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If os The slug test can be used on production wcllc, test wells, obscn anon w ells, and monitoring w cll% Objectives for the measurements include charac- tcrization of aquifer hydraulic conductivity for modeling, ground-water recharge studies, and ground-water pollution studies The method is e particularly useful in ground-water contamination E o,l • studies because the slug test can be carried out on the same wellc used for ground-water quality monitoring Also, combining the resulting values of t hydraulic eonducti%ity K ith the porosity of the rn aquifer and slopes of the ground-water table or Cr piezometric surface permits the prediction of porn water velocities and, hence, the rate of movement W of pollution plumes and transport of contaminants Z The slug test can also be useful in determining vertical distribution of hydraulic eonduetn ities in an aquifer system and other spatial variability of 001 hydraulic conducts%ity in studies of macrodisper- sion and movement of contaminants i Over the years, a number of questions and 1 comments about the slug test have been recer►cd These questions and comments are addressed in the following sections r 1 DOUBLE STRAIGHT LINE EFFECT Users of the slug test havc observed that when plotting log yt versus t as in Figure 3, they some- 00011 to 20 �0 `o times get a double straight line as shown schemat- ically in Figure 4 The first part (AB) is straight t IN SECONDS and steer, whercac the next part (BC) is straight E Fig 3 Graph of lop yt versus i for slug test on well in Salt and less steep Then, at point C, the points begin River Bed,27th Avenue, Phoenix, Arizona their expected dc►iation from the straight lint as Because y and t art tl' t'i iltiie• �� equation (3), a plot of In % , << 1 mt"O %11()%% -1 LOG yt straight line Thus insttad W tabulating K on the A basis of two measurement% of ) and 10 a at t 0 and yt at t), a number of� anis t mrasurcmcnts can be taken and J In(yp/yt)J A determined as the yo slope of the best-fitting lint through the y versus 6 t points on senulogarithmie pape r (Cigurc 3) T he straight line through the data point% can also be utcd to select two%slues of y, narneW, yo and yt, along with the time interval t hetwctn them for substitution into equation (3) Because drawdown of the ground-water table around the well becomes increasingly significant as the test progresses, the points as in Figure 3 begin to de%iatc from the straight line for large t and small X Thus, only the straight line portion of the data points should be used to evaluate (ln(yo/yt)) /t for calculation of K 0 t with equation (3) Fig 4 Schematic of double straight line effect. t