Environmental assessment of stormwater pond impacts on a Rouge River tributary

This study was conducted to evaluate impacts of stormwater ponds in the Municipality of the Town of Richmond Hill on select physical (temperature, dissolved oxygen, and pH) chemical (nutrients) and biological (macroinvertebrate community, macrophyte and experimental Hyalella azteca and Daphnia magna enclosures) aspects of a Rouge River tributary. Over a five-month period five sites along the tributary close to the outfall of the stormwater ponds were sampled to determine if there were any impacts, cumulatively (with increasing number of pond outfalls along the tributary) and locally (above and below an outfall). Physical and nutrient parameters showed no signifiant degradation in water quality, either cumulatively or locally. Macrophytic data showed some decrease in biomass at downstream sites, but no decrease in diversity or species richness. Survivorship in the enclosures containing Hyalella azteca and Daphnia magna showed no significant cumulative change. Analysis of the macroinvertebrate community showed no cumulative or local impact until the farthest downstream site.

Environmental assessment of stormwater pond impacts on a Rouge River tributary

This study was conducted to evaluate impacts of stormwater ponds in the Municipality of the Town of Richmond Hill on select physical (temperature, dissolved oxygen, and pH) chemical (nutrients) and biological (macroinvertebrate community, macrophyte and experimental Hyalella azteca and Daphnia magna enclosures) aspects of a Rouge River tributary. Over a five-month period five sites along the tributary close to the outfall of the stormwater ponds were sampled to determine if there were any impacts, cumulatively (with increasing number of pond outfalls along the tributary) and locally (above and below an outfall). Physical and nutrient parameters showed no signifiant degradation in water quality, either cumulatively or locally. Macrophytic data showed some decrease in biomass at downstream sites, but no decrease in diversity or species richness. Survivorship in the enclosures containing Hyalella azteca and Daphnia magna showed no significant cumulative change. Analysis of the macroinvertebrate community showed no cumulative or local impact until the farthest downstream site.

Stormwater Pond Management: What You Need to Know about Aeration

This new 6-page document is intended to provide Floridians and their communities with information on a specific management practice in stormwater ponds: the use of fountains and other aeration approaches. These practices may provide opportunities both to improve water quality within the pond and protect downstream water quality. Specifically, this document gives basic information on fountains and the pros and cons of fountain installation and use. In addition, we provide information for pond managers or community decision makers on how to best manage ponds for effective pollutant removal in the pond and downstream water quality protection. Written by Samantha T. Howley, Steven P. Hohman, and Alexander J. Reisinger, and published by the UF/IFAS Department of Soil and Water Sciences.https://edis.ifas.ufl.edu/ss695

No Clear Response in the Stormwater Phytoplankton Community to Biocide Contamination

This study investigated the responses of natural phytoplankton communities of an urban stormwater pond to biocide contamination. The biocides carbendazim, terbutryn, diuron, and irgarol 1051, and their mixture, were used in two laboratory microcosm and one outdoor mesocosm studies at concentrations of 10, 100, and 1000 ng L−1. The water samples were collected in a pond receiving significant biocide contamination. The mesocosm study was carried out in the same pond. The phytoplankton community response was evaluated after 10–15 days of exposure, with respect to its taxonomic composition, abundance and biovolume. No significant changes were observed in any of the experiments. Only at the highest applied terbutryn concentration were lower numbers of taxa identified in both microcosm and mesocosm experiments. Additionally, increases in Chlorophyta abundance and biovolume, along with an increase in irgarol concentration, were observed throughout the three experiments. Nevertheless, the statistical analysis did not confirm any significant differences among the biocide treatments. These results suggest that the biocide concentrations probably were below the harmful or toxic threshold to the stormwater pond phytoplankton. On the other hand, as the investigated pond phytoplankton taxa face biocide inputs throughout the year, they could have already adapted to the tested biocide contamination.

Preserving Critical Stormwater Storage Assets at Pipeline Terminal

A slope failure compromised the integrity of a critical stormwater storage facility at a petroleum storage terminal within northern Alberta. Through periodic ground inspections and a review of LiDAR and aerial imagery, significant lateral deformation of a lined stormwater pond was identified. The potential for pond overflow and uncontrolled stormwater release into the natural environment due to compromised discharge outlets and liner integrity posed an operational and environmental risk. A fast-tracked review and assessment of both the historical and as-built construction details, a good understanding of the regional geology, and geotechnical investigation and instrumentation were required to identify remedial measures that could be implemented to restore the pond prior to the onset of major storm events. Geotechnical investigation and assessment showed weak zones in the bedrock at shallower depths than were historically encountered at the site. Spatial constraints, uncontrolled fill placement in close proximity to the pond, expansion of the pond following original construction, and compromised subsurface drainage were identified as factors that may have contributed to the failure. Assessment of remedial options considered impacts relative to both local and global factors of safety. The selected remedial option was a combination of slope unloading, shear key construction, and improved drainage with the design and construction occurring within a timeframe of 3 months to minimize the time that the pond was out of service. The paper highlights the challenges associated with the slope unloading and shear key construction that were required to control the ground movements. An approach involving sequential excavation and replacement was adopted to manage the risks associated with shear key construction. In addition, directional drill methods were incorporated to install some of the drainage measures due to the risk associated with an open cut approach. The project was fast-tracked to minimize exposure to high precipitation and limited stormwater storage capacity.