Admin Order 58-12-14 - Laserfiche WebLink

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* Cluster development, * Minimize soil compaction, * Minimize total disturbed area, * Protect natural flow pathways, * Protect riparian buffers, * Protect and enhance sensitive areas and native vegetation, * Reduce impervious surfaces, * Disconnect impervious surfaces /downspouts, * Rainwater catchment/harvesting. * Split flow infiltration methods that preserve predevelopment stormwater flows in terms of rate, quality, frequency, duration, and volume, and thus more closely mimic natural systems. This is important for groundwater recharge, and preservation of surface water flow and natural channels and landscapes. Section 4: Water Quality Evaluation 4.2 Evaluation of existing and expected future water quality conditions The pollutant load estimates seem based on very shaky assumptions. First, no actual data was collected from our Basin about pollution levels, but data from other areas of Eugene was used to estimate it. Second, pollutant loads for Total Suspended Solids (TSS) were used as a general indicator of other pollutants, though "TSS has not been shown to directly relate to all other pollutants ". Third, when computing pollutant loads, decommissioning of drywells is assumed to result in 100% of those discharges being transferred, untreated, to surface waters. This seems like a very high estimate given the discontinuous nature of our drainage system, and the relatively high permeability of soils. In any case, it is unclear how these questionable pollution estimates are even used - -they don't seem to be driving particular actions or sizing of treatment facilities. On pg. 4 -5, the Plan does conclude that "pollutant loads in the RR -SC basin could potentially increase by up to 85% as a result of future development and drywell decommissioning, if treatment and /or other forms of infiltration are not provided for flows associated with drywell decommissioning." But in fact, Figures 4 -1 through 4 -3 show that the treatment of flows associated with drywell decommissioning would handle only a small part of the additional pollution that is projected--and this is the case even with the seemingly very exaggerated assumption about pollution that will be re- directed from drywells. In fact, the data presented show that most of the projected future pollution will be from new development. Thus, "treatment and infiltration of the flows associated with drywell decommissioning" appears to be NOT very helpful at reducing the potential 85% increase in pollution that is mainly from other sources. Instead, it seems that development standards to address pollution from private development would be more effective, and the logical top priority for this Plan. The sentence would be less misleading if it said "pollutant loads in the RR- SC basin could potentially increase by up to 85% as a result of future development, if treatment and /or other forms of infiltration are not provided for flows associated with future development." 4.3.1 Capital projects alternatives We understand that the existing drywells in our area are considered potential sources of pollution to groundwater, and that they need to be decommissioned to meet federal and state laws. However, not much else is very clear or convincing in this section about how (surface water) pollution will be addressed in our Basin, or what pollutants are of concern, or how the Basin Plan contributes to solving identified problems. In particular,