SEEPAGE OF MUNICIPAL WATER AT A COFFERDAM SITE

The City of Jeddah extends 45 kilometers in length along the eastern Red Sea coast, and about 15 kilometers in width. About 2.5 million inhabitants are living in the city. Dumping of the sewage waste is a major problem to the city. The municipal dumping site of Jeddah is located at the east side, over the valley surface surrounded by medium to low relief mountains, causing a lake of almost 1.5 x 1 km in size. The city is surrounding the site from west and south. The general slope topography is from north to south and from east to west. The lake of municipal waste is continuously increasing, and moves towards south, almost 3 km away to reach the city houses. Coferdam was built on the south side of the lake, as a temporary solution to stop the lake movement towards siuth. Intensive in-situ field study along the whole site include performing detailed tests such as soil sieve analyses, permeability tests, field density, and Mackintosh tests. In addition, detailed lineament analysis was performed around the dam site was commenced as well. Field investigation proves two sources of leakage of municipal water are observed: 1) under the dam site throuhg the valley soils and 2) from the abutments of the dam through the rock masses fractures system. The investigation prove the unsuitability of the site to be used as a temporary cofferdam for sewage dumping for Jeddah city, and the environmental hazards are obvious.