Long-term Effectiveness of a Bioretention System Treating Road Runoff in Northeastern Kansas

1. Long-term Effectiveness of a Bioretention System Treating Road Runoff in Northeastern Kansas Edward Peltier, Xiaolu Chen, Kelly Kindscher and C. Bryan Young University of Kansas

2. Stormwater Management in Northeastern Kansas Changes in Population Patterns Image from Mid-America Regional Council (MARC)

3. Project Objectives Assess contaminant loadings from roads/paved surfaces Determine effectiveness of bioretention system for treatment of road runoff Hydrological Contaminant removal Develop recommendations for system design and operation Stormwater Treatment Options for Johnson County • Why Bioretention? • Small footprint • No permanent standing water • Potential to treat multiple contaminants • Low maintenance systems • No permanent standing water • Potential Issues or Concerns • Lack of region specific performance data • Long term effects of contaminant accumulation

4. Local Climate Annual Average Rainfall: 40.4 in Snowfall: 17.3 in (Nov.-March) Frost free Days: ~180 Data from NWS station in Olathe, KS

5. Bio-retention Cells Mize Lake Field Site: Mize Lake Bioretention Cells (Lenexa, KS) Located next to Mize Lake, a 7.5 acre recreational lake 0.1 acre sites constructed in 2005 to treat runoff from Mize Boulevard Studied north cell performance

6. Bioretention Cell • 2.5’ custom sand-soil mixture with wood chip mulch layer on surface • Collects runoff from two storm sewers on Mize Boulevard • Overflow structure limits standing water to ~ 9’’ depth • Additional standpipes provide direct access to underdrain

7. Water Quality Monitoring • Three sampling locations: • Roadside storm sewer • Bioretention cell influent • Bioretention effluent at underdrain outfall • Sample collection • 2007- Composite samples • 2008- Time-resolved sampling at cell influent • Storm sewer- passive sampling • Sample analysis • Suspended solids • Salts • Metals- Cu and Zn • NO3-N and PO43-

8. Rainfall and Runoff • Rainfall data collected from Johnson County ALERT raingage stations • 2 stations within 3 miles of field site • Hourly and daily rainfall data available • Compared with on- site total rainfall measurements

9. Runoff calculated using tabulated runoff curve values over the full watershed area • Total area = 0.83 acres • 40% paved surface • 12% Bioretention Cell

10. Effluent Flow Patterns • Effluent flow monitored by pressure sensor in effluent sampling pipe • Flow typically 0.1-0.5’’ in pipe during storm events • Substantially higher peaks • Peak flow within 1-3 hours after rainfall • Early peaks likely due to short-circuiting through standpipe drains • Low flow continued for up to 5 days after storm events 0.5’ rainfall October 6, 2008

11. Site Drainage • Data on water levels after severe storms collected using time-series photography with an automated camera • Hourly pictures of water level at given point in the cell • Estimate standing water drawdown rate of ~0.2 in.hr • Corresponds to soil infiltration rate of 0.45-0.55 in/hr • Full drainage takes 24-30 hours after storm event • 1 incident during study period with standing water on site > 7 days • 3-4 overflow events in 2008, 1 (so far) in 2009

12. Bioretention Cell Drawdown 1.1 inch rainfall beginning at ~ 5:00 am

16. Road Runoff: Water Quality Parameters • Data from storm events between September, 2007 and December, 2008. • Samples collected after snow melt that contained deicing salts are not included in these numbers.

17. Concentration vs. Time Profiles Suspended Solids Total Zn Total Cu Salts

18. Contaminant Concentrations By Sampling Location Change to bar graph Values are averages over all samples collected from 2007-08

19. Effectiveness of Sewer Sediment Removal • Substantial drop in TSS values between storm sewer and cell influent • Numbers are heavily dependent on small number of storm events • Total metals removal is lower, indicating association with fine particles

21. Nutrient Data Average nitrate removal of 40% for bioretention cell Pattern not observed for ‘non-reactive’ anions (chloride, sulfate) Significantly lower removal for phosphate

22. Conclusions • Stormwater quality typical of paved surface runoff • Substantial removal of suspended solids and associated metals in storm sewer sediment traps • Increased maintenance requirements, but likely prolongs cell lifespan • Cell performance generally in line with expectations and published studies • Good removal of influent suspended solids, total metals • Less removal of dissolved metals and phosphate • Natural development of vegetative cover, especially after 2008 flooding • Issues with short-circuiting and standing water under extreme conditions • Nitrate removal appears to be quite good • Possibly related to lower drawdown rates, high biological activity • Ongoing/future work includes • Soils analysis • Improved hydrological model • Analysis of site vegetation patterns

23. Acknowledgements • Tom Jacobs and Rob Beilfuss, City of Lenexa • Lee Kellenberger, Johnson County Stormwater Management Program • Dr. Stacy Hutchinson, Biological and Agricultural Engineering, Kansas State University • Students: Xiaolu Chen, Sarah Lacy and Lara Pracht • Funding was provided by the Transportation Research Institute at the University of Kansas, the City of Lenexa, the Johnson County Stormwater Management Advisory Council, and by the University of Kansas General Research Fund

24. Questions?