I went by the rain garden at the Beebe School during this afternoon's heavy rains to check-out its performance (see video). So far the rain garden looks to be working pretty well, with a few issues to monitor and potentially work out:
Some of the water flow from the parking lot is still going directly into the catch basin, without entering the rain garden basin and being treated. However, that interception of water does seem to be preventing flooding.
Water is pooling in the rain garden basin as it should, in order for infiltration to occur. It may be pooling too much though, limiting treatment by the plants and soils in the rain garden.
We will continue to monitor the rain garden as a pilot "green infrastructure" project for Malden, and hope to make improvements as necessary.