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Park City hydrant research group
 

Optimizing Stormwater BMP Performance 

Logan City and surrounding municipalities are seeking to address storm water quality and quantity issues, but they need locally generated quantitative research to accurately depict the effectiveness of their storm water retention activities. This ongoing study is providing valuable data for local decision makers.

 
 

Citric acid applied to vegetationApplying citric acid to vegetation at field demonstration site.

Study Area:

Logan, UT (Cache Co.)

Principle Investigators:

R. Ryan Dupont
(ryan.dupont@usu.edu)
Joan McLean
(joan.mclean@usu.edu)

Co-Researchers

Bill Young (Logan City Public Works) 
iUTAH Research Coalition
Cache County Stormwater Coalition, Salt Lake City Public Utilities

outline map of Utah

Students:
Trixie Rife (PhD), Sarah Guzman (MS), Darriane Willey (BS), Joydino Beyale (BS), Holly Flan (BS), Mitch Steele (BS)




Project Description

The Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) water pollution control program mandates that municipalities across Utah install structural storm water best management practices (BMP) as a means of reducing polluted runoff from major industrial facilities, city storm sewers, and construction sites that disturb five or more acres of land. Storm water detention basins are often used in response to this federal mandate. This program aims to minimize discharge volumes and pollutant loadings from urbanized areas entering receiving water bodies and to address the increased water quality problems and flooding from urban and rural non-point sources.

Logan City and surrounding municipalities are beginning to address storm water quality and quantity issues, and they need locally generated quantitative research to accurately characterize the effectiveness of vegetative species within storm water management facilities. This study measured biomass production and water quality improvement in a controlled laboratory environment and has validated findings at a field demonstration study site. The laboratory scale study provided controlled replicates of storm water retention basins to measure plant biomass production and total nutrient and metal removal.  Water and pollutant uptake for seven vegetative species was quantified in the laboratory under simulated (frequency and duration) rainfall events. The field demonstration site (the Green Meadows subdivision storm water detention area in Logan) produced quantitative water quality improvement effectiveness data for plant production and contaminant removal in response to periodic plant harvesting for three species. Pollutant uptake by these three species has been compared to naturally propagated weed species and non-vegetated control plots. A study has also been completed evaluating the potential for increasing plant metal uptake through addition of citric acid, a metal chelator. Additional studies evaluating green infrastructure performance for stormwater capture and treatment have been initiated.

biomass graphic
metalsin plant tissue
Biomass and metal (copper and zinc) mass in the aboveground plant tissue at the Green Meadows field demonstration site per unit area from 2011 to 2014. Error bars represent ± standard error. Letters represent significant differences based on Tukey HSD (P<0.05)

Results

Data analysis for nutrient and metal removal data from the lab greenhouse study show evidence of species differences in nutrient and metal concentrations accumulated in the harvestable, above-ground biomass, suggesting that common reed and sedges are optimal plants to improve the quality of stormwater in arid, northern Utah.

Long-term field-scale performance monitoring at the Green Meadows field demonstration site during FY11-FY15 provided data on contaminant removal performance during summer and fall 2015 in response to citric acid addition. These data continue to indicate significant storm water retention and infiltration capacity within the collection system. The demonstration site continues to provide total containment of stormwater generated from the subdivision, resulting in 100% pollutant removal from surface water discharge. All data collected were added to the database of nutrient and metal uptake and harvesting performance.

Plant biomass production (sedge, sunflower, cattail, naturally seeded plots), and nutrient and metal mass recovery from the treatment areas, as a function of seasonal harvesting (mid- and end-season versus only end-season), was evaluated and complete for FY11 through FY14 growing seasons. With no surface discharge from the planted areas, maximum nutrient and metal removal is possible in these systems. Biomass significantly increased every year from 2011 to 2013 for sedge, sunflower, and cattail, but did not increase from 2013 to 2015 indicating that these species had reached steady-state levels after 2 to 3 years of growth. The naturally seeded, mixed plant community initially provided significantly higher biomass than other single test species, but by FY15, biomass densities did not vary among any of the planted treatments.

Citric acid was added to the site to investigate the potential for increased metal and nutrient uptake into the harvestable plant tissue. It was found to increase metal solubility in the soil-water, but did not significantly increase uptake into the aboveground tissue. However, species differences were found in metal uptake performance. The sedge treatment took up significantly more Cu and Zn in the aboveground plant tissue than sunflower and cattail in 2014, indicating that species selection can have a significant impact on metal uptake, and on-going control of metal accumulation in storm water treatments systems.

A study to investigate the effectiveness of green infrastructure modifications to conventional curb and gutter stormwater systems (300 East between 9th and 10th South in Logan) in order to intercept and treat the first flush of contaminants in stormwater began in FY15. Curb flow meters to monitor gutter flow interception through curb cut outs  were designed, tested, calibrated and installed at the 300 East site to evaluate the hydraulic efficiency of the curb cut system. Soil pore water lysimeters were installed to monitor nutrient uptake by grasses in the bioswale, and samples of soil below the bioswale are being collected for metal uptake and transport analysis.

curb flow meter

 curb flow meter

Instrumentation / Workflows

ICP-MS. Are there any instruments or workflows you would like to highlight? or other information to add here?

root samplesroot samples1root samples 2root samples 3sampling

Benefits to Utah

This study is providing data about the effectiveness of local vegetation species in removing storm water nutrient and metal runoff pollution for Utah municipalities to use to optimize stormwater BMP systems.  The data are specific to Utah’s climate and geologic conditions. Logan City officials intend to utilize this information in the upcoming TMDL regulations that target reductions in the nutrient loading (particularly phosphorous) of discharges into Cutler Reservoir. Additionally, the quantitative results will prove critical to Utah’s BMP designers and managers who are responsible for species selection under local/regional site conditions and nutrient and metal removal requirements.

New EPA Grant 

Stormwater management is changing, and UWRL researchers are among the experts who will decide just how that happens. R. Ryan Dupont and several other UWRL and USU faculty members will study the  feasibility of harvesting stormwater to recharge underground aquifers as part an EPA grant that totaled $3.3 million and is split between five proposals nationwide. (Read More)