MN Water Resources Conference October 16, Eric Macbeth, Tom Colbert, Russ Matthys, Gregg Thompson, Jessie Koehle

Transcription

1 Paying Fair Share for Runoff Impacts: Tailoring Stormwater Utility Fees in Eagan, MN MN Water Resources Conference October 16, 2012 Eric Macbeth, Tom Colbert, Russ Matthys, Gregg Thompson, Jessie Koehle

2 Presentation Summary Introduction Stormwater Utility Fee Eagan Growth 2010 Ad Hoc Committee Summary/Citywide Implications

3

4 City of Eagan Area: 34.5 mi 2 Storm Sewer System: 340 mi. 1,270 Lakes, Wetlands, Storm Basins

5 Stormwater Utility Fee (1990) (Eagan City Code 3.07) Residential Equivalent Factor (REF) 1. Low Density Residences (singles & duplexes): REF = 1.0 per unit 2. Medium Density Residences (townhomes): REF = 0.8 per unit 3. All Other Land Uses (apartments, offices, retail, business parks, schools, churches): REF = Impermeability ratio (%) vs. REF/acre

6 Impermeability Ratio vs. REF/Acre

7 Eagan Growth Population 70,000 60,000 50,000 40,000 30,000 20,000 10,000 1,185 3,382 10,398 20,700 47,409 63,557 64, : 35% increase

8 Eagan Growth Estimated Impervious Acres ~31% citywide coverage 8,000 6,000 5,500 6,000 6,900 >25% increase residential 4,000 2, : 25% increase >30% increase commercial/industrial >40% decrease open/undeveloped

9 After 20 Years Refitting to Eagan s Quilted Land Use

10 Fitting Stormwater Fees to Runoff Load Costs $ LD Residential $$ Office/Retail/BP

11 Challenge:

12 2010 Ad Hoc Committee: Are Land Use Types Paying Fair Share for Stormwater Runoff Impacts? Build on: Stormwater Utility Fee (1990), Nondegradation Report (2007), 2030 Comprehensive Plan (2009), Utility User Rate Analysis (2010) Runoff Impacts = Volume, Phosphorus, Suspended Solids Loads Versus Pollutant Impact Charge or Loading Surcharge, Establish Equity Adjustment Factor

13 Existing Land Uses Source: 2030 Comprehensive Plan (2009)

14 Stormwater Runoff Impacts of Land Uses Source: Nondegradation Report (2007)

15 2009 SW Impacts vs. Revenue Sources: Nondegradation Report (2007); Eagan Finance Dept.

16 2010 Projected Revenue vs. Obligation Sources: Eagan Finance Dept.; Utility User Rate Analysis (2010)

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18 Quarterly Summary # Accts. Ave. REF 2010 Rate Rate 2 LD Residential 15, $8.46 $8.18 MD Residential 3,232 HD Residential 214 Office/Retail/BP 642 Quasi P/Instit $6.77 $8.46 $8.46 $8.46 $5.08 $11.48 $9.71 $11.18 Quarterly Scenario Stormwater Fee Per Average Account Differ. LD Residential $8.46 * -$0.28 MD Residential $10.83 * -$2.70 HD Residential $61.76 * +$22.04 Office/Retail/BP $ * +$25.00 Quasi P/Instit $ * +$ Rate 2 Equity Adjustment Factor Applied

19 Summary # Accts. Ave. REF 2010 Rate 2011 Rate@ LD Residential 15, $8.46 $8.18 MD Residential 3,232 HD Residential 214 Office/Retail/BP 642 Quasi P/Instit $6.77 $8.46 $8.46 $8.46 $5.08 $11.48 $9.71 $11.18 Quarterly Scenario Stormwater Fee Per Average Account Differ. LD Residential $8.46* -$0.28 MD Residential $10.83* -$2.70 HD Residential $61.76* $22.04 Office/Retail/BP $169.20* $25.00 Quasi P/Instit $263.11* $ Rate 2 Equity Adjustment Factor Applied

20 Citywide Implications: Quarterly Differences Difference LD Residential -$4,240 -$12,966 MD Residential -$8,726 HD Residential $4,717 Office/Retail/BP $16,050 $26,012 Quasi P/Instit $5,245 NET TOTAL $13,046

21 Actual Revenue vs. Projected Obligation ($1,000s) Actual 1 Projected 2 % Diff $1, $1,159 $1, % 2011 $1,240 $1, % 2012? $1,305? 2013? $1,361? 2014? $1,420? Sources: 1 Eagan Finance Dept.; 2 Utility User Rate Analysis (2010)

22 (651)

23 City of Eden Prairie, Pond Inventory and Maintenance Assessment Leslie Stovring City of Eden Prairie Joe Bischoff Eileen Weigel Wenck Associates, Inc. October 16, 2012 Minnesota Water Resources Conference

24 Schedule of Compliance Notice of Intent 1/8/09 Final SOC 1/28/10 Stilling Basin and Floodplain Pond Plans Approved 4/7/10 Stilling basin repaired Inventory & Maintenance Plan Approved 3/18/11 Replacement Plan 7/10/12 Floodplain Pond Winter 2012/13

25 Inventory & Maintenance Plan Developed to ensure cost-effective maintenance of City s stormwater system Over 900 waterbodies that receive stormwater Create streamlined approach to: Prioritize inspections and maintenance needs Verify basin performance Quantify impact on receiving waters Review system on a watershed basis Is current water quality treatment adequate? If not, where can improvements be made?

