Impacts of Dredging and Marine Excavation Activities on the Marine Water Quality of the Ajman Creek in the Al Zorah Development in Ajman, United Arab Emirates.

Abstract

The study investigated the potential impacts of dredging and marine excavation activities on the marine water quality of the Ajman Creek during the Stage 1 and Sector 2 of the South Marine works of the Al Zorah development in Ajman, UAE. Permission was secured from the Project Manager to use the information from the two (2) year environmental monitoring activity where the author was commissioned as the environmental consultant. This descriptive research used the marine water quality monitoring data collected during the two-year construction. Two (2) statistical analysis tools, ANOVA and bivariate correlation were used in this study. The main analytical method for this study is semi-quantitative in nature. Quantitative data was gathered from the laboratory sampling and chemical analysis, but the analysis was more descriptive supported by statistical analysis. The study was limited on the data gathered from the laboratory sampling and chemical analysis at three (3) sampling locations within the project site at the mid water depth, and physical water quality parameters measured were temperature, pH, salinity, turbidity, Dissolved Oxygen (DO), total dissolved solids (TDS) and total suspended solids (TSS). Sampling and testing were performed every two (2) weeks at the same three (3) locations. Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), heavy metals and others were not tested.

The result of the monitoring showed that pH had increased from the baseline of 6.16 to 8.30 at the end of Sector 2 phase; however, this was still within the standard set by authority. The percentage change in the salinity and TDS exceeded the limit during several monitoring activities (<5% and <2% respectively) due to release of carbonates from the excavation sites. TSS and turbidity readings also exceeded the limit; however, the average TSS and turbidity were within the maximum limit (EAD, <33 mg/L, DM 25 mg/L max for TSS; 10 NTU for turbidity). The DO reading was affected by both release of sediments from the excavation and decrease in the oxygen solubility due to increase in temperature of water. In general, DO was maintained at the allowable limit (>4 mg/L). As a conclusion, statistically there was no significant difference among three locations based on the following parameters: temperature, pH, conductivity, salinity, TSS, TDS, turbidity, and DO. Direct correlation among temperature, pH, conductivity, salinity, TDS, TSS, and turbidity was noted. However, there was an inverse correlation between temperature and DO. Results suggest that the construction of the quay walls, revetments and marinas during the Stage 1 and Sector 2 of the South Marine work were implemented sufficiently with mitigating measures in place. It is then recommended to include chemical marine water quality parameters such as BOD, COD, chlorophyll and heavy metals; extend to assess the potential impact on the benthic organisms and migratory bird species for ecological equilibrium.