The coordinates will take you to the middle of three information boards. You will need to get info off all three boards to complete this multi.
This area is of course the site of the Old Dock built in 1715 by Thomas Steers, the world's first enclosed commercial dock which within a century catapulted Liverpool from being just another provincial British port to one of the most important ports in the world. It revolutionised cargo handling allowing ships to be unloaded and loaded within a day at a quayside, instead of taking days or even weeks by tender or by beaching the ship at low tides.
By 1800 Liverpool was dealing with one fifth the commercial tonnage of all the other ports within the Empire combined. For periods during the 19th century the wealth of Liverpool exceeded that of London and Liverpool's Custom House, which was also sited here but never survived WWII, was the single largest contributor to the British Exchequer. Liverpool was the only British city ever to have its own Whitehall office and the port was so important to the fledgling US of A that the first American Consulate anywhere was opened in Liverpool in 1790. The building that housed it is still there on Paradise Street, now a Bistro. The consulate closed after the Second World War as Liverpool's importance as an international port declined.
Parts of the Old Dock are still there under your feet and you can go underground to see it. Liverpool Museums offer tours on Mondays, Tuesdays and Wednesdays at 10.30, noon and 14.30. Search for "Liverpool Old Dock Tours" to get the phone number to book. The tour used to be free but now incurs a charge of £6.50 per adult - I still thoroughly recommended it though if history is your thing!
The cache:
From the middle information board, starting where the text reads "In the early 1700s":
A = number of letters in seventh line, seventh word.
B = number of letters in fourth line, seventh word.
C = number of letters in third line, fourth word.
D = number of letters in sixth line, third word.
From the riverside information board, which bullet points mention the "first dock" (this is E), the "Norman castle" (this is F), "the face of the Moon" (this is G), the "Lyver Pool" (this is H) and the "psychoanalyst" (this is J)?
From the cityside information board, for how many years did the Dock-Master measure the tides? This is KL. NOTE - the board no longer contains this info so KL = 29.
The cache can be found at:
North (D+H)(G-F) (J-D)((L-B)²).(K-A)(K*D)(J/F) West (C/E) (E+K)(B+F).(H*E)(C/J)(L-E)
Note that the difficulty rating is for the area being a regular Muggletopia.