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Metropolitan Wastewater Management Commission Capital Improvement Program <br />Biosolids Management Facility -Groundwater Protection <br />FY 02-03 Capital Budget = $100,000 <br />Biosolids are stored in four facultative lagoon cells at the Biosolids Management Facility. The <br />lagoon cell slopes are lined with high density polyethalene plastic to protect against wave erosion <br />but the bottoms are lined only with bentonite amended soil which is not completely <br />impermeable. Several monitoring wells were installed when the lagoons were constructed and <br />others were subsequently added. Staff has conducted routine groundwater monitoring since the <br />lagoons went into service. Recent monitoring indicates the groundwater quality has changed. A <br />change in groundwater quality requires a Preliminary Assessment Plan under Oregon <br />Administrative Rules that includes an assessment of the extent and potential migration of <br />pollutants. The Preliminary Assessment Plan helps determine the need. for remedial action. The <br />need for additional groundwater monitoring wells and specific siting requirements will be <br />evaluated during implementation of the Preliminary Assessment. Plan in calendar year 2002. <br />Potential remedial actions to stop the leakage at the source are currently under evaluation. If <br />plans for remedial action are not initiated in FY 02-03 and further assessment is necessary to <br />determine the extent of degradation, then this would be better defined by adding at least five <br />wells. <br />• Two deep monitoring wells screened from 30-50 feet may need to be installed up gradient of <br />the facultative lagoons. Existing upgradient wells are completed from 15-25 feet and do not <br />provide a means for comparing water quality at down gradient monitoring wells completed to <br />50 feet. <br />• Three additional down gradient wells may be needed beyond the compliance boundary. <br />These should be nested wells completed from 15-25, 30-50, and 55-75 feet. <br />The FY 02-03 budget for this capital project can accommodate either development of the new <br />monitoring wells, or the initialization of engineering design work necessary to begin relining in <br />FY 03-04. It appears that the most prudent course of action is to reline the lagoon cells with an <br />impermeable material. Relining of the four cells would be over a 10-12 year period. Since the <br />Biosolids lagoon is approaching 20 years in service and does not meet current permitting <br />standards, scheduled liner replacement should be considered anyway. <br />Page 28 FY 02-03 BUDGET <br />