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When precipitation falls to the ground it generally does one of three
things: it evaporates, it percolates, or it becomes stormwater.
Evaporated water forms clouds. When precipitation soaks into the
soil and fills spaces between grains of sand and gravel it forms
groundwater. The saturated ground forms the aquifer from which we pump
our drinking water.
Stormwater is the portion of precipitation that does not
naturally evaporate or percolate into the soil. This stormwater
can flow over land, in channels or pipes into a surface water channel,
or to a facility designed to place the stormwater into the ground.
Stormwater that is filtered into the ground is called stormwater
infiltration.
Precipitation and stormwater infiltration sustain the aquifer that
Redmond uses to supply 40% of its drinking water. Percolation in
natural, undisturbed areas provides clean water to the groundwater
aquifer. Stormwater collected from man-made areas such as clean
roof run-off can also beneficially recharge the aquifer. Stormwater from
roads, parking lots, and industrial areas however, may pick up oils,
metals, and other contaminants not beneficial to the aquifer. The
shallow groundwater aquifer in the valley areas of Redmond may be only a
few feet below the surface and is highly susceptible to contamination,
so infiltration of contaminated stormwater is a potential problem.
Owners or operators of any facility within the City of Redmond's
Wellhead Protection Zones 1 and 2
are required to evaluate and upgrade their stormwater infiltration
systems to ensure protection of the drinking water resource. The City
of Redmond's 2003 Wellhead Protection Ordinance established the
requirement to evaluate and upgrade stormwater infiltration systems to
protect groundwater in the areas closest to our drinking water wells.
The Washington State Department of Ecology (Ecology) and U.S.
Environmental Protection Agency also require registration and assessment
of many of these same infiltration systems. The City changed its
ordinance in October 2008 to
coordinate registration of stormwater infiltration systems with
Ecology's registration and assessment requirements.
The City of Redmond recently changed its ordinance to give owners and
operators more time to complete registration, evaluation, and upgrades
to their stormwater infiltration systems, and to allow the City
additional time to plan and implement a regional approach to managing
stormwater in some areas without stormwater conveyance systems.
You can learn more about the changes to the wellhead protection
ordinance by reading the
staff report submitted to the City Council on September 16, 2008.
The City Council adopted the revised
ordinance on October 21, 2008.
In November 2008, the City will send a letter with more information
to all known businesses and owners that have stormwater infiltration
systems.
Owners must register stormwater
infiltration systems with Ecology and/or the City of Redmond by February
3, 2009.
Owners will have to perform an assessment
of their stormwater systems to ensure protection of the groundwater
resource by February 3, 2011.
The City's ordinance applies to all stormwater infiltration systems
located in Wellhead Protection Zones 1 and
2.
There are two general classifications of stormwater infiltration
systems. Click on the link provided to see
examples of the typical
stormwater infiltration systems.
- The first type of system is called an
Underground Injection Control, or UIC.
This is a system that generally
uses a perforated pipe casing or similar structure to infiltrate the
stormwater below the ground surface. Common examples of this
type of infiltration system include a dry well, bottomless catch
basin, a French drain, or trench with perforated pipe. These systems are defined by Ecology as
part of a class of underground injection wells in the UIC regulation
and are referred to as UIC wells.
The Ecology regulation for UIC wells is found in the
Washington Administrative Code
(Chapter 173-218 WAC).
- The second type of system is an unlined pond or trench without
perforated piping. The City of Redmond refers to these as
non-UICs. These systems
perform the same function of infiltrating stormwater, but do not
have pipes or meet the strict Ecology definition of UIC.
Ecology does not require registration of ponds or trenches without
pipe, however the City does require their
registration in Wellhead Protection Zones 1 and 2.
It should be noted that a lined
detention pond or solid-bottomed vault would not generally be
considered an infiltration system.
The City does not regulate or require registration of stormwater infiltration systems
outside of Wellhead Protection Zones
1 and 2, but Ecology may require registration of these systems.
