HomeMy WebLinkAboutEdina Street Sweeping Plan_FINAL
City of Edina, MN
Street Sweeping Management Plan
October, 2015
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Table of Contents
Table of Contents .......................................................................................................................................... ii
Table of Tables ............................................................................................................................................. iv
Table of Figures ............................................................................................................................................. v
Executive Summary ....................................................................................................................................... 1
1. Purpose ................................................................................................................................................. 3
2. Background ........................................................................................................................................... 3
3. Water Resources ................................................................................................................................... 4
3.1. City of Edina Lake and Pond Amendment to the Comprehensive Water Resources
Management Plan (CWRMP) .................................................................................................................... 4
3.2. Impaired Waters and TMDLs ........................................................................................................ 6
4. Stormwater Management Goals ........................................................................................................... 7
4.1. Non-degradation Policies .............................................................................................................. 7 4.2. Minnehaha Creek Watershed District (MCWD) ........................................................................ 7 4.3. Good Housekeeping/Maintenance ............................................................................................. 7
5. Methods ................................................................................................................................................ 8
5.1. Identification of Sweeping Zones .................................................................................................. 8
5.2. Methods for Estimating Load Recovery and Load Reductions ................................................... 10
5.2.1. Tree Canopy Assessment .................................................................................................... 10
5.2.1. Spatial Analysis of Edina Roads ........................................................................................... 11
5.2.2. Solids Recovery Rates ......................................................................................................... 12
5.2.3. Load Reduction Estimates ................................................................................................... 12
5.2.4. Estimating Load Recovery for Different Sweeper Types ..................................................... 13
6. Load Recovery and Load Reduction Estimates ................................................................................... 14
6.1. Baseline Street Sweeping ............................................................................................................ 14
6.1.1. Load Recovery ..................................................................................................................... 14
6.1.2. Load Reductions .................................................................................................................. 14
6.2. Enhanced Sweeping Scenario 1 – Monthly Street Sweeping ..................................................... 16
6.2.1. Load Recovery ..................................................................................................................... 16
6.2.2. Load Reductions .................................................................................................................. 16
6.3. Enhanced Sweeping Scenario 2 – Bi-Weekly Street Sweeping ................................................... 18
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6.3.1. Load Recovery ..................................................................................................................... 18
6.3.2. Load Reductions .................................................................................................................. 18
6.4. Costs Benefit Analysis ................................................................................................................. 20
6.4.1. Cost Effectiveness of Baseline Sweeping ............................................................................ 21
6.4.2. Cost Effectiveness of Monthly Sweeping ............................................................................ 21
6.4.3. Cost Effectiveness of Bi-weekly Sweeping .......................................................................... 22
7. Recommendations .............................................................................................................................. 26
8. References .......................................................................................................................................... 27
Appendix A .................................................................................................................................................. 28
Appendix B .................................................................................................................................................. 41
Appendix C .................................................................................................................................................. 46
Appendix D .................................................................................................................................................. 49
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Table of Tables
Table 1. Summary of priority waterbodies by HUC 12 with associated service level and land cover characteristics. Street sweeping was evaluated within the drainage areas of waterbodies shown in bold font. ...................................................................................................................................................... 5
Table 2. Impaired waters located within the City of Edina jurisdiction. ................................................. 6
Table 3. Tree Canopy Rating Scheme ....................................................................................................... 10 Table 4. Summary of sweeping zone characteristics including service level of the waterbody, average over-street tree canopy cover, and total curb-miles of street (length of street x 2).............. 11
Table 5. Estimated load recovery rates (lb/curb-mile/yr) for total solids and total phosphorus for three levels of effort, sweeping with a regenerative air (or comparable) sweeper. ............................ 12
Table 6. Discounts applied to load recovery predictions to estimate recoverable loads for mechanical
broom sweepers. ........................................................................................................................................ 13
Table 7. Estimated total solids and phosphorus recovery and load reduction estimates for baseline
sweeping effort using mechanical broom and regenerative air technologies. .......................................... 15
Table 8. Estimated total solids and phosphorus recovery and load reduction estimates for monthly sweeping effort using mechanical broom and regenerative air technologies. ..................................... 17 Table 9. Estimated total solids and phosphorus recovery and load reduction estimates for bi-weekly sweeping effort using mechanical broom and regenerative air technologies. ..................................... 19
Table 10. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) at the
baseline effort by major subwatershed. ..................................................................................................... 21
Table 11. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) for
monthly sweeping by major subwatershed................................................................................................ 22
Table 12. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) for bi-
weekly sweeping by major subwatershed. ................................................................................................. 22
Table 13. Summary of estimated costs and cost-efficiencies of phosphorus recovery within direct
drainage areas for each waterbody (see 5.1) for baseline, monthly, and bi-weekly sweeping scenarios. 23
Table 14. Summary of estimated costs and cost-efficiencies of phosphorus recovery within direct
drainage areas for each waterbody (see 5.1) for baseline, monthly, and bi-weekly sweeping scenarios. 24
Table 15. Summary of estimated costs and cost-efficiencies of phosphorus recovery within the TOTAL
drainage area for each waterbody for baseline, monthly, and bi-weekly sweeping scenarios. ................ 25 Table 16. Comparison of overall pick-up efficiencies for different sweeping technologies and loading intensities (Sutherland, 1995). Efficiencies are based on pick up of street dirt simulant, NURP particle size distribution 13% fine (d < 63 µm), 40% medium (250 µm ≤ d ≤ 2000 µm), and 47% coarse (d ≥ 2000 µm). ...................................................................................................................... 47 Table 17. Ratio of fine (< 2mm) to coarse organic (>2mm) solids by month for different tree canopy cover ratings. (Kalinosky, et. al, 2014). Medium canopy is taken to represent ‘average’ ratios. ....... 47
Table 18. Summary of P8 ponds by priority water. Priority waters modeling in P8 are shown in bold font.
.................................................................................................................................................................... 49
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Table of Figures
Figure 1. Direct drainage areas for priority waters (as defined for street sweeping goals) in the City of Edina, MN. ................................................................................................................................................ 9 Figure 2 . Direct drainage area for Arrowhead Lake includes upstream catchments of non-priority ponds. The service level for Arrowhead Lake is ‘high’. ......................................................................... 28 Figure 3. Direct drainage area for Cornelia Lake North (includes upstream catchments of non-priority ponds). The service level for Cornelia Lake North is ‘high’. .................................................... 29 Figure 4. Direct drainage area for Cornelia Lake South (includes upstream catchments of non-priority ponds). The service level for Cornelia Lake South is ‘high’. .................................................... 30 Figure 5. Direct drainage area for Harvey Lake. The service level for Highlands Lake is ‘low’. ......... 31 Figure 6. Direct drainage area for Hawkes Lake (includes upstream catchments of non-priority ponds). The service level for Hawkes Lake is ‘low’. ............................................................................... 32 Figure 7. Direct drainage area for Highland Lake (includes upstream catchments of non-priority ponds). The service level for Highland Lake is ‘low’. ............................................................................. 33 Figure 8. Direct drainage area for Indianhead Lake (includes upstream catchments of non-priority ponds). The service level for Indianhead is ‘medium’. .......................................................................... 34 Figure 9. Direct drainage area for Lake Edina. The service level for Lake Edina is ‘high’. ................. 35 Figure 10. Direct drainage area for Melody Lake. The service level for Melody Lake is ‘high’. ......... 36 Figure 11. Direct drainage area for Mirror Lake (includes upstream catchments of non-priority ponds). The service level for Mirror Lake is ‘low’. ................................................................................. 37 Figure 12. Direct drainage area for Mud Lake (includes upstream catchments of non-priority ponds). The service level for Mud Lake is ‘low’. ..................................................................................... 38 Figure 13. Direct drainage area for Minnehaha Creek (does not include drainage areas for upstream priority waters or landlocked subbasins). Water quality concerns include the Lake Hiawatha TMDLs for excess nutrients and Minnehaha Creek 303d listings (see Section 3.2). ........................... 39 Figure 14. Direct drainage area for Ninemile Creek (does not include drainage areas for upstream priority waters or landlocked subbasins). Water quality concerns include impairments for aquatic life and aquatic recreation for Ninemile Creek (see Section 3.2). ......................................................... 40 Figure 15. Comparison of removal efficiencies, mechanical broom and vacuum sweeper technologies, fine and coarse particle size ranges as reported in MNDOT, 2008. ............................... 46 Figure 16. Seasonal pattern in the partitioning of solids and nutrients between the fine and coarse fractions of sweeper waste. ...................................................................................................................... 48
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Executive Summary Street sweeping practices were evaluated to quantify the water quality benefits of current sweeping practices and proposed enhanced street sweeping within the drainage areas of Edina’s priority waters. Priority waters were identified based on review of the Edina Comprehensive Water Resources Management Plan (CWRMP) including the recent Lake & Pond Management Policy Amendment. Total solids (TS) and total phosphorus (TP) recovery for street sweeping within the drainage of individual priority waters were estimated using a street sweeping planning calculator tool developed by the University of Minnesota. Load recovery was estimated for sweeping with a mechanical broom sweeper and for sweeping with a regenerative air sweeper at each defined level of effort. Load reductions (total solids, total phosphorus) for priority waters were estimated using pollutant removal efficiencies for stormwater catchments estimated by Barr (2011) through P8 modeling. A simple cost-benefit analysis was also completed for each level of effort/sweeper type evaluated. Costs were estimated based on the cost of current practices, manufacturer’s literature, and through comparison with a recent university of MN study, Quantifying Nutrient Removal
through Street Sweeping. Pollutant load recovery and load reductions were estimated for three levels of effort: baseline sweeping (current practice), which consists of one sweeping each in the spring and fall using a mechanical broom sweeper; monthly sweeping, which was approximated as 7 sweeping per year (Apr-Oct); and bi-weekly sweeping, which was approximated as 14 sweepings per year (Apr-Oct). Differences in load recovery for the two sweeper types (mechanical broom, regenerative air) were based on review of manufacturer’s literature, street sweeper pick-up efficiency studies, and solids loading patterns observed in University of MN study. Current sweeping practices are estimated to recover about 208,926 lb solids and 185 lb phosphorus each year within the drainage area of priority waters. Within the Minnehaha Creek watershed area current practices are estimated to reduce phosphorus loads to Minnehaha Creek by about 48 lb. Enhanced sweeping is expected to increase load recovery by the following amounts:
• Sweeping with a regenerative air sweeper (or similar technology) would increase load recovery by about 47% for TS and 37% for TP to 305,064 lb solids per year and 253 lb phosphorus per year for baseline sweeping.
• Within the Minnehaha Creek watershed area, sweeping with a regenerative air (or similar high-efficiency sweeper) is expected to increase the load reduction achieved through current practices by 29% to 62 lb/yr. The proposed sweeper upgrade would nearly achieve the target load reduction (67 lb/yr) required by the Minnehaha Creek Watershed District Management Plan at the current sweeping frequency.
• Sweeping monthly with a regenerative air sweeper would increase load recovery by about 250% for TS and 200% for TP over baseline to 731,559 lb solids per year and 564 lb phosphorus per year.
