Evaluating the hydrologic and water quality performance of novel infiltrating wet retention ponds

Joshua B Baird,William F Hunt,Ryan J Winston

doi:10.2166/bgs.2020.010

Joshua B Baird, William F Hunt + Show 1 more

Open Access

https://doi.org/10.2166/bgs.2020.010

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Abstract

Abstract Wet retention ponds temporarily store and slowly release stormwater to mitigate peak flow rates and remove particulate-bound pollutants. However, with sandy underlying soils, wet retention ponds may provide additional benefits through infiltration, thereby recharging groundwater and supporting baseflow in streams. Current design guidance often requires lining wet ponds to prevent infiltration; however, modern stormwater management strategies recommend maximizing runoff volume reduction through infiltration. Two infiltrating wet retention ponds in Fayetteville, NC, USA, were monitored for one year to assess volume reduction, peak flow mitigation, and water quality. In some months, 100% of stormwater runoff infiltrated and evaporated, with cumulative annual volume reductions of 60 and 51% for the two ponds. For events up to 76 mm (equivalent to the local 1-yr, 24-hr storm), measured peak flow reductions were similar to those of typical (non-infiltrating) wet ponds (median 99% reduction). Dissolved nitrogen species, total and dissolved phosphorus, and total suspended solids (TSS) concentrations were significantly reduced in both ponds; mean percent reductions were greater than 30% for each of these pollutants. Effluent concentrations were on par with typical (non-infiltrating) wet ponds previously monitored in North Carolina. Due to the aforementioned runoff reduction, nutrient and TSS loads were reduced by (at minimum) 35 and 67%, respectively. Infiltrating wet ponds were able to meet both peak flow and volume mitigation goals, suggesting that they could be a common tool in regions with sandy soils.

Highlights

Urbanization augments stormwater runoff volumes and peak flow rates, concomitantly increasing transport of anthropogenic pollutants to receiving water bodies (Leopold 1968; Bannerman et al 1993; Jennings & Jarnagin 2002; Line & White 2007)
Total and dissolved phosphorus, and total suspended solids (TSS) concentrations were significantly reduced in both ponds; mean percent reductions were greater than 30% for each of these pollutants
The Bingham pond was monitored for hydrology and water quality from May 15, 2013, through May 31, 2014

Summary

Introduction

Urbanization augments stormwater runoff volumes and peak flow rates, concomitantly increasing transport of anthropogenic pollutants to receiving water bodies (Leopold 1968; Bannerman et al 1993; Jennings & Jarnagin 2002; Line & White 2007). Stormwater Control Measures (SCMs) are employed to mitigate some of these deleterious impacts. One such SCM is the wet retention pond (Figure 1), which has a permanent pool of water to promote sedimentation and provides additional storage capacity above the permanent pool to detain and slowly release (i.e., draw down) stormwater runoff, thereby mitigating peak flow rates (Hossain et al 2005; Smolek et al 2015). A drawdown orifice in the outlet structure (Figure 1) controls the release rate of the water quality volume (2–5 days in North Carolina) (NCDEQ 2017). Wet ponds mitigate peak flows, but typically provide little volume reduction, one of the key tenets of Low Impact Development (LID) strategies (Dietz 2007; Dietz & Clausen 2008; Wilson et al 2014)

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