Eia Clanwilliam Dam

Project Description

The Department of Water and Sanitation (DWS) identified two existing flow gauging weir structures that are not perpendicularly aligned to the direction of flow in the Olifants and Doorn Rivers.

The initiation of the proposed project is driven by the need to obtain accurate flow measurements of the associated watercourses. The existing flow gauging weir structures were not constructed according to international accepted standards, which have compromised the accuracy of the recorded flow within the watercourses.

Therefore, this necessitates the decommissioning of the existing flow gauging weir structures and associated infrastructure, and the construction of new and realigned flow gauging weir structures.

The DWS intends to realign these weirs to be located at a right angle (i.e. perpendicular) to the direction of water flow, further upgrading the existing gauging instrumentation, as well as engineering the additional scour and erosion prevention infrastructure along the flanks.

The proposed flow gauging weirs will be designed in accordance with internationally and nationally accepted design parameters, which will in turn ensure that the weir structures are capable of accurately measuring the watercourse flows. The new flow gauging weir structures will continue to provide information on the magnitude of flows in the Olifants River System and will also assist in the operational management of Clanwilliam Dam and Bulshoek Dam river releases to ensure sufficient water is available to all water users, including ecological reserve requirements of the Olifants River and estuary.

Scope of Services

The proposed project will comprise of the following overarching activities:

• Decommissioning of the existing infrastructure which will entail demolishing and removing the existing weir structures
• Site preparation and construction of the new weirs perpendicular to the watercourse flow; and
• Site preparation for the realignment of the Doorn River weir will necessitate the blasting of an existing rock outcrop to produce an estimate 270 m3 of rock. The blasted rock will be utilised for erosion protection through the placement of a rip-rap structure including a geo-textile layer along the flanks of the watercourse.

Zitholele Consulting (Pty) Ltd was appointed by DWS through Tlou Integrated Tech to undertake the Basic Assessment Process for the proposed project. The Department of Environmental Affairs has permitted the submission of one application for the realignment of both the flow gauging weir downstream of the Bulshoek Dam as well as the flow gauging weir in the Doorn River.

The proposed project included a field investigation which identified the need to undertake an aquatic assessment; wetland delineation; heritage impact assessment; a floodline assessment as well as a groundwater and surface water opinion. The public participatory process in terms of Section 19 of the National Environmental Management Act (107 of 1998)

Environmental Impact Assessment Regulations, 2014, was carried out through the entire Basic Assessment process. All commenting authorities as well as registered interested and affected parties were involved and their comments and responses were recorded and considered in the Basic Assessment Process. The outcomes of the field investigation, specialist studies and the public participatory process informed Final Basic Assessment Report.