CAVE DIVING AND THE ENVIRONMENT

FORAME SPRING

(Giavera, del Montello,TV 1993 - 97)

The Forame spring is sited at the foothill of Montello, a karstic area of 12 sqkm in NE Italy. The hill is highly forested, the average elevation is 100-300 m. a.s.l. and annual rainfall around 1200 mm. Surface topography is characterised by dolinas and blynd valleys. Rock formation is conglomeratic of Messinian age (10 M.Y.), with clay and sandstones interbedded. Bedding is slightly horizontal plunging 10° SE (see top figure). Many caves have been explored and mapped to present (80) and one of them is counted as the second in the world in conglomeratic rocks (more than 15 km). Sources are scarce and temporary and their flood discharges are less than 20-30 lt/sec. The Forame spring with its normal 100 lt/sec and peaks of 1500 lt/sec is by far the most important. After the II World War some places in the forest have been occupied by military bases for various purposes. In an area upslope the source, some underground fuel storages have been digged. The reservoirs were hidden in the natural dolinas, covered by concrete roofs with green grass on top. In 1973 one of these tanks was destroyed during a severe storm by two flashes, losing its entire content of 2000 ton of gasoline. Since than hydrocarbon compounds were slowly released from the source, with higher percentages during floods (see middle figure). The spring is located 400 m from the destroyed tank. After a preliminary hydrogeological study and a complete exploration and survey of the spring, we discovered that hydrocarbons still come from a buried tunnel at 120 m from entrance and 20 m below surface water. Passages are all underwater, with low visibility, height is between 0,6 m and 3 m. Our group have been appointed by the Corps of Engineers to assess the pollution level and prepare and coordinate a first rehabilitation project, performed during september october 1997. Four cave divers carried a submersible pump (averaging 10 lt/sec) to the farthest point from the entrance (see middle figure and below), lowering the level progressively. Another pump was positioned to the oil-water interface, and a third more powerful one, to 8 m depth (suction type). All the fluid was conveyed by a 1600 m pipe through the forest, to an oil-water separation system. After 20 days of continuous pumping, almost 10 ton of hydrocarbon compounds were extracted from the source, but most of contaminants still lay in some natural galleries above phreatic level. To complete cleanup, we have been appointed by a second project in 1998.

SCUOLA NAZIONALE di SPELEOLOGIA SUBACQUEA

(Società Speleologica Italiana)

via G.da Coderta 15, 31100 Treviso (tel. 0422/411520)

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