Michael D. Campbell, P.G., P.H.

The development and maintenance of a water supply are of importance to many people, especially in suburbs or rural settings. In large cities, water usually is supplied by a network of underground pipes from either a surface reservoir or from a system of high-capacity water wells. As population centers have expanded over the years, water wells often co-exist with nearby oil and gas wells.

The selection process of deciding between a surface-water or ground-water source depends on many factors:

  • geographic location (topography, climate-precipitation, temperature and population density)
  • hydrogeologic conditions (depth to aquifers, suitability of aquifers, water quality)
  • engineering controls (cost sensitivity, political preferences)
  • contamination issues (surface-water vulnerability, ground-water vulnerability and operator responsibility.
Litigation can result from disagreements between landowners and well contractors, the municipal utility district (MUDs) and the operators and/or residents over a number of issues, e.g., water costs, water quality, etc.

Geographic Factors
In regions where the land surface is hilly or has some relief, a surface source of water can be developed by damming a river or large stream or by sculpturing a reservoir out of lowlands that receive regular runoff. These projects are usually large engineering efforts that require large capital expenditures and a multidisciplinary team involving the U.S. Corp. Engineers, state and federal wildlife regulatory agencies and local groups.

The political issues, which involve a large population, are often major but usually surmountable if the project makes sense to the majority of those interest groups involved. Projects usually are promoted on the basis of the multiple use of the land involved. The reservoir would not only hold a supply of water but also would be used for fishing, boating and swimming as well as a focal point for surrounding developing residential subdivisions.

Hydrogeologic Factors
Ground-water supplies are usually available. Regional variation in water quality depends on the local makeup of the subsurface aquifer produced as a water supply. In high rainfall areas, the depth to water will be minimal, usually less than 20 feet below the surface, depending upon the time of the year.

The top of the ground-water reservoir is known as the water table. It varies over the year and adjusts to infiltrating local rainfall. During droughts, the water table declines; during years when rainfall is above normal, the water table will rise, sometimes high enough to create a temporary bog or swampy area. If this happens on a regular basis over the years, a wetland develops.

For all practical matters, the water table should be considered a dynamic surface. For example, houses in the Gulf-Coast area do not have basements because the rainfall is high, and the water table is shallow. Only minimal engineering is needed to recovering gound water for a small population base (Ref# 4, 5 and 7). Some large municipalities also use ground water instead of surface water. These projects involve only minimal real estate, few permits and little interference from state and federal agencies or polarized interest groups.

Engineering-Control Factors
The difference in cost between surface-water and ground-water sources is substantial for obvious reasons. Surface-water sources require large expenditures, ground water require small expenditures. Based on the cost-per-1000-gallons-of-water delivered, surface-water costs run in the range of $ 0.25 to $ 0.35/1000 gallons while many ground-water sources range from $ 0.09 to $ 0.17/1000 gallons (not including unusual treatment costs for special problems).

It should be noted here that the surface-water cost does not account for the other benefits provided by the presence of a surface water reservoir, i.e., fishing (less the license, bait and tackle costs), boating (less the jetty fees paid, license, and fuel costs). The water-quality issues involved in the two sources of water are substantial and make selection difficult. Surface water is usually soft water (makes good suds for washing and showering) while ground water tends to be hard water and additional treatment adds a few more cents per thousand gallons.

Contamination Factors
Surface water is vulnerable to widespread contamination by accidents involving railroad chemical tank cars or trucks. It is also subject to bacterial contamination from septic tanks surrounding the reservoir, and some dams are subject to breaching by flooding. Although chances are relatively small, the impact of any such occurrences would be widespread and paralyzing to the local residents involved.

Ground water is not as vulnerable to widespread rapid contamination from surface spills but is subject to subsurface contamination from oil and gas wells (abandoned and operating fields, mining, road-salting activities and nearby gasoline stations).

Since 1991, U.S. EPA requires that all drinking water supplies (surface water as well as ground water) are to be tested on a regular basis for a number of potential contaminants, such as benzene, and for pesticides and other chemical constituents. The design and construction of water-supply wells and ground-water monitoring wells have been well documented in the technical literature for many years (Ref # 2 and 6). However, adherence to established procedures has declined in recent years.

