The first components of the Mulberry harbours were brought across the Channel on D+1 and the structures were in use for unloading by mid-June. One was constructed at Arromanches by British forces, the other at Omaha by American forces. A severe storm on 19 June destroyed the Omaha harbour. The Arromanches harbour was repaired and remained in use for the next ten months, with a maximum capacity of of stores per day. Of the British supplies landed in Normandy by the end of August, via the Mulberry harbour and in via the small harbours at Port-en-Bessin and Courseulles-sur-Mer. Most shipments were brought in over the beaches until the port of Cherbourg was cleared of mines and obstructions on 16 July. The most important use of the Mulberry harbour was the unloading of heavy machinery that could not be brought across the beaches. Artificial breakwaters (Gooseberries) sheltered hundreds of ships during the storm of 17–23 June, and provided shelter for craft unloading stores at Juno and Sword. A joint Anglo-American oil depot was constructed at Port-en-Bessin, fed via buoyed pipes known as "Tombola" from oil tankers moored offshore. Using this method, of petrol (half for the Second Army) was delivered by the end of August, by which time the underwater pipelines constructed in Operation Pluto were ready.