North St. Paul Resilient Communities Reduction in Total Phosphorus to Silver Lake

Prepared by: Matthew Bonnema, Gwyneth Perry, Nathan Warner and Christopher YoungPrepared for: Prof. John Gulliver and the City of North St. Paul

Valley Branch Watershed DistrictSilver Lake Watershed

Provided by N. St Paul

Current Stormwater Control Measure (SCM)Bio-infiltration Basin

Photograph by Nathan Warner

Current TP Loading

Bucheck, et al. 2013

● 40 ug/L 4.57 lb/year

Initial P8 Model● Precipitation File● Particle File (National Urban Runoff Program

(NURP))● Subwatershed Data

Initial P8 ModelBio-infiltration Basin Parameters

Additional Rain GardensMethods

Bio-retention Cell -3’ Mixed Media, 40% voids-14.4” ponding depth (B soils)

Minnesota Stormwater Manual

Additional Rain GardensMethods

Image: City of N. St Paul, GIS work: Nathan Warner

Placement:-R.O.W.-Soils/Infiltration-Groundwater -Road Grading-Drainage Area-Current Land Use-Curb Cuts

Additional Rain GardensResults

Bio-retention (Rain Gardens)

(Weiss, et al., 2007)

$ = 152 x (WQV)^0.776

WQV = water quality volume ~

volume infiltrated in

m^3

Adjustment for 2014 Cost

(CPI, Bureau of Labor and Statistics)

2007 Cost ($) x 1.14 “Unit” WQV = 503 cf

30’ x 7’

Additional Street SweepingMethods● Modeled in Dr. Baker’s spreadsheet

○ Prior Lake Study○ Tymco Model 600 regenerative air

sweeper○ Simple Inputs

● Frequency: 4 sweeps/year to 10 sweeps/year

Additional Street SweepingResults

Street Sweeping Frequency

TP removed [lb]

Cost per lb TP removed [$/lb]

Current Condition: 4 times a year

15.7 $47.81

6/year (spread from April to October)

20.7 $54.52

7/year from April to November

25.7 $58.54

10/year (from April to November)

31.4 $60.00

● SHASAM model by BARR Engineering

● Create Plot: % Removal vs. Avg Runoff○ Det % Removal for

Silver Lake● Convert TSS to TP

Additional SumpsMethods

* Based on http://revolutionarybaffle.com/store/. **Maintenance costs account for two cleanouts per year priced at $80 each.

Additional SumpsResults

*Based on Installation, Unit, and Maintenance costs for the 20 years of removal design life. **SLV-7 has pipe diameter 30”, all others are 15”.

● Efficiency comparison● Removal efficiency depends highly on flow

through sump and pipe diameter● Only considered NURP for SCM comparison

Summary

SCM (Most Efficient) TP Removed [lb/yr] Cost/lb TP removed

Standard Sump (per unit) 0.007-0.102 $6,583-39,013

SAFL Baffle (per unit) 0.013-0.196 $6,267-33,302

Rain Gardens* (per unit) 0.098-0.145Avg = 0.109

$8,008-13,739Avg =$8,197

Street Sweeping (4/year) 15.7 $47.81

*based on 1% imp.

Conclusions and Recommendations

• Recommend: Street Sweeping• Further work:

• develop more realistic particle file• more hydrologic data