THIS IS FOR INFORMATION PURPOSES ONLY. DO NOT REGISTER FOR PLANS AND SPECIFICATIONS AT THIS TIME. THE DRAFT PLANS (30% AND 60%) are AVAILABLE FOR REVIEW ON OUR WEBSITE (see instructions below). The Government may consider comments and inquiries while preparing the final plans and specs; however, the Government is not seeking comments and may not provide responses to inquiries. A solicitation will be issued on or about the 21 January 2009 with proposals due on or about 21 March 2009. The purpose of the L-31 North (L-30) Seepage Management Pilot Project (SMPP) is to identify, test, and determine the relative effectiveness of seepage management technologies in order to recommend features to control groundwater flow and levee seepage from Everglades National Park. Additionally, the project will help determine the constructability of a seepage management barrier to various depths/lengths within the semi-confining unit of the aquifer and may also yield results beneficial to the implementation of the full-scale Everglades National Park Seepage Management Project. The proposed project is located in Miami-Dade County, north of Tamiami Trail (U.S. Highway 41) and Krome Ave (Route 997). The L-30 borrow canal and levee mainly runs north-south but makes roughly a 45-degree southwesterly departure from Krome Avenue until it intersects Tamiami Trail, thereby forming what is commonly known as the L-30 triangle. This 1.25 mile segment of the L-30 Canal, between S-335 and S-334, has been found to be an extremely thick portion of the Biscayne Aquifer with very high measured transmissivity. A field drawdown test performed as a part of the L-31N SMPP and a Preliminary Seepage Report based on historical data for the area both found the triangle to have the highest seepage rate per mile between S-335 and S-334. Conceptual Design - The tentatively selected alternative will include the design, installation, and testing of a subsurface seepage management barrier augmented with collection pipes and seepage recovery wells located within the barrier, adjacent to a sheet pile window in the L-30 levee located north of US Highway 41 (Tamiami Trail) between water control structures S-335 and S-336. The barrier will have dimensions of approximately 80100 feet in depth and approximately 1,0002,200 feet in length. The selected alternative proposes the placement of a barrier feature using a soil-cement-bentonite (SCB) mix and sheetpile construction technique. The seepage barriers exact length and depth will be determined using detailed field data, engineering expertise from technical team members, and the A-E contractor. It is anticipated that installation of the seepage barrier through the geologic layers in the project area will be hard limestone may prove difficult, and will most likely require creative engineering techniques for excavating. This design proposes a SCB slurry wall with a 6 ft. wide trench. A 100-ft long shallow sheet pile wall section is proposed as a gap in the slurry wall that will act as a shallow window to direct any desired seepage flow. During periods of high water flow in the aquifer, seepage flows passing through the window will be captured by the system of wells and pumps. Wells and pumps will be installed to capture the desired quantity of flow and pump it into the Water Conservation Area 3B as surface water or into adjacent canals. The pumping system design will allow for the pumps to be controlled locally as well as from a remote location using telemetry. Flow measurement devices will be installed at the ends and at the mid-point of the barrier. An approximate 10-ft by 10-ft control building will be required to house electrical controls and panels at the mid-point of the barrier. It is anticipated that the sheet pile depth can also be adjusted to create varying window size as needed. Preliminary design concept places the sheet pile at a depth of approximately 50 ft. General Construction - The following engineering features are conceptual in nature and may or may not represent the final design of this project. Soil-Cement Bentonite Slurry Wall - The Soil-Cement-Bentonite (SCB) slurry wall will be placed in a 3-ft wide trench cut out of a 6 ft. wide pre-blasted zone. By possibly pre-blasting this zone the properties of the porous limestone will change to a zone containing less permeable materials. The trench is to be excavated through the pre-blasted zone of limestone down to a pre-established invert elevation with a base in the less permeable Tamiami Sands. Typically soil-cement-bentonite (SCB) walls are 24 to 30 inches wide and match the width of the equipment. In this case the blasted zone is anticipated to be approximately six (6) feet wide which allows for ~30 inch trench centered within the blasted lower permeability zone leaving lower permeability material on both sides of the trench. It is reasoned that the engineered filter will enable the wall to be constructed using conventional excavating equipment (e.g., extended stick backhoe or similar) is probable, while minimizing loss of the bentonite slurry mixture. After the six feet wide trench has been blasted, the 30-inch trench will be excavated. As the excavation proceeds, bentonite-water slurry is continuously added to build a filter pack and ensure that the trench remains open. After the blasted material has been excavated, it is replaced with a backfilled mixture of soil-cement-bentonite. The preliminary mix design assumes 10 to 15% cement and 2 to 5% bentonite mixed with the excavated rock materials. Sheet Pile Wall - A sheet pile wall will be constructed at the midsection of the slurry wall. This 100 ft long shallow sheet pile wall will be inserted to bridge the gap between the 2 sections of slurry wall to act as a shallow window directing or funneling any seepage flow. The pumps could be possibly used to divert excess seepage. The sheet pile depth of emplacement and size may be varied or later changed to create a window of varying size depending on need. The method of installation may require a creative exaction technique (ex. Blasting through limestone layers), followed by pile driving to a pre-established invert elevation by hammer or vibratory methods. There is likely to be some disturbance surrounding the piles so there is possible need for seepage tightening of the wall by grouting or other sealing methods. This seepage tightening will seal any holes or gaps in between individual piles that remain after installation would be plugged. Disposal - All unsuitable material will be disposed of within the L-31N right-of-way. Cleared, grubbed and excavated materials that are suitable for reuse may be stockpiled on site for grading and erosion control of the embankment. Staging - It is anticipated that the A-E contractor will need approximately 1 acre for staging construction trailers and 3-4 acres for the staging heavy construction equipment. Access to the project site could be from State Rd 997 (Krome Ave.) and/or from U.S. Highway 41 (Tamiami Trail) by S-334 or S-356. As a first option, the team would like to the contractor to use the area is within the L-31N right-of way located along L-31N (south bank), beginning 0.5 mile south of the north gate at U.S. Highway 41, then southward about 0.25 mile. The second option, the staging are would be located on the L-29 (north bank & levee), between S-334 and the south entrance of the L 30 levee. Testing - After construction is completed, testing of the barrier system will be performed within a period of two years (two wet and two dry seasons) to determine the relative effectiveness of the seepage barrier. The proposed work is located in Miami-Dade County, North of Tamiami Trail (US Highway 41) and Krome Avenue (Route 997). The Magnitude of Construction is between $5,000,000.00 to $10,000,000.00. Award will be made to the offeror whose proposal represents the best value to the Government. Proposals will be evaluated on technical, past performance and price. The draft plans (30%) are available on the Federal Business Opportunities website at http://www.fedbizopps.gov/. REMEMBER: DO NOT REGISTER AS A PLAN HOLDER AT THIS TIME. THE FINAL PLANS AND SPECIFICATIONS WILL CARRY A DIFFERENT IDENTIFICATION NUMBER AND REGISTRATION WILL BE REQUIRED AT THAT TIME. You must be registered in the Central Contractor Registration in order to be eligible to receive an award from any Government solicitation. Call
+1 (555) 000-0000 for more information or visit the CCR website at http://www.ccr.gov. You must be registered in the Online Representations and Certifications Application (ORCA) in order to be eligible to receive an award from any Government solicitation. For more information, visit the ORCA website at http://www.bpn.gov. NAICS Code is 237990 and the Small Business size standard is $31 million.
