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Home My WebLink AboutAGENDA REPORT 1998 0415 CC REG ITEM 11JITEM 110 D '7 A ? . r O (-1 O) CITY OF MOOP R_ AR� & CALIFORNIA City Council Meeting AGENDA REPORT of A a r t' 1 1 50_199 S C=TY OF MOORPARK ACTION: Ap Oro ✓e4 TO: The Honorable City Council — BY: � ��- FROM: Kenneth C. Gilbert, Director of Public Works DATE: April 3, 1997 (Council Meeting 4- 15 -98) SUBJECT: Consider Approval of the Conceptual Design for the Retaining Walls to be Constructed on the North Side of Los Angeles Avenue West of South Condor Drive (Los Angeles Avenue - East] EXECUTIVE SUMMARY As you may recall, this project requires the acquisition of additional street right -of -way on the north side of the street and the construction of retaining walls to accommodate same. The area of the easements required for the retaining walls is dependent upon the type of construction used. The purpose of this report is to determine the type of construction for the retaining walls so that the legal descriptions for the easements can be defined. BACKGROUND The City Council has taken the following actions with respect to the subject project: le_est6 1. Approved the future roadway alignment for Los Angeles Avenue East to shift the centerline to the north (Alt. #2); 2. Approved a corridor width for this street segment of eighty -eight feet (881) -- a street width wide enough to accommodate possible ultimate street improvements to include the following: • four 12' wide travel lanes; • one 14' wide raised / landscaped center median; • two 8' wide Bike Lanes; • curb and gutter; and, • two 5' wide sidewalks; 3. Approved the conceptual design for the construction of earthwork and retaining walls for the project, sufficient to accommodate the above described ultimate improvements; 4. Directed the City Engineer to proceed with the preparation of a preliminary design for the required earthwork and retaining walls, in order to determine the limits of the right -of -way acquisition required for the project. r OL 0181 Los Angeles Avenue East Widening Retaining Wall Design April 15, 1998 Page 2 5. Also directed the City Engineer to proceed with the preliminary design for the construction of street improvements within the above described corridor, which would to provide for only one travel lane in each direction, said street improvements more particularly described as following: • two 12' wide travel lanes; • 8' of paved surface beyond the sideline in each direction; • one 14' wide center paved median (total pavement width of 381); and, • two 8' wide unpaved shoulders; 6. Directed staff to proceed with the title work, engineering work and appraisal work necessary to prepare the final Deeds for all of the right -of -way required, and to determine estimated cost of said acquisition; and, 7. Directed staff to report back to the City Council when these efforts are completed, to seek authorization to proceed with right -of -way acquisition. DISCUSSION A. Retaining Walls -- General Description As shown on the Retaining Wall Profiles attached as Exhibit 1, the right -of -way "take" on the north side of the street will require the removal of a portion of the "natural" hillside in this area and the construction of retaining walls ranging in height from approximately one foot (11) to approximately nineteen feet (191). B. Design Alternatives la_est6 1. Type 1 Reinforced Concrete Wall: This is a standard steel reinforced concrete wall. As stated above, the retaining walls will have a vertical face ranging from one foot high to over nineteen feet (191) high. The retaining walls are to be located immediately adjacent to the street right -of- way line, within a perpetual easement for the placement and maintenance of the walls. When and if the roadway is ever widened to four lanes, the then existing walls would be located adjacent to a five feet (51) sidewalk. Los Angeles Avenue East Widening Retaining Wall Design April 15, 1998 Page 3 2. Interlocking Block Wall: Under a separate Memo distributed to the City Council with the agenda materials, the City Council has been provided with a copy of a brochure from a company which manufactures an interlocking block system for the construction of retaining walls. This brochure shows a number of applications of this product. As shown in the brochure, this type of block wall is constructed in a manner which allows it to be anchored into the hillside. The resulting wall is slightly less than vertical with a texture resulting from a combination of the rough surface of the blocks and the interlocking pattern. 