Lake Facts

So what’s going on with Como Lake?

Como Lake Watershed

The Issue: Como Lake is “sick.” It is currently listed by the Minnesota Pollution Control Agency as impaired (a legal designation) due to excessive concentrations of nutrients in the water, especially phosphorus, and more recently because of excessive salt.  This means our lake is not able to meet its designated use, which includes recreation and support of aquatic life.  The result of the excessive phosphorus is an explosion of algae growth – many different kinds of algae, with blue-green algae (cyanobacteria) being the most harmful.  The algae overwhelm our lake making the water look pea-green, covered in muck, sometimes very smelly, and making survival difficult for the aquatic life trying to live there. Ultimately the algae prevent clean water in our lake needed to sustain a balanced, healthy ecosystem.

How excessive phosphorus gets into our lake: Our neighborhood stormwater conveyance system is set up to move rain and snowmelt away from our homes and into local waters as quickly as possible to prevent flooding.  Rain and snowmelt immediately becomes “runoff” when it flows across hard surfaces, such as our streets, and heads to the nearest storm drain (also called catch basins).  Our storm drains connect to large underground pipes called storm sewers that discharge our runoff directly into Como Lake and the Mississippi River.  When leaves and other organics accumulate on our streets, our runoff flows through this material. Mixed with water organic debris quickly breaks down and releases nutrients like phosphorus and nitrogen into the runoff. This nutrient infused water then flows into our storm sewers and into our lake and river. Sometimes the debris itself will get washed into storm drains that have grit chambers where it soaks for days or weeks and releases more and more nutrients.

Organic material is the biggest source of phosphorus: Believe it or not, organic debris is a bigger source of phosphorus in Como than lawn fertilizer.  Thanks to a MN law that severely limits the use of phosphorus for residential lawn fertilizing, the vast majority of lawn fertilizer in use today is phosphorus free.  Leaves, grass clippings, soil, and other tree parts like seeds and flowers that accumulate in our neighborhood – these are major sources of phosphorus. Organic debris that falls on the earth, such as our yards, gardens and our parkland, will break down into the soil.  Not a problem.  But when the debris falls on hard surfaces, that’s when it can seriously impact Como Lake.  As mentioned above, organics on our streets are especially problematic as they soak in our runoff and leach nutrients into our local waters.

Hard Surfaces + Organics + Stormwater = Nutrient pollution in our lake and river

The Scale: In a natural setting it’s normal for a lake to take in nutrients from organic material, such as leaves and other material that fall into a stream that flow to a lake, or from plants that naturally grow in or near a lake.  But nearly all of the Como neighborhood and parts of Falcon Heights and Roseville – over 1,700 acres of land area – drain stormwater into Como Lake. That’s over 1,000 football fields in size.  Como Lake itself is only 1/24th the size of the land area that drains runoff into it.  What’s worse, over 1/3 of this area is “impervious” or hard surfaces – sidewalks, driveways, parking lots, roof tops, and streets.  Because of our stormwater conveyance system, nutrient rich runoff from this vast area is fast-tracked from these hard surfaces into our lake. Many of our neighborhood blocks are lined with mature trees and bordered by urban lawns, so lots of organic debris – literally tons of it – accumulates in this large “lakeshed” area.

Internal vs. External phosphorus sources: Capitol Region Watershed District has completed an assessment of our lake and determined 65% of the phosphorus in our lake’s water is coming from “internal” sources.  That is, from dead and decaying plants (including all that algae) and the lake-bottom sediment layer that has built up over the last century.  In other words, once phosphorus gets into our lake it never really leaves. Phosphorus that’s in the water is taken up and released over and over, year after year, with the coming and going of the growing season.  But the source of the other 35% of the phosphorus present in the water column is coming from “external” sources – new phosphorus that comes in every year.  It comes from the surrounding “lakeshed” (outlined in red on the map above) – the land area that drains stormwater runoff into our lake via underground storm sewers.  So in addition to the excessive phosphorus already present in Como Lake, there is a continuous influx of new phosphorus entering our lake every year from our neighborhood.  60% of this new phosphorus comes from leaves alone, according to Dr. Sarah Hobbie, one of our Como neighbors and an ecology professor and researcher at the University of Minnesota.