• Sweeping bi-weekly with a regenerative air sweeper would increase load recovery by over 400% for TS and nearly 400% for TP over baseline to 1,165,494 lb solids per year and 905.3 lb phosphorus per year.
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Although the vehicle cost is greater, sweeping with a high-efficiency sweeper is more cost effective than sweeping with a mechanical broom sweeper due to the increased load recovery that is possible with this vehicle type. Monthly sweeping with a high-efficiency sweeper was found to be the most cost-effective option with an average cost of $152/lb for phosphorus recovery compared to the baseline cost-efficiency of $205/lb. Given the advantage in load recovery and cost-effectiveness when a higher efficiency sweeping is used, it is recommended that mechanical broom sweepers be replaced, or supplemented with a higher efficiency sweeper. It is also recommended that sweeping frequency be increase to about monthly sweeping (or greater) during the snow-free season.
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1. Purpose The purpose of this investigation was to estimate the water quality benefits, defined as the total solids (TS) and total phosphorus (TP) load reductions to priority waters, of current street sweeping practices in the City of Edina and the projected benefits of enhanced street sweeping. A simple cost-benefit analysis was completed to compare the cost-effectiveness of different sweeping practices and to identify the optimal practice from a cost-effectiveness standpoint.
2. Background Most cities do some amount of street sweeping each year to improve road safety and appearance, but when considering best management practices (BMPs) for water quality, street sweeping is often overlooked. Intuitively, street sweeping makes sense. Pollutants removed from the street are not available for transport to the storm sewer network. In agreement with this, several recent studies, which make use of newer sweeping technologies and advances in stormwater management, have reported that street sweeping offers a very cost-effective and efficient means to reduce pollutant loads to storm sewer infrastructure and to downstream waters (Beretta et. al (2011), SPU (2009), Kalinosky et. al (2013), others). Additional benefits of street sweeping include reduced clogging and flooding of storm drains, reduced maintenance to downstream stormwater infrastructure, improved safety for pedestrians, and even reduced presence of pests. Under the current MS4 Stormwater Pollution Prevention Plan (SWPPP, reissue date August 1, 2013), the City of Edina has established street sweeping as a BMP with the following measureable goal and timeframe:
The City will brush or vacuum sweep street a minimum of twice annual in an effort to reduce the amount of sediment, trash, and organic material from reaching the storm sewer system and water resources.
Street sweeping efforts in Edina have increased since the previous SWPPP authorization in 2006.
At that time, the measureable goals included sweeping once annually and the pollution prevention/good housekeeping BMP under item MCM 6.0 included the following language on
street sweeping:
The City will continue with the current street sweeping program, identify improvements, and implement changes to reduce storm water pollutants.
This investigation is consistent with the goal to identify improvements as stated above.
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3. Water Resources There are over two hundred water bodies, ranging in size from lakes to small stormwater detention basins within the city limits of Edina. Most of these waterbodies are part of larger flow networks that drain to Minnehaha Creek (HUC 070102060605) or Ninemile Creek (HUC 070200121108), both of which flow through the City of Edina. Many of Edina’s lakes and ponds are integral to the stormwater system. This means that they provide water management services such as flood storage and pollutant capture which protects downstream waters. It also means that they are vulnerable to degradation if the stormwater they receive carries excessive pollution. Source control BMPs, such as street sweeping, limit the amount of pollution that is transferred from urban landscapes to Edina’s waterbodies through the stormwater system. The City of Edina Comprehensive Water Resources Management Plan (CWRMP) was reviewed to identify water quality goals and priorities that can be addressed through enhanced street sweeping. Identified priorities and stormwater management goals described in sections 3.1-3.2 and section 4. Priorities include nutrient management/aquatic vegetation management; pollutant load reductions required by regional TMDLs; and adherence to non-degradation policies.
3.1. City of Edina Lake and Pond Amendment to the Comprehensive
Water Resources Management Plan (CWRMP) In 2014, the city of Edina established services levels for aquatic vegetation management of lakes and ponds in the City of Edina Lake & Pond Management Policy Amendment to the Comprehensive Water Resources Management Plan (CWRMP). Lake and pond management was prioritized and assigned a service level of ‘none’, ‘low’, ‘medium’, or ‘high’ using a rating scheme that included the following criteria: waterbody size, water quality, aesthetics and nuisance abatement, shoreline owner involvement, and public access. The prioritization scheme adopted in the Lake & Pond Policy Amendment was used to define sweeping zones for evaluation of current sweeping and enhanced sweeping practices (Table 1). A full description of the prioritization scheme and policy development is given in the Lake & Pond Management Policy Amendment (City of Edina, 2014).
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Table 1. Summary of priority waterbodies by HUC 12 with associated service level and land cover characteristics. Street sweeping was evaluated within the drainage areas of waterbodies shown in bold font.
HUC 12 Major Drainage Waterbody
Service
Level Land Use Types
Minnehaha Creek
070102060605
Northwest Minnehaha
Creek*
Harvey Lake Low R
Lake Pamela High R
Melody Lake High R
Minnehaha Creek
(direct drainage) (TMDLs) R (87%), PCD (2%); APD
(1%);
Northeast Minnehaha
Creek* Minnehaha Creek (TMDLs) R (97%), PCD/PID (11%);
MDD (2%)
Southeast Minnehaha
Creek* Minnehaha Creek (TMDLs) R
Ninemile Creek
070200121108
Ninemile Creek - North
Hawkes Lake Low R
Highland Lake Medium R
Mirror Lake Low R
Unnamed nr Schaefer
and Harold Wood l§ Low R
Mud Lake Low R
Unnamed nr
Parkwood & Knoll§ Low R
Other Parkwood
Ponds§ Low/none R
Ninemile Creek - Central Creek Valley Pond§ Low R
Ninemile Creek - South
Fork
Arrowhead Lake High R
Indianhead Lake Medium R
Southwest Ponds Long Brake Trail Low R
Lake Cornelia/Lake
Edina/Adam's Hill
Cornelia - North High R 95%); POD/PCD (6%)
Cornelia - South High R
Lake Edina High R/PSR (96%); POD/PCD
(4%)
Lake Nancy§ Medium R
Otto Pond§ Low R
Point of France§ Low PCD (71%), R (14%); RMD
(8%); POD (6%); APD (1%);
Swimming Pool Pond§ Medium R (86%), PSR (4%); RMD
(7%); APD (2%); POD (1%)
(West Garrison) (none) R (89%); PCD (11%)
Ninemile Creek
(direct drainage not listed above)
(Future
TMDLs) (not quantified) * Also part of the drainage area for Lake Hiawatha (Lake Hiawatha Phosphorus TMDL, 2014).
§Included in sweeping zone for a downstream waterbody.
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3.2. Impaired Waters and TMDLs The current 303d list for Minnesota includes four waterbodies that lie within the City of Edina municipal boundaries, one of which has an approved TMDL (Table 2). In addition to these, the City of Edina is included in the categorical wasteload allocation for MS4 stormwater permits in the Lake Hiawatha total phosphorus TMDL. In the Lake Hiawatha TMDL, the allowable stormwater load for the City of Edina (424.4 lb/yr) is about half the estimated existing load (841.4 lb/yr for 2001-2011, Tetra Tech 2013). As additional TMDLs are approved and implementation plans are developed, the City of Edina may need to provide documentation of pollutant load reductions. TMDLs addressing nutrient impairments will most likely be written for total phosphorus (TP). Excess phosphorus is also a candidate cause for low dissolved oxygen (DO). Total suspended solids (TSS) is a candidate cause for fish and macroinvertebrate bioassessment impairments.
Table 2. Impaired waters located within the City of Edina jurisdiction.
Lake Name (MN DNR LAKE ID) HUC 12 Listing Year TMDL Target Start/Completion
Affected Use Pollutant/Stressor
Impaired Waters Located Within the City of Edina
Lake Cornelia (North)
27-0028-01
Nine Mile
Creek 070102061302
2008 2014/2018 Aquatic Recreation:
Nutrients/Eutrophication Biological Indicators Lake Edina 27-0029-00 2008 2014/2018
Nine Mile Creek 07020012-518 2004 2024/2028 Aquatic Life Chloride
Fish Bioassessment
Minnehaha Creek 07010206-539
Minnehaha Creek
070102061108
2008 2020/2024
Aquatic Life
Chloride
2014 2009/2015 Fish Bioassessment
2008 2020/2024 Macroinvertabrate
Bioassessment
2004 2020/2024 Dissolved Oxygen
2010 Approved 2014 Aquatic Recreation Fecal Coliform
Downstream Impaired Waters
Lake Hiawatha 27-0018-00
Minnehaha
Creek 070102061108 2002 Approved 2014 Aquatic Recreation Nutrient/Eutrophication Biological Indicators
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4. Stormwater Management Goals
4.1. Non-degradation Policies Two major watershed districts have jurisdictions which lie within the City of Edina municipal boundaries – the Nine Mile Creek Watershed District (NMCWD) and the Minnehaha Creek Watershed District (MCWD). Stormwater management rules for both of these watersheds included non-degradation policies that apply to both water quality and volume control. Enhanced street sweeping may provide assurance for non-degradation of water quality by reducing pollutant loads, and may address non-degradation of stormwater volume by reducing loss rate of storage volume through siltation/sedimentation of stormwater ponds.
4.2. Minnehaha Creek Watershed District (MCWD) Per the MCWD Comprehensive Water Resources Management Plan the City of Edina is required to reduce its annual phosphorus load to Minnehaha Creek by 67 pounds1. This requirement has been fulfilled with the implementation of capital improvements since 2000, but additional reductions may be achieved through recent capital improvements and best management practices (BMPs) including street sweeping. Phosphorus reductions achieved through current sweeping practices were estimated at 350 lb/yr city-wide by Barr (2011). The estimated load reductions for current sweeping practices outlined in section 6.1 are defined instead by major drainage area. Current sweeping practices in the Minnehaha Watershed area of the City of Edina are expected to reduce phosphorus loads to Minnehaha Creek by about 48 lb. Sweeping with a regenerative air (or similar high-efficiency sweeper) is expected to increase the load reduction achieved by current practices to 62 lb/yr.
4.3. Good Housekeeping/Maintenance In addition to water quality benefits, regular street sweeping may reduce needed maintenance on stormwater ponds and infrastructure by reducing sedimentation, siltation and clogging. Increased dead storage volume is listed as a potential implementation activity for several stormwater ponds throughout Edina in Section 15, Table 15A of the Edina CWRMP. Enhanced sweeping within stormwater pond drainage areas may extend the maintenance cycle for these and other ponds.
1 As stated in Section 15.2.1 of the City of Edina Comprehensive Water Resources Management Plan.
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5. Methods
5.1. Identification of Sweeping Zones The sweeping zones (direct drainage areas) for which pollutant load recovery were estimated are shown in Figure 1 (all areas combined) and Appendix A (individual zones). Sweeping zones were identified based on the priorities outline in Sections 3 and 4. With a few exceptions, sweeping zones were defined for all ponds with a priority rating higher than ‘none’ (City of Edina, 2014) and for Minnehaha Creek and Nine Mile Creek. Sweeping zones include all streets located within the direct drainage areas of the water body of interest. For the purpose of estimating recoverable loads, the direct drainage area is defined as any street draining to the water body of interest that cannot be included in the direct drainage area of another priority water. The estimated pollutant load recovery within the total drainage area and the total load reduction to each priority water are reported in section 6. For some water bodies, the total drainage area includes the direct drainage areas of other (upstream) priority lakes or ponds (see also section 5.2.2 and section 5.2.3). Streets located in landlocked basins were not included in load recovery estimates for priority waters, however, sweeping may be useful in these areas to extend the life of local stormwater BMPs.
