Interceptor System

It is difficult to know exactly when the leakage of heavier-than-water chemicals  from the chemical waste ponds first began to reach the river.  The chemical ponds were constructed in close proximity to the river and it is probable that leakage occurred shortly after construction.

In the late 1970's, excavations carried out in the area of the old chemical ponds found a layer of black, viscous tars that were almost 12 inches in thickness.  It was believed that the tars were migrating to the river and into the open ditches that carried chemical waste waters to the General WWTP.

Approximately 20 years after the flowing tars were discovered, Dow began to construct an underground collection system that intercepted the flow of organics, including dioxins and furans, that had previously leaked into the river.

In future years, a hydrogeology study of the Midland plant site would confirm that there was a large sand layer that connected a portion of the chemical waste ponds to the river.

Initially, the collection system had one design failure.  In the springtime, when the height of the river is above the top of the sheet piling barrier, the collection system was turned off.  The collection system was re-started when the river level drops below the top of the piling. 

It is possible that strong hydraulic forces may cause the collected organics to flow into the river.  In a sense, Dow has returned to one of its  historic practices... the release of chemicals during times of high river flow.

Dow has made improvements to the collection system and, beginning in 2004, the interceptor system is now operated throughout the entire year, including during the springtime floods.

Portions of the interceptor system on the west side of the river are not totally effective in stopping all of the flow of contaminated ground water from reaching the river.  With the recent discovery that a chemical waste pond may have been located on the west side of the river in the 1950's, an upgrade of the westside system is needed.

Please be patient as this section of the website is completed.