One of the primary changes in the new Manual is a larger focus on Low Impact Development (LID) stormwater techniques. The objective of LID is to have developed land mimic the hydrologic characteristics of pre-developed land in its natural state of vegetation. This means more rain water going back into the ground, instead of being stored in vaults and ponds before ultimately being conveyed to the rivers and Puget Sound. Once the new Manual is adopted, proponents for new development will be required to check to see if on-site infiltration is possible for treating stormwater.
Many jurisdictions are used to the old way of doing things, so the codes and regulations are not set up to encourage this type of development. One element of adopting the new Manual is to revise the codes to remove “barriers” to LID, and instead encourage it in new development. These changes must be made prior to, or at the same time as adoption of the new Stormwater Manual.