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Figure 1. Direct drainage areas for priority waters (as defined for street sweeping goals) in the City of Edina, MN. See Appendix AAppendix for maps of individual sweeping zones.
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5.2. Methods for Estimating Load Recovery and Load Reductions Pollutant recovery was estimated using a street sweeping planning calculator tool developed by the University of MN, ‘Estimating Nutrient and Solids Load Recovery through Street Sweeping’ (Kalinosky, et. al, 2014). The tool predicts average solids and nutrient load recovery based on the timing and frequency of sweeping; and density of tree canopy cover over the street. The tool was calibrated using street sweeping data from Prior Lake, MN and is intended for use in comparable settings (climate and geography). In order to calculate estimated solids recovery, it was necessary to first determine the length of street surfaces located within each drainage area shown in Figure 1 (section 5.2.1); and to estimate the average over-street tree canopy for these streets (section 5.2.1).
5.2.1. Tree Canopy Assessment Tree canopy covers were visually inspected using 2013 color FSA aerial photographs of the Edina area. Areas of street with similar canopy cover were assigned a score of 1-5 corresponding to the range of canopy cover densities described in Table 3. Visual examples of tree canopy covers are included in Appendix B. Using tree canopy cover scores for individual street segments, a weighted average tree canopy cover was calculated for each street sweeping zone. Weighted average canopy cover scores were then translated to an over-street percent canopy cover for the purpose of estimating recoverable solids loads. Over-street percent tree canopy covers were assigned based upon comparison to tree canopies quantified in Prior Lake, MN (Kalinosky, et. al, 2013).
Table 3. Tree Canopy Rating Scheme
Assigned Score Canopy Description Over-Street Canopy Cover*
0 None None over street, very few or no immature tree in
yards/lots. 0%
1 Very Low Immature trees near street, very little/no over street
canopy, very low tree density in yards/lots. 2%
2 Low Some visible cover over the street, mostly immature
trees, general low density of trees. 5%
3 Medium Visible cover over portions of the street, mix of
immature and mature trees in yards/lots. 10%
4 Medium-
High
Visible canopy over portions of the street, fairly dense,
uniform canopy across yards, or stands of mature tree
in backyards/common areas.
14%
4.5 High
Visible canopy along the majority of the street,
uniform canopy of mature tree across yards/stands of
mature trees in backyards/common areas.
18%
5 Very
High
Very dense canopy, canopy cover fairly continuous
across lot and street boundaries on aerial photos. 25% *Based on comparison to quantified tree canopies in Prior Lake, MN (Kalinosky, et. al, 2013).
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5.2.1. Spatial Analysis of Edina Roads Streets length was summarized by sweeping zone using digital maps of Edina roads and the sweeping zones defined in Appendix A (GIS). The distance to be swept in each sweeping zone (number of curb-miles) was defined as twice the length of polylines representing the roadway, or approximately one sweeper pass along each curb line of the street. In reality, some roadways have two or more driving lanes in each direction of traffic. In such cases, load recovery estimates represent a lower bound for expected load recovery. Additional driving lanes are expected to increase the recovery of inorganic particulates compared to streets in similar settings with a single driving lane in each direction. Note that state and federal highways were excluded from sweeping zone summaries since maintenance responsibilities fall to other jurisdictions. The assigned service level, curb-miles of street, average tree canopy cover, and land use characteristics for sweeping zone are outlined in Table 4. The total curb-miles of street for which pollutant load recovery was estimated are 345.0, about 82% of total curb-miles of street in the City of Edina. Estimates do not include state and federal highways or streets in areas outside of defined sweeping zones.
Table 4. Summary of sweeping zone characteristics including service level of the waterbody, average over-street tree canopy cover, and total curb-miles of street (length of street x 2).
Major Drainage
Waterbody/Sweeping
Zone Service Level
Estimated Over-
street % Canopy
(weighted average)
Curb-miles of Street in
Direct Drainage Area
Minnehaha Creek
HUC 070102060605
Harvey Lake Low 14% 1.1
Lake Pamela High 13% 14.4
Melody Lake High 9% 11.5
Minnehaha Creek (all other) (TMDLs) 14% 65.5
Ninemile Creek HUC
070200121108
Hawkes Lake Low 13% 16.6
Highland Lake Medium 13% 10.6
Mirror Lake Low 16% 8.9
Mud Lake Low 13% 17.1
Arrowhead Lake High 12% 5.7
Indianhead Lake Medium 16% 4.8
Long Brake Trail Low 15% 1.0
Cornelia - North High 12% 43.5
Cornelia - South High 12% 3.7
Lake Edina High 12% 20.1
Ninemile Creek (all other) (Future TMDLs) 12.0% 116.0
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5.2.2. Solids Recovery Rates Total solids and nutrient recovery were estimated for streets located within the direct drainage areas of priority waters. Pollutant recovery was estimated three levels of effort: 1. Baseline effort – all streets are swept once in the spring and once in the fall. 2. Monthly sweeping – all streets are swept once per month during the snow-free season (taken as April – October). 3. Bi-weekly sweeping – all streets are swept twice per month during the snow-free season (April – October). In the monthly and bi-weekly sweeping scenarios, a sweeping season of April through October was assumed. For the initial sweeping event in each scenario (the first sweeping in April), load recovery was estimated as the average of predicted recovery for single sweepings in March and April. In the calculator tool, initial sweepings in these two months represent the high and low end of loading intensities encountered during spring cleaning operations. Pollutant load recovery estimated using the calculator tool depends on the density of over-street tree canopy cover. Total solids and phosphorus loading rates for each of the three defined levels of effort are outlined for a range of over-street tree canopy covers in Table 5.
Table 5. Estimated load recovery rates (lb/curb-mile/yr) for total solids and total phosphorus for three levels of effort, sweeping with a regenerative air (or comparable) sweeper.
Baseline Sweeping Monthly Sweeping Bi-weekly Sweeping
Canopy Cover
Description*
Over-street %
Canopy Cover§ TS TP TS TP TS TP
None 0 522 0.4 1363 1.0 2265 1.6
Very Low 2 616 0.5 1467 1.1 2439 1.8
Low 5 688 0.6 1639 1.2 2725 6.5
Medium 10 827 0.7 1972 1.5 3278 2.5
Medium-High 14 959 0.8 2286 1.8 3801 3.0
High 18 1112 1.0 2651 2.2 4406 3.5
Very High 25 1440 1.3 3433 16.1 5707 4.8 * See Appendix B for examples. §Average for the street length under consideration.
5.2.3. Load Reduction Estimates To estimate pollutant reductions to priority waters (as opposed to pollutant recovery from streets) it was necessary to take into account pollutant removal through BMPs located along flow paths to priority waters. Load reductions were estimated by applying removal efficiencies for P8 ponds (Barr, 2011) to the recovered load estimates for streets located within the direct drainage area of each P8 pond. Individual P8 pond removal efficiencies are summarized by sweeping zone in Appendix D. Pollutant removal estimates were applied recursively to account for serial removal of pollutants along flow paths to priority waters. Expected pollutant load reductions to priority waters are reported as the recovered load minus any expected removal through modeled BMPs (P8 ponds). Load reductions estimates are based on the following assumptions:
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• All solids on street surface will be transferred to the stormsewer system and on to downstream waters over time.
• The design efficiency of modeled BMPs can be applied to solids which typically collect on street surfaces (including organic material).
• The design efficiency of modeled BMPs is preserved through regular maintenance. Pollutant reductions to priority waters are expected to vary somewhat from estimates. Structural BMPs and other practices, such as curbside rain garden or vegetated swales, which were not included in the P8 model, would increase overall pollutant removal and therefore decrease the overall pollutant reduction through street sweeping. Factors which decrease pollutant removal such as decreased efficiency of BMPs between maintenance periods would increase the pollutant reduction to priority waters through street sweeping. It should be noted that regular street sweeping is expected to extend the useful life of structural BMPs by reducing solids loads. This benefit, although not quantified here, should be considered in setting street sweeping policy.
5.2.4. Estimating Load Recovery for Different Sweeper Types Because the pick-up efficiency of street sweepers varies among different makes and models, the amount of pollutant that can be recovered through street sweeping depends not only on factors that contribute to pollutant accumulation, but also on the type of sweeper used. Currently, all street sweeping in the City of Edina is done using mechanical broom sweepers which have been shown to have lower overall pick-up efficiency compared to higher efficiency technologies, such as regenerative air and vacuum assist street sweepers. The calculator tool used to estimate pollutant load recovery, however, is based on results for regenerative air technology. To get a more accurate estimate of load recovery at the baseline effort, discounts reflecting the lower pickup efficiency of mechanical broom sweepers were applied to estimates predicted by the calculator tool. Discounts were also applied at increased levels of effort in order to compare load recovery for mechanical broom and regenerative air (or similar) technologies. The rationale for the discounts applied is described in detail in Appendix C.
Table 6. Discounts applied to load recovery predictions to estimate recoverable loads for mechanical broom
sweepers.
Mar-Apr, Sep-Nov May-Aug
TS TP TS TP
32% 26% 38% 35%
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6. Load Recovery and Load Reduction Estimates
6.1. Baseline Street Sweeping The baseline street sweeping effort consists of one sweeping each in the spring and fall.
6.1.1. Load Recovery Estimated solids and phosphorus recovery for the baseline sweeping effort in the area of interest is outlined by priority watershed in Table 7. Current sweeping practices are expected to remove approximately 56 lb-TP per year in the Minnehaha Creek subwatershed area and approximately 129 lb-TP per year in the Ninemile Creek subwatershed area. Recovery of phosphorus could be increased by approximately 40-47% (72 lb-TP/yr, 181 lb-TP/yr) if regenerative air (or similar) technology were used for sweeping.
6.1.2. Load Reductions In the Ninemile Creek subwatershed overall pollutant loading to priority waters is reduced by from 3% - 94% (median value 39%) by structural BMPs that intercept stormwater. This rate of pollutant removal is based on design efficiencies for modeled BMPs. Actual removal by these structures may decline as sediment accumulates in structures between scheduled maintenance practices. The estimated overall pollutant reduction to waterbodies within the Ninemile Creek subwatershed area is about 66 lb TP/year for baseline sweeping with a mechanical broom sweeper. Load reductions could be increased to about 93 lb-TP/yr if a higher efficiency sweeper technology were used. Note that load reductions to individual priority waters in the Minnehaha Creek subwatershed area are equal to recovered loads for the same priority waters. Structural BMPs that were included in the P8 model for the Minnehaha Creek Watershed were located largely in landlocked areas or the watersheds of ‘low’, or ‘no’ priority waters (section 3.1). For the priority waters listed in Table 7, no modeled BMPS were located in the upstream drainage area and therefore the load reduction is equal to load recovery in the direct drainage area. Pollutant removal was, however, modeled for the priority waters themselves. Modeled removal efficiencies for Harvey Lake, Lake Pamela, and Melody Lake are included in Appendix D. These removal efficiencies were taken into account in estimating the total load reduction to Minnehaha Creek for each sweeping scenario. Based on the information available, the pollutant reduction to Minnehaha Creek for the baseline sweeping effort is 47.8 lb-TP/yr. The load reduction can be increased to 61.5 lb-TP/yr if a higher-efficiency sweeper is used.