26 Approach GIS - Quantify basins and target inspections Drainage watersheds Sediment Accumulation Volumes Permanent Pool and Flood Pool Volumes P8 Evaluate existing conditions and potential improvements (i.e. clean-out or expansion) of stormwater basins BATHTUB model - Evaluate loading to lakes and determine reductions needed to meet state standards

27 Prioritize, Prioritize, Prioritize Why prioritize? Fiscal limitations Limited resources Number of water resources What to prioritize for? Watershed Impacts Subwatershed Impacts Project cost Budget cycle

28 Staring Lake Watershed Phase I - Staring Lake watershed ( ) Current RPB Watershed District Restoration project University of Minnesota Carp Study Key recreation area for the City Does receive drainage outside of City boundary

29 Stormwater System Analysis Staring Lake Identified Basins in City GIS database Stormwater ponds Stormwater wetlands Mitigation wetlands Delineated drainage areas Excluded basins: Private ponds or Ponds that do not receive runoff from City-owned property or ROW

30 Data Collection Review grading plans or as-built drawings Survey grade GPS field survey Bathymetry Sediment depth Outlet elevations Permanent and flood pools

31 Identified Stormwater Basins Phase I and II = 237 basins Phase I & II = $284,939 (approx. $1,657 / basin) Survey results: 172 Basins met study criteria 101 do not meet NURP standards 14 basins under-built compared to design 5 basins had high estimated sediment (3 are wetlands)

32 Subwatershed Assessment Regional Trail Area Treatment train of 7 stormwater basins 2 constructed ponds and 5 stormwater wetlands

33 Results of Pond Assessments Pond ID Surveyed Permanent Pool Volume (AF) NURP ratio 1 Sediment Volume (AF) P8 Predicted TSS (mg/l) P8 TSS Removal (%) P8 Predicted TP (mg/l) P8 TP Removal (%) Basin Type F CP A SW A SW B CP C SW A SW A SW

34 Engineering Cost Estimates Pond Excavation Volume (acre-feet) Approximate Unit Cost ($ per ac-ft) 0 to 0.5 $138, to 1 $107,315 1 to 5 $51,207

35 Drainage Group Pond ID Surface Area of As- Built Permanent Pool (acres) Surface Area of Surveyed Permanent Pool (acres) Permanent Pool Volume Difference (AF) Sediment Volume (acrefeet) Estimated Excavation Costs Priority TSS Reduction (lb/yr) TP Reduction (lb/yr) Constructed Ponds North Purgatory Creek B $107,006 High 2, Staring Lake Direct C $33,764 High B $116,550 High Purgatory Creek Park Direct Purgatory Creek to Highway A C $63,121 High $41,367 Medium McCoy Lake Area D $16,981 Medium Valley View Road and Highway 494 Interchange C $61,484 Medium Highway 5/212 Interchange E $79,411 Medium 1, Wetlands North Purgatory Creek Purgatory Creek Park Direct Highway 5/212 Interchange C $62,213 Medium C $67,943 Medium A $155,642 Medium A $75,803 High E $60,899 High 2, B $43,882 Medium

36 Approximately $300,000 to remove 4.6 pounds phosphorus annually Cost is $2,174 per pound P over 30 year life cycle

37 Staring Lake P Budget Main Watershed Flow Total Suspended Solids Total Phosphorus TP Reduction Acrefeet mg/l lbs /yr µg/l lbs /yr lbs /yr % Upstream 1 5, , ,346 1,396 60% Purgatory Creek 2 3, , , % Staring Direct , % McCoy Lake 1, , % Total 11, ,307, ,756 2,830 60%

38 Phosphorus Reductions BATHTUB model indicated load reduction required to meet state standard for Staring Lake is 2,830 pounds Total Phosphorus per year Additional treatment associated with cleanout and expansion of all identified high priority basins was 36 pounds TP / year Total cost to complete all projects $1.2 Million $33,333 / pound of annual TP reduction $1,111 / pound of TP reduction on a 30 year life cycle

39 Conclusions P8 model indicates that cleanout and expansion of the stormwater basins would result in 1.4% of total TP reduction needed to meet State Standards in Staring Lake. Only a few ponds had measurable amounts of sedimentation Need to have flexibility to work on watershed projects that may not include excavation or expansion For example, would money be better spent on projects such as in-lake alum, carp removal, iron-enhanced sand filtration on key treatment ponds or others? Looking at the resource ensures dollars used effectively

40 Next steps Phase III Field work for Duck and Red Rock Lake watersheds in 2012 Draft Phase I Report - November Retrofit - 2 basins from Phase I P8 model being used to determine where additional projects could be located Applying for Grants Town Center Study Potential for additional retrofit projects

41 Questions?