Infrastructure - South Bank
The South Bank is the most exposed of the banks of the pond and consequently has a very chequered history with many varied repairs. The picture below shows the view looking north.
The existing clay-fill stone-clad bank has been strengthened with a facing of rock-filled gabions capped with a concrete strip. It is thought that the stone was brought in as ballast in unloaded grain barges which were placed and cemented together.
In the early 1990's the South-West corner of the bank was breached. The SMPPA with the Conservancy repaired the bank with gabions, a Terram mat and a concrete capping strip behind to protect the bank from further erosion. The gabions have moved, helped by the youth who found they provided a wonderful supply of stones for throwing into the water. To thwart this the upper section in the critical areas has been judiciously sealed.
The inside face has been repaired in the past with a concrete plinth and heavy timbers which, by 2005, had almost completely rotted. That year a large work party of volunteers helped replace them with a concrete fillet. The 2011 repairs to the West Bank were wrapped round the corner.
Inside of South West Bank before repair - 2003
Outer Wall of South West Bank
Inner Wall after repair - mass concrete behind timbers
Sluice & Apron
There was no sluice structure in the bank when the mill was functioning - it was constructed in 1936 by local builders, Louch & Co.
The traditional hand-operated guillotine sluice is used to help lower the Pond for maintenance and emergency purposes, but is only effective when the sea is below pond level and the flows through the pond are moderate. It was renovated in 2005 and replaced in 2020 (see below). It discharges through a brick-lined culvert to a protective apron extending into the mill poool. The apron has suffered over the years and it too is now in need of urgent replacement as the fissured surface has generated flows underneath it which have extended and are threatening the South bank itself.
Outfall - 2004
Inside of Culvert showing Sluice Gate
Volunteers from the Hampshire Mill Group repairing the Sluice - 2005
The gates are operated by the tide. They start to open when the sea level equals the pond level (at spring tides of around 4.7m), and then close by themselves as the tide drops. They can be manually tied back once open, if required, but this cannot be done at neap tides due to the upstream water flows. Sometimes during the non-breeding season (late September to January) the gates are tied back (during spring tides only) to assist with the removal of silting. High flows (ideally tides >5 metres and heavy rainfall) assist to sluice the accumulated silt away.
The structure is substantial as the retained water is some 2 metres deep and in addition it has to cope with the dynamic loads as they close. In 1976 the then dilapidated gates were rebuilt and the crest level lowered by some 30cm at the request of the National Rivers Agency.
The gates have been regularly checked and repaired - overhaul being needed about every five years; they were last replaced in 2014. The barnacle growth and worm casts that cover the gates, restraining chains and frame are regularly removed to ensure that the seals and mechanisms function freely.
Unfortunately in the 1950s a boy was swimming upstream as the tide was dropping when he got his foot trapped in the gates as they closed and was drowned.
New Sluice Gate
The Pond was drained for a month in November-December 2020, to enable the replacement of the tired 80 year old Sluice Gate which had been leaking badly. Nick Gates, a timber boat builder based at Emsworth Marina, used local English oak, and refurbished the original ironwork - the structure should now last another 100 years.
We have drawn on our reserves to pay for this, assisted by some very generous bequests. Sadly the Sluice concrete outfall to the south is in a parlous state and will also require costly repair requiring specialist help (and external funding) in the near future.
More photos on Nick Gates Facebook page.
Old Sluice gate
New Sluice gate
Nick Gates and his Team
View through the Sluice Gate
Gates open during repair
(Paul Russell 1999)
Gate Block Work
West Wall crack and monitoring points
All considered, the blue engineering brick flanking walls are in reasonable condition though specific problems have been experienced with the West sea frontage.
The crack in the West wall has not changed much in the past few years and is regularly monitored. The bank behind is reasonably stable and no material has been seen leaching out from it.
In 1997 stainless steel wires were cut into the brickwork to try to stop movement in a significant diagonal crack (see left).
In 2004 it was discovered that the sand bag repair at its foot was crumbling and that the foundations were undermined. Volunteers rapidly installed a concrete plinth to both replace the foundation and to strengthen the toe of the wall (see right).
Plinth strengthening tide gate wall
When the gates were refurbished a concrete slab bridge with tubular section handrails and balustrade was constructed. The section deteriorated and was reinforced in 1989 by casting a second layer on a 150mm "Bison" precast concrete plank. The lower slab continues to show obvious signs of deterioration in a marine environment - the underside concrete continues to spall exposing the rusting reinforcement.
The earlier railings were replaced in 1993 and the main members are now made up of 100mm square larch timbers placed at 45 degrees to discourage the young from climbing and diving. It is routinely inspected and volunteers replace any damaged members, with the latest repairs done in 2019.
This section covers the pond bank from the East corner to the start of the engineering brick abutment of the Tidal Gates.
The bank was probably originally faced with boards on both sides and filled with clay from the Roundhouse Meadow brick-earth clay pit.
Outside face (South)
Originally the Mill and Mill House were built over the sea to the South of the wall - and the "Slipper Mill" building was just the grain store. By 1936 the old mill house had been demolished, the timberwork of the mill itself was precarious and tales abound of its demolition.
in the 1940s the outer face of the bank was replaced with a concrete plinth which turned out to have inadequate footings. A toe was added to the wall and the sea had its way and undermined this too. It is now protected from wave action with plastic-encased gabions.
Inside face (North)
At the East corner of the pond reeds (sea club rush) are forming a beach and protecting the bank. Further along towards the gate structure the bank is made up of old timbers (railway sleepers?) with a mass concrete fill behind. This is in a parlous condition in places and will need attention.
As the mill became defunct the intake channel was filled but by the 1980s this proved inadequate. The leaking filled channel was resealed by placing a polythene sheet on the pond bottom..
A kissing gate and adjacent cycle rack were installed on the bank in 2004 as part of the path improvement programme. The bank below the path was reinforced in the gate area with galvanised wire gabions filled with stone.
East Section viewed from the South
East Section viewed from the North
East Bank - sea side - about 1920
East Bank sea side - 2005
looking along the line of the wall
where the mill house once stood