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Table 7. Estimated total solids and phosphorus recovery and load reduction estimates for baseline sweeping effort using mechanical broom and regenerative air technologies.
Estimated Watershed Load* Recovery (lb) Reduction to Waterbody through Sweeping (lb) % Increased Recovery
Sweeper Upgrade†
Mechanical Broom
Sweeper Vacuum/Regen Air Sweeper Mechanical Broom
Sweeper
Vacuum/Regen Air
Sweeper
HUC 8 Waterbody Curb-miles * Service Level TS TP TS TP TS TP TS TP TS TP
Minnehaha Creek
HUC 070102060605
Harvey Lake 1.1 Low 831 0.7 1,121 0.9 831 0.7 1,121 0.9
47% 32%
Lake Pamela South 8.1 High 5,648 4.9 7,501 6.2 5,648 4.9 7,501 6.2
Lake Pamela North1 14.4 (6.3) High 9,885 8.5 13,334 11.0 9,885 8.5 13,334 11.0
Melody Lake 11.5 High 6,603 5.9 9,707 7.8 6,603 5.9 9,707 7.8
Minnehaha Creek
(direct drainage) 65.4 (TMDLs) 46,565 40.8 62,815 52.4 46,565 40.8 62,815 52.4
Minnehaha Creek Subtotal** 63,883 55.9 86,977 72.1 48,616 47.8 65,591 61.5
Ninemile Creek
HUC 070200121108
Arrowhead Lake (Landlocked
basin) 5.7 High 3,803 3.5 5,591 4.6 2,322 2.6 3,413 3.5
Centennial Lakes 6.7 Low/No 5,960 5.0 8,761 6.7 5,140 4.7 7,556 6.3
Cornelia North 43.5 High 19,731 17.7 29,008 23.2 10,415 12.6 15,311 16.8
Cornelia South2 47.2 (3.7) High 21,571 19.4 31,713 25.5 2,357 8.9 3,465 11.7
Hawkes Lake3 27.2 (16.6) Low 17,132 14.1 25,187 20.7 6,984 9.7 10,763 13.5
Highland Lake 10.6 Low 5,755 5.9 9,816 8.1 5,565 5.4 9,492 7.4
Indianhead Lake
(Landlocked basin) 4.8 Medium 2,954 2.8 4,342 3.7 2,411 2.4 3,544 3.2
Lake Edina4 67.3 (20.1) High 40 37.1 60,099 48.8 4467 18.7 6,567 22.4
Long Brake Trail 1.0 Low 40,879 0.7 1,091 0.9 742 0.7 1,091 0.9
Mirror Lake 8.9 Low 4,350 4.1 6,394 5.4 2,726 3.5 4,007 4.6
Mud Lake5 43.6 (17.1) Low 27,908 23.0 41,022 33.8 7,254 13.8 10,663 20.3
Ninemile Creek
(direct drainage) 122.6 (Future TMDL) 71,163 63.9 109,482 92.0 34,870 31.3 53,646 45.1
Ninemile Creek Subtotal** 145,043 128.8 218,087 180.8 48,616 66.3 75,973 93.2
§ Total recoverable watershed load - includes recoverable loads in upstream catchments.
§§Load reduction estimate to priority water body based on P8 pond removal efficiencies (Barr, 2011). Removal efficiencies were applied to recoverable loads within the catchment of any modeled P8 pond or priority water and applied in series to determine overall reduction to a given water body. Expected reductions in total solids (TS) are approximated using TSS removal efficiencies although the two constituents are not equivalent. *Total drainage area. Curbmiles of street located within the subwatershed of upstream priority waters are shown in parenthesis. **Recovered loads and load reductions in upstream priority waters are not double counted in HUC 12 subtotals. Subtotals for major drainage areas (HUC12) are based on the total watershed load (not including landlocked basins) or reduced load based on P8 pond linkages (see Appendix D). 1 Upstream priority water = Pamela South 2 Upstream priority water = Cornelia North 3 Upstream priority water = Highland Lake 4 Upstream priority waters = Cornelia South, Cornelia North 5 Upstream priority waters = Hawkes Lake, Highland Lake
†Compares watershed load recovery using regenerative air technology to load recovery using mechanical broom, median value of reported.
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6.2. Enhanced Sweeping Scenario 1 – Monthly Street Sweeping The monthly sweeping scenario is defined as 7 sweepings per year- one each in the months April – October.
6.2.1. Load Recovery Estimated solids and phosphorus recovery for monthly sweeping is outlined by priority watershed in Table 8. Monthly sweeping practices are expected to remove approximately 113 lb-TP per year in the Minnehaha Creek subwatershed area and approximately 279 lb-TP per year in the Ninemile Creek subwatershed area. Recovery of phosphorus could be increase by approximately 43% (164 lb-TP/yr, 400 lb-TP/yr) if a higher efficiency sweeper were used, a 200% increase over baseline sweeping with a mechanical broom sweeper.
6.2.2. Load Reductions The estimated overall pollutant reduction to Minnehaha Creek is 96.3 lb-TP/yr for monthly sweeping with mechanical broom (see also discussion in section 6.1.2). For Ninemile Creek, the estimated overall pollutant reduction to waterbodies is about 144 lb-TP/year. Load reductions could be increased to about 135 lb-TP/yr and 209 lb-TP/yr in Minnehaha Creek and Ninemile Creek respectively if a higher efficiency sweeper technology were used. Estimated load reductions represent an increase of almost 200% over load reductions for baseline sweeping with a mechanical broom sweeper.
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Table 8. Estimated total solids and phosphorus recovery and load reduction estimates for monthly sweeping effort using mechanical broom and regenerative air technologies.
Estimated Watershed Load§ Recovery (lb) Reduction to Waterbody through Sweeping§§ (lb) % Increased Recovery
Sweeper Upgrade†
% Increased Reduction
compared to baseline,
mechanical††
Mechanical Broom
Sweeper
Vacuum/Regen Air
Sweeper
Mechanical Broom
Sweeper
Vacuum/Regen Air
Sweeper
Major Drainage
(HUC 12) Waterbody Curb-miles* Service
Level TS TP TS TP TS TP TS TP TS TP TS TP
Minnehaha Creek
HUC
070102060605
Harvey Lake 1.1 Low 1,705 1.5 2,625 2.1 1,705 1.5 2,625 2.1
54% 43% 244% 195%
Lake Pamela South 8.1 High 11,798 9.9 17,881 13.7 11,798 9.9 17,881 13.7
Lake Pamela North1 14.4 (6.3) High 20,647 17.4 31,788 24.3 20,647 17.4 31,788 24.3
Melody Lake 11.5 High 14,755 12.1 22,722 17.3 14,755 12.1 22,722 17.3
Minnehaha Creek
(direct drainage) 65.4 (TMDLs) 97,255 81.9 149,733 114.6 97,255 81.9 149,733 114.6
Minnehaha Creek Subtotal** 134,362 112.8 211,941 163.8 101,549 96.3 156,344 134.9
Ninemile Creek
HUC
070200121108
Arrowhead Lake
(Landlocked basin) 5.7 High 8,500 7.1 13,090 10.1 5,192 5.3 7,996 7.6
Centennial Lakes 6.7 Low/No 13,314 9.9 20,504 14.2 11,479 9.4 17,678 13.4
Cornelia North 43.5 High 44,090 35.9 67,898 51.0 23,271 26.0 35,856 37.0
Cornelia South2 47.2 (3.7) High 48,205 39.2 74,236 55.8 5,267 18.0 8,141 26.7
Hawkes Lake3 26.5 (15.9) Low 36,547 30.3 60,044 45.9 15,619 19.7 25,658 29.9
Highland Lake 10.6 Low 12,870 11.4 23,400 17.9 12,448 11.0 22,628 16.3
Indianhead Lake
(Landlocked basin) 4.8 Medium 6,603 5.7 10,168 8.1 5,390 5.0 8,300 7.1
Lake Edina4 67.3 (20.1) High 93,040 76.9 143,282 109.4 10,166 35.3 15,713 52.3
Long Brake Trail 1.0 Low 1,659 1.4 2,555 2.0 1,659 1.4 2,555 2.0
Mirror Lake 8.9 Low 9,723 8.4 14,973 12.0 6,093 7.2 9,385 10.2
Mud Lake5 43.6 (17.1) Low 66,531 50.9 97,792 74.8 17,293 30.5 25,418 44.9
Ninemile Creek
(direct drainage) 122.6 (Future
TMDL) 169,491 141.5 261,015 202.3 83,050 69.3 127,898 99.1
Ninemile Creek Subtotal** 340,445 279.0 519,618 400.4 118,261 143.6 180,969 208.5
§ Total recoverable watershed load - includes recoverable loads in upstream catchments.
§§Load reduction estimate to priority water body based on P8 pond removal efficiencies (Barr, 2011). Removal efficiencies were applied to recoverable loads within the catchment of any modeled P8 pond or priority water and applied in series to determine overall reduction to a given water body. Expected reductions in total solids (TS) are approximated using TSS removal efficiencies although the two constituents are not equivalent. *Total drainage area. Curbmiles of street located within the subwatershed of upstream priority waters are shown in parenthesis. **Recovered loads and load reductions in upstream priority waters are not double counted in HUC 12 subtotals. Subtotals for major drainage areas (HUC12) are based on the total watershed load (not including landlocked basins) or reduced load based on P8 pond linkages (see Appendix D). 1 Upstream priority water = Pamela South 2 Upstream priority water = Cornelia North 3 Upstream priority water = Highland Lake 4 Upstream priority water = Cornelia South, Cornelia North 5 Upstream priority water = Hawkes Lake, Highland Lake †Compares watershed load recovery using regenerative air technology to load recovery using mechanical broom, median value reported.
††Compares reduction to waterbody using regenerative air technology to reduction to water body for baseline sweeping (mechanical broom), median value reported.
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6.3. Enhanced Sweeping Scenario 2 – Bi-Weekly Street Sweeping
The bi-weekly sweeping scenario is defined as 14 sweepings per year- two each in the months April – October.
6.3.1. Load Recovery Estimated solids and phosphorus recovery for bi-weekly sweeping is outlined by priority watershed in Table 9. Bi-weekly sweeping practices are expected to remove approximately 183 lb-TP per year in the Minnehaha Creek subwatershed area and approximately 460 lb-TP per year in the Ninemile Creek subwatershed area. Recovery of phosphorus could be increased by 32% - 44% (241 lb-TP/yr, 665 lb-TP/yr) if a higher efficiency sweeper were used, an increase of 223% over baseline sweeping with a mechanical broom sweeper.
