Agenda - Public Works Committee - 11/20/2007

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Board member Olds stated that the pervious surface roadways and sidewalks are designed to absorb water rather than have' runoff. The pervious sidewalk is not designed for a parking lot or a driveway because of its porous nature. Rain gardens can be used to retain storm water rather than directing it into a culvert that runs into a pond. . Board Member Max stated that the arboretum parking 'lots are pervious but. typical roadways are not commonly pervious. . Environmental Coordinator Anderson stated that iri one of the parks in Town Center, Netlawn is being used to create a pervious parking lot. SOUle of those concepts are being explored and utilized. Some new town home developments include rain gardens. Board Member Max stated that increasing the density of topsoil could impact runoff. Board Member Olds stated it would depend on how compacted the soil is. ,- Board Member Max stated that the intent is water conservation. Board member Olds stated that if six (6) inches of topsoil is required, it has to be at a level of compaction that <ioesn 'texceed something. Mr. Bruce Bacon stated the purpose of this requirement is to establish plant growth. If it is compacted, the organic matter will compact harder than sand because it's finer. He stated research has been done on forest soils for the' origin of the nutrients that support microorganisms in the soil. People assumed it was due to leaf liter and debris.' It turns' out more nutrients in the soil are from the roots of growing trees th~ from the leaf litter. To put black dirt out with no establishment of growth doesn't support the function of plant growth; If the plants are not growing, they don't buffer runoff to the extent that they should. .The roots of the growing plants are what make it resilient and support life. Environmental Coordinator Anderson stated what this boils down to is that something needs to be put in place so people don't have their irrigation systems running constantly and cut down on water usage. . Board member Ma~ stated that a rain garden takes the place of irrigation, which results in using sprinklers less. Board Member Bentz stated, that if the water goes straight into the sandy soil because of . sprinkling, there is a cycle. If everything works through the natural cycle there should be no point to establish conservation methods. He wondered how the 'amount of topsoil necessary to make a difference was determined. He felt that people would still run sprinklers and try to get their green grass to grow. Mr. 13ruce Bacon explained that evaporation should be considered in the natural cycle. 58 Environmental Policy Board/July 23,2007 Page 12 of 16 .