Ground-water quality varies from region to region because of differences in the local geology of the aquifers produced as a water supply. Taste and odors may, from time to time, become a problem in smaller ground-water supplies where operators are not present on a continuous basis to monitor water treatment systems.

Slight changes in regulation of the chlorinating equipment can affect the taste (and odor) of the produced water. Many wells also develop non-pathogenic iron and manganese bacteria that can affect the water by creating taste and odor anomalies. Sulfate-reducing bacteria, for example, can develop in a supply well, which impart additional taste and odor problems. The familiar "rotten eggs" odor arises when hydrogen sulfide is produced in very small quantities from the sulfate-reducing bacteria living in the anaerobic microcosms under crusts of aerobic iron-oxidizing bacteria. Both problems will tend to give the water a yellow-brown to light orange appearance.

Regular monitoring of the water's inorganic chemistry, combined with appropriate water treatment, can control such problems. The cost will depend upon their severity (add an additional $ 0.02 to $ 0.04 per thousand-gallons-of-raw-water produced).

Water well maintenance is a critical factor in controlling water quality. Many individual rural water wells are not maintained appropriately or regularly. In addition, many wells are initially located down-gradient from the septic tank and leach fields.(Ref# 4 and 7).

Well maintenance usually consists of regular check-ups of the downhole conditions of the well screen or intake, the submersible pump and motor, wiring and fittings, for all practical purposes, the well should be maintained as often as the family car. Too often, however, the well is forgotten until a problem in quantity or quality develops.

In municipal utility wells, maintenance is usually performed on a regular basis by the operator/contractor. With the EPA monitoring requirements in place, water quality can be monitored effectively. Before 1991, monitoring small water supplies was difficult for states to conduct on a regular basis without an indication of a problem with water quality. Some common types of contamination from gas stations and other sources, however, naturally degrade with time because of specialized indigenous bacteria that are in the contaminated aquifer.

Ground water is not as vulnerable to widespread, rapid contamination from surface spills as surface water, but ground water is subject to subsurface contamination from oil and gas wells (both abandoned fields as well as operating fields, from mining activities, road-salting activities, and nearby gasoline stations). Since 1991, U.S. EPA requires that all large-scale drinking water supplies (surface water as well as ground water) are to be tested on a regular basis for a number of potential contaminants, such as benzene, and for pesticides, and other chemical constituents.

The design and construction of water-supply wells and ground-water monitoring wells have been well developed in the technical literature of the field for many years to minimize contamination as a result of faulty well construction. (Ref # 2 and 6). The safety of drinking water from individual wells in the rural setting is the responsibility of the home owner. However, cases of bacterial contamination ( by E. coli, etc.) of such wells are known and indicate that young children and older persons are at serious risk. Regular testing and simple treatment should be a part of every water-supply system in rural areas, especialy where septic systems, cattle and other agricultural factors may be present. For a recent case involving an ELA Principal, click (here, see case #7).

Ground-water quality will vary from region to region because of differences in the local geology of the aquifers produced as a water supply. Taste and odors may, from time to time, become a problem in smaller ground-water supplies where operators are not present on a continuous basis to monitor water treatment systems. Slight changes in regulation of the chlorinating equipment can affect the taste (and odor) of the produced water.

Other issues that can be involved in water supply cases:

Tank Corrosion
Water Quality (water chemistry & microbiology)
Toxicology
Industrial Health & Safety



ELA can also provide technical support in these areas.

Special Educational Seminar for Municipal Utility District Personnel, Consultants, and Contractors

The last seminar was presented on April 16, 1998 in Houston, Texas concerning new ground-water-supply issues.

Dewatering & Mining Factors
Dewatering is usually required to control subsurface water when excavating for construction purposes. Dewatering is also required in surface or underground mining of coal, lignite or other natural resources. Both methods must control the subsurface water in order to remove the commodity for processing into a product required by society.

The need to remove water from the subsurface is most prevalent in the Gulf Coast area of the US where the water table is high as a result of abundant rainfall. The method applied to accomplish dewatering involves pumping systems of many designs and sizes. Usually, it is a matter of depressing the water table for a period of time which will allow for the construction to be completed. When the pumps are removed, the water table will return to near its initial elevation.

