ornamental bridge was erected at the western end. The project took 15 years to complete, and cost £6,612. The bridge, which consists of three unequal arches with balustrading along the top, was designed by Stephen Wright, and is long. It is a Grade II* listed structure. Improvements to the lake were carried out in 1786 under the direction of Mr Marson the estate manager. The 4th Duke of Newcastle built a cascade below the bridge in 1823, and a new one in 1835, when the work was completed by Mr Grey. The duke described the construction as "ingenious and well managed." There were problems in 1842, when the culvert feeding water from the lake to an engine which supplied water to the house was found to be clogged with fine tree roots. In spring 1845, 1846 and 1847, the duke drained the lake to make it wider and to improve the banks, which he felt looked "neither natural nor handsome" in places. Below the ornamental bridge, a weir drops the level by around . In Victorian times, the park had two independent water supply systems, one supplying the house and its associated buildings, and the other supplying the farm and Hardwick village. About 500 people lived on the estate at the time. The house supply came from an artesian well, and was pumped to an underground reservoir, which held , from where it travelled by gravity. The difference in levels of the two parts of the lake was sufficient to power a Gilbert Gilkes and Gordon turbine, which drove the pump. The two systems became one in 1931, when a treble ram vertical pump was installed, driven by the existing turbine. Pumping is now done by electric pumps, but the original machinery is still in place, and was for a number of years used to supply the park with water if there was a power cut. The lake covering some has been affected by subsidence caused by coal mining, and UK Coal funded remedial work in the 1980s and in 2004. The lowering of the water level during this work revealed the charred remains of the Lincoln, a one-third scale naval frigate which the Duke bought in 1871, and which was destroyed by fire in the 1940s. The river leaves the lake by a weir and cascade near Hardwick village, beyond which there is a ford, and another weir beyond