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58 Attachment IX TO: Northern Human Services Center Task Force FROM: Paul Thames, PE, County Engineer DATE: July 27, 2000 SUBJECT: Wastewater treatment system options for the Northern HSC In March 2000, the, Kennedy tract portion of the Northern HSC property complex was evaluated by Orange County Environmental Health staff to determine the specifics of its utility for on -site wastewater treatment nitrification (ground absorption) fields. Environmental Health staff's preliminary finding was that the Kennedy tract contained an area (approximately 6 acres in a more or less contiguous area generally described as being from its southern and southeastern boundaries toward the center of tract) of soils suitable for conventional ground absorption technology wastewater disposal at a rate of approximately 5000 to 6000 gallons per day (gpd) with 100 percent repair area. Environmental Health staff have indicated that more extensive site evaluation and system layout/design work (involving site topography survey and soil test pit excavation) must be completed before an exact system treatment capacity can be determined. Unfortunately, the portion of the Kennedy tract containing soils suitable for use as nitrification field is also that which contains the large hardwood trees. Many, if not most, of the hardwood trees located in active nitrification fields would have to be removed during the construction of the nitrification fields. Furthermore, recreational activities in the hardwood tree area that would be set aside for nitrification field repair area would be severely restricted. Activity in this area would be limited to low impact trails and the like. The task force has expressed . an interest in evaluating the possibilities of obtaining additional properties in this area to either enhance recreational opportunities or to provide alternative sites for wastewater treatment nitrification fields. Environmental health staff have done some preliminary desktop evaluation (staff cannot do on -site soils evaluation without property owner permission) of a large parcel (the 25 acre Vanhook property) north of the Kennedy tract and one small parcel (the 2.33 acre Jones property) south of the Kennedy tract. The soils mapping and on -site soils evaluation near these tracts indicate that the Jones property may have soil types suitable for use as nitrification field while the Vanhook property appears unlikely to have suitable soil types. Furthermore, even if the small parcel does contain suitable soil types, there may be limitations (topographical constraints such as poor slopes, ditches, creeks, etc. or insufficient soil depths) to its use for nitrification field. The treatment capacity of the existing wastewater treatment system serving the Northern HSC is rated at 2400 gpd. System operational records show that wastewater flow to the system often exceeds a 3000 gpd average for as much as weeks at time. This hydraulic overloading will unquestionably shorten the life of the existing system. It is, however, impossible to predict how much the life of the system will be shortened or how much longer the existing system will continue to provide an acceptable level of wastewater treatment.