Found this bit of info and a pic
During the latter half of the 19th century, clay was excavated from the fields in the New Ferry area, including the site where New Ferry Park now stands.
The largest clay pit was dug where the Mayfields football pitches now stand. In the days before the silting ponds were built out into the river (in the late 1920s) a brickworks stood on the old shoreline. Bricks were pressed, baked in kilns and then loaded onto barges to be taken down the river either to Birkenhead or over to Liverpool.
The work must have been hard and the pay poor. In this picture, the boy on the right and the young man in the centre both have bare feet. The large chimney stack - behind the boy on the right - was demolished in 1924 (the event was photographed and appears on the next page). The brickworks were demolished to make way for the Bromborough Dock and silting pond (now the landfill site) that was built out into the river in 1931.
This very spot is now occupied by the United Utilities water treatment works which is next to the football pitches. The rest of the massive pit resulting from decades of clay extraction were used as a landfill site which today sits under the football pitches.