The Commissioner — Winter 2001

Protecting Drinking Water Resources under the Source Water Assessment Program

By Jon D. Witten, AICP

The Safe Drinking Water Act (SDWA) remains one of the federal government's most aggressive attempts at managing land use at the local level of government. Although certainly not billed as a land use control statute, the SDWA, particularly as revised in 1996 with the creation of the so-called "SWAP" program (source water assessment program), set in motion a process by which local governments and suppliers of drinking water are encouraged to take proactive steps, including but not limited to the regulation of private property to protect drinking water resources.

This latter point — the regulation of private property to fulfill a public purpose — remains controversial, even though zoning and land use controls have become a staple of virtually every metropolitan and suburban community across the nation.

This article highlights key provisions of the SDWA, particularly the "SWAP program" and then concludes with an abbreviated menu of the zoning techniques available to local governments as they seek to fulfill the goals and requirements of the SWAP initiative.

Federal Safe Drinking Water Act

Section 1453 of the 1996 SDWA Amendments requires states to develop comprehensive State Source Water Assessment Programs, commonly referred to as SWAPs. Each state is required to submit to US EPA a SWAP that includes the following four components:

  • Delineation of the source water protection area: that portion of a watershed or groundwater area that may contribute contamination to the water supply;
  • Identification of all significant potential sources of drinking water contamination within the protection areas identified above. The resulting contamination source inventory must describe the sources (or categories of sources) of contamination either by specific location or by area;
  • Determination of the water supply's susceptibility to contamination from identified sources. The susceptibility analysis can be either an absolute measure of the potential for contamination of the water supply or a relative comparison between sources within the protection area; and
  • Distribution of the source water assessment results to the public.

The SWAP requires information pertaining to drinking water supplies be developed, and not that the supplies necessarily be protected. In other words, despite going to great lengths to require states and local governments to "do the right thing" with respect to resource protection, the protective actions are left solely to state and local governments. And, despite some examples of aggressive state actions, the vast majority of public water supplies in the nation are reliant on the steps taken by local governments.

Step One: Source Water Protection Areas:

A source water protection area is the watershed or groundwater area that may contribute pollution to the water supply. The purpose of the source water protection area delineation is to establish priority focus areas for the source water assessment, described in Component 2.

Public water supplies that rely on surface waters must include in their delineated areas the entire watershed upstream of the water supply's intake structure, up to the state's border with another state or jurisdiction.

In addition, surface water based public water supplies must include in their delineations the impacts of groundwater upon the surface water resource. This requirement is tricky. The source water protection areas must include both surface watersheds and ground water recharge areas (so-called zones of contribution or wellhead protection areas) to public surface water supplies.

Step Two: Contamination Source Inventory:

A contamination source inventory is an inventory — identification — of all present and potential sources of drinking water contamination within the source water protection area described above. Potential sources of contamination are historical (they existed in the past and still pose a threat to drinking water), current (they exist today) and future (they could exist in the future according to the local comprehensive plan, local regulations governing land use and/or market forces).

Contaminants of concern include a wide range of "raw" water contaminants regulated under the Safe Drinking Water Act including those that may present a threat to public health such as viruses and bacteria.

The contamination source inventory must include a clear description of the sources of contamination (or categories of sources) either by specific location or by area. And as noted above, these descriptions must include past, present and future sources. This latter requirement is of great importance to public officials planning for the future protection of drinking water resources. The contamination source inventory will allow public officials to focus — prioritize — their efforts with respect to drinking water protection. By knowing where likely contamination sources are, local officials can pinpoint and target their labor and dollar resources efficiently and with high probabilities of success.

It is important to note that groundwater and surface water supplies are threatened in different ways and by different contaminants. Surface waters are vulnerable to contamination from both runoff and groundwater infiltration. Runoff of contaminants from the surface areas in a watershed, either near a drinking water supply intake or in upstream tributaries can cause contamination. Similarly, contaminated groundwater can recharge streams or lakes.

Groundwater can become contaminated through infiltration from the surface, injection of contaminants (e.g. septic systems and injection wells) or by naturally occurring substances in the soil or rock through which it flows. Depending upon the hydro geologic setting, contaminants in ground water may migrate far from the source and pollute water supplies thousands of feet, even miles away.

Step Three: Susceptibility Determinations:

The third required component of a SWAP is the susceptibility determination: the determination of the susceptibility of the water supply to each contaminant source identified in Component 2. US EPA has encouraged susceptibility determinations for several years, arguing that they are useful for decision making with regard to prioritizing management decisions. The thinking goes something like this:

City A has identified 22 contaminant threats within the watershed to its primary surface water reservoir. These threats include past, present and potential future contaminant sources. The susceptibility determination provides the City with additional information; essentially a relative risk ranking of which of those threats are the most imminent versus the least likely.

While this prioritization of actions may, at first glance, appear economical (the City has limited resources and cannot solve all 22 problems at once), each of the 22 threats are real and each must be dealt with. In other words, while the City may seek to remediate or fix the most menacing of threats immediately and postpone the others until a future date, the City must nevertheless respond to all 22 contaminant sources. This point is underscored by the sheer complexity, particularly with respect to drinking water derived from groundwater resources, of the movement of contaminants within the subsurface.

