1. Field Performance Assessment of
Pretreatment Practices for Bioretention
Andy Erickson, Research Associate
St. Anthony Falls Lab, University of Minnesota
Minnesota Stormwater Research Council
June 27, Minneapolis, MN

2. Bioretention Practices
Shallow Depressions
Infiltrate Stormwater Runoff
Aesthetic Amenity
Maintenance?

3. Bioretention Maintenance
Inspection, Inspection and Maintenance of pretreatment unit(s), Pruning, Mowing, Mulching, Watering (first 1-2 months), Vegetation Replacement, Weeding, Trash Removal, Clear Outlet Structures, Sediment Removal.

4. Study Objectives
Synthetic runoff testing to measure removal of sediment and gross solids
Rock-lined inlet
Grass-lined inlet
Rain Guardian Bunker
Rain Guardian Turret (matching funds)
Non-proprietary Sump/Trench (optional)
Report results as mass-based percent removal

5. Study Site – Anoka, MN
600 ft2 Surface Area
10.5 ac drainage Area

6. Study Site Adaptations

7. Preparation for Testing
Test Flow Rates = 0.25 cfs & 0.5 cfs

8. Preparation for Testing
Sediment conc. = ~160 mg/L
d50 = 1.17mm; d50 = 0.41mm; d50 = 0.12mm
Gross Solids Conc. = ~40mg/L

9. Post-Test Quantification
Rock-Lined Inlet
Known feed & pre-rinsed rock (influent)
Remove and rinse rock (captured)
Remove and clean fabric (captured)

10. Rock Cleaning

11. Post-Test Quantification
Grass-Lined Inlet
Known feed & pre-rinsed grass (influent)
Remove and clean fabric downstream of grass-lined inlet (effluent or bypass)

12. Gross Solids Feed

13. Tests to Date Rock-lined Inlet Grass-lined Inlet 0.25 cfs x 2 reps
Procedure
Clean site
Install pretreatment
Pre-rinse, clean
Test
Collect sediment & gross solids
Prepare for next test, or restore site
Rock-lined Inlet
0.25 cfs x 2 reps
0.5 cfs x 2 reps
Grass-lined Inlet
0.25 cfs x 2 reps
0.5 cfs x 2 reps

14. Field Tests

15. Preliminary Results
Rock-Lined Inlet

16. Preliminary Results
Grass-Lined Inlet

17. Summary
Approximately 50% of proposed field testing has been completed (analysis still required)
Preliminary results suggest Rock-lined and Grass-lined inlets capture sediment and gross solids
Next Steps:
Complete testing,
Consider optional testing,
Analyze results,
Write report
Outreach (LID 2018, WRC, O&M of SCMs 2019, etc.)

18. Acknowledgements THANK YOU!! Collaborators:
SAFL: Matt Hernick, Rob Gabrielson, Peter Olson
Anoka Conservation District: Chris Lord, Jared Wagner, Green Corps
Sponsors & Partners:
Minnesota Stormwater Research Council (MSRC), Anoka Conservation District, City of Anoka
THANK YOU!!

19. Thanks for your attention! Questions? Andy Erickson eric0706@umn.edu