6.3.2. Load Reductions The estimated overall pollutant reduction to Minnehaha Creek is 158 lb-TP/yr for monthly sweeping with mechanical broom (see also discussion in section 6.1.2). For Ninemile Creek, the estimated overall pollutant reduction to waterbodies is about 236 lb-TP/year. Load reductions could be increased to about 226 lb-TP/yr and 342 lb-TP/yr in Minnehaha Creek and Ninemile Creek respectively if a higher efficiency sweeper technology were used.
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Table 9. Estimated total solids and phosphorus recovery and load reduction estimates for bi-weekly sweeping effort using mechanical broom and regenerative air technologies.
Estimated Watershed Load§ Recovery (lb) Reduction to Waterbody through Sweeping§§ (lb) % Increased Recovery
Sweeper Upgrade†
% Increased Reduction
compared to baseline,
mechanical††
Mechanical Broom
Sweeper
Vacuum/Regen Air
Sweeper
Mechanical Broom
Sweeper
Vacuum/Regen Air
Sweeper
Major Drainage
(HUC 12) Waterbody Curb-miles* Service Level TS TP TS TP TS TP TS TP TS TP TS TP
Minnehaha
Creek
HUC
070102060605
Harvey Lake 1.1 Low 2,430 2.1 3,767 3.0 2,430 2.1 3,767 3.0
55% 44% 426% 344%
Lake Pamela South 8.1 High 19,480 16.3 29,726 22.9 19,480 16.3 29,726 22.9
Lake Pamela North1 14.4 (6.3) High 34,090 28.5 52,846 40.7 34,090 28.5 52,846 40.7
Melody Lake 11.5 High 21,182 17.6 32,832 25.3 21,182 17.6 32,832 25.3
Minnehaha Creek (direct
drainage) 65.4 (TMDLs) 160,580 135.3 248,933 193.2 160,580 135.3 248,933 193.2
Minnehaha Creek Subtotal** 218,282 183.4 304,694 240.8 167,635 158.3 259,868 226.2
Ninemile Creek
HUC
070200121108
Arrowhead Lake (Landlocked
basin) 5.7 High 12,159 10.3 18,847 14.8 7,408 7.8 11,482 11.2
Centennial Lakes 6.7 Low/No 18,765 14.7 29,086 21.2 14,934 9.8 23,147 20.0
Cornelia North 43.5 High 63,057 52.1 97,741 74.9 33,283 37.7 51,668 54.3
Cornelia South2 47.2 (3.7) High 68,943 57.1 106,864 82.0 7,533 26.2 11,722 37.7
Hawkes Lake3 26.5 (15.9) Low 52,221 44.4 99,821 76.8 22,319 29.7 42,656 50.1
Highland Lake 10.6 Low 18,355 16.4 38,901 29.9 17,750 11.0 37,618 27.3
Indianhead Lake (Landlocked
basin) 4.8 Medium 9,406 8.3 14,579 11.9 7,676 5.6 11,898 10.5
Lake Edina4 67.3 (20.1) High 111,178 92.6 238,192 181.7 16,790 58.0 26,127 83.5
Long Brake Trail 1.0 Low 2,989 2.1 4,632 3.0 2,989 2.1 4,632 3.0
Mirror Lake 8.9 Low 13,844 12.2 21,458 17.5 8,676 10.4 13,444 14.9
Mud Lake5 43.6 (17.1) Low 110,605 85.1 162,575 125.1 28,749 51.1 42,257 75.1
Ninemile Creek (direct drainage) 122.6 (Future TMDL) 282,063 234.3 433,943 337.2 138,211 114.8 212,632 165.2
Ninemile Creek Subtotal** 563,168 460.2 860,800 664.5 195,414 236.4 299,093 341.7
§ Total recoverable watershed load - includes recoverable loads in upstream catchments.
§§Load reduction estimate to priority water body based on P8 pond removal efficiencies (Barr, 2011). Removal efficiencies were applied to recoverable loads within the catchment of any modeled P8 pond or priority water and applied in series to determine overall reduction to a given water body. Expected reductions in total solids (TS) are approximated using TSS removal efficiencies although the two constituents are not equivalent. *Total drainage area. Curbmiles of street located within the subwatershed of upstream priority waters are shown in parenthesis. **Recovered loads and load reductions in upstream priority waters are not double counted in HUC 12 subtotals. Subtotals for major drainage areas (HUC12) are based on the total watershed load (not including landlocked basins) or reduced load based on P8 pond linkages (see Appendix D). 1 Upstream priority water = Pamela South 2 Upstream priority water = Cornelia North 3 Upstream priority water = Highland Lake 4 Upstream priority water = Cornelia South, Cornelia North 5 Upstream priority water = Hawkes Lake, Highland Lake †Compares watershed load recovery using regenerative air technology to load recovery using mechanical broom, median value reported.
††Compares reduction to waterbody using regenerative air technology to reduction to water body for baseline sweeping (mechanical broom), median value reported.
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6.4. Costs Benefit Analysis Total costs and cost-efficiencies ($/lb-P) were estimated for baseline, monthly and bi-weekly sweeping scenarios. The cost-basis of street sweeping ($/curb-mile) is not constant and depends on the sweeper type and financing; and the cost of vehicle maintenance, labor, and fuel. Total costs for each sweeping scenario were calculated using the component costs and assumptions outlined below.
Category Cost Basis
Sweeper Mechanical Broom $18,200 - vehicle depreciation* $3,700 - vehicle maintenance* Higher Efficiency $23,700 - vehicle depreciation $4,800 - vehicle maintenance Labor (wages + benefits) $75/hr Diesel Fuel $3/gal
* City of Edina, Public Works Department Cost Basis Assumptions:
• Sweepers are owned by the City of Edina.
• Sweeper operational speed = 4.5 mph
• An additional 1.5 hrs of labor is required for every 4 hrs of sweeping time
• Total transit miles (brush off) are about 3 times total swept miles
• On average, sweeper fuel consumption is 5 mpg
- [ (brush off time, empty) + (brush on time)+ (brush off time, full capacity)]
• 1 vehicle is sufficient for baseline and monthly sweeping, 2 vehicles are required for sweeping above this level of effort based on labor hours required compared to sweeping timeframe.
• Sufficient staffing is assumed. Sweeping is most cost-effective when solids loading to streets is greatest. Since solids loading varies over the course of the year adding sweepings at certain times of the year (summer) is less cost-effecting than adding sweepings at peak loading intensities (spring, fall). Although sweeping operations can be further optimized to take advantage of these differences, the cost calculations presented here are based on regular sweeping at the frequency specified for each level of effort. Estimated sweeping costs at each defined level of effort are summarized in sections 6.4.1 - 6.4.3. Cost are outlined in detail for loads recovered within the direct drainage area of priority waters in Table 13 for sweeping with mechanical broom and Table 14 for sweeping with a high efficiency sweeper. Costs are also outlined in detail for load recovery within the total drainage area of each priority water for sweeping with a high efficiency sweeper in Table 15.
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6.4.1. Cost Effectiveness of Baseline Sweeping Solids loading tends to peak in the spring (winter residuals) and again in the fall (leaf drop) which makes the singular spring and fall sweepings that make up the baseline sweeping effort among the most efficient (lb/curb-mile). However, at the baseline effort, the cost of sweeping is driven by the flat cost of vehicle financing. This drives the cost-effectiveness of sweeping down compared to monthly sweeping (section 6.4.2). Based on the assumptions outlined above, the cost basis for baseline sweeping with a mechanical broom sweeper and with a higher efficiency sweeper are $56.50 and $66 per curb-mile of sweeping respectively. Estimated total costs and cost-efficiencies for baseline sweeping are summarized in Table 10 and outlined in detail in Table 13 - Table 15 . Note that while sweeping is less expensive for a mechanical broom sweeper on a per-mile basis, it is less cost effective ($/lb-P recovered) due to the reduced solids recovery compared to higher efficiency sweepers.
Table 10. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) at the baseline effort
by major subwatershed.
Sweeper Type HUC 12 Watershed Cost ($)
Cost-efficiency,
Phosphorus Recovery
($/lb-P)
Cost-efficiency,
Phosphorus Reduction*
($/lb-P)
Mechanical
Broom
Minnehaha Creek 10,348 185 194
Ninemile Creek 27,532 214 415
Higher
Efficiency
Minnehaha Creek 12,048 167 196
Ninemile Creek 32,050 177 344
*Based on estimated sub-catchment pollutant removal efficiency, see section 6.1.2.
6.4.2. Cost Effectiveness of Monthly Sweeping Since monthly sweeping can be completed using a single sweeper, the vehicle financing cost does not increase for monthly sweeping compared to baseline sweeping. Labor and fuel costs increase such that the total cost is approximately 2X the cost of baseline sweeping; however, solids recovery increases by more than 2-fold over baseline, making monthly sweeping more cost-effective than the baseline effort. Based on the assumption outlined above, the cost basis for baseline sweeping with a mechanical broom sweeping is $34, and with a regenerative air sweeper $37 per curb-mile of sweeping. Estimated total costs and cost-efficiencies for monthly sweeping are summarized in Table 11 and outlined in detail in Table 13 - Table 15 .
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Table 11. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) for monthly
sweeping by major subwatershed.
Sweeper Type HUC 12 Watershed Cost ($)
Cost-efficiency,
Phosphorus Recovery
($/lb-P)
Cost-efficiency,
Phosphorus Reduction*
($/lb-P)
Mechanical
Broom
Minnehaha Creek 21,943 194 204
Ninemile Creek 58,343 209 406
Higher
Efficiency
Minnehaha Creek 26,631 144 175
Ninemile Creek 62,860 157 301
*Based on estimated sub-catchment pollutant removal efficiency, see section 6.2.2.
6.4.3. Cost Effectiveness of Bi-weekly Sweeping Based on the number of vehicle hours required, bi-weekly sweeping cannot be completed in all defined sweeping zone during the period April-October unless a second vehicle is used. Although a second sweeper might not be financed in the same manner a primary sweeper, for the sake of keeping cost estimates simple, the vehicle finance cost was doubled to account for the additional sweeper in the bi-weekly sweeping scenario. Labor and fuel costs also double compared to monthly sweeping making the total cost for bi-weekly sweeping 2X the cost of monthly sweeping. Total load recovery increases over baseline and monthly sweeping when street are swept bi-weekly, but sweeping efficiency (lb/curb-mile recovered) tends to decrease as sweeping intervals decrease. For this reason, bi-weekly sweeping is less cost-effective than monthly sweeping; however, the cost-effectiveness of bi-weekly sweeping with a higher-efficiency sweeper is comparable to baseline sweeping with a mechanical broom sweeper. Based on the assumption outlined above, the cost basis for baseline sweeping with a mechanical broom sweeping is $34, and with a regenerative air sweeper $37 per curb-mile of sweeping. Total cost ad cost-efficiencies for bi-weekly sweeping are summarized in Table 12 and outlined in detail in Table 13 - Table 15 .
Table 12. Cost and cost-efficiency of street sweeping in defined sweeping zones (Appendix B) for bi-weekly
sweeping by major subwatershed.