For example, US EPA and several states have recommended that local governments focus on a "time of travel" priority for contaminants. This approach views those contaminants that are closest to a drinking water well to pose the greatest threat; those furthest away posing a lesser threat. Unfortunately, this approach presumes that contaminants will flow uniformly through the subsurface: essentially a race through the aquifer, the closest getting to the well first. But few groundwater environments are uniform and over-reliance on time of travel may minimize the threats of contaminant sources distant from pumping wells. Again, the point is simply that the susceptibility determination should not lead to an ignorance of distant threats: all known and foreseeable contaminant sources must be responded to in order to adequately protect drinking water supplies.

Step Four: Publicizing the SWAP Results

States are required to publicize the results of their SWAP efforts to individual municipalities. The publication requirement can take several different forms, but is intended to be in "plain-language" and must include maps of the delineated source water protection areas and the sources of contamination described in the contaminant source inventory.

It is important to note that the four components described above amass and assess data relative to public drinking water supply protection. The next, and perhaps most important step is left to the state's respective local governments.

Prior to reviewing a handful of the zoning tools available to local governments in the pursuit of drinking water protection, it is worth noting that local governments may have a legal obligation to protect public drinking water resources from contamination.

This obligation stems from tort law: the body of law defining civil actions and responsibilities of private individuals and, more recently, public agencies. While a more lengthy discussion is beyond the scope of this article, it is worth remembering that a local government's failure to protect a drinking water supply from a known contamination threat may be tantamount to negligence, establishing liability to an injured consumer of contaminated water.

Generally speaking, negligence liability of a municipal government is dramatically reduced where it can demonstrate that it acted reasonably — took reasonable steps — toward the protection of drinking water resources. Adoption of the following techniques is a good start toward protecting drinking water resources.

Local Regulatory Options for Protecting Drinking Water Resources

It should be noted at the outset that there are two broad categories of techniques available for protecting drinking water supplies. They are best divided into regulatory and non-regulatory approaches. The following discussion focuses solely on the former and within this category, solely on zoning techniques. (Note, however, that local governments have had success with a variety of other regulatory controls as well as non-regulatory approaches, including land acquisition, best management practices and public education).

With few exceptions, the following zoning tools are available to local governments throughout the nation. Each has proven successful in the protection of drinking water supplies.

Using Zoning Controls to Protect Drinking Water Supplies

Zoning is a household word in some portions of the nation. In others, the concept of zoning remains an affront to private property rights and represents government intrusion at its worst. As for the protection of drinking water supplies, however, zoning remains one of the most appropriate and successfully used regulatory techniques available and one that even the most reluctant community needs to consider.

There are many variations of zoning regulations that are used to protect drinking water supplies. They include:

Overlay districts. A zoning overlay district is the marriage between the source water protection area(s) and zoning (or other land use) regulation. Given the requirement that all source water protection districts must be mapped and the information made available to each municipality, few excuses exist for not linking the delineation to a regulatory program. Moreover, the adoption of an overlay district allows the municipality to expand both its regulatory and non-regulatory protection efforts in the future. The areas of concern are mapped, made official through the adoption process and remain available for the public to view and identify as areas of special concern.

Large lot zoning. Perhaps the most controversial of the techniques used, large lot zoning is straightforward. Its goal is to minimize the numbers of dwellings and thus impervious surfaces associated with residential development. When applied in areas of a community without advanced wastewater treatment facilities, large lot requirements reduce the number of septic systems and associated bacteria, viruses and household contaminants. The controversy stems from the debate as to whether large lots contribute to (or in fact, define) sprawl and whether large lot zoning is equitable given the shortage of affordable housing nationwide. Nevertheless, within a source water protection area, fewer lots, dwellings and associated impacts is generally better.

Performance standards. This technique remains my favorite. It is based upon the assumption that a drinking water resource has a threshold beyond which its ability to function deteriorates to an unacceptable level (as dictated by statute or public acceptance). Adoption of performance standards allows a municipality to establish limits to development density, type and location within a source water protection area. By articulating the protection area's carrying capacity (the threshold limit of contaminants) the municipality can regulate development such that the capacity is not exceeded. The opposite approach, of course, allowing development without regard to the drinking water supply's carrying capacity, ultimately and inevitably leads to the degradation of the water supply.

Transfer of development rights. Given the requirements for identifying source water protection areas and susceptibility assessments, local governments are now in an ideal position to embrace and begin to use transfer of development rights to protect drinking water supplies. TDR has been used successfully throughout the nation to protect water supplies.

Development agreements. Another of my favorites, development agreements are contractual and binding agreements between a landowner and governmental agency that establish the rules for the development of land. Development agreements require both parties to adhere to the public hearing and meeting process, but typically can lead to development approval with greater public benefits than would be associated with the typical project. In that regard, development agreements often allow the municipality to achieve greater protections for drinking water supplies than would otherwise be possible under the standard development and permit review process. In exchange, the land owner/developer can often secure protections from future zoning changes and obtain permitting support from various public departments and commissions thus ensuring approval in shorter than normal time periods.

Using SWAP Information to Protect Drinking Water Supplies Using SWAP Information to Protect Drinking Water Supplies

Over the next two years, all states will have completed the four components of the Source Water Assessment Plans described above. This information will be made available to every county, city, town, Reservation and parish in the nation. It is left to these jurisdictions however, to use the information contained in the SWAPs to protect drinking water supplies. While some states may mandate certain levels of land use controls, it is likely that most of the protection efforts will need to occur at the local level of government.

The use of an array of zoning techniques, such as the ones discussed in this publication, might provide the most immediate protection from a range of drinking water contaminants.