Avoiding
Filtration:
Groundwater Under the Direct
Influence of Surface Water
A source water or wellhead protection plan (SWPP) can be used as a watershed protection program for sources that are ground water under the direct influence of surface water [PWS Rules - Subchapter 2 Subpart A 141.71 (b) (2)]. For systems that are determined to be groundwater under the direct influence of surface water (GWUDISW), an approved wellhead protection program developed under section 1428 of the Safe Drinking Water Act may be used to meet the requirements of a watershed program. These systems may, under certain circumstances, be approved to limit treatment application to disinfection of their public water supply, thus avoiding filtration.
The
information compiled in this factsheet is intended to guide source water
protection plan development to support the avoidance of filtration. Other
requirements to avoid filtration not described here (such as water quality
monitoring, disinfection, and annual inspections) must also be addressed.
A certified SWPP does not automatically translate into an approved watershed protection program that can be used to avoid filtration. The risk to public health is too great when using an unfiltered GWUDISW source to leave anything to chance. A more comprehensive or expanded assessment of the watershed may be needed when a SWPP is to be used for a very specific purpose such as avoiding filtration. For example, the size of a source water protection area will need to be increased to extend to the boundary of the watershed. Also, land ownership and land use information will need to be enhanced to provide more detail.
In general, a SWPP that is intended to be used as a watershed protection program must minimize the potential for contamination of the source water by giardia, cryptosporidium, and viruses. The adequacy of a SWPP to minimize microbial contamination is determined by:
q the comprehensiveness of the watershed review,
q the ability to monitor and control detrimental activities in the watershed, including recreation such as swimming, camping, boating, sewage and septic system discharges, or other activities that may impact microbiological water quality or interfere with disinfection treatment, and
q the extent to which land use is controlled within the watershed.
In order for a source water protection plan to be considered comprehensive, it should identify all landowners in the watershed upgradient from the source water intake structure and all land uses within the spill response region by individual land parcel.The ability to monitor and control detrimental activities in the watershed can be addressed by developing a local source water protection ordinance using the authorities granted to the city, town, or county government. The ordinance should assign monitoring responsibilities and should control detrimental activities. The extent of control necessary is site specific. For example, Missoula restricted fishing, swimming, livestock, and pets from the watershed area in order to keep feces from being introduced directly to the Rattlesnake Creek drinking water source; other activities in the watershed were not restricted.
Public education concerning activity restrictions should be a component of the plan. For example, public education can occur on a daily basis by posting signs to indicate that you are entering a source water protection area. Informational materials can be distributed through annual direct mailings to landowners within the watershed.
The extent to which land use is controlled within the watershed can also be addressed through ordinances. These may be existing such as septic system regulations, or built into a new source water protection ordinance. Another option to achieve land use control might be conservation easements, subdivision covenants, or cooperative agreements with individual landowners.
The Montana Public Water Supply Section at DEQ is the regulatory authority responsible for establishing the criteria and approving all plans to avoid filtration. Questions regarding the use of a watershed protection program to avoid filtration should be directed to the public water supply supervision program at (406) 444-4400. Questions regarding a Source Water Protection Plan can be directed to the Source Water Protection Section of the Pollution Prevention Bureau at (406) 444-6697.
Montana Watersheds
