Onsite vs. Regional Facilities Plan

Onsite Stormwater Management (Traditional)
program

Using individual, onsite structural stormwater controls like vaults, ponds, and swales for each development is the traditional approach for controlling stormwater quantity and quality. The developer finances the design and construction of these controls. In commercial sites, property owners are responsible for maintaining the facilities. In residential neighborhoods, these may be turned over to the City to maintain. 
 

Onsite Facility

 

Onsite Facility

 
   

Regional

 

Regional Facility

 

Regional Stormwater Management
program

Regional stormwater controls are facilities designed to manage stormwater runoff from multiple projects and/or properties through a City-sponsored program, where the individual properties may assist in the financing of the facility, and the requirement for onsite controls is either eliminated or reduced. In Redmond, developers pay a fee, in lieu of constructing onsite facilities. This may be optional or mandatory depending on the location of the site. More information about how the City administers its regional facilities program is available in the Stormwater Technical Notebook.

Onsite Stormwater Management (LID)
program

One way of reducing the size of traditional stormwater management facilities, is to use the concept of low impact development. The low impact development approach to developing land and managing stormwater is to imitate the natural movement of water through a site. Before development came to Redmond, almost all rainfall was dispersed along the forest floor, where it infiltrated into the ground, was taken up by the roots of plants and trees, or evaporated. Where forests and natural open spaces have been cleared, and buildings, roads, parking areas and lawns dominate the landscape, rainfall now becomes stormwater runoff, carrying pollutants to nearby waters. The city and state are moving toward requiring developers to use onsite, low impact development techniques to reduce the requirement for traditional onsite stormwater management or regional facilities. The developer finances the design and construction of these controls, and the property owner(s) are responsible for maintaining them following construction.

The City of Redmond uses all three techniques to manage stormwater, favoring regional stormwater facilities in highly urbanized areas, favoring low impact development techniques outside of wellhead protection zones and in less urban areas, and using traditional onsite facilities to finish the job of stormwater management as needed.

Advantages of Regional Stormwater Controls
program

  • Reduced construction costs.  Design and construction of a single regional stormwater control facility can be far more cost-effective than numerous individual onsite structural controls.
  • Reduced operation and maintenance costs.  Rather than multiple owners and associations being responsible for the maintenance of several stormwater facilities on their developments, it is simpler and more cost-effective to establish scheduled maintenance of a single regional facility.
  • Higher assurance of maintenance.  Regional stormwater facilities are far more likely to be adequately maintained as they are large and have a higher visibility, and are typically the responsibility of the City.
  • Maximum utilization of developable land.  Developers are able to maximize the utilization of the proposed development for the purpose intended by minimizing the land normally set aside for the construction of stormwater structural controls.
  • Retrofit potential.  Regional facilities can be used by a community to mitigate existing developed areas that have insufficient or no structural controls for water quality and/or quantity, as well as provide for future development. The City is doing this in the Downtown and Overlake neighborhoods.
  • Other benefits.  Well-sited regional stormwater facilities can serve as a recreational and aesthetic amenity for a community.

Disadvantages of Regional Stormwater Controls
program

  • Location and siting.  Regional stormwater facilities may be difficult to site, particularly for large facilities or in areas with existing development.
  • Capital costs.  The community must typically provide capital construction funds for a regional facility, including the costs of land acquisition.  However, if a downstream developer is the first to build, that person could be required to construct the facility and later be compensated by upstream developers for the capital construction costs and annual maintenance expenditures.  Conversely, an upstream developer may have to establish temporary control structures if the regional facility is not in place before construction. 
  • Need for planning.  The implementation of regional stormwater controls requires substantial planning, financing, and permitting.  Land acquisition must be in place ahead of future projected growth.