An overview and critique of methods Como Lake TMDL An overview and critique of methods

Capital Region Watershed District Formed in 1998 in response to a citizen initiative to protect Como Lake Community continues to play an active role in watershed management

Como Lake Strategic Management Plan Prior to 303d listing of Como Lake, CRWS undertook a study of the lake to develop a management plan. The resulting management plan was completed in 2002 and formed the basis for the later TMDL. Source: 2009 CRWS survey http://www.capitolregionwd.org/documents/Wilder_Report.pdf

Scope of 2002 Management Plan Review and evaluate available watershed & water quality information Prioritize management concerns Identify management goals and objectives Enumerate implementation activities Evaluate citizen agency roles

Background on Como Lake Area (acre) Located in the north-central portion of the Capitol Regional Watershed District (CRWD) Roughly 1783 acre watershed (not including the lake area) Defined as a shallow lake by the MPCA. Mostly used for recreation (fishing, boating and aesthetics) City Saint Paul 1205 Falcon Heights 230 Roseville 420 Total 1,855

Background Cont. Majority of the watershed's water contribution to Como Lake is delivered through 22 storm sewers discharging directly into the lake. Gottfried's Pit collects the drainage from parts of Roseville, Flacon Heights, Ramsey County right-of-ways, and the City of St. Paul.

Permitted Point Sources MS4's (stormwater program for municipal separate storm sewer systems) are designed to reduce the amount of sediment and pollution that enters the surface and ground water from storm sewer systems to the maximum extent predictable.

Beneficial Uses Como Lake is classified as: http://www.historicalartforum.com/catalog/images/IceComo16x22.jpg Como Lake is classified as: 2B – Cool and warm fisheries 3B – Industrial consumption 4A - Agricultural use, irrigation 4B – Agricultural use, livestock and wildlife watering 5 – Aesthetic enjoyment, navigation 6 - other ← most stringent

303d Listings First year listed: 2002 Impairment: Aquatic Recreation Pollutant or stressor: Nutrient/Eutrophication Biological Indicators http://nonizamboniblue.blogspot.com/2009_08_01_archive.html

Pollutants of Concern Phosphorus loading is the main concern in Como Lake. Related to Chlorophyll-a concentration, which is negatively correlated to Secchi depth. Standards in this ecoregion are 60 ug/L Total [P] growing season means ranged from 100-400 ug/L from 1993-2007.

Water Quality Standards To be listed as impaired, monitoring data must show BOTH: WQS for TP violated AND Chlorophyll-a WQS violated OR Secchi Depth WQS violated Parameter Eutrophic Standard, Shallow Lake Lake Como, GSM 1998-2007 Trophic Status Index TP (µg/l) TP > 60 173 78 (hypereutrophic Chlorophyll-a (µg/l) chl < 20 25 62 (eutrophic) Secchi depth (m) SD > 1.0 1.6 53 (eutrophic) High TP/chl-a or Secchi suggests that phosphorus does not limit algae growth. (Some other factor limits growth).

Total Mean Phosphorus

Chlorophyll-a v. Total P

Secchi Depth v. Total P

Secchi Depth v. Chlorophyll-a

Modeling Source Loads P8 (Program Predicting Polluting Particle Passage thru Pits, Puddles, and Ponds) Pro’s simulates flow conditions and pollutant transport in urban environments. Discretely model BMP’s. Model set-up, calibration, and validation requirements are moderate. Con’s The initial model was set up by Barr Engineering in 2000. Only minor (insignificant) changes in hydrology do to installation of BMP’S. Recalibration with more recent data may yield somewhat different results. http://www.extension.umn.edu/projects/nre/Stormwater/images/InstallationInstructionsforP8ModelingSoftware.pdf

Existing Load Allocations Watershed Load 34% of total load All permitted sources (all MS4’s)

Existing Load Allocations Internal Load 65% of the total load Result of years of Phosphorus accumulation! Anoxic conditions at sediment-water interface causes phosphorus release from sediment. Bottom-feeding fish disturb sediments Decaying curly-leaf pondweed. Physical disturbance due to wind mixing Atmospheric Deposition = 1% of total load http://www.lmvp.org/Waterline/spring2005/algae2.htm

Estimate of Assimilative Capacity WiLMS (Wisconsin Lake Modeling Suite, Version 3.3.18) Empirical Model, input parameters minimal Chosen for ability to predict response of in-lake loading to changes in external load Walker 1987 Reservoir Model Addition modeling of lake sediment Allows of chlorophyll and transparency Lake Area (acres) Volume (ac-ft) Mean Depth (ft) Drainage Area (ac) Total Unit Runoff (inches) Watershed TP load to Lake (lbs/yr) TP, GSM, (µg/L) 72 525.6 7.3 1767 5.4 625 173

Estimate of Assimilative Capacity Model calibrated unsing 1998-2007 GSM averages TP standard (60 µg/L) used as endpoint Loads adjusted until model prediction = WQS Assimilative Capacity found to be 306 lbs/yr Overall Reduction of 83% from existing load!

