California Code of Regulations › Title 23 - Waters › Division 1 - Central Valley Flood Protection Board › Chapter 1 - Organization, Powers and Standards › Article 8 - Standards › Section 120 - Levees

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
(a)
				  Levees constructed, reconstructed, raised, enlarged, or modified within a
				  floodway shall be designed and constructed in accordance with the U.S. Army
				  Corps of Engineers manual, "Design and Construction of Levees" (EM 1110-2-1913
				  dated March 31, 1978, which is incorporated by reference) and as supplemented
				  with the following standards:
(1) Levee
				  construction or reconstruction shall be designed by a civil engineer.
(2) An engineering analysis that evaluates
				  levee embankment and foundation stability shall be submitted to the board with
				  the permit application. The analysis must verify that the levee is adequately
				  designed and will be constructed to remain stable under loading conditions for
				  "Case IV - Steady seepage from full flood stage" as defined in the Department
				  of the Army manual, "Design and Construction of Levees" (EM 1110-2-1913),
				  pp.6-6, 6- 7.
(3) A detailed
				  settlement analysis, using procedures such as those described in the Department
				  of the Army manual, "Settlement Analysis" (EM 1110-1-1904, dated September 30,
				  1990, which is incorporated by reference), must be submitted to the
				  board.
(4) A copy of all
				  geotechnical studies and tests used in the design determination of the levee
				  shall be provided to the board when applying for a permit.
(5) The applicant shall provide the board
				  with a permanent easement granting the Sacramento and San Joaquin Drainage
				  District all flood control rights upon, over, and across the property to be
				  occupied by the proposed flood control works. The easement must include the
				  area within the proposed floodway, the levee section, and the area at least ten
				  (10) feet in width adjacent to the landward levee toe if the area is not
				  presently encumbered by a board easement. The board may require an easement
				  over a larger area and over any property when it is foreseeable that the
				  proposed activities subject to a permit would be injurious to or interfere with
				  the adopted plan of flood control.
(6) All drains and abandoned conduits shall
				  be removed from the proposed construction site prior to start of
				  construction.
(7) Prior to
				  construction or enlargement of the embankment, all holes, depressions, and
				  ditches in the foundation area shall be backfilled and compacted to a density
				  equal to that of the adjacent undisturbed material.
(8) Prior to construction or enlargement of
				  the embankment, all surface vegetation shall be removed from the area to
				  receive fill to a depth of six (6) inches. Organic soil and roots one and
				  one-half (1- ½ ) inches in diameter or larger, shall be removed from the
				  area to receive fill to a depth of three (3) feet.
(9) An inspection trench shall be excavated
				  to a minimum depth of six (6) feet beneath levees being constructed or
				  reconstructed to a height of six (6) feet or greater. If necessary to ensure a
				  satisfactory foundation, the depth of the inspection trench may be required to
				  exceed six (6) feet.
(A) The minimum depth of
				  an inspection trench excavated beneath levees to be constructed or
				  reconstructed less than six (6) feet in height must be equal to the height of
				  the design water surface above natural ground adjacent to the levee.
(B) The inspection trench must have a minimum
				  bottom width of twelve (12) feet, and the side slopes must be one (1) foot
				  horizontal to four (4) feet vertical, or flatter.
(C) The centerline of the inspection trench
				  shall be located approximately under the outer edge of the shoulder of the
				  waterside levee crown.
(10) When subsurface explorations disclose a
				  pervious substratum underlying a levee to be constructed or reconstructed, a
				  cutoff trench must be excavated to an impervious stratum, where
				  practical.
(11) Cutoff trenches
				  shall have a minimum bottom width of twelve (12) feet and the side slopes shall
				  be one (1) foot horizontal to four (4) feet vertical, or flatter.
(12) Impervious material, with twenty (20)
				  percent or more of its passing the No. 200 sieve, and having a plasticity index
				  of eight (8) or more, and having a liquid limit of less than (50), must be used
				  for construction of new levees and the reconstruction of existing levees.
				  Special construction details (e.g., 4:1 slopes) may be substituted where these
				  soil properties are not readily attainable. Where the design of a new levee
				  structure utilizes zones of various materials or soil types, the requirements
				  of this subdivision do not apply.
(13) Fill material must be placed in four (4)
				  to six (6) inch layers and compacted with a sheepsfoot roller, or equivalent,
				  to a relative compaction of not less than ninety (90) percent per ASTM
				  D1557-91, dated 1991, which is incorporated by reference and above optimum
				  moisture content, or ninety-seven (97) percent per ASTM D698-91, dated 1991,
				  which is incorporated by reference and at or above optimum moisture
				  content.
