SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

to occur for the particular constituent at the specific site ! EXAMPLES OF ENVIRONMENTAL of discharge is approximated by an "environmental FATE CHARACTERISTICS WHICH attenuation factor". The greater the amount of attenua- INFLUENCE ATTENUATION FACTORS tion that is expected to Occur, the larger the attenuation As Me following cwracterist increase... EFFECT ON pec ATTENUATION FACTOR factor that would be assigned. FOR THE PROTECTION OF GROUND WATER— INCREASE DECREASE • Depth to Hl"t Gound Water(incl.utiwry fringe) Net Recharge (i.e.,[rainfalQ—fevaporal As shown in Figure 6,there are a variety of site-specific . Charactedsncs of the vadow zonr Permeability,am Porosity and constituent-specific characteristics which influence clay content the magnitude of attenuation that may be ex IonEx ted toOrganic Made Content Ion rharga Capacity am off occur. Also shown are how increases in these environ- • Pollutant Charectadsda: Polarity mental characteristics effect the magnitude of the bnb Strength(mane w4111w) Volanllty(powwi for wcor transport) anticipated attenuation and,therefore, the selection of Vis0Osity Degradability,or Blologc Activity environmental attenuation factors. OcfanolM'aear,Partition tae lir enu owl • Other Constituents that Could Increase Mobility Topography(ststepnasa of teminl a • Total Pollucant Load(mass loading) If ground water is threatened by waste constituents, . Un:"fntyof t e Data aM Assummons increases in the depth to ground water (thickness of the vadose zone),in the clay content,organic matter FOR THE PROTECTION OF SURFACE WATERS— content,ion exchange capacity or pH of vadose zone • Distance from Drainage caure • Topography(steeprrss of lanai l t materials,and in the ionic strength, viscosity, a Pollutant charecterisoa: VNannty(loss to atraosonere) degradability oroctanol/water partition coefficient ReacuMtyarDegracill Polarity (the affinity of the chemical for octanoi or soil organic OcbnollWil Pamuon Coe(ncknt(Raw) Mobility matter versus its affinity for water)of the waste • omen elution Upoaintsn That c Reaching fur ce Waters• Intel Dilution upon Bathing Surface waters constituent will cause the attenuation factor to be larger lar (min.sunace Ovate naw n.me pollutant now) g Intarconnecdurn of GmuM and Surface Water (greater attenuation expected). Increases in the net Total Poiluunt Load(mass Ioaang) xpeC • Unwuinty,of lir Data aM Assumptions recharge rate(a driving force for movement of waste constituents),in the permeability or porosity of vadose I Figure 6 zone materials,in the polarity or volatility of the waste constituent,in the concentrations of solvents or other chemicals that can increase the permeability of soils or Undoubtedly the most important characteristic that act as carriers for the constituent,or in the mass must be evaluated in the derivation of environmental loading of waste constituents will cause the attenuation attenuation factors is the relative uncertainty of the factor to be smaller(less attenuation expected as the data and assumptions used to quantify environmental constituent migrates to ground water). fate processes. The more uncertainty involved in the estimation of environmental attenuation factors,the If surface waters are threatened by constituents in a more the assumptions being used in their derivation waste,increases in the distance of travel from the site should lean toward underestimating the amount of of waste discharge to surface water,in the volatility, attenuation expected to occur. In this way,a greater reactivity,degradability or ottani/water partition assurance of water quality protection is provided. The coefficient of the waste constituent,and in the amount degree of uncertainty in the estimation of environmen- of initial dilution that the waste or leachate would tal attenuation should also be reflected in the amount receive upon entering surface waters will cause the of vadose zone and ground water monitoring that is attenuation factor to be larger. Increases in the steep- required for a waste management unit. Greater ness of the terrain,in the polarity of the constituent,in uncertainty necessitates a greater monitoring effort to the amount of interconnection between ground and assure that the attenuation factor setting process was surface waters,in the concentrations of solvents or sufficiently protective of water quality. other chemicals that can act as carriers for the constitu- ent,and in the total constituent loading will lower the Site-and constituent-specific information regarding attenuation factor. key environmental fate characteristics under reason- Page 12 California's Water Quality Standards