The City will provide a letter to known owners of stormwater infiltration
systems located in Wellhead Protection Zones 3 and 4 with information on
how to register their systems with Ecology. Again, the City does
not require registration of systems outside of Wellhead Protection Zones
1 and 2.
The City of Redmond requires registration of all stormwater
infiltration systems located in
Wellhead Protection Zones 1 and 2.
Infiltration systems with perforated
pipe, also known as UICs, are regulated by both the City of
Redmond and Ecology. Registration requirements are as follows:
- Register the system with Ecology by February 3, 2009. It is a
State requirement. This
link will take you directly to where you can
register your UIC-type stormwater infiltration system with the
Department of Ecology.
- When you complete your registration, make a copy of the
completed registration form for your records and one extra copy.
- Submit the extra copy of the registration to the City of
Redmond. That copy can be sent electronically as an email
attachment to
groundwater@redmond.gov or by mail to the City of Redmond,
Wellhead Protection Program, PO Box 97010, M/S 2NPW, Redmond WA
98073-9710.
Infiltration systems such as infiltration
ponds or trenches, are regulated by the City only (not by
Ecology). These systems will have a separate registration form
that will be submitted directly to the City.
- For a pond or trench stormwater infiltration system you will
need to complete the City of Redmond registration form for your
stormwater infiltration system and submit it to the City of Redmond
by February 3, 2009. Click on the links provided to access the
registration form as a
pdf (which will need to be printed and completed by hand) or as
a Word document
that can be completed and saved electronically.
- The completed form should be sent electronically as an email
attachment to
groundwater@redmond.gov or by mail to the City of Redmond,
Wellhead Protection Program, PO Box 97010, M/S 2NPW, Redmond WA
98073-9710.
All UIC stormwater infiltration systems, such as drywells and
French drains, must be registered with Ecology by February 3, 2009.
This requirement applies to every UIC in the
State. This link will take you directly to the
Department of Ecology website where you can register your UIC-type
stormwater infiltration system.
Ponds and trenches without perforated pipe outside of Wellhead
Protection Zones 1 and 2 do not have to be registered.
An assessment of each stormwater infiltration system located in
Wellhead Protection Zones 1 and 2
will be required to ensure that it is not a hazard to the groundwater.
The assessment will need to be completed by the owner and submitted to
the City of Redmond by February 3, 2011.
During the winter of 2008-2009 the City of Redmond will collaborate
with local businesses and property owners to formulate reasonable
compliance expectations for these stormwater infiltration systems and to
develop standards for assessments and upgrades that will help protect
the City of Redmond's drinking water resources. Updates on the
development of these standards will be provided on this webpage and to
registered stormwater system owners in the coming months.
You can ensure that activities at your facility are not creating a
stormwater or groundwater hazard by ensuring chemicals are handled and
stored safely, spills are avoided, and that chemical use is minimized
where possible to help protect our drinking water resource.
Please use best management practices
found in the
Stormwater Management Manual for Western Washington Volume IV
to help protect stormwater and groundwater.
City of Redmond code requires that "any facility, activity, or
residence in the City in which hazardous materials or other deleterious
substances are present shall be operated in a manner that prevents their
release to the environment" and ensures that they do not "pose a
significant groundwater hazard."
You may download
a map showing approximate shallowest depth to groundwater in many
areas of the City. You will need this information when completing your
registration form. If you need other information related to your
site you may contact the City. We will need your parcel number,
address, and/or closest cross street to help find groundwater or
infiltration data for your location. You may contact us at
groundwater@redmond.gov.
In addition, the following links will help you complete your
registration and assessment:
WASHINGTON STATE DEPARTMENT OF ECOLOGY
KING COUNTY
GEOMAP NORTHWEST
(information and data on groundwater depth and geology maintained at the
University of Washington)
UNITED STATES ENVIRONMENTAL PROTECTION
AGENCY
The Office of Ground
Water and Drinking Water
THE U.S. GEOLOGICAL SURVEY
Ground Water Information Pages
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