Temporal variability of suspended solids in construction runoff and evaluation of time-paced sampling strategies

The construction sites have been considered the type of land use with the highest pollution potential, especially due to the erosion of exposed soil surfaces. The runoff monitoring of the construction site was carried out since June 2011 through December 2015. Based on land use land cover (LULC) classification, the monitoring period was divided into active and post-construction phases. Total suspended solids (TSS) showed evident inter-phase variability in average annual event mean concentration (AAEMC) and wash-off pattern. We suggested that stringent runoff control measures should be adopted during active construction phase. Similarly, Personalized Computer Storm Water Management Model (PCSWMM) was applied to evaluate the performance of the time-paced discrete and composite sampling scheme in continuously changing LC scenario. It was found that even though the time-paced composite sampling scheme is more cost effective, it showed lower performance in EMC estimation when compared with the time-paced discrete sampling approach. The results also showed that the storm event monitored at a time discrete frequency of 5 min, 10 min, and 15 min, the maximum expected mean bias will be under the accepted level of 10% of the true EMC value. We concluded that construction phase-specific modifications in sampling scheme provides a view to generate near accurate estimates.