Rain gardens will improve Como Lake


Some of the most visible additions to the Como Park neighborhood with the recent street renovations are four mulch-filled depressions strategically placed around the neighborhood.
These are to be the new rain gardens the Capitol Region Watershed District is installing this spring. With help from local volunteers, they will be planted on Saturday, June 3.

The Arlington-Pascal Residential Street Vitality Program is a two-year project, and another four rain gardens will be added next spring, for a total of eight in the neighborhood.

The rain gardens were created to alleviate the algae problem in Como Lake, one of St. Paul’s most popular lakes. Neighbors and visitors have complained about a decrease in water clarity and quality, and an increase of odors.

Before this area was settled in the early 1900s, wetlands dotted the landscape. Rainwater pooled in these depressions, allowing the water to filter through the soil before arriving in the lake.

Today, impervious surfaces such as roofs, driveways, roads and parking lots cause water to flow directly into the lake. Lawn care chemicals and sediment from roads are carried with the excess water directly into Como Lake.

A rain garden mimics the function of a natural wetland. One of the new rain gardens will be on the corner of Midway Parkway and Hamline Avenue, where many trees were removed last summer.

To reduce flooding, the 75-year-old storm sewers were upgraded. This spring, 500 perennials, shrubs and trees will be planted. Plantings include many native species and those that can withstand wet conditions.

In addition to the rain gardens, the Capitol Region Watershed District is installing nine large infiltration trenches beneath the newly renovated streets. Storm water runoff will flow from catch basins to a perforated pipe surrounded by rock, which allows water to slowly infiltrate into the ground.

On the southeast corner of Arlington and Hamline avenues, a new underground infiltration structure will be installed. It holds two acre-feet of water and will shepherd the runoff into the ground rather than the storm sewers.

Water from sewers runs through the heavily fertilized Como Park Golf Course and then directly into Como Lake.

In collaboration with St. Paul Parks, the Capitol Region Watershed District is modifying the golf course ponds so that water can be treated before it enters the lake.

In total, $1.5 million of improvements to aid the water quality of Como Lake will be completed by the end of the fall.

Capitol Region Watershed District Water Resource Specialist Bob Fossum cautions that major improvements in the Como Lake algae problem will not be seen immediately.

“It may take several years before there is a noticeable improvement, and a lot of that has to do with internal loading,” he said.

The new rain gardens, trenches and underground structures will help reduce the nutrient load from surface runoff entering the lake, also referred to as external loading.

With internal loading, nutrients are introduced into the water from sediment at the bottom of the lake. This also leads to algal blooms and a depletion of the lake’s oxygen supply.

Removing the sediment can help, said Fossum. The Capitol Region Watershed District sponsored a sediment delta removal project where six deltas were removed from Como Lake.

This project was executed with help from the St. Paul Parks and Recreation Department, Ramsey Soil and Water Conservation District, and Ramsey County Public Works. Still, this is not an immediate fix, and internal loading remains a problem in Como Lake, said Fossum.

The speed of Como Lake’s recovery also has to do with climate conditions. More rain throughout the summer will increase the amount of nutrients and sediments that wash into the lake.

Still, because of all the improvements to the Como Park neighborhood, the water quality of Como Lake will certainly improve.

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