St. Mary's Greek Orthodox Church

3450 Irving Avenue South
Project Status: 
Completed
Year Completed: 
2011
About this project: 

In 2010 the MCWD helped fund construction of permeable pavers with infiltration tanks and bio-retention basins at St. Mary’s Greek Orthodox Church.

Stormwater Management BMPs

  • Existing flat rooftops for detention
  • Five subsurface ‘soy based’ plastic storage chambers
  • One subsurface corrugated metal storage reservoir
  • One infiltration basin w/turf
  • One detention basin w/turf
  • Five bio-retention basins w/rain garden plants
  • 3,550 square feet of permeable pavers

Water Quality and Volume Control

This multi-prong approach significantly reduced the amount of phosphorus pollution in Lake Calhoun. By reducing the amount of impervious surface, adding water-friendly landscaping, and increasing stormwater infiltration capacity, the project reduced the amount of phosphorus going into the lake by about 30 percent. 

Narrative

From Stormwater Magazine

St. Mary’s Greek Orthodox Church sits above the shore of Lake Calhoun in the Minneapolis suburb of East Calhoun. Runoff from the church’s parking lot and property carried pollutants directly into the lake. 

The church’s parishioners and clergy felt an obligation to stop this pollution of the environment. They also were motivated to reduce their stormwater utility bill, which was $10,000 per year.

Landscape architect Mitchell Cookas of Solution Blue designed a green infrastructure plan for managing the church’s stormwater on site. “The system can accommodate 100% of the 10-year event—4.2 inches in 24 hours—onsite,” explains Cookas. “It also maintains the discharge rates to meet the predevelopment conditions to match the 100-year event rate, 6 inches in 24 hours.”

Cookas had green, soy-based plastic Triton storage chambers installed underground, enough to provide 12,250 cubic feet of storage. Above the chambers are permeable concrete pavers and a parking lot totaling 3,550 square feet. The church’s flat roofs were left as they were. Because the roof drain inlets are 0.5 to 0.75 inch above the roof surface, the design team factored in 0.5 inch of storage before the runoff drains into the roof drains, he notes. Five separate rain gardens totaling 4,650 square feet now grace St. Mary’s 3.5-acre campus. The exposed soils’ infiltration rate was tested during excavation. But after the rain gardens were installed, their soils infiltrated faster than expected, yielding higher runoff volume reduction and decreased discharge rate.“Construction staging was very challenging because construction took place over eight weeks while the church was hosting several weddings, Sunday worship, and other weekly events,” says Cookas.

The cost of the project was $60,000 more than for comparable “grey” or traditional infrastructure. Before the work was done, St. Mary’s had been paying $10,000 in annual stormwater usage fees. Because the project was such a dramatic improvement, the church became the first property owner to have 100% of these fees were waived in perpetuity. When the church chose to install the green infrastructure measures, it estimated a six-year return on investment. In addition, the more attractive parking lot and the rain gardens enhanced the look of the overall property.