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ass. standards,contained in Title 22 of CCR,Division 4, EXAWLES OF ENVIRONAIENTAL FATE Chapter 15,are designed to protect waters for domestic CHARACTERISTICS WHICH INFLUENCE THE and municipal supply. The Water Quality Control Plan SELECTION OF ATTENUATION FACTORS Reports of the nine Regional Water Quality Control Boards include"water quality objectives" for a variety EFFECT ON of uses of specific bodies of water. Under the recently As the following characteristics increase ATTENVej FACTO® enacted Safe Drinking Water and Toxics Enforcement FOR THE PROTECTION OF GROUND WATER— ZZLIM Act of 1986(Proposition 65),the Health and Welfare •Depth to Highest Ground Water(including capillary fringe) Agency is establishing additional criteria for concentra- Net Recharge (i.e.,(raintalf)—[evaporation]) Characteristics of the Vadose Z01116: tions of carcinogens and reproductive toxins to protect Perrreat011ity and Porosity clay Content 71 public health. The Sanitary Engineering Branch of Organic Matter Content DHS promulgates State"action levels"that are also Ion Exchange Capacity and PH Pollutant Characteristics: designed to protect human health from chemical Polarity Ionic Strength(more positive) constituents in drinking water. The U.S. Environ- Volatility(potential for vapor transport) mental Protection Agency(EPA)and the National Viscosity Dgradabilly or Biologic Activity .1 Academy of Sciences publish numerous water quality O'etanofflater Partition Coefficient(KOW) .Other Constituents;that Could Increase Mobility criteria for human health and aquatic life protection. Top""(steepnim of terrain) The California Department of Fish and Game can be Total Pollutant Load(mass loading) Volumetric Ground Water Flow Rate consulted for aquatic life and wildlife protection Uncertainty of the Data and Assumptions criteria. Publications by the State Water Resources Control Board,the Food and Agriculture Organization FOR THE PROTECTION OF SURFACE WATERS— of ATERS—of the United Nations,the World Health Organization, Distance from Drainage Courses ii Topography(steepness of terrain) and others provide additional guidelines. Often Pollutant Characteristics: several water quality limits can be found for the same Volatility(loss to at"otepners) Reactivity or Degradability chemical. In these cases,the most limiting value that is Potarity OclanoMater Partition Coefficlenit(KOW) applicable to the situation in question should be Other Constituents That Could Increase Watfillity selected as the water quality goal for use in calculating Initial Dilution Upon Reaching Surface Waters (ritinlifitim surface water flow vs.maxinvirm Pollutant flow) Designated Levels. •interconnection of Ground and Surface Waters •Total Pollutant Load(niast;loadrig) •Environmental Attenuation Factors MINNINEORM Uncertainty of the Data and AmffokM There are a variety of natural processes which act to Figure 5 attenuate(reduce the concentrations of)waste constitu- ents as they migrate through the environment. These anticipated attenuation and,therefore,the selection of processes,which are collectively grouped under the environmental attenuation factors. If ground water is term"environmental fate",include sorption,chemical threatened by waste constituents,increases in the binding,ion exchange,filtration,diffusion,dispersion, depth to ground water(thickness of the vadose zone), dilution,chemical reaction,biodegradation,and in the clay content,organic matter content,ion ex- partitioning. By collecting data on the waste constitu- change capacity or pH of vadose zone materials,in the ents and on the site in question,the amount or degree ionic strength,viscosity,degradability or octanol/ of attenuation which would be expected to occur as the water partition coefficient(the affinity of the chemical constituents migrate from the location of discharge to for octanol or soil organic matter versus its affinity for either ground or surface water may be estimated. In water)of the waste constituent,in the steepness of the the Designated Level Methodology,the smallest degree terrain,and in the rate of flow of ground water will of attenuation that would be expected to occur for the cause the attenuation factor to be larger(greater particular constituent at the specific site of discharge is attenuation). Increases in the net recharge rate(a approximated by an"environmental attenuation driving force for movement of waste constituents),in factor". The greater the amount of attenuation that is the permeability or porosity of vadose zone materials, expected,the larger the attenuation factor that would in the polarity or volatility of the waste constituent,in be assigned. the concentrations of solvents or other chemicals that can increase the permeability of soils or act as carriers As shown in Figure 5,there are a variety of site-specific for the constituent,or in the mass loading of waste and constituent-specific characteristics which influence constituents will cause the attenuation factor to be the magnitude of attenuation that may be expected to smaller(less attenuation as the constituent migrates to occur. Also shown are how increases in the environ- ground water). mental characteristics effects the magnitude of the Designated Level Methodology Summary Page 4