Economic Impact Analysis: 1st Progress Report, January 4, 2001
Section IV: Enhanced Aquifer Protection Scenario


To assess the economic costs, benefits and impacts of additional measures to protect LPRV water quality, assumptions must be made concerning the types of measures that would be implemented and how they would work. These assumptions are collectively termed the "Enhanced Aquifer Protection Scenario."

If the citizens of the LPRV ultimately decide to implement a strategy to provide additional protection for their aquifer, extensive public discussions will likely occur and additional refinements or modifications may be made to the protection strategy(ies). In fact, certain elements of the protection scenario are already in place in some form or under consideration by local governmental entities, but are not applied and enforced across the LPRV in a coordinated fashion. The scenario described herein is intended to reflect reasonable assumptions for purposes of analysis, not to proscribe the strategies that may ultimately be chosen.

As defined for this study, the Enhanced Aquifer Protection Scenario is based on the following considerations:



The Rathdrum Prairie Aquifer is the sole source of potable water for the residents and businesses of Coeur d'Alene, nearby communities and unincorporated residents in Kootenai County. Across the state border in Washington, the aquifer (termed "Spokane Valley") also provides the sole source of potable water for the City of Spokane and its environs. Since the late 1970s — and spurred further by $1 million annual Congressional appropriations to Spokane County, Idaho DEQ and Panhandle Health District from 1988-1994 — the aquifer has been the subject of extensive monitoring and analysis and considerable effort to develop and implement water quality protection measures.

The work accomplished, and the experience gained in protecting the Rathdrum Prairie aquifer provides relevant and important information for this study for several reasons:



To address the first of the three protection scenario objectives, reducing future potential contamination from septic and sewer discharge to the aquifer, the following measures are assumed:

  • limiting the density of future home development relying on septic discharge to one home per five acres, unless the location of the future development is within a Sewage Management Area (SMA).

  • SMA's created under local ordinance or through state regulation. These would be areas, presumably proximate to existing sewerage service, that are contractually committed to future sewer system development under specified development progress conditions. Contracts would be between the developer, an existing sewage disposal entity and the local health district or other regulatory authority.

  • Higher densities could also be permitted if the homeowner and developer agree to install a septic pretreatment system, approved by the health district or other regulatory authority, and to submit to periodic monitoring of pretreatment system maintenance by the health district or other regulatory authority.

  • Any sewage effluent discharge over the aquifer must either be discharged into the Lower Portneuf River or must employ the "slow-rate application" to crop lands best management practices (BMP) developed in the Hayden Land Application Pilot Study. The BMP is reflected in the Special Supplemental Guidelines to the Idaho Wastewater Land Application Guidelines published in 1995.

These measures are drawn largely from the Rathdrum Prairie list, adapted to more closely fit the nitrate and chloride issues in the LPRV.



To address the second of the three protection scenario objectives, avoiding contamination from stormwater runoff and non-domestic wastewater disposal, the following measures are assumed:

  • New developments larger than a single family home must develop and implement a stormwater management plan, consistent with the BMP discussed below. The local health district or other regulatory authority would register and review all new stormwater disposal systems.

  • Stormwater management plans would reflect BMPs, such as the recommendations in the Handbook of Best Management Practices for Stormwater Management and Erosion and Sedimentation Control (1992). For example, for isolated systems this generally means the development of grassy swale areas at the lowest point on the property with an appropriately designed dry well (with a raised casing) in the midst of the swale to capture extraordinary runoff events.

  • Non-domestic wastewater discharge to the aquifer (such as wastewater streams associated with production, cleaning and vehicle washwater) would be prohibited and these types of wastewater would be required to be sent to a local wastewater treatment plant. In some cases, as required by the wastewater treatment operator, this may require pre-treatment of the waste stream by the commercial facility.

This list of measures is drawn entirely from the Rathdrum Prairie experience.



The final protection objective, management of critical materials, involves the following measures:

  • The health district or other regulatory authority would develop a list of "critical materials" and establish threshold quantities of those materials for purposes of the following procedures. These materials would include potentially significant contaminants to the aquifer if they were accidentally spilled or leaked. Examples of such materials could include certain fuels, industrial solvents and cleaners, etc.

  • Facilities that store, handle or use materials included in the list would be required to submit a report on the types and quantities of listed materials used. If quantities exceeded the thresholds established by the health department, the facility would need to submit a plan demonstrating that the material(s) cannot get into the aquifer under either normal operations or in the event of spills.

  • The health district or another regulatory authority will have the authority to either approve the plan proposed by the facility or require additional measures.

  • The critical materials management regulations would apply to both new facilities and new uses at existing facilities.

The management of critical materials is drawn entirely from the Rathdrum Prairie where it has been effectively utilized.



In addition to the specific protection measures just identified, important components of aquifer protection include:

  • land management of recharge areas;

  • enhanced public education; and

  • ongoing water quality data collection.

The recharge area for the LPRV, particularly the Bannock Range, is largely undeveloped at this time. Potential water quality impacts arising from future developments may be important for county planning and land use agencies to consider in protecting aquifer water quality. Additional monitoring wells and data collection and analysis would be included under the protection scenario to both enhance understanding of the LPRV aquifer and its water quality and to monitor changes in water quality over time. Additional funding for public education measures is also envisioned.