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management strategies. Serious damage to the trees will have already occurred. Leaf and branch death occurs in response to root dieback, and it can occur in just a few weeks. Cottonwood trees should not be exposed to hydrologic conditions beyond their ability to survive. If by predicting only the most limited and unrealistic water table changes that could be produced by pit dewatering, conditions beyond the tolerance of cottonwoods could be rapidly created, and trees could be subjected to water stresses causing their dieback or death. It is essential that ground water monitoring.wells occur in the vicinity of all cottonwoods to measure water table depth every few days during the summer. It must be recognized that water table under cottonwoods should not be dropped any lower than that which has naturally occurred in late summer as controlled by low river flows. In Mr. Golfer's report he suggested that if trees exhibit water stress (leaf yellowing and death) surface water (irrigation) could be applied to recharge soil water and relieve the stress. This concept is from my reseazch along the South Platte River. However, Mr. Golfer has only represented '/: of this story from the report I sent to him. First, by the time tree leaves are yellowing, it's too late to save them and their branches. Second, irrigation works fine in gravel soils where water can percolate down through the root zone, but we found that 'vrigation was only partially effective in finer-textured soils, and I suspect it would be ineffective in the much finer-textured neaz surface soils that occur in the area of the proposed Milner gravel pit. Thus, irrigation should not be accepted as a fail-safe method because if applied either once visible impacts are observed or in areas with fine- textured surface soils, it will be ineffective. To understand the potential effects of the proposed gravel mining and dewatering, I suggest that a set of analyses must be completed. First, the groundwater modeling effort is necessary to adequately identify potential areas where severe water table declines are likely to occur. The model can identify these areas spatially, and identify whether water tables will wet surface soils, and how deep water tables will be in summer. Second, more information on the permeability of the floodplain soils are necessary to determine whether surface application of irrigation water could be an effective mitigation measure for providing water to cottonwood root systems. Third, an analysis should identify the cur.cnt condition of trees :n the study area.~f cottomvoods are akeadv in peer condition. they could be more susceptible to water stress than could be predicted from previous studies. This could be done with an analysis of tree rings, and canopy condition. Fourth. if you should decide to permit this project, much better post implementation monitoring, and mitigation measures aze necessary. Cottonwood trees naturally dry out during hot days and recover this water at night. We can measure this nightly recovery, as the pre- dawn water potential (measures of tree sap pressure in the hours just before dawn). If diurnal tree recovery diminishes when water tables change, the trees aze in imminent danger of what scientists call uncontrolled cavitation, which will led to rapid root, leaf and branch death in a matter of days. None of these analyses are complex, expensive, or unduly burdensome. My students and I could assist the gravel mine company, or the county in these tasks if requested.