each step in a timely manner to assure flexibility and implementation of alternative procedures or approaches in place of those that are problematical or do not work.
A moderate number of the tasks in the PMP are not described in enough detail to allow for a substantive critique of methods at this stage. While this is understandable given the scope of the effort, these include such important topics as tracer tests, numerical modeling, interpretation of bioassay results, packer test intervals, and sampling frequency. These topics deserve additional attention in later drafts.
Ecological and water quality studies are described both in descriptions of tasks 10 through 13 and, somewhat independently, in Appendix L. Unfortunately, the task descriptions and the appendix are not well integrated, and sometimes appear contradictory. The writers of the PMP are urged to make these sections more consistent with each other.
Based on the points raised in comments the specific tasks and functional area plans, the following recommendations are of particular importance:
The proposed additional monitoring at the pilot sites is a good step, but probably still does not go far enough in terms of numbers of wells and well nests to characterize both hydraulic and biogeochemical processes. Vertical and horizontal heterogeneity of the aquifer system will make this a difficult task that will require extensive testing. Likewise, recharge of the ASR wells should continue, if at all possible, until some time after the injection water is detected at all of these monitor wells, to understand the physical and chemical behavior of the system as fully as possible.
Likewise, improved understanding of potential geochemical reactions should be a priority all pilot sites. This may require additional monitoring during cycle testing beyond that anticipated in the PMP. Given the heterogeneity of the Florida Aquifer system (FAS) with respect to salinity and physical properties at existing ASR sites, there may be significant variability in these properties from site to site.
Some of the funds necessary to expand such monitoring and sampling should come through de-emphasizing continuous coring. While coring can be useful, it is costly and may yield unreliable and non-representative data. Given these limitations, it might be prudent to reduce the coring program and use the savings to support installation of additional monitoring wells for field tests of hydraulic properties and for hydrogeochemical characterization.
Column studies are proposed to assess interactions between microorganisms and the subsurface materials. Due to the presence of fractures and other features in the FAS, it will be difficult, if not impossible, to obtain representative, quantitative information on transport using column studies. Such results should be treated with caution.
The proposed bioassays and mesocosm studies emphasize response of individual taxa rather than community- and ecosystem-level effects. However, these studies may reveal only sublethal effects (e.g., altered growth rates) of contaminants on the sampled organisms. Such results would be difficult to extend to impacts on the larger ecosystem (e.g., shifts in community composition or changes in frequencies of algal blooms), for which little monitoring is proposed. Thus, the ASR Regional Study’s ecological monitoring and research components are poorly connected to the ecosystem- and community-level restoration objectives of CERP. This can be remedied by adding monitoring and assessment of ecological indicators to the proposed bioassays of Task 13. In coordination with other CERP science initiatives such as RECOVER, an opportunity exists to develop indicators that can be employed in both system-wide monitoring and the ASR Regional Study.