(14) Fill material placed
				  within two (2) feet of a structure must be compacted by appropriate hand
				  operated compaction equipment.
(15)
				  Levee fill material must be free of stones or lumps exceeding three (3) inches
				  in greatest dimension, and must be free of vegetative matter or other
				  unsatisfactory material.
(16) Fill
				  material may only be placed within the area indicated on the submitted
				  plans.
(17) Fill on levee slopes
				  must be keyed into the existing levee section whenever there is substantial
				  fill, as determined by the board.
(18) Each layer of fill material applied on a
				  levee must be keyed into the levee section individually in four (4) to six (6)
				  inch layers.
(19) Density tests by
				  a certified soils laboratory will be required to verify compaction of levee
				  fill and trench backfill.
(20)
				  Ditches, power poles, standpipes, distribution boxes, and other above-ground
				  structures located within ten (10) feet of the levee toe must be relocated a
				  minimum distance of ten (10) feet beyond the levee toes.
(21) Pipelines located alongside and within
				  ten (10) feet of the levee toe must be relocated a minimum distance of ten (10)
				  feet beyond the levee toe.
(22)
				  Construction work of any type may not be done on levees or within the floodway
				  during the flood season (see Table 8.1) unless authorized by the Executive
				  Officer.
(23) The areas adjacent to
				  the levee must drain away from the levee toes for a minimum distance of ten
				  (10) feet.
(24) The finished slope
				  of any project levee construction or reconstruction must be three (3) feet
				  horizontal to one (1) foot vertical, or flatter, on the waterside and two (2)
				  feet horizontal to one (1) foot vertical, or flatter, on the landside of the
				  levee.
(25) The finished slope of
				  any bypass levee must be four (4) feet horizontal to one (1) foot vertical, or
				  flatter, on the waterside and three (3) feet horizontal to one (1) foot
				  vertical, or flatter, on the landside of the levee.
(26) An existing levee section being
				  reconstructed, realigned, or otherwise altered, and having encroachments that
				  are located within the levee that are to be replaced or changed, must have
				  detailed plans of the proposed encroachment changes approved by the board prior
				  to start of construction.
(27) The
				  board may require the modification, as necessary, of existing pipelines within
				  a levee section that is being raised to accomodate a higher design water
				  surface elevation in order to prevent seepage along the pipeline and to prevent
				  backflow through the pipeline during the design event.
(28) A set of "as constructed" drawings of
				  any levee project shall be submitted to the board, the department and the Corps
				  of Engineers upon completion of the project.
(29) Stone revetment may be required on levee
				  slopes where turbulence, flow, or wave action may cause erosion.
(30) Grasses or other approved ground covers
				  may be required on levee slopes.
(31) The minimum crown width of a levee is
				  normally twelve (12) feet on minor streams and twenty (20) feet on major
				  streams. The levee crown width for a levee on a specific stream is defined by
				  the project document and/or operations manual in current use and must be
				  consistent with minimum width requirements of existing levees on the specific
				  stream.
(32) A levee having a crown
				  width of fifteen (15) feet or less must have vehicular turnouts at
				  approximately two thousand-five hundred (2,500) foot intervals if there is no
				  existing access ramp within that distance.
(33) As used in this section, the term
				  "approved risk-based analysis" means an analysis which uses simulation modeling
				  of river discharge versus probability of occurrence, river stage versus river
				  discharge estimates, and river stage versus flood damage estimates and accounts
				  for uncertainty in these functions to determine the performance of a proposed
				  flood control feature.
(A) All levees
				  constructed or reconstructed must have a minimum of three (3) feet of freeboard
				  above the design flood plane, or a crown elevation no lower than designed using
				  an approved risk-based analysis.
(B) Unless designed using an approved
				  risk-based analysis, the design freeboard of a levee to be constructed or
				  reconstructed must be appropriately increased when any of the following
				  conditions exist:
(i) High velocity
				  streamflow.
(ii) Excessive wave
				  action.
(iii) Excessive hydrologic,
				  hydraulic, or geotechnical uncertainty in the levee design
				  parameters.
(C) Unless
				  designed using an approved risk-based analysis, levees within one hundred (100)
				  feet of a bridge, or other structure which may constrict floodflows, must have
				  one (1) foot of additional freeboard.