Sweeper Type HUC 12 Watershed Cost ($)
Cost-efficiency,
Phosphorus Recovery
($/lb-P)
Cost-efficiency,
Phosphorus Reduction*
($/lb-P)
Mechanical
Broom
Minnehaha Creek 43,887 239 249
Ninemile Creek 116,685 254 494
Higher
Efficiency
Minnehaha Creek 47,261 196 209
Ninemile Creek 125,720 189 368
*Based on estimated sub-catchment pollutant removal efficiency, see section 6.3.2.
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Table 13. Summary of estimated costs and cost-efficiencies of phosphorus recovery within direct drainage areas for each waterbody (see 5.1) for baseline, monthly, and bi-weekly sweeping scenarios. Estimates are based on recovery using a mechanical broom sweeper. The cost basis for estimates is $56.50 (baseline) or $34 (monthly, bi-weekly) per curb-mile of sweeping.
Recovered Phosphorus (lb)* Baseline Sweeping Costs Monthly Sweeping Costs Bi-weekly Sweeping Costs
HUC 8 Waterbody Service Level Curb-miles, Direct
Drainage Area Baseline Monthly Bi-weekly $ $/lb-P $ $/lb-P $ $/lb-P
Minnehaha Creek
HUC 070102060605
Harvey Lake Low 1.1 0.7 1.5 2.1 $ 124 $ 178 $ 264 $ 176 $ 527 $ 251
Lake Pamela South High 8.1 4.9 9.9 16.3 $ 917 $ 188 $ 1,944 $ 196 $ 3,888 $ 239
Lake Pamela North High 6.3 3.7 7.4 12.2 $ 713 $ 195 $ 1,510 $ 203 $ 3,020 $ 247
Melody Lake High 10.6 5.9 12.1 17.6 $ 1,199 $ 203 $ 2,541 $ 210 $ 5,082 $ 289
Minnehaha Creek (all other*) (TMDLs) 65.5 40.8 81.9 135.3 $ 7,407 $ 182 $ 15,700 $ 192 $ 31,401 $ 232
Minnehaha Creek Subtotal* 91.6 55.9 112.8 183.4 $ 10,348 $ 185 $ 21,932 $ 194 $ 43,865 $ 239
Ninemile Creek HUC
070200121108
Arrowhead Lake
(Landlocked basin) High 5.7 3.5 7.1 10.3 $ 645 $ 184 $ 1,366 $ 192 $ 2,733 $ 265
Centennial Lakes Low/No 6.7 5.0 9.9 14.7 $ 758 $ 152 $ 1,606 $ 162 $ 3,212 $ 219
Cornelia North High 43.5 17.7 35.9 52.1 $ 4,921 $ 279 $ 10,427 $ 291 $ 20,854 $ 400
Cornelia South High 3.7 1.8 3.4 4.9 $ 419 $ 239 $ 887 $ 263 $ 1,774 $ 359
Hawkes Lake Low 16.6 14.1 30.3 44.4 $ 1,799 $ 127 $ 3,811 $ 126 $ 7,622 $ 172
Highland Lake Low 10.6 5.5 11.4 16.4 $ 1,199 $ 218 $ 2,541 $ 223 $ 5,082 $ 310
Indianhead Lake
(Landlocked basin) Medium 3.9 2.8 5.7 8.3 $ 543 $ 194 $ 1,151 $ 202 $ 2,301 $ 277
Lake Edina High 20.1 17.7 37.7 69.4 $ 2,274 $ 128 $ 4,818 $ 128 $ 9,636 $ 139
Long Brake Trail Low 1.0 0.7 1.4 2.1 $ 113 $ 167 $ 240 $ 173 $ 479 $ 232
Mirror Lake Low 8.9 4.1 8.4 12.2 $ 1,007 $ 246 $ 2,133 $ 254 $ 4,267 $ 350
Mud Lake Low 17.1 23.0 50.9 85.1 $ 1,934 $ 84 $ 4,099 $ 81 $ 8,198 $ 96
Ninemile Creek (all other*) (Future TMDL) 122.6 44.3 99.8 173.5 $ 13,868 $ 313 $ 29,387 $ 294 $ 58,774 $ 339
Ninemile Creek Subtotal* 244.1 128.8 279.0 460.2 $ 27,532 $ 214 $ 53,343 $ 209 $ 116,685 $ 254
* Recovered TP loads for direct drainage areas only (does not include loads recovered from
streets located in upstream drainage areas). Recovery with mechanical broom sweeper.
**Includes Landlocked areas.
TOTAL** $ 37,880 $ 205 $ 80,275 $ 205 $ 160,550 $ 250
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Table 14. Summary of estimated costs and cost-efficiencies of phosphorus recovery within direct drainage areas for each waterbody (see 5.1) for baseline, monthly, and bi-weekly sweeping scenarios. Estimates are based on recovery using a regenerative air (or similar) sweeping technology. The cost basis for estimates is $66 (baseline) or $37 (monthly, bi-weekly) per curb-mile of sweeping.
Recovered Phosphorus (lb)* Baseline Sweeping Costs Monthly Sweeping Costs Bi-weekly Sweeping Costs
HUC 8 Waterbody Service Level Curb-miles Baseline Monthly Bi-weekly $ $/lb-P $ $/lb-P $ $/lb-P
Minnehaha Creek
HUC 070102060605
Harvey Lake Low 1.1 0.9 2.1 3.0 $ 145 $ 161 $ 284 $ 135 $ 568 $ 189
Lake Pamela South High 8.1 6.2 13.7 22.9 $ 1,068 $ 173 $ 2,094 $ 153 $ 4,189 $ 183
Lake Pamela North High 6.3 4.8 10.6 17.8 $ 1,830 $ 167 $ 3,590 $ 148 $ 7,180 $ 176
Melody Lake High 10.6 7.8 17.3 25.3 $ 1,396 $ 179 $ 2,738 $ 158 $ 5,475 $ 216
Minnehaha Creek (all other*) (TMDLs) 65.5 54.4 114.6 193.2 $ 8,612 $ 164 $ 16,890 $ 147 $ 33,780 $ 175
Minnehaha Creek Subtotal* 91.6 72.0 158.3 262.2 $ 12,048 $ 167 $ 23,631 $ 144 $ 47,261 $ 196
Ninemile Creek HUC
070200121108
Arrowhead Lake
(Landlocked basin) High 5.7 4.6 10.1 14.8 $ 751 $ 163 $ 1,472 $ 146 $ 2,944 $ 199
Centennial Lakes Low/No 6.7 6.7 14.2 21.2 $ 882 $ 132 $ 1,730 $ 122 $ 3,461 $ 163
Cornelia North High 43.5 23.2 51.0 74.9 $ 5,728 $ 247 $ 11,234 $ 220 $ 22,468 $ 300
Cornelia South High 3.7 2.3 4.8 7.1 $ 6,215 $ 244 $ 12,190 $ 218 $ 24,380 $ 297
Hawkes Lake Low 16.6 12.7 27.1 40.3 $ 3,582 $ 173 $ 7,025 $ 153 $ 14,049 $ 183
Highland Lake Low 10.6 8.1 16.3 23.6 $ 1,396 $ 173 $ 2,738 $ 153 $ 5,475 $ 183
Indianhead Lake
(Landlocked basin) Medium 3.9 3.7 8.1 11.9 $ 514 $ 139 $ 1,007 $ 124 $ 2,014 $ 169
Lake Edina High 20.1 23.3 35.0 51.4 $ 8,862 $ 182 $ 17,381 $ 159 $ 34,762 $ 191
Long Brake Trail Low 1.0 0.9 6.2 9.2 $ 132 $ 146 $ 258 $ 129 $ 517 $ 174
Mirror Lake Low 8.9 5.4 12.0 17.5 $ 1,172 $ 217 $ 2,299 $ 192 $ 4,597 $ 263
Mud Lake Low 17.1 13.0 19.3 32.2 $ 5,741 $ 170 $ 11,260 $ 151 $ 22,520 $ 180
Ninemile Creek (all other*) (Future TMDL) 122.6 92.0 202.3 337.2 $ 16,143 $ 176 $ 31,662 $ 157 $ 63,325 $ 188
Ninemile Creek Subtotal* 243.4 180.8 400.4 664.5 $ 32,050 $ 177 $ 62,860 $ 157 $ 125,720 $ 189
* Recovered TP loads for direct drainage areas only (does not include loads recovered from
streets located in upstream drainage areas). Recovery with high efficiency sweeper.
**Includes Landlocked areas.
TOTAL** $ 46,244 $ 173 $ 90,700 $ 152 $ 181,401 $ 190
TOTAL regenerative air – TOTAL mechanical broom $ 6,570.00 $ (29.85) $ 6,570.00 $ (50.93) $ 13,140.00 $ (58.29)
% Increase over mechanical broom 17% -15% 8% -25% 8% -23%
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Table 15. Summary of estimated costs and cost-efficiencies of phosphorus recovery within the TOTAL drainage area for each waterbody for baseline, monthly, and bi-weekly sweeping scenarios. Estimates are based on recovery using a regenerative air (or similar) sweeping technology. The cost basis for estimates is $66 (baseline) - $37 (monthly, bi-weekly) per curb-mile of sweeping. Load recovery for monthly sweeping (bold red font) is the most cost-effective among the scenarios.
Baseline Sweeping Costs§ Monthly Sweeping Costs§ Bi-weekly Sweeping Costs§
HUC 8 Waterbody Service Level Total Curb-
miles* $ $/lb-P recovered $/lb-P reduced† $ $/lb-P recovered $/lb-P reduced† $ $/lb-P recovered $/lb-P reduced†
Minnehaha Creek
Harvey Lake Low 1.1 $ 145 $ 161 $ 242 $ 284 $ 135 $ 203 $ 568 $ 189 $ 284
Lake Pamela South High 8.1 $ 1,068 $ 173 $ 173 $ 2,094 $ 153 $ 153 $ 4,189 $ 183 $ 183
Lake Pamela North1 High 13.9 $ 1,830 $ 167 $ 167 $ 3,590 $ 148 $ 148 $ 7,180 $ 176 $ 176
Melody Lake High 10.6 $ 1,396 $ 179 $ 269 $ 2,738 $ 158 $ 238 $ 5,475 $ 216 $ 325
Minnehaha Creek
(all other*) (TMDLs) 96.8 $ 8,612 $ 164 $ 164 $ 16,890 $ 147 $ 147 $ 33,780 $ 175 $ 175
Minnehaha Creek Subtotal 122.4 $ 12,048 $ 167 $ 196 $ 23,631 $ 144 $ 175 $ 47,261 $ 196 $ 209
Ninemile Creek
Arrowhead Lake
(Landlocked basin) High 5.7 $ 751 $ 163 $ 214 $ 1,472 $ 146 $ 194 $ 2,944 $ 199 $ 263
Centennial Lakes Low/No 6.7 $ 882 $ 132 $ 140 $ 1,730 $ 122 $ 129 $ 3,461 $ 163 $ 173
Cornelia North High 43.5 $ 5,728 $ 247 $ 341 $ 11,234 $ 220 $ 304 $ 22,468 $ 300 $ 414
Cornelia South2 High 47.2 $ 6,215 $ 244 $ 531 $ 12,190 $ 218 $ 457 $ 24,380 $ 297 $ 647
Hawkes Lake3 Low 27.9 $ 3,582 $ 173 $ 265 $ 7,025 $ 153 $ 235 $ 14,049 $ 183 $ 281
Highland Lake Low 8.7 $ 1,396 $ 173 $ 189 $ 2,738 $ 153 $ 168 $ 5,475 $ 183 $ 201
Indianhead Lake
(Landlocked basin) Medium 3.9 $ 514 $ 139 $ 160 $ 1,007 $ 124 $ 142 $ 2,014 $ 169 $ 192
Lake Edina4 High 66.6 $ 8,862 $ 182 $ 396 $ 17,381 $ 159 $ 332 $ 34,762 $ 191 $ 416
Long Brake Trail Low 1.0 $ 132 $ 146 $ 146 $ 258 $ 129 $ 129 $ 517 $ 174 $ 174
Mirror Lake Low 8.9 $ 1,172 $ 217 $ 255 $ 2,299 $ 192 $ 225 $ 4,597 $ 263 $ 309
Mud Lake5 Low 39.1 $ 5,741 $ 170 $ 283 $ 11,260 $ 151 $ 251 $ 22,520 $ 180 $ 300
Ninemile Creek
(all other*) (Future TMDL) 122.6 $ 16,143 $ 176 $ 358 $ 31,662 $ 157 $ 319 $ 63,325 $ 188 $ 383
Ninemile Creek Subtotal 243.3 $ 32,050 $ 177 $ 344 $ 62,860 $ 157 $ 301 $ 125,720 $ 189 $ 368
TOTAL** $ 46,244 $ 173 $ 276 $ 90,700 $ 152 $ 244 $ 181,401 $ 190 $ 298
*Total curb-miles and include upstream areas.
