Item A: Delta Sand and Gravel - Laserfiche WebLink

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We find that approval of the application will not result in flooding conflicts with adjacent land uses. Groundwater EGR recommends that a low permeability barrier, groundwater dam or other flow restriction of the upper aquifer should be constructed, at the applicant’s expense, as the excavation proceeds to the west. EGR concludes that the construction of a low permeability barrier could actually result in lower pumping of water, with significant benefit to the aquifer and area groundwater users. That low permeability barrier has been termed the “aquaclude” by EGR and the applicant. EGR recommends that excavation should begin on the east side of the expansion area and that the aquaclude should proceed ahead of the excavation to the west. Construction of the aquaclude should occur before excavation comes within 400 feet of its location. The aquaclude should be at least 12 feet wide at the bottom and slope upward through the upper aquifer from 1:5 to 2:1 to the original ground surface. The aquaclude should be placed within the setback area to insure its separation from the excavation proper and to place its outer edge as close as possible to the surrounding off-site shallow aquifer. EGR also recommends that a buttress of native material be left between the aquaclude and the excavation area proper. EGR’s ultimate conclusion is that placement of a low permeability barrier around most of the excavation should result in restoring groundwater levels around the excavation pit to near pre- development levels. DOGAMI has provided the applicant with its preliminary concurrence with EGR’s ultimate conclusion. A copy of correspondence from the agency to the applicant is included with EGR’s evaluation attached to the application. The correspondence states that “there may actually be a slight mounding of the ground water in the shallow aquifer within close proximity to the barrier thus eliminating the possibilities of drawdowns which could impact supply wells within the area.” Construction of the aquaclude within the setback area requires an administrative variance pursuant to Lane Code that Lane County has approved (should the Metro Plan amendments succeed). As discussed above in our findings regarding flooding, EGR has provided adequate and significant evidence that the existence and operation of the aquaclude will not result in flooding of adjacent lands. The applicant and EGR testified that the trench constructed for the aquaclude will be filled with clay material excavated from other locations on the applicant’s adjacent ownership and operation. We find that the proposed clay material for the aquaclude is a natural soil that will not decompose and will not pollute underground waters. Both Planning Commissions found unanimously that there was a conflict due to groundwater. The low permeability barrier (aquaclude) is proposed as mitigation, and the applicant should map the specific proposed location for the low-permeability barrier. The Eugene Planning Commission found unanimously that the aquaclude would minimize conflicts with groundwater to an adequate level. The Lane County Planning Commission voted 4-2 that the aquaclude would not minimize the conflict with groundwater to an adequate level. We find that the proposed aquaclude is sufficient mitigation to minimize conflicts. (ORS 215.296 Standards for approval of certain uses in exclusive farm use zones. (1) A use allowed under ORS 215.213 (2) or 215.283 (2) may be approved only where the local governing body or its designee finds that the use will not: (a) Force a significant change in accepted farm or forest practices on surrounding lands devoted to farm or forest use; or Ordinance - 22