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

Transcription

1 Street Sweepers as Cost-Effective Stormwater BMPs for Municipal Parking Lots in Charlotte Jason Hunt Charlotte-Mecklenburg Storm Water Services September 19, 2017

2 Background City Solid Waste Services Sweeps City streets, mostly for aesthetics Storm Water Services Water Quality Program Post Construction Stormwater Ordinance Charlotte-Mecklenburg BMP Design Standards Manual» Pilot SCM Program Pollution Control Watershed Planning

3 Background (continued) How do the cost-effectiveness of different BMPs/SCMs compare? How do you compare the cost-effectiveness? $/lb/yr? Which pollutant(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?

4 Street Sweeping Research 2011 Lower Monocacy Implementation Plan

5 Street Sweeping Research (continued) From: Roger C. Sutherland, 2013 «Clean Streets Mean Clean Streams»

6 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

7 Parking Lots Selected for Study Parking Lot Heavy Use Address Area Lot Use Charlotte Department of Transportation 6001 General Commerce Dr., Charlotte, NC, ,930 ft 2 11,049 m acres Heavy Truck Traffic, Landscape and Construction Material Sugar Creek Waste Water Treatment Plant Light Use LYNX Woodlawn ParknRide Charlotte Landscape Management Lot 5301 Closeburn Rd, Charlotte, NC, Old Pineville Rd, Charlotte, NC, Tuckaseegee Rd. Charlotte, NC, ,154 ft 2 17,573 m acres 132,289 ft 2 12,290 m acres 134,527 ft 2 12,498 m acres Storage, Staff Parking Staff Parking, Service Vehicle Use. Commuter Parking Staff Parking, Landscape Material Storage and Distribution

8 CDOT Northeast Street Maintenance Division

9 Sugar Creek Wastewater Treatment Plant

10 CATS Woodlawn Park and Ride

11 Landscape Management

12 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

13 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

14 Example: Cats Park and Ride Results Sample # Wet Weight Water Content Dry Weight Yield ADD (days) Intervening Precipitation (lbs.) % (lbs.) (lbs/acre) (inches) 1 10/20/ /20/ /19/ /26/ /29/ /25/ /9/ /20/ /15/ /20/ /11/ /28/ /28/ Sum 2086 Average Max Min

15 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 Max 3,532 3, Avg 1, Total dry sediment lbs/acre collected (Oct 2015 Dec 2016) CDOT WWTP P&R LM

16 Cost per lb sediment removed Site Number of Collections Particulate Mass Collected Cost for Collections Cost per Unit Mass (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.

17 Nitrogen and Phosphorus Site TN Lbs TP Lbs TN $/lb. TP $/lb. CDOT $5,254 $4,363 WWTP $830 $1,462 P&R $4,728 $65,466 LM $984 $9,107 Overall $1,484 $3,371

18 Metals Removed Cu Ni Zn Cr Cd Pt Pb mg/g mg/g mg/g mg/g mg/g mg/g mg/g CDOT WWTP PnR LM

19 Charlotte TSS metrics compared to literature $0.52/lb - $3.30/lb TSS Charlotte Sutherland, 2013

20 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 BMP s CWP, 2013 Illicit Discharge Control $35-$71 Program Pet Waste Programs $3.35 Street Sweeping $1,400-$2,200

21 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 BMP s Illicit Discharge $8.82-$17.62 Control Program Pet Waste Programs $0.43 Street Sweeping $3,500-$14,600 CWP, 2013

22 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

23 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

24 Other Considerations for Sweeping Pros Speed of implementation Not limited by available space Cons No peak flow attenuation Rain events wash off pollutants between sweepings

25 Conclusion Parking lot sweeping can be a very cost-effective BMP for sediment reduction based on literature values for variety of SCMs/BMPs

26 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?

27 Questions? Jason Hunt Water Quality Planner Charlotte-Mecklenburg Storm Water Services