Street Sweepers as Cost-Effective BMPs for Municipal Parking Lots in Charlotte

Jason Hunt Charlotte-Mecklenburg Storm Water Services September 19, 2017 Background

• City Solid Services – Sweeps City streets, mostly for aesthetics

• Storm Water Services – Program • Post Construction Stormwater Ordinance – Charlotte-Mecklenburg BMP Design Standards Manual » Pilot SCM Program • Pollution Control • Watershed Planning Background (continued)

• How do the cost-effectiveness of different BMPs/SCMs compare? • How do you compare the cost-effectiveness? – $/lb/yr? – Which (s)? – What is the lifespan of a conventional SCM? – How to account for maintenance costs? – What about dredging and disposal of accumulated sediment? – Translating hydrograph data into $/lb/yr? Street Sweeping Research

2011 Lower Monocacy Implementation Plan Street Sweeping Research (continued)

From: Roger C. Sutherland, 2013 « Clean Streets Mean Clean Streams » Street Sweeping in City of Charlotte

• Solid Waste Services – ~35,500 miles swept/yr – Focus on aesthetics, larger debris – Data available for $/tons/yr/mile swept but how much sediment? – What about City owned parking lots?

• Sweeping pilot – We have a lot of data for other BMPs – Literature values mostly for street sweeping and not parking lots – Calculations and assumptions behind literature values can be hard to verify Parking Lots Selected for Study

Parking Lot Heavy Use Address Area Lot Use Charlotte 6001 General 118,930 ft2 Heavy Truck Traffic, Department of Commerce Dr., 11,049 m2 Landscape and Transportation Charlotte, NC, 28213 2.73 acres Construction Material Storage, Staff Parking Sugar Creek 5301 Closeburn Rd, 189,154 ft2 Staff Parking, Service Waste Water Charlotte, NC, 28210 17,573 m2 Vehicle Use. Treatment Plant 4.34 acres Light Use LYNX Woodlawn 4756 Old Pineville Rd, 132,289 ft2 Commuter Parking ParknRide Charlotte, NC, 28217 12,290 m2 3.03 acres Charlotte 701 Tuckaseegee Rd. 134,527 ft2 Staff Parking, Landscape Charlotte, NC, 28208 12,498 m2 Landscape Material Management Lot 3.09 acres Storage and Distribution CDOT Northeast Street Maintenance Division Sugar Creek Wastewater Treatment Plant CATS Woodlawn Park and Ride Landscape Management Study Design

• 1 year pilot • 2 heavy use lots – sweep 2 times/month • 2 lighter use lots – sweep 1 time/month • Don’t sweep if it has rained at least 0.5 inches in the 48 hrs • Empty sweeper before and after sweeping • Weigh contents of each lot separately • Analyze contents from each lot – Dry weight sediment – Nutrients – Metals Pilot Implementation (Oct 2015 – Dec 2016)

• Supreme Sweepers – Swept each lot with empty sweeper & weighed contents individually – Stewart Amos S-4 broom sweeper – Used weigh stations for heavy loads & bagster totes for lighter loads

• UNC Charlotte – Homogenized material collected for each lot – Collected 5 gal subsamples for analysis – Conducted all laboratory dry weight, grain size and chemical analyses – Coordinated with Supreme Sweepers on schedule and forecast Example: Cats Park and Ride Results

Wet ADD Intervening Sample # Weight Water Content Dry Weight Yield (days) Precipitation (lbs.) % (lbs.) (lbs/acre) (inches) 1 10/20/2015 184.62 0.79 183 60 10 -- 2 11/20/2015 312.6 1.08 309 102 1 8.4 3 12/19/2015 106 0.38 106 35 2 3.12 4 1/26/2016 75.6 6.40 71 23 4 12.67 5 3/29/2016 324.4 4.30 310 102 2 5.38 6 4/25/2016 98.3 0.26 98 32 3 1.27 7 5/9/2016 91.8 0.55 91 30 6 2.91 8 6/20/2016 170.6 0.07 170 56 5 5.74 9 8/15/2016 181.8 0.44 181 60 10 3.29 10 9/20/2016 130.4 0.54 130 43 18 1.97 11 10/11/2016 25.5 1.28 25 8 3 6.97 12 11/28/2016 67.2 8.31 62 20 48 0.05 13 12/28/2016 357.5 2.24 349 115 22 2.66

