Abstract
A field-scale data collection plan to monitor and evaluate the performance of a sediment basin design was developed and implemented using portable automatic stormwater samplers, flow modules, a rain gauge, and inflow weirs. The design configuration consisted of a skimmer as the primary dewatering device, three coir baffles installed inside the basin, polyacrylamide flocculant blocks and ditch checks in the inflow channel. A sediment basin built on a highway construction site in Franklin County, Alabama, U.S. using the aforementioned design configuration was monitored over 16 rainfall events from 15 November 2011 to 6 February 2012. The basin effectively removed sediments during the early stages of construction when the correct type of polyacrylamide flocculant blocks was used, e.g., 97.9% of sediment removal after a rainfall event on 16 November 2011. It is difficult and challenging to dose sediment-laden stormwater inflow with an exact amount of flocculating agent across all runoff producing events since rainfall is a stochastic variable. Based upon results from this study, it is recommended that a minimum volume of 251.9 m3/ha of contributing drainage area be used to sufficiently size a basin, which is still significantly under-designed for a 2-year, 24-h storm event in the southeast. This paper presents challenges and lessons learned regarding sediment basin design, monitoring, and performance that are beneficial to future studies.
Highlights
Sediment-laden stormwater runoff from poorly managed construction sites is one of the leading causes of nonpoint source (NPS) pollution in the U.S and over the world [1]
The objective of this paper is to summarize the monitoring data collection plan developed and implemented, along with results of the data analyses performed in a basin constructed on a highway construction site
Using 251.9 m3/ha design standard the basin associated with 3.73 ha watershed would provide 938.9 m3 of storage, which would be sufficient to hold the observed volumes produced by rain events during both Phase I and Phase
Summary
Sediment-laden stormwater runoff from poorly managed construction sites is one of the leading causes of nonpoint source (NPS) pollution in the U.S and over the world [1]. Protection Agency (USEPA), sediment entrained in construction-site stormwater runoff is one of the most widespread pollutants affecting rivers and streams, second only to pathogens [1]. Construction-site sediment yields can be 10 to 20 times greater than those from agricultural lands, and about 1000 to 2000 times greater than those from forested lands [1]. These concerns coupled with growing pressure from regulatory agencies and public scrutiny have resulted in demands to provide enhanced methods for controlling erosion and preventing sediment-laden stormwater discharges from construction sites. The USEPA withdrew the federal numeric effluent limitation [2], many state environmental agencies enforce numeric effluent limitations.
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