The Citizen Intervention: The fact so much organic debris accumulates in our neighborhood and leaches phosphorus that flows to Como Lake is not the fault of the residents who live in the Como neighborhood.  (Not unless you are one of the misinformed souls who sweeps their leaves and grass clippings into the street intentionally).  The truth is, our highly impervious neighborhood and the underground storm sewer system that sends everything straight to our lake and river is the “built environment” we inherited from many decades ago.  This is how the system was intended to operate, to keep our homes and streets from flooding.  But today our lake is impaired, so we find ourselves in the position of needing to “intervene” and mitigate the existing system to reduce or prevent a worsening phosphorus problem for our beloved Como Lake.

Government’s Role: We are not alone in this challenge. Today there are modern technologies that help filter or “settle out” pollutants from urban stormwater.  As they are able, the cities (St. Paul, Roseville, Falcon Heights) that have storm sewers flowing to Como Lake are working with Capitol Region Watershed District to replace some of the older, less sophisticated stormwater infrastructure.  But this is expensive and will take time to replace.  All three cities run a street sweeping program and remove organic material at least once in spring and once in fall from streets and curbs.  This is a critical function, but costs money to operate.  Given current economic circumstances, increasing the frequency of street sweeping is not likely in the short term.

The Public’s Role: The residents who live on the streets that drain to our lake and river can play a critical “source reduction” role, by preventing organic debris and other pollutants from accumulating on our neighborhood’s hard surfaces in the first place.  Given that Como Lake is already impaired for phosphorus, cleaning up organics from our streets and curbs in addition to City street sweeping is an especially vital role residents can play to slow the influx of new phosphorus sources into our lake.  If we can significantly reduce the “external” (watershed) contribution to our lake’s phosphorus load, it will then make economic sense for our local government agencies to invest in solutions to address the “internal” phosphorus load problem.  But we have to turn off the outside “faucet” first, otherwise our investments in internal phosphorus loading remedies will be a waste of tax dollars.

It is in this spirit of shared responsibility and shared contribution to watershed governance (shared between government and the public) that the Como Active Citizen Network seeks to organize fellow Como neighbors and other local partners in a collaborative effort to reduce the phosphorus flowing to Como Lake.  We are trying to do “our part” – the citizen role – by preventing phosphorus at the source.  We firmly believe, working together is our lake’s best and perhaps last hope for recovery.

Como Lake TMDL final report (2013)

TMDL stands for “total maximum daily load.”  When a lake is assessed and determined to NOT be meeting state water quality standards due to a particular pollutant a process is launched to determine exactly how much of the offending pollutant that lake can continue to take in on a daily basis and still recover.  So for example, Como Lake is impaired due to excess phosphorus.  The TMDL report states that a 60% reduction in “external” phosphorus loading (coming from the surrounding watershed) is needed and a 90% reduction in “internal” phosphorus loading (coming from the plant material and lake bed already in the lake) in order for our lake to recover.

Como Lake Monitoring Results (2014)

Como Lake receives water from the surrounding watershed (1,856 acres), which consists of runoff coming primarily from residential areas and from Como Park. Runoff from the residential areas is directed to the lake through a system of stormwater pipes located under the streets. Located upstream of Como Lake, Gottfried’s Pit receives drainage from Roseville, Falcon Heights, Ramsey County right-of-ways, and the City of St. Paul before being pumped into Como Lake. Water occasionally outflows from the lake at the southeast corner, discharging into the Trout Brook storm sewer system which is routed to the Mississippi River. The shallow depth of the lake, coupled with the large nutrient inputs from upland runoff sources, has had significant negative impacts to the lake’s overall health.

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