Sum 2086 Average 2.0 160 53 10.3 4.54 Max 8.31 349 115 48 12.67 Min 0.07 25 8 1 0.05 Results – Dry Weights

Total dry sediment lbs collected (Oct 2015 – Dec 2016) CDOT WWTP P&R LM Total 22,470 20,831 2,086 3,523 Min 79 60 25 67 Max 3,532 3,603 349 439 Avg 1,021 992 160 415

Total dry sediment lbs/acre collected (Oct 2015 – Dec 2016) CDOT WWTP P&R LM 374 228 53 71 Cost per lb sediment removed

Site Number of Particulate Cost for Cost per Collections Mass Collections Unit Mass Collected (dry) collected CDOT 22 22,470 $11,633 $0.52/lb.

WWTP 21 20,831 $11,104 $0.53/lb.

P&R 13 2,086 $6,874 $3.30/lb.

LM 16 3,523 $8,460 $2.40/lb.

Overall 72 48,910 $38,070 $0.78/lb. Nitrogen and Phosphorus

Site TN TP TN TP Lbs Lbs $/lb. $/lb.

CDOT 2.21 2.666 $5,254 $4,363

WWTP 13.37 7.594 $830 $1,462

P&R 1.45 0.105 $4,728 $65,466

LM 8.60 0.929 $984 $9,107

Overall 25.64 11.294 $1,484 $3,371 Metals Removed

Cu Ni Zn Cr Cd Pt Pb

mg/g mg/g mg/g mg/g mg/g mg/g mg/g

CDOT 0.052 0.005 0.022 0.017 0.077 0.000 0.005

WWTP 0.049 0.008 0.077 0.014 0.112 0.001 0.010

PnR 0.012 0.021 0.113 0.016 0.071 0.004 0.006

LM 0.115 0.008 0.141 0.013 0.117 0.004 0.026 Charlotte TSS metrics compared to literature

• $0.52/lb - $3.30/lb TSS Charlotte

Sutherland, 2013 Charlotte TP metrics compared to Literature

• Total Phosphorus – Sweeping $1,462 - $65,466/lb ($3,371/lb average) Structural BMP’s Bioretention $338-$2,000 Bioswales $2,642 Detention Basins $10,500-$21,000 Infiltration Basin $3,237-$3,383 Media Filtration $4,500-$4,900 Porous Pavement $12,000-$70,000 Non Structural Illicit Discharge Control $35-$71 BMP’s Program Pet Waste Programs $3.35 Street Sweeping $1,400-$2,200 CWP, 2013 Charlotte TN removal $/lb Compared

• Total Nitrogen – $830/lb - $5,254/lb TN ($1,484/lb average) Charlotte Structural BMP’s Bioretention Units $338-$2,000 Bioswales $308

Detention basins $1,100-$4,600 Infiltration Basin $486-$494 Media Filtration $975-$1,060 Porous Pavement $1,900-$14,000 Non Structural Illicit Discharge $8.82-$17.62 BMP’s Control Program Pet Waste Programs $0.43 Street Sweeping $3,500-$14,600

CWP, 2013 Summary

• TSS – More cost effective ($0.78/lb) than Sutherland (2013) for sweeping – More cost effective than all other BMPs summarized by Sutherland (2013) • Phosphorus – Cost effectiveness similar to CWP for sweeping – Charlotte results highly variable – More cost effective than detention basins, infiltration basins, porous pavement, media filtration – Less effective than pet waste programs, IDDE, and bioretention Summary (continued)

• Nitrogen – More cost effective than CWP values for sweeping – More cost effective than porous pavement – Comparable to detention basins and media filtration – Less cost effective than bioretention, bioswales, infiltration basins, porous pavement, IDDE programs, pet waste programs Other Considerations for Sweeping

Pros Cons • Speed of • No peak flow implementation attenuation • Not limited by • Rain events wash available space off between sweepings Conclusion

• Parking lot sweeping can be a very cost-effective BMP for sediment reduction based on literature values for variety of SCMs/BMPs Next Steps…

• Compare to local metrics for other BMPs ($/lb/yr) • UNCC further analysis on what fraction of sediment likely to be transported with runoff – Days since last rain did not have noticeable impact on lbs pollutants removed • Determine costs if City swept instead of contractor • Consider how to implement more widely in Charlotte – Stormwater funding to Solid Waste Services? – Buy a street sweeper and hire staff? Questions?

Jason Hunt Water Quality Planner Charlotte-Mecklenburg Storm Water Services [email protected] 704-650-4255