REQUEST FOR CONSTRUCTION BIDS February 22, 2010

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1 REQUEST FOR CONSTRUCTION BIDS February 22, 2010 Roaring Branch Channel and Floodplain Restoration Project 1.0 Project Background Roaring Branch (watershed area ~ 41 square miles) flows generally west through most of Bennington to its confluence with the Walloomsac River (see location map in Attachment A). The channel is currently confined, mostly disconnected from its floodplain, and energized during storms to excessively erode its banks and bed. The Roaring Branch is located on an alluvial fan where large historic deposits of unstable sediment are commonly being eroded and deposited. The Roaring Branch is caught in a high risk and costly cycle of flooding, sediment deposition, channel instability, channel migration, dredging, berming, and armoring at which point the cycle is repeated as larger floods and erosion/deposition events take place. This project primarily consists of floodplain restoration where several non-engineered berms on the north side of the river will be removed to reconnect portions of historic floodplain back to the Roaring Branch. At the same time, a new engineered berm will be constructed at the back of the available floodplain with improved scour protection. Hydraulic modeling of the preferred alternative illustrates that the combination of the wider floodplain and engineered berm accomplishes the primary project goals lowering flood levels, decreasing flood water velocity, providing space for the channel to deposit sediment and naturally migrate on the alluvial fan, and reducing the excessive sediment deposition upstream of the Park Street Bridge. In addition to floodplain restoration, the project design includes sediment removal of the excessive deposits existing up- and downstream of the Park Street Bridge. This sediment management activity is planned to remove the exposed sediment bars down to the 2-year flood level to increase flood conveyance at the structure. Sediment removal is also planned near Congress Street to allow better drainage at existing flap gates. Floodplain restoration is possible as the Town of Bennington has acquired a parcel of land in the floodplain formerly owned by Jard Company Inc. The Town has adopted an ordinance to protect the Vermont Fluvial Erosion Hazard Zone, and thus plans to return this dynamic flood-prone area next to Roaring Branch back to floodplain in this location. The Town has also provided space for locating a town garage in the future uphill of the proposed engineered berm. This Request for Proposals is being re-issued as previous bids were higher than the available project budget. The Town is seeking competitive bids based on the revised construction timeline to begin in May Changes to the scope of work have been made including a single equipment mobilization, reduced erosion and sediment requirements, a small reduction in rock volume, and a small reduction in clearing and recovery area. Roaring Branch Restoration RFP Page 1

2 2.0 Project Location & General Scope of Work Phase 1 of the project that is being announced in this Request for Proposals includes rehabilitating armor on 150 +/- feet of existing berm upstream of Park Street, 550 +/- feet of combined berm removal and construction working upstream from Park Street, and excavation of accumulated sediments in the channel around Park Street Bridge and near the outlet from the flap gates near Congress Street. A minimