Chilled water thermal storage (CWTS) systems in excess of 1,000,000 gallons represent an aquatic environment or ecosystems that, by virtue of size, chemically and microbiologically respond very slowly to positive or negative influence. In order to preserve long term mechanical integrity, cleanliness and water quality of such systems it is essential to recognize the key system-wide environmental factors that either promote or retard corrosion, mineral deposition or undesired microbiology. Change in any key environmental factor can establish a negative trend initially not easily identified, but once realized may be extremely difficult, costly or nearly impossible to correct. It is also essential to understand the logic behind manipulation of these environmental factors to correct deleterious trends and sustain a trouble free environment. An example is presented and extensively documented involving a CWTS system of 8,500,000 gallons capacity where seriously corrosive conditions developed over a seven year period, and were then corrected and totally kept from reoccurring over a ten year period. This was accomplished without chemical cleaning, water discharge or use of traditional chemical additives by employing only a strategy of environmental management.