by the rapid change in specific

conductance measurements when the probe was emplaced after

manual sampling at the beginning of the interval and the 40

percent difference between the final passive measurement and

the subsequent manual specific conductance measurement.

Patent Status

A patent application has been submitted on this process and

apparatus. It is now available for licensing.

For More Information

For more information about licensing of this and other patents

and for cooperative research opportunities with the USGS

please contact:

Technology Enterprise Office

U.S. Geological Survey

12201 Sunrise Valley Drive, MS 211

Reston, VA 20192

Tel: (703) 648-4450

Fax: (703) 648-5068

Email: tto@usgs.gov

For information about the technical details of this invention

please contact the inventors:

Kirk P. Smith

email: kpsmith@usgs.gov

Gregory E. Granato

email: ggranato@usgs.gov

U.S. Geological Survey

Water Resources Division

Massachusetts, Rhode Island District

10 Bearfoot Road

Northborough, MA 01532

(508) 490-5055

(508) 490-5068

http://ma.water.usgs.gov/automon/

Report by:

Kirk P. Smith and Gregory E. Granato