Or. Admin. Code § 340-071-0265 - Capping Fills
(1) Criteria for
approval. Each site approved for a capping fill system must meet all the
following conditions:
(a) Slope does not
exceed 12 percent.
(b) Temporary
water table is not closer than 18 inches to the ground surface at any time
during the year. A 6-inch minimum separation must be maintained between the
bottom of the absorption trench and the temporary water table.
(c) Where a permanent water table is present,
a minimum 4-foot separation must be maintained between the bottom of the
absorption trench and the water table.
(d) Except as provided in subsection (e) of
this section, where material with rapid or very rapid permeability is present,
a minimum 18-inch separation must be maintained between the bottom of the
absorption trench and soil with rapid or very rapid permeability.
(e) Sites may be approved with no separation
between the bottom of the absorption trenches and soil with rapid or very rapid
permeability (as defined in OAR
340-071-0100 (148)(a) or (b)),
and absorption trenches may be placed into such soil if any of the following
conditions occur.
(A) A confining layer
occurs between the bottom of absorption trenches and the temporary groundwater
table and a minimum 6-inch separation is maintained between the bottom of
absorption trenches and the top of the confining layer.
(B) A layer of non-gravelly (less than 15
percent gravel) soil with sandy loam or finer texture at least 18 inches thick
occurs between the bottom of the absorption trenches and the groundwater table.
(C) The projected daily sewage
flow does not exceed a loading rate of 450 gallons per acre per day.
(f) Effective soil depth is 18
inches or more below the natural soil surface.
(g) Soil texture from the ground surface to
the layer that limits effective soil depth is no finer than silty clay loam.
(h) A minimum 6-inch separation is
maintained between the bottom of the absorption trench and the layer that
limits effective soil depth.
(i)
The system can be sized according to effective soil depth in Table 4. [NOTE:
All tables are found in OAR
340-071-0800.]
(2) Installation requirements. The cap must
be constructed as the permit requires. Unless the agent requires otherwise,
construction must follow this sequence:
(a)
The agent must examine and approve the soil before placing the cap. The texture
of the soil used for the cap must be the same textural class as or one textural
class finer than the natural topsoil unless otherwise allowed in this division.
(b) Capping fills must be
constructed between June 1 and October 1 unless the agent allows otherwise. The
upper 18 inches of natural soil must not be saturated or have a moisture
content that causes loss of soil structure and porosity when worked.
(c) The absorption area and the borrow site
must be scarified to destroy the vegetative mat.
(d) The system must be installed as specified
in the construction-installation permit with a minimum 10-foot separation
between the edge of the fill and the absorption facility.
(e) Filter fabric must be used between the
drain media and the soil cap, unless the agent authorizes otherwise.
(f) Fill must be applied to the fill site and
worked in so that the two contact layers, native soil and fill, are mixed. Fill
material must be evenly graded to a final depth of 10 inches over the drain
media for an equal system or 16 inches over the drain media for a serial system
to allow for appropriate settled depths. Both initial cap and repair cap may be
constructed at the same time.
(g)
The site must be landscaped according to permit conditions and be protected
from livestock, automotive traffic, and other activity that could damage the
system.
(3) Required
inspections. Unless the agent waives it, the following inspections must be
performed for each capping fill installed.
(a) Inspecting both the absorption area and
borrow material before cap construction for scarification, soil texture, and
moisture content.
(b) Inspecting
the installed absorption facility before covering.
(c) Inspection after the cap is placed to
determine adequate contact between fill material and native soil (no obvious
contact zone visible), adequate depth of material, and uniform distribution of
fill material.
(d) Final inspection
after landscaping or other erosion control measures are established.
[NOTE: All tables are found in OAR 340-071-0800.]
Notes
Tables referenced are available from the agency.
Statutory/Other Authority: ORS 454.625 & 468.020
Statutes/Other Implemented: ORS 454.615 & 454.775
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