Current through Register Vol. 24-18, September 15, 2024
The requirements of this section do not apply to suction
dredging for mineral prospecting covered in WAC
220-660-300, or to diver-operated
dredging for aquatic plant control covered in WAC
220-660-290.
(1)
Description: Sand and gravel
deposited by river processes is used as construction aggregate for roads and
highways (base material and asphalt), pipelines (bedding), septic systems
(drain rock in leach fields), and concrete (aggregate mix) for highways and
buildings. In some areas, people remove aggregate mainly from river deposits,
either from pits in river flood plains and terraces, or by removing gravel
directly from riverbeds with heavy equipment.
(2)
Fish life concerns: Removing
sand and gravel from the active channel bed may affect sediment movement if it
disrupts the sediment balance in the river. This disruption may cause channel
adjustments that extend considerable distances beyond the excavation site.
Removing instream sand and gravel changes the channel shape and bed elevation
and may involve extensive clearing of vegetation, flow diversion, sediment
stockpiling, and excavating deep pits. Removing sand and gravel can also
produce a local sediment shortage that can reduce spawning potential and
success in gravel-starved stream reaches. Disturbance or loss of gravel can
create significant channel head cutting upstream from the project. Trenches or
pits in the bed can trap fish. Other effects of removing instream gravel
include a reduction of large woody material that is important as cover for
fish, and short-term loss of insects and stream bugs that are food for
fish.
(3)
Sand and gravel
removal design:
(a) Limit sand and
gravel removal to exposed bars. Sand and gravel removal must not result in
lowering the average channel cross-section profile either in the work area or
downstream of it.
(b) The
department requires a quantitative site assessment to document habitat changes.
This includes preproject and post-project channel cross-section surveys for
commercial sand and gravel removal projects. As a provision of a multiyear HPA,
the department may require surveys to be conducted each fall. The surveys must
reference cross-sections vertically to a permanent benchmark and horizontally
to a permanent baseline. The cross-sections must be surveyed perpendicular to
the high flow channel every one hundred feet through the work area and at
cross-sections upstream and downstream at adjacent channel riffles. The HPA
application submitted to the department must include the preproject survey
information. A person must submit the post-project survey to the department
within ninety days after removal of sand and gravel is finished or the
expiration date of the HPA, whichever occurs first.
(4)
Sand and gravel removal
construction:
(a) The department must
establish an excavation line, which is then identified in the HPA.
(b) The permittee must place boundary markers
to identify the excavation zone. The department must approve the location of
the boundary markers before a person starts to remove sand and
gravel.
(c) Excavation must start
at the excavation line and proceed toward the bank or the center of the bar,
perpendicular to the alignment of the watercourse.
(d) Do not remove bed material from the
waterward side of the excavation line.
(e) Do not place or operate equipment within
the wetted perimeter of the watercourse.
(f) Remove sand and gravel within the
excavation zone from a point starting at the excavation line and progressing
upward toward the bank or the center of the bar on a minimum two percent
gradient. The department may require a survey of the excavation zone upon
completion of the sand and gravel removal operation to ensure the operation
maintained a two percent gradient and that no depressions remain. When
required, the permittee must pay for the survey.
(g) At the end of each workday, the
excavation zone must not contain pits, potholes, or depressions that may trap
fish because of fluctuating water levels.
(h) Limit stockpiling of material waterward
of the OHWL, after the initial bed disturbance, to protect fish life. If the
department has approved stockpiling waterward of the OHWL, completely remove
the material before fish start spawning in the area or stream flow starts
increasing. The department will determine timing restrictions for each site
individually. If the water level rises and makes contact with stockpiles,
further operation of equipment or removal of the stockpiles may not proceed
unless the department authorizes the work.
(i) Leave the upstream end of the sand and
gravel bar undisturbed to maintain watercourse stability waterward of the
OHWL.
(j) Retain large woody
material waterward of the OHWL. Large wood within the excavation zone must be
repositioned within the watercourse. Other debris must be disposed of so it
will not reenter the watercourse.
(k) Sand and gravel washing or crushing
operations must take place above the limits of anticipated
floodwater.