The design of a dewatering system depends on the permeability of the subsurface materials to be dewatered. Hydrogeologic tests conducted by hydrogeologists determine the rate of removal and volume of the water produced. Such tests aid in determining the type, size, configuration and number of pumps needed for the dewatering system.

In some construction and many coal and lignite mining projects, not only will ground water be removed but pore pressures will need to be reduced to minimize uplift pressure on the base of the coal or lignite bed. In northern Louisiana and eastern Texas, high pore pressures create problems during mining. As the overburden materials were removed, the uncovered coal beds produced water piping and fountains up through the fractured coal beds. In places, large blocks of the coal bed itself were raised, creating an uneven horizon of coal for the large bucket excavators to follow. This produced a high-ash product for burning at the nearby coal-fired power plant.

The higher the ash (clay-sand under-bed material), the lower the BTUs at the time of burning. Once the water and the pressure were removed by pumping and bleeding off, however, the coal beds ceased producing "artesian" water and stopped moving. Other areas that are dewatered before overburden removal remain essentially flat, improving mining efficiency. The coal quality is optimized; and coal access, improved.

Dewatering and the use of wells are also important activities in commercial uranium production by the in-situ method which often replaces open-pit mining because of cost and environmental considerations (Ref #8). Since 1972, one of the sources of new technical information on ground-water supply development is the searchable database of the National Ground Water Association. For the cost of membership only, more than 80,000 papers, publications and texts are searchable by key words. The link to this service, as well as other Internet and World Wide Web sources of technical information, are maintained at the IET Technical Resources site. For further information on the discipline, the Institute of Environmental Technology sponsors an Internet Resources Portal, click (here). For additional information on this discipline and associated technical support, see AEG-TX.ORG and AIPG-TX.ORG.

References

* The following are only a few of the many technical references on the topics available in the field today. Those cited below represent the foundation literature for the subjects discussed.1. Borden, R.C., et al., 1995, "Geochemical Indicators of Natural Bioremediation," Ground Water, Vol. 33, pp. 180-189.
2. Campbell, M.D. and J.H. Lehr, 1973, Water Well Technology, McGraw-Hill, New York, 681 p.
3. Campbell, M.D., and J.H. Lehr, 1973, Rural Water Systems Planning and Engineering Guide, Commission on Rural Water, Washington, D.C., 150 p.
4. Campbell, M.D., et al., 1974, Operation and Maintenance Guide for the Support of Rural Water-Wastewater Systems, Commission on Rural Water, Washington, D.C., 283 p.
5. Campbell, M.D., 1974, Rural Water Systems Operation and Maintenance: A Guide for the Engineer and Operator, Commission on Rural Water, Technical Research Office, Rice University, Houston, Texas, 591 p.
6. Campbell, M.D., et al., 1975, Manual of Recommended Water Well Construction Standards, U.S. E.P.A. Office of Research and Development, Contract 68-01-92, NWWA Research Facility, Rice University, Houston, Texas, 177 p.
7. Campbell, M.D. and S.N. Goldstein, 1975, "Engineering Economics of Rural Water Systems, Part 1-Elements of Design, and Part 2-Application of Economic Criteria to the Evaluation of Project Feasibility, A Case Study," in Proc. Rural Environmental Engineering Conference on Water Pollution Control Technology in Low-Density Areas, University of Vermont, pp. 145-180.
8. Campbell, M.D., et al., 1977, Geology {and Environmental Impact} of Alternate Energy Resources, Houston Geological Society, Houston, Texas, 364 p.
9. Lehr, J.H., et al., 1988, "Treatment Techniques for the Removal of Taste, Odor, Color, and Turbidity," Water Well Journal, Vol.42, No.6, pp. 51-57.
10. Pettyjohn, W.A., 1972, "Good Coffee Water Needs Body," Ground Water, Vol.10, No.5, pp. 47-49.

Note: The environmental field is multidisciplinary by nature, and ELA incorporates input from complimentary disciplines for maximum effectiveness whenever appropriate.