The second area is flat, but it has only a small area of open space and a great proximity of mature trees. Large trees would be at risk if we dug deeply around their root systems. Standard practice is not to dig deeply within a tree's "drip line" (the furthest out that the tree's branches reach). Storm water remediation underneath trees is more costly than projects in open areas. The engineer suggested using "filtration cells" to help maximize the space use. These cells temporarily collect and pond one foot of rain runoff, and they have two feet of sand and stone underneath to promote infiltration. Excess water is absorbed by native plants. Overflow goes into the storm system. Implementing this type of solution means the majority of the storm water is absorbed into a planted area instead of running into the parking lot.
|Assessing the trees: |
lots of drip line here
|Thinking about ways to redirect runoff|
so it doesn't go into the parking lot
|Standing at the top of the steep|
swale to the cul-de-sac