What makes this assumption plausible

Firstly, we need to mention that groundwater contamination near the waterworks must not necessarily be connected to Buna only, as there are other known contamination sources in the area (e.g. Leuna). Also, there are other reasons that might have led to the shutdown of the waterworks. Over the decades, despite regular improvements of the well-system, the Saale meadows could just not provide enough clean water for the whole city of Halle anymore and it became more convenient to use the distant water supply. The latter explanation would be in line with the official press statement (Lohmann 2007), but we felt compelled to dig a little deeper than that.

Most conspicuous in this situation is the direct adjacency of the waterworks and the Buna Werke. Not only did the waterworks retrieve their water from the Saale-Elster meadows, on the very banks of which Buna lies. As can be seen in Figure 2, the southernmost part of the pumping system reaches as far as several hundred meters away from the plant, divided from it only by the village of Korbetha and the Saale river itself. Usually, according to the geologist we spoke to, a river acts as a barrier for groundwater flow. However, he specified, in cases of strong consumption by the waterworks and the resulting subsidence of the groundwater level, both of which were the case here, this barrier can be broken. Then, groundwater from the other side of the river is drawn over, which in this case is favored by the water-conducting gravel layer reaching from the boundaries of the Buna site far underneath the Saale and its meadows.

But there is another factor that makes it very plausible, that the waterworks had a pollution problem. As was already mentioned earlier, Kater and Koch (2007) describe that the high water-output of Beesen waterworks causing the fall of local groundwater levels was counteracted by artificial infiltration of groundwater (ibid.: 88). However, they also explain that this intensive groundwater use increases the groundwater flow velocity, thus decreases the dwell time of the water in the soil, and thereby the effectiveness of natural water filtration, causing a decline in water quality not only in the wells closest to the contaminator, but also in those further away (ibid.: 86).

Additionally, the described phenomena of disabling the natural boundary of the Saale river as well as deteriorating natural filtration paths both take effect if the extracted quantity of water is too high (which it apparently was). The function of the waterworks might not, however, be compromised, as long as they are only used in cases of emergency, as they have been since the shutdown.