PLEASE ACT RESPONSIBLY AT ALL TIMES. THE BANAGHER DAM STRUCTURE IS NOT ACCESSIBLE AND IS MONITORED BY THREE CAMERAS AND A PA SYSTEM.
There may be restrictions on access to parts of the forest from time to time to facilitate forest operations, if so please adhere to safety signage which will be posted for your safety.
The Cache
The cache is a small tablock box, in a cammo'd bag, containing a log, pencil and a few swaps.
The cache can be approached from any of the three waypointed car parking areas. I use the Birren Road access (PARK1) and it takes the hour to get to the dam but with the reservoir for company along the way. Most of the walk is on forestry roads, with the exception when coming from the Dungiven side(PARK2), as this is tarred the whole way to the dam and could be cycled and is pushchair friendly.
GZ is just off a little slip road from the main forestry road. There is no need to go 'cross country'. GZ is at a safe distance from deep water, as always, keep geokids on a short leash near water.
The Bumph
The Altnaheglish Reservoir supplying the surrounding district and the city of Derry was built between 1920 and 1939. It is of mass concrete construction with a curved dam 42m in height from the foundations, making it the highest dam in Northern Ireland and the 8th highest in Great Britain. Repairs carried out in the 1950s have masked the original stepped appearance, but the detail is still preserved beneath. The dam impounds some 2270 million litres of water and supplies approximately 20 million litres per day.The filter house located in Banagher Glen was built in 1937 and went out of use following the building of the new filter buildings at Caugh Hill in 1968.
In 1952 fragmentation of the concrete on the downstream face was first noticed. In 1964 pressure grouting of the concrete and foundations had no effect on the high water pressure in the rock and, accordingly, the 77ft long central spillway was lowered in 1968 by some 6ft. This reduced the capacity from 500million gallons too 390 million.
The increasing demand for water in the 1980's lead to a re-examination of the dam. In order to restore full storage, a new overflow was constructed to the side of the dam and the old overflow sill was built up. A rock berm was placed in front of the concrete dam, and these two elements, when taken together, provided an adequate factor of safety. The works were completed in 1987 and the dam as seen today contains 500million gallons of water. If you are REALLY lucky and the reservoir is over capacity then the sluice will be in use and the sight and sound of this is something to behold.
Banagher Glen is a secluded, steep wooded glen leading to Altnaheglish Reservoir and Banagher Dam (from PARK2). Banagher Glen contains one of the largest intact examples of old sessile oak woods in Northern Ireland. One of the oldest ancient oak woodlands in Ireland, Banagher Glen is a Nature Reserve and Special Area of Conservation, preserving one of the few surviving examples of old-growth deciduous woodland in Ireland. A peaceful place the Glen itself offers a tranquil place to walk whilst a 14 km circular walk is available through extensive Banagher Forest, Co. Derry’s largest commercial forest. Banagher Glen and Forest is open all year around. Main car parking and toilet facilities (09.00 – 2100 Saturday + Sunday, June and September and until 2100 daily July and August) are available at waypoint PARK2. The Glen is the largest surviving intact block of semi-natural woodland in Northern Ireland and contains oak, rowan, hazel, hawthorn and holly. Ferns and mosses thrive in the shady parts and in spring the glen floor is carpeted with wild flowers; bluebells, wood anemone and sorrel. Wildlife includes stoats, squirrels, silver-washed fritillary butterflies and common hawker dragonflies, and birds of prey such as buzzards and sparrow hawks.
The 8.7mile circular walk in Bangher Forest takes in the Glen, Altnaheglish Reservoir, Banagher Dam and the Glenedra River valley. More caches to follow to guide round this route.