What exactly are polychlorinated biphenyls?
Let’s play the fool and pretend that PCBs possess excellent characteristics such as low thermal conductivity, low flammability and good ageing and temperature resistance. Thus, they could be used in many fields, for example as flame retardant and impregnating agent, as lubricant, as plasticizer in adhesives and plastics and as additive in cements, fillers and sealing compounds. Furthermore, PCBs possess bad characteristics. How that? Unfortunately, PCBs are toxic. Each day we ingest PCB via food, airways and our skin. Over the years, PCB is continuously accumulated in our adipose. On the one hand, the current toxicity is regarded as low, but on the other, the carcinogen characteristics of PCB have been proven. In the meantime, the use of this substance has been prohibited. Production has been discontinued.

How did PCB get into the school?
Even if no new PCB is put in circulation, it used to be extensively added to building material until the early 70ies. Structures exceeding the maximum permissible values for ambient air contamination must be remediated. Such as the Fürst-Johann-Ludwig School in Hadamar, where various series of measurements determined elevated PCB values between 100 and 900 ng/m³. Prior to commencing remedial action, it has to be determined how PCB was released into the air: in short, where it comes from. HPC is retained to carry out a PCB source investigation in the school, i.e. building material is sampled and analyzed for PCB contents. This source investigation is mainly based on experience and sometimes on the “good nose”. After completion of the source investigation, we know the primary and secondary sources. In the school, these were represented by old joints at windows, joints at interior supporting pillars and façade joints as primary sources and floorings as secondary sources.

Sample Remediation
What we need now is a cost-saving remediation concept making the ambient air values drop below 300 ng/m³ of ambient air without closing the school down for certain periods of time. HPC applies a sample remediation during which the effects of various types of remedial action and the phased removal of various materials are tested in a classroom. Subsequently, the results obtained can be transferred to the entire school. We commence our sample remediation by initially removing PCB-containing façade joints and joint compounds around windows. For this purpose, the windows have to be removed. The windows have to be renewed because of rusted anchorages. The result is a contaminant reduction in ambient air, however not below the legal value of 300 ng/m³. The results required are neither achieved by cleaning nor subsequent aeration of the rooms. Therefore, we concentrate on the flooring as secondary source. The PCB-containing dust of the ambient air is also encountered in the upper sealing of the plastic floor. From there, PCB is again released into the air. The floor represents a potential risk not to be neglected because of its important surface compared to the space volume. We remove the upper sealing layer and re-seal the floor. Well done: The ambient air value falls below 300 ng/m³.

HPC is retained by the competent authorities
The results of the sample remediation are also satisfactory for the competent authorities, i.e. the rural district, which request a remediation concept for the entire school. However, the regular schooling is not to be disturbed. The pupils cannot be relocated because there exists no suitable building in the near surroundings. The only possibility for individual classes to be accommodated would be the installation of 10 – 15 containers. The big complex of buildings provides space for 2500 pupils, approximately, and consists of four coherent building sections with nested ground plans. Within one month, HPC submits the remediation concept for the entire school. This concept includes the removal of all windows with associated preparatory works, dewaxing of the floorings and the complete clean-up of all rooms with inventories. A total remediation period of 2 years is scheduled during which each building section is scaffolded and remediated from top to bottom taking one story at a time. Each story has to be sealed off and remediated separately. The classes housed in the individual stories have to be relocated to the containers. For this purpose, we elaborate an additional time schedule coordinating all works required. What proves difficult is the logistic organization: The nested ground plans of the four building sections require separate access routes for teachers and pupils.In addition, all necessary escape routes have to remain clear. The classrooms for special school subjects cannot be relocated due to their particular equipment and have therefore to be remediated during the summer holidays.