§Cost-efficiency based on cumulative phosphorus recovery and load reductions (recovered loads and load reductions as reported in Table 7 - Table 9)
**Includes Landlocked areas. 1 Upstream priority water = Pamela South 2 Upstream priority water = Cornelia North 3 Upstream priority water = Highland Lake 4 Upstream priority water = Cornelia South, Cornelia North 5 Upstream priority water = Hawkes Lake, Highland Lake
EOR: water | ecology | community Page | 26
7. Recommendations Although current street sweeping practices are expected to be among the most efficient (lb/curb-mile), the cost-efficiency ($/lb recovered) of sweeping could be improved significantly by using a regenerative air or other high efficiency street sweeper. Based on the expected recovery for different sweeper types and sweeping frequencies, the following recommendations are made:
• Upgrade street sweeping vehicle(s) to regenerative air or other high-efficiency sweeper type to realize an increase in cost-efficiency of about 24% for baseline sweeping. This is expected to increase total cost for baseline sweeping by about 4%, but will increase load recovery of solids by 47% and recovery of phosphorus by 37%.
• Increase the number of sweeping to monthly sweeping during the snow–free season or similar. Utilizing street sweeping vehicles during a greater portion of the year decreases the cost-basis ($/curb-mile) of sweeping compared to baseline and improves cost-efficiency. Sweeping at monthly intervals with a high efficiency sweeper in priority watersheds is expected to increase the recovery of solids by 250% and the recovery of phosphorous by 200% compared to current practice. The cost-basis is lowered from about $66/curb-mile to about $37/curb-mile of sweeping and the cost-efficiency is improved from $173/lb-P recovered to $152/lb-P recovered.
• Consider additional sweeping in high priority watersheds (waterbodies with high service level). Addition sweeping may require increasing the size of the street sweeping fleet. Depending on how well sweepers are utilized, the cost-efficiency of sweeping at bi-weekly (or higher) frequency may be comparable to that of current practices and the cost of phosphorus recovery relatively inexpensive compared to recovery through structural BMPs.
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8. References
Barr Engineering. 2011. City of Edina Comprehensive Water Resources Management Plan.
Berretta C., S. Raje, and J.J. Sansalone. Quantifying Nutrient Loads Associated with Urban Particulate
Matter (PM), and Biogenic/Litter Recovery Through Current MS4 Source Control and Maintenance
Practices. University of Florida, College of Engineering, Gainsville, Florida: Florida Stormwater
Association Education Foundation (FSAEF); 2011 Final Report: 31 May 2011.
City of Edina, 2011. City of Edina, Comprehensive Water Resources Management Plan, available through
the City of Edina: http://edinamn.gov/?section=engineering_water_resource
City of Edina, 2014. Lake & Pond Management Policy, Amendment to the Comprehensive Water
Resources Management Plan, available through the City of Edina:
http://edinamn.gov/?section=engineering_water_resource
Emmons and Olivier Resources, Inc. 2014a. Phase I – Preliminary Assessment of Data and Proposed Strategy for
Sweeping Prioritization. Technical memo to the City of Edina, 8/11/2014.
Emmons and Olivier Resources, Inc. 2014b. Preliminary estimates of pollutant load recovery through enhanced
street sweeping. Technical memo to the City of Edina, 10/6/2014.
Emmons and Olivier Resources, Inc. 2014c. Preliminary estimates of pollutant load recovery through enhanced
street sweeping. Technical memo to the City of Edina, Revision dated 10/27/2014.
Kalinosky, P., Baker, L., Hobbie, S., Bintner, R., Buyarski, C. 2013. Quantifying Nutrient Removal through
Targeted, Intensive Street Sweeping, Presentation, LID Symposium, August 20, 2013.
Minnesota Department of Transportations (MNDOT). 2008. Resource for Implementing a Street
Sweeping Best Practice, MN/RC – 2008RIC06.
Minnesota Pollution Control Agency (MPCA) 2013. MS4 SWPPP Application for Reauthorization, City of
Edina, MN, reissue date August 1, 2013. Also available through the City of Edina:
http://edinamn.gov/?section=engineering_storm_water
Appendix A
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Appendix A
Street sweeping zones
Figure 2 . Direct drainage area for Arrowhead Lake includes upstream catchments of non-priority ponds. The service level for Arrowhead Lake is ‘high’.
Appendix A
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Figure 3. Direct drainage area for Cornelia Lake North (includes upstream catchments of non-priority ponds). The service level for Cornelia Lake North is ‘high’.
Appendix A
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Figure 4. Direct drainage area for Cornelia Lake South (includes upstream catchments of non-priority ponds). The service level for Cornelia Lake South is ‘high’.
Appendix A
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Figure 5. Direct drainage area for Harvey Lake. The service level for Highlands Lake is ‘low’.
Appendix A
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Figure 6. Direct drainage area for Hawkes Lake (includes upstream catchments of non-priority ponds). The service level for Hawkes Lake is ‘low’.
Appendix A
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Figure 7. Direct drainage area for Highland Lake (includes upstream catchments of non-priority ponds). The service level for Highland Lake is ‘low’.
Appendix A
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Figure 8. Direct drainage area for Indianhead Lake (includes upstream catchments of non-priority ponds). The service level for Indianhead is ‘medium’.
Appendix A
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Figure 9. Direct drainage area for Lake Edina. The service level for Lake Edina is ‘high’.
Appendix A
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Figure 10. Direct drainage area for Melody Lake. The service level for Melody Lake is ‘high’.
Appendix A
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Figure 11. Direct drainage area for Mirror Lake (includes upstream catchments of non-priority ponds). The service level for Mirror Lake is ‘low’.
Appendix A
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Figure 12. Direct drainage area for Mud Lake (includes upstream catchments of non-priority ponds). The service level for Mud Lake is ‘low’.
Appendix A
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Figure 13. Direct drainage area for Minnehaha Creek (does not include drainage areas for upstream priority waters or landlocked subbasins). Water quality concerns include the Lake Hiawatha TMDLs for excess nutrients and Minnehaha Creek 303d listings (see Section 3.2).
Appendix A
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Figure 14. Direct drainage area for Ninemile Creek (does not include drainage areas for upstream priority waters or landlocked subbasins). Water quality concerns include impairments for aquatic life and aquatic recreation for Ninemile Creek (see Section 3.2).
Appendix B
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Appendix B
Tree Canopy Examples
Examples of very low canopy cover (canopy rating score =1)
Appendix B
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Examples of low canopy cover (canopy rating score=2)
Appendix B
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Examples of medium canopy cover (canopy rating score=3.0)
Appendix B
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Examples of medium-high canopy cover (canopy rating score =4.0)
Appendix B
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Examples of very high canopy cover (canopy rating score =5).
Appendix C
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Appendix C
Excerpted from EOR, 10/6/2014
III. Load Recovery for Different Sweeper Types The range of reported street sweeper pick-up efficiencies is fairly broad, but some trends are consistent across different sources. In general, the pickup performance of street sweepers decreases with particle size, but the difference across particle size classes is greater for mechanical broom technologies than for higher efficiency sweepers (regenerative air or vacuum) (Figure 15). Higher efficiency sweepers generally outperform mechanical sweepers across all particle size classes, however, for the largest material (rock, trash), differences may be minimal.
Figure 15. Comparison of removal efficiencies, mechanical broom and vacuum sweeper technologies, fine and coarse particle size ranges as reported in MNDOT, 2008.
In addition to variation with particle size, sweeper pick up efficiency tends to decrease with loading intensity and the gap in performance between higher efficiency and mechanical broom sweepers tends to widen as load intensities decreases (Table 16). Based on the influence of particle-size and loading intensity, discount levels for mechanical broom were set at two levels. For those months of the year when load intensity tends to be greatest (March through April and mid-September through mid-November), predicted load recovery was reduced 10-15% for coarse material (>2mm) and 30% for fine material (< 2mm). At other times of the year, predicted loads were reduced by 20% for coarse material and 40% for fine material. The expected proportion of fine and coarse material for different months of the year was taken from monitored load recovery in Prior Lake, MN (Table 17). Fine material tends to dominate street accumulations in the early spring but the ratio of fine to coarse material decreases from spring to autumn (Kalinosky, 2014). The ratio of fine to coarse material also depends on over-street tree canopy density. Fine to coarse ratio for ‘medium’ canopy cover were used to estimate the reduced efficiency of mechanical broom compared regenerative air technology at different time of the year.
Appendix C
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The classification of ‘fine’ and ‘coarse’ material in Table 17 is different than the NURP particle sizes classes. For this reason, the discount in pick-up performance for fine material was decreased compared to the reported average for silt and clay shown in Figure 15. The discount for coarse material was increased somewhat compared to the reported average to for very fine sand to gravel because organic material, which can make up a significant portion of recovered loads, was not included in performance testing.
Table 16. Comparison of overall pick-up efficiencies for different sweeping technologies and loading intensities (Sutherland, 1995). Efficiencies are based on pick up of street dirt simulant, NURP particle size distribution 13% fine (d < 63 µm), 40% medium (250 µm ≤ d ≤ 2000 µm), and 47% coarse (d ≥ 2000 µm).
Pavement
Loading (lbs/acre)
Pickup Efficiency* (%)
NURP
Mechanical
Newer
Mechanical
Regenerative
Air
Vacuum
Sweeper
10 0% 31% 50% 70%
100 28% 55% 87% 89%
250 45% 66% 89% 89%
500 53% 70% 90% 89%
1000 57% 71% 91% 89%
Table 17. Ratio of fine (< 2mm) to coarse organic (>2mm) solids by month for different tree canopy cover ratings. (Kalinosky, et. al, 2014). Medium canopy is taken to represent ‘average’ ratios.