3. Crib Wall: Also included in the above mentioned Memo to the City Council is a copy of a brochure from a company which manufactures crib wall materials. This brochure also shows numerous applications available using this construction method. As shown on page 14 of the brochure, this construction technique allows for the integration of the cribs into the hillside. The resulting wall is not vertical, but is constructed with a 6:1 slope to allow some relief from the imposing vertical face of the Type 1 wall. C. Cost Comparison The City Engineering Department's "rough' estimate for the construction cost for each of these types of walls is summarized as follows: • Type 1 reinforced Concrete Wall . . . . . . $875,000 • Interlocking Block Wall . . . . . . . . . . $706,000 • Crib Wall . . . . . . . . . . . . . . . . . $740,000 D. Aesthetic Considerations la_est6 A comparison of certain other aesthetic considerations is as follows: 1. Type 1 Retaining Wall: • Impact: high, vertical wall next to possible future five feet (51) wide sidewalk; • Visual Relief: vertical, high, imposing, flat surface; • Surface: flat surface, unless an expensive surface treatment is added; and, • Graffiti: easy target for graffiti. 0bo sta Los Angeles Avenue East Widening Retaining Wall Design April 15, 1998 Page 4 2. Interlocking Block Wall: • Impact: slight angle • Visual Relief: not as much relief as crib wall, but more than retaining wall; • Surface: rough interlocking block wall surface; and, • Graffiti: not an easy target 3. Crib Wall: • Impact: 80' angle • Visual Relief: sloped varied surface • Surface: cells may be filled with dirt, gravel, concrete or landscaping • Graffiti: not an easy target E. Additional Width of Easement As shown on the cross section attached as Exhibit 2, the crib wall alternative may require a wider easement. 1. It not recommended that Type 1 concrete retaining walls be constructed for this project. It is the view of staff that the other two options discussed in this report are preferable. 2. The depth of the area required for the construction of either the crib wall or the inter - locking block wall is about the same. Either type of construction will require about the same width of an easement. Given that one of these two construction methods is to be used, there is no need to choose one over the other at this time. It may even be preferable to require bids for both of these options at the time the City is ready to proceed with construction. 3. It is necessary at this time, however, to determine the width of the easements required for the required retaining walls. Staff recommends that the City Council direct staff to acquire retaining wall easements sufficient to accommodate the width of either crib wall or inter - locking block wall construction, for the retaining walls required for the subject project. la_eat6 1.36 ft Visible 1.36 ft Visible �1Nall Height WCI Height / / rTOP OF +50 14 ft Visible all Height 24+00 24 +50 11 ft Visible 311 Height ft Visible 7.60 ft Visible Height .. Nall Height / /-TOP OF 3 ft Visible Height 13.80 ft Visible Wall Height 25 +50 6 ft Visible Hei ght 10.80 ft Visible /wo l l Height 9.41 ft Visible r- Wall Height BACKFILL ELEVATION BEHIND WALL FOOTING `BACKFILL ELEVATION IN FRONT OF WALL 27 +50 28 +00 28 +50 29 +00 29 +50 30 +00 11.70 ft Visible 11.88 ft Visible 10-73 ft Visible 9.93 ft Visible 9.23 ft Visible 8.83 ft Visible 8.43 ft Visible 8.11 ft Visible 6.11 ft Visible Wall Height Wall Height Wall Height Wall Height Wall Height Wall Height Wall Height Wall Height Wall Height TOP OF WALL TOP OF WALL 3ACKFILL ELEVATION BEHIND WALL-/ FOOTING BACKFILL ELEVATION IN FRONT OF WALL FOOTING BACKFILL ELEVATION BEHIND WALL 32 +50 33 +00 33 +50 34 +00 34 +50 35 +00 35 +50 36 +00 36 +50 7.82 ft Visible 6.47 ft Visible Wall Height Wall Height 6.14 ft Visible Wall Height BACKFILL ELEVATION IN FRONT OF WALL 37 +00 37 +50 38 +00 CITY OF I I LOS ANGELES AVENUE EAST d MW STA. 23+50.00 TO STA. 38 +00.00 • ° - X G :T' tiJ ,� 5.86 ft Visiblev Wall Height ft Vi ible 6 78 ft Vi ible 1.25 ft Visible Heigh all Heigh all Height BACKFILL ELEVATION BEHIND WALL - 1+50 2 +00 2 +50 50 ft Visible Height BACKFILL ELEVATION BEHIND WALL 10+ 00 10 +50 11+00 6 +00 ft Visible Height v wiuie ly.l / R Visible Wall Height Wall Height 16.53 ft Visible Wall Height 4.91 ft Visible Wall Height FOOTING ACKFILL ELEVATION IN FRONT OF WALL 3 +00 3 +50 4 +00 4 +50 TOP OF WALL 4.36 ft Visible 6.36 ft Visible Woll Height Wall Height 6 +50 7 +00 7 +50 17 ft Visible I Height 15:13 ft Visible all Height TOP OF ALL 7.32 ft Visible r1Nall Height 4.73 ft Visible all Height 0.66 ft Visible Wall Height BACKFILL ELEVATION IN FRONT OF WALL )6 ft Visible loll Height FOOTING 11 +50 12 +00 12 +50 IN 13 +00 13 +50 ft Visible Height 7 50 lot Visible 1WaII Hei h isible TOP OF WALL w 9 5.1 8 ft Visible O.84 ft Visible all Height 9 1.12 ft Visible TOP OF ALL Wall Height LL ELEVATION BEHIND WALL FOOTING ACKFILL ELEVATION IN FRONT OF WALL BACKFILL ELEVATION BEHIND WALL OOTING BACKFILL ELEVATION IN FRONT OF WALL I 15 +00 15 +50 16 +00 16 +50 16 +50 17 +00 17 +50 T.T. T.T. oIO® AIT`� M^ psb' 1 A[+ ♦ \1/�r1 r!' • \.r \II11� r \� 1.5:1 MAX OR EXIST. PLANTABLE CRIB WALL ('LOFFELSTEIN" OR EQUAL) (SEE CALTRANS STD. C7B FOR CONST. DETAILS) 1.5:1 OR E RET PER / A Z PROP WILY / r R/W _I I- PROP SLY PROP a R/W PLAN q - % % 2:, 20'. 4"4" N E ST. PAVEMENT FUTURE CURB, GUTTER & SIDEWALK SEE PLAN FOR LOCATION ALTERNATE 2 TYPICAL WALL SECTION (N.T.S) PER CALTRAS STD. 83 -1 ALTERNATE 1 TYPICAL WALL SECTION (N. T.