Deep-well disposal is one possible method for disposing of waste liquids. Serious concern must be given to the degrading effects on the subsurface environment that such a practice may involve. Yet probably there are geohydrologic basins suitable for injection of waste. At the same time, need for the detailed, and probably very costly, investigations of such basins that must precede injection should not be minimized.

The attractiveness of deep-well disposal usually is related to the favorable costs for injection compared with other disposal methods, such as high-temperature incineration, encapsulization, or others. Presuming that a given sedimentary unit has been evaluated thoroughly and found quantitatively and qualitatively suitable for waste injection, one still must evaluate whether it is more economically desirable to have each operator drill his own disposal-well facility, or whether it is more advantageous to collect the waste of several operators for disposal in a common well or wells. The economic scale advantages of centralized processing must be balanced against the costs of transporting the waste to the centralized facility. The optimal configuration of a centralized disposal system de ends on the relative level of these costs. An additional advantage of centralized waste disposal is the greater effectiveness with which local, state, and federal development and operating regulations may be enforced.

We have developed a general mathematical model which allows rough optimization of a multisource, variably distributed system based on limited data. The model is expressed in terms of a decision map which indicates the optimal configuration to serve distributed sources of waste and illustrates the sensitivity of the configuration to important parameters, such as mean-source separation and waste load, which characterize the source population. Application of this economic model provides additional input to the waste-management authority who must integrate these data with environment authority who must integrate these data with environmental factors to produce a final recommendation.

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