Canopy Mar Apr May Jun Jul Aug Sep Oct Nov
Low 180.3 43.6 24.0 20.2 25.0 15.0 8.7 3.2 14.1
Medium 22.1 14.5 10.8 15.2 10.4 6.6 3.9 1.3 1.4
High 22.8 7.0 6.5 7.5 10.0 5.9 3.7 0.9 1.2 Finally, since the character of the material that accumulates on street changes from one season to the next, the concentration of nutrients in each particle size fraction also varies with season (Figure 16). To estimate the total phosphorus recovered by mechanical broom sweepers, the same discounts for coarse and fine loads were applied to expected phosphorus recovery, but the ratio of coarse to fine loads were based on results for phosphorus recovery in Prior Lake (coarse : fine phosphorus as opposed to coarse: fine total solids). The discounts reported in Table 6 are the average for months included as high or low loading intensity with the value for each month computed as follows: Total discount, high intensity months = (10-15% X expected ratio of coarse solids/phosphorus) + (20% X expected ratio or fine solids/phosphorus)
Appendix C
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Total discount, low intensity months = (20% X expected ratio of coarse solids/phosphorus) + (40% X expected ratio or fine solids/phosphorus)
Figure 16. Seasonal pattern in the partitioning of solids and nutrients between the fine and coarse fractions of sweeper waste.
0%
20%
40%
60%
80%
100%
Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecPercent Total Load as Coarse Organic Dry Solids Phosphorus Nitrogen
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Appendix D
Table 18. Summary of P8 ponds by priority water. Priority waters modeling in P8 are shown in bold font.
(Pollutant removal efficiencies for priority waters were applied in estimates of load reduction to downstream
waterbodies).
Priority Watershed
Device
Name
Device
Type
TP Removal
Efficiency
TSS Removal
Efficiency Comment
Arrowhead Lake AH_1 pond 95% 100% landlocked basin
Arrowhead Lake AH_32 pond 41% 73%
upstream to landlocked
basin
Arrowhead Lake AH_4 pond 61% 94%
upstream to landlocked
basin
Arrowhead Lake AH_6 pond 57% 89%
upstream to landlocked
basin
Colonial Ponds CO-2 pond 82% 99%
Colonial Ponds CO_1 pond 57% 95%
Colonial Ponds CO_4 pond 51% 94%
Colonial Ponds CO_7 pond 67% 98%
Colonial Ponds CO_5 pond 73% 97%
Colonial Ponds CO_3 pond 63% 97%
Eden Prairie EP_1 pond 44% 76%
Hawkes Lake HL_24 pond 63% 96%
Hawkes Lake HL_1 general 43%
Hawkes Lake HL_44 pond 100% 100%
Hawkes Lake HL_40 pond 66% 98%
Hawkes Lake HL_28 pond 50% 96%
Hawkes Lake HL_9 pond 57% 91%
Hawkes Lake HL_39 pond 100% 100% landlocked basin
Hawkes Lake HL_13 pond 64% 97% landlocked basin
Hawkes Lake HL_50 pond 99% 100% landlocked basin
Harvey Lake MHS_22 69% 99% (no P8 ponds upstream)
Highlands Lake HI_22 pond 62% 97%
Highlands Lake HI_21 pond 60% 99%
Highlands Lake HI_20 pond 100% 100%
Highlands Lake HI_17 pond 59% 97%
Highlands Lake HI_5 pond 44% 94%
Highlands Lake HI_1 general 58%
Highlands Lake HI_18 general 44% 98%
Highlands Lake HI_13 pond 100% 100% landlocked basin
Indian Pond IP_1 pond 100% 100% landlocked basin
Indianhead IH_1 pond 100% 100% landlocked basin
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Priority Watershed
Device
Name
Device
Type
TP Removal
Efficiency
TSS Removal
Efficiency Comment
Indianhead IH_14 pond 61% 93%
upstream to landlocked
basin
Lake Cornelia - North NC_62 pond 44% 95%
Lake Cornelia - North NC_88 general 51% 82%
Lake Cornelia - North NC_30 general 73% 99%
Lake Cornelia - North NC_2 general 31% 88%
Lake Cornelia - North NC_5 general 62% 93%
Lake Cornelia - North NC_4 general 52% 82%
Lake Cornelia - North NC_3 general 37% 78%
Lake Cornelia - North NC_78 pond 67% 99% landlocked basin
Lake Cornelia - North NC_72 pond 46% 86% landlocked basin
Lake Cornelia - North NC_135 pond 100% 100% landlocked basin
Lake Cornelia - North NC_6 pond 100% 100% landlocked basin
Lake Cornelia - South SC_1 general 12% 93%
Lake Cornelia - South SC_2 pond 21% 56%
Lake Cornelia - South SC_3 pond 66% 97%
Lake Edina LE_38 general 39% 71%
Lake Edina LE_1 general 28% 94%
Lake Edina LE_51 pond 100% 100% landlocked basin
Lake Edina LE_54 pond 100% 100% landlocked basin
Lake Edina LE_44 pond 100% 100% landlocked basin
Lake Pamela North LP_14 18% 63%
Lake Pamela South LP-26 48% 94% (no P8 ponds upstream)
Long Brake Trail SWP_4 pond 41% 97%
Melody Lake ML_8 65% 96% (no P8 ponds upstream)
Mirror Lake ML_40 pond 36% 98%
Mirror Lake ML_38 pond 45% 98%
Mirror Lake ML_16 general 58% 99%
Mirror Lake ML_32 pond 37% 93%
Mirror Lake ML_2 pond 57% 91%
Mirror Lake ML_3 pond 63% 98%
Mirror Lake ML_19 pond 10% 43%
Mirror Lake ML_6 pond 66% 98%
Mirror Lake ML_15 pond 71% 100%
Mirror Lake ML_1 general 62% 99% Lake
Mirror Lake ML_28 pond 100% 100% landlocked basin
Mirror Lake ML_26 pond 100% 100% landlocked basin
Mirror Lake ML_27 pond 100% 100%
upstream to landlocked
basin
Mud Lake MD_1 pond 26% 96%
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Priority Watershed
Device
Name
Device
Type
TP Removal
Efficiency
TSS Removal
Efficiency Comment
Mud Lake MD_50 pond 8% 93%
Mud Lake MD_11 pond 7% 61%
Mud Lake MD_2 pond 45% 99%
Mud Lake MD_28 pond 67% 99%
Mud Lake MD_7 pond 66% 98%
Mud Lake MD_21 pond 74% 100%
Mud Lake MD_27 general 79% 85%
Mud Lake MD_29 pond 64% 97%
Mud Lake MD_39 pond 100% 100%
Mud Lake MD_3 pond 13% 72%
Mud Lake MD_4 pond 66% 96%
Mud Lake MD_13 pond 68% 99%
Mud Lake MD_15 pond 6% 58%
Mud Lake MD_25 general 55% 97%
Nine Mile Central NMC_114 pond 37% 88%
Nine Mile Central NMC_77 pond 69% 99%
Nine Mile Central NMC_112 pond 65% 97%
Nine Mile Central NMC_70 pond 51% 91%
Nine Mile Central NMC_44 pond 66% 98%
Nine Mile North NMN_62 pond 39% 91%
Nine Mile North NMN_63 pond 59% 86%
Nine Mile North NMN_77 pond 71% 97%
Nine Mile North NMN_55 pond 74% 99%
Nine Mile North NMN_76 pond 100% 100%
Nine Mile North NMN_49 pond 40% 78%
Nine Mile North NMN_48 pond 61% 94%
Nine Mile North NMN_27 pond 49%
Nine Mile North NMN_20 pond 53% 89%
Nine Mile North NMN_24 pond 30% 68%
Nine Mile North NMN_84 pond 61% 94% landlocked basin
Nine Mile North HL_25 pond 100% 100% landlocked basin
Nine Mile North NMN_73 pond 62% 86% landlocked basin
Nine Mile North NMN_74 pond 92% 99% landlocked basin
Nine Mile North NMN_50 pond 100% 100% landlocked basin
Nine Mile North NMN_75 pond 75% 100% landlocked basin
Nine Mile South NMS_28 pond 63% 92%
Nine Mile South NMS_40 pond 64% 93%
Nine Mile South NMS_103 pond 60% 93%
Nine Mile South NMS_88 pond 62% 99%
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Priority Watershed
Device
Name
Device
Type
TP Removal
Efficiency
TSS Removal
Efficiency Comment
Nine Mile South NMS_23 pond 2% 13%
Nine Mile South NMS_104 pond 17% 45%
Nine Mile South NMS_72 pond 15% 40%
Nine Mile South NMS_74 pond 14% 48%
Nine Mile South NMS_79 pond 53% 90%
Nine Mile South NMS_76 pond 49% 79%
Nine Mile South NMS_84 pond 100% 100% landlocked basin
Nine Mile South Fork NMSB_3 pond 37% 76%
Nine Mile South Fork NMSB_57 pond 31% 83%
Nine Mile South Fork NMSB_90 general 3% 22%
Nine Mile South Fork NMSB_8 pond 66% 91%
Nine Mile South Fork NMSB_86 pond 1% 16%
Nine Mile South Fork NMSB_85 general 31% 69%
Nine Mile South Fork NMSB_7 pond 27% 59%
Nine Mile South Fork NMSB_5 pond 50% 99%
Nine Mile South Fork NMSB_62 pond 18% 96%
Nine Mile South Fork NMSB_33 pond 68% 100%
Nine Mile South Fork NMSB_12 pond 3% 13%
Nine Mile South Fork NMSB_6 pond 48% 96%
Nine Mile South Fork NMSB_2 pond 11% 35%
Nine Mile South Fork NMSB_34 pond 77% 100%
Nine Mile South Fork NMSB_15 general 16% 49%
Nine Mile South Fork NMSB_59 pond 95% 99% landlocked basin
Pawnee Pond PA_6 pond 64% 96%
Pawnee Pond PA_1 general 61% 97%
Pawnee Pond PA_9 pond 100% 100% landlocked basin
Southwest Ponds SWP_47 pond 62% 94%
Southwest Ponds SWP_34 pond 36% 87%
Southwest Ponds SWP_59 pond 62% 95%
Southwest Ponds SWP_35 pond 53% 89%
Southwest Ponds SWP_2 pond 24% 89%
Southwest Ponds SWP_1 pond 5% 71%
Southwest Ponds SWP_3 pond 67% 98%
Southwest Ponds SWP_10 pond 67% 96%
Southwest Ponds SWP_5 pond 24% 80%
Southwest Ponds SWP_14 pond 65% 99%
Southwest Ponds SWP_57 pond 100% 100%
Southwest Ponds SWP_37 pond 74% 99% landlocked basin
Southwest Ponds SWP_40 pond 100% 100% landlocked basin
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Priority Watershed Device
Name
Device
Type
TP Removal
Efficiency
TSS Removal
Efficiency Comment
Southwest Ponds SWP_31 pond 100% 100% landlocked basin
Southwest Ponds SWP_33 pond 100% 100% landlocked basin
Southwest Ponds SWP_58 pond 74% 99% landlocked basin
Southwest Ponds SWP_9 pond 100% 100% landlocked basin