Stormwater Facility Maintenance

Stormwater detention facilities such as pond and underground vaults have been required for developments since 1980. Surfaces such as roads, pavement and roofs increase storm water runoff which ends up in streams. Without ponds or vaults erosion, water pollution and damage to streams and pipes could occur.

Detention ponds store stormwater above ground. Detention vaults store stormwater underground. They both collect water and release it slowly in order to prevent flooding and property damage. In newer developments water quality requirements require installing stormwater vaults with media filters that remove total suspended solids, bacteria, metals and nutrients after going into a standard detention facility. It is important that detention ponds and vaults are maintained in order for them to function properly.
Responsibility for Maintaining Detention Facilities
Detention facilities serving residential neighborhoods are generally owned and maintained by the homeowners in that subdivision. When plats are developed there are provisions written on the recorded plat map that will state who owns and is responsible for maintaining the detention

The City of Mill Creek Municipal Code (15.14.110) Maintenance, repair and operation of the stormwater system, notes that if a private stormwater facility serves multiple lots and has not been specified on a subdivision plat, shot plat or other legal document, maintenance, operation and repair responsibilities shall rest on the homeowners association. In the cases within that subdivision. Detention facilities are typically located in tracts that are owned by the homeowners in the subdivision it is located in.

Detention facilities serving commercial property are owned and maintained by the owner of the property that the facility is located. The requirements are the same for maintaining detention facilities.

The City currently maintains approximately 27 public stormwater facilities (i.e. ponds, vaults, storm media-filter units, etc.), through a combination of annual inspections and, when needed, cleaning, replacing filters, etc.  The CIty also maintains approximately 4,000 public catch basins, through a combination of inspection every two years and, when needed, cleaning.

 Your homeowners association president may receive a letter with items that need to be addressed after detention ponds are inspected. The letter will give you a timeline of when the items need to be fixed. If at any point there are questions or you need more time to complete the items listed on the letter feel free to call 425-551-7254.
Responsibility for Maintaining Catch Basins on Private Property
The City cleans and maintains catch basins in the public right of way. Any catch basins that are located on private property are to be maintained, and repaired by the property owner. If you have a catch basin in your backyard your homeowners association would be responsible for maintaining that catch basin.

The basic guideline for maintaining a catch basin is to have them cleaned when the sediment exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe. On commercial property the City recommends cleaning catch basins once a year due to the fact that there is more traffic and possibility of pollutants in the soils in the catch basin. If you have questions regarding if your stormwater system needs cleaning, contact the Public Works and Development Services department at 425-551-7254.
Technical Assistance for Maintaining Detention Facilities
Homeowners associations, homeowners and businesses that own and maintain stormwater facilities can contact the Public Works and Development Services department at 425-551-7254 for technical assistance. Common maintenance can include debris and trash removal, vegetation management, sediment removal, damage to the structure, fence repair (for fenced areas) and structural repair.