Environmental impacts of the construction phase of an intensive development project on a coastal forest wetland : case study : Seaward Estates, Ballito.

Abstract

Storm water runoff is a leading cause of degradation in the water quality of receiving

water bodies. Although legislation requires that Environmental Impact Assessments

(EIA) are performed and Environmental Management Plans (EMP) put in place for the

construction of high density housing developments, there is generally very little

evidence that real measures are developed to monitor and actually assess the extent

of the impact that construction activities have on the environment during the physical

construction stage.

The water quality of stormwater runoff from a mixed use catchment including

construction sites in Seaward Estates, Ballito, KwaZulu-Natal that enters a coastal

forest wetland system was characterised by monitoring programmes established at

three study areas. The effect thereof on the quality of the wetland water and sediments

was further monitored at five points along the drainage line of the system. The

investigation focussed on obtaining representative stormwater samples in order to

quantitatively identify pollutant constituents transported within stormwater runoff from

construction sites during rainfall events.

Storm water runoff event mean concentration (EMC), atmospheric deposition and

wetland water and sediment samples were collected over an eight month period. The

characterisation of stormwater runoff for this investigation included heavy metals,

oxygen demanding substances, sediments and physico-chemical analysis for pH,

conductivity and ammonia and nitrates. The majority of contaminant EMC exceeded

the South African wastewater discharge general and special limits.

The findings from this investigation will provide planners and decision-makers with a

greater understanding of the pollution dynamics of construction sites aiding in improved

best management practice decisions with regard to minimizing impacts on coastal

forest wetlands and water resources. This will lead to improved EMP and stormwater

management plans (SWMP) incorporating stormwater pollution prevention plans

(SWPPP) for construction sites.