C-111 DETENTION AREA CONTRACT 8A
The C-111, Contract 8A project features consist of the construction of internal flowway berms with weirs, modification of an existing levee and concrete weir, and a levee section crossing with associated roadway improvements. Work also includes clearing, grubbing, stripping, scraping, grassing, and environmental monitoring. The items to be constructed are as follows:
A total of 5 flowway berm segments will be constructed for C-111, CNT 8A. All of the flowway berm segments will have a crest width of 10 feet with 1V to 3H side slopes and shall be constructed from processed cap rock material.
The following describes each berm segment:
Two Flowway Berms within the 8.5 Square Mile Detention Cell:
L-360W, with a length of about 3,990 feet and at a crest elevation of 7.8′ NAVD88. L-360E, with a length of about 3,845 feet and at a crest elevation of 7.8′, NAVD88. Both flowway berm segments within the 8.5 square mile Detention Cell start southwest of the existing S-357 Pump Station outlet and end near the existing S-360W concrete weir structure.
Two Flowway Berms within the South Detention Area are described as follows:
The L-321N flowway berm segment is north of the existing S-332C Pump Station outlet. This flowway berm segment has a length of about 14,142 feet. The north end of the L-321N berm starts at elevation 9.3′ NAVD88 and transitions to elevation 7.3′ NAVD88. At the south end the elevation transitions from elevation 7.3′ NAVD88 to elevation 8.8′ NAVD88 when it ties into the L-322 levee. The L-321N flowway berm segment includes one 800 foot weir identified as S-321A. The L-321S flowway berm segment is south of the existing S-332C Pump Station outlet. This flowway berm segment has a length of about 13,343 feet. The north end of the L-312S berm starts at elevation is 8.8′ NAVD88 and transitions to 7.3′ NAVD88. At the south end the elevation 7.3′ NAVD88 ties into the existing levee, just east of S-332DX1 gated culvert structure. The L-321S flowway berm segment includes two weirs. Each weir is 800 feet long and are identified as S-321B and S-321C.
There will be a total of three weirs along the flowway berm system as follows:
The L-321N flowway berm in the South Detention Area (SDA) will have one 800 foot long weir identified as S-321A. The L-321S flowway berm in the SDA will have two 800 foot long weirs and are identified as S-321B and S-321C. The crest elevation of all four weirs will be 6.5′ NAVD88 and the crest width will be 10 feet. The weirs will be constructed from processed cap rock material.
The existing S-360W concrete weir is located at the south end of the proposed L-360W and L-360E flowway berms in the 8.5 square mile detention cell. This concrete weir is located closer to the L-360E flowway berm. A 350 foot degraded section with 1V on 10H side slopes will be centered between the proposed flowway berms. This will require the partial removal of the existing concrete weir (S-360W) and the connecting levee on the west side of this weir. The degraded section will match adjacent ground elevation. All disturbed areas will be left with a compacted 6 inch layer of processed cap rock material to design grade.
L-357W Richmond Dr. Extension:
Construction will extend the existing L-357W levee to cross Richmond Drive (SW 168th St.), between SW 213th Ave. and SW 218th Ave. The length of this levee crossing is about 879 feet. A shell rock road ramp over the L-357W crossing and a shell rock cul-de-sac, east of the crossing, will also be constructed inclusive of drainage ditch modifications and installation of roadway signage. Three vehicular gates will be installed in this area. Two gates will be installed on the levee crest, one on each side of the shell rock road ramp and will have connecting guardrails along the slopes of the levee crossing. The third gate will be between the eastern side of the levee crossing and the shell rock cul-de-sac. Sections of the existing L-357W levee, located north and south of Richmond Drive, and the borrow source north of SW 136th Street and east of C-111 will be used for the construction of the levee crossing.
Turnout and Turn-Arounds:
There will be 6 turnouts and 5 turn-arounds along the flow-way berm systems. For the L-321N there will be 2 turnouts and 2 turn-arounds. For the L-321S there will be 2 turnouts and 2 turn-arounds. For the L-360E there will be 1 turnout and 1 turn-around. For the L-360W there will be 1 turnout.
TITAN provided a Site Safety and Health Officer and QC Manager to the project.