There were two proposals to extend the navigation at this time. The first was for a canal to North Chapel, to the north of Petworth, in 1791, and the second was for a canal to Horsham in the following year. The route was surveyed by John Rennie, who estimated that it would cost £18,133 to build, but negotiations with the existing proprietors failed, and the scheme was dropped in 1794. Meanwhile, a second Act of Parliament was obtained by the harbour commissioners in 1793, as there was serious silting of the estuary. Groynes were constructed and the existing piers were made longer. In addition, a towpath was built from the mouth of the river up to Arundel. The Act stated that the capital borrowed to finance the harbour under the previous act had been repaid, and that tolls would all be used for maintenance of the harbour and river up to Arundel, once further borrowings had been repaid. Because the inhabitants of Arundel had spent £28,300 on the harbour, boats which belonged to the port of Arundel did not have to pay any tolls. As a result of the works, the port of Arundel enjoyed its most prosperous period for the next thirty years, with ships of 200 and 300 tons able to reach the town on . Facilities improved, and there were four docks by 1840.