MN Stormwater News — July 2019

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Heavy rains and construction sites

BMP failure on a construction site

Climate change is making Minnesota a wetter place. Rainfalls in the state have increased in both frequency and volume. The past three years have been some of the wettest, and climate projection data show the trend getting worse.

Construction site owners and operators may struggle to maintain BMPs or even access their sites in very wet conditions. Failing BMPs can be the source of water quality issues in nearby waters. Preparing for heavy rainfall and having materials like plastic sheeting or other ground cover available will help meet these challenges. The MPCA's construction stormwater general permit requires that permittees inspect BMPs at construction sites within 24 hours of a more than half-inch rainfall. Non-functional BMPs must be repaired, replaced, or supplemented by the end of the next business day. More frequent and heavy rainfalls may mean your increased presence at the site, and more repairs.

Consider beefing up erosion and sediment controls. Look for problem areas. If a silt fence is frequently breached in one location or an inlet is constantly filling up and needs cleaning, either upgrade to more effective BMPs or consider adding redundant controls such as straw, compost or rock logs, or other measures. Covering exposed soils when storms are imminent will protect against erosion, water quality impacts, and potential violations.