Comment:
From about 1850 flood water pumped from the haematite mines
around Lindal in Furness flowed to Urswick Tarn via a large
underground drain constructed from stone. This water had a
significant content of solids including haematite and
accompanying heavy metals and this severely polluted the tarn
and caused major problems of sedimentation in Gleaston Beck
which drains the tarn to Morecambe Bay. This sedimentary burden
now remains at the bottom of the tarn and at one location where
a core sample was taken it was found to be over 2 metres thick
resting on top of the natural pre-1850s organic sediments.