A topographic survey of the site had been made by the Survey Directorate of the Ministry of Housing in September 1980. No contours were shown but spot elevations in metres to hundredths were recorded on a base map with a north-south, east-west grid overlay on a 50 m interval. Datum base was Bahrain National Level Datum (BNLD). This survey was sufficient for the initial engineering accomplishment. Before construction on the two ponds proceeds, a detailed topographic survey of the pond area approach road and the pond area must be made in order to determine the exact quantities of fill required.
The wet laboratory, dry laboratory and a generator substation are currently being constructed as a part of the Ras Haiyan project. The topographic survey done by the Public Works Department in connection with the land filling of the laboratories area was referenced to a temporary benchmark established on the main north-south road fronting the property, rather than to BNLD used by the survey Directorate. This makes direct correlation of the two surveys difficult and one of the tasks of the next survey crew will be to relate the elevations of these surveys.
Investigation and discussion with government engineers indicates that, if the ponds area is filled to the level of the fill in the laboratories area, this will be adequate for the ponds' base (see Soils discussion in Section 3, below). Based on the fill recently placed for the project main access road, the laboratory construction and the adjacent Ministry of Information antennae farm, the fill required under the ponds to keep their bottoms reasonably above tidal infiltration was preliminarily estimated at 0.5 m, with an additional 0.1 m for planned settlement of the subgrade. The exact quantity and thickness of fill required will have to be calculated when the pond site survey is made prior to construction.