Margin of Safety Implicit MOS incorporated into TMDL Based on conservative assumptions for : Sedimentation rates likely under-predict rate for shallow lakes. Model results reflect meeting MQS while lake is still in the turbid phase = underestimate of the lake’s loading capacity under clear-water phase.

Critical Condition TP levels peak and clarity is worst in Jul-Aug WQS based on growing season averages Load reduction designed so lake will meet WQS over entire growing season

TMDL Load Allocations TMDL = Load Allocation + Wasteload Allocation 306 lbs/yr = 57 lbs/yr + 249 lbs/yr 0.83 lbs/day = 0.15 lbs/day + 0.68 lbs/day Total = Internal Load + Watershed Loading

Wasteload Allocations Source Existing Load (lbs/yr) Load Allocation (lbs/yr) Required Load Reduction (lbs/yr) Percent Reduction Internal Load 1190 37 1153 97% Atmospheric Load 20 20 0% Watershed Load 625 249 376 60% Total 1835 306 1529 83% Watershed Load = Wasteload allocation for MS4’s WLA is shared by all NPDES permitted entities Load reduction will met by the group as a whole For implementation, assessments made at sub-watershed level

Implementation Strategy: External Load REDUCE WATERSHED LOAD FIRST Structural BMP’s Ex. Pascal-Arlington Stormwater Improvement Project Eight raingardens, Eight underground infiltration trenches, An underground stormwater storage and infiltration facility A regional stormwater pond. Sub-watersheds 7 & 8 have reached target Sub-watershed 3 is underway Non-Structural BMP’s Increase street sweeping from 2x to 4x/year Stormwater education Support for raingardens, citizen involvement http://sustainablestormwater.org/2007/05/23/infiltration-trenches/

Implementation Strategy: Internal Load ADDRESS INTERAL LOAD AFTER REDUCTION FROM WATERSHED Management Options: Fisheries management reduce benthivorous/increase piscivorous Shoreline management Waterfowl management Optimize aeration practices Consider addition of phosphorus stabilizer (alum, CuSO4) http://www.phoslock.com.au/about.php

Why Target External Load? Internal Load is the result of accumulation from watershed load Measures taken to addressing Internal Load will be temporary at best unless External Load is decreased

TMDL Critique Focus of TMDL: Excess nutrients, is on TP. The TMDL is a formatted version of an earlier water quality management plan. Focus of TMDL: Excess nutrients, is on TP. Focus on reducing the "turbid, algal-dominated state to clear state". Implementation plan focuses on reductions in external loading. currently evaluating switching attention from external to internal load reductions solutions (Como Lake implementation audit underway soon) Existing Load (lbs/yr) Allocated Load (lbs/yr) % Reduction Permitted sources (watershed runoff) Non-permitted sources (atm. and internal load) 625 249 60 1210 57 95 Total 1835 306 83

TMDL Critique - cont. Categorical wasteload allocation approach. Requires the participation and shared responsibility to achieve reductions between 3 municipalities, various government agencies and residents.  Data used in analysis dates to late 1990's. No significant change to land use  Time and effort spent on converting the early WQ mgmt plan to a TMDL format. Additional strain on limited resources Potential confusion of stakeholders danger of focusing on assessment and not implementation

Como Lake TMDL Public Outreach Work Group City of Falcon Heights City of Roseville City of Saint Paul City of Saint Paul, Div of Parks and Recreation City of Saint Paul Public Works CRWD Board of Managers CRWD Citizens Advisory Committee Community Council District 6 Community Council District 10 Como Northtown Credit Union Como Shoreline Interests Neighborhood Energy Consortium Metropolitan Council Environmental Services Minnesota Department of Natural Resources Minnesota Pollution Control Agency Minnesota State Legislature Ramsey County Ramsey County Public Works Ramsey Soil and Water Conservation District Emmons & Olivier Resources Lynch Associates University of Minnesota Water Resources Center

Feasibility of Proposed Goals There are Federal, State, Watershed and Local authorities in place to ensure that the plan for Como Lake is moving forward.  Estimated cost of the plan is ~$2.5 million. Considerable input from the watersheds stakeholders. Addressing the needs of the public.

This leads us to believe that….. The emphasis on public policy and checks and balances elicited by various governmental policies, along with a coherent budget makes the goals put forth by the Como Lake TMDL lofty, but overall, attainable.