Mass balance equations govern the design or analysis of environmental engineering systems. The fragment constant method is very powerful and is used for estimates in approximately 84 percent of compounds. Universal Quasi Chemical Functional Group Activity Coefficient (UNIFAC) is the most common estimation method. UNIFAC has a strong theoretical base and is a computer based technique. The goal of control technologies is to confine or contain existing region of contamination, preventing any further spread of contamination. Slurry walls were developed in the mid-1940s for dam projects. A trench is excavate: a trench under a water/bentonite slurry and backfilled with PC or soil bentonite mix. Suspension grouts are often used as pre-grout for chemical grout. In the US suspension grouting is most common and accounts for fifty percent of the grouting in Europe. Sheet pile cut off walls are installed by first driving a web section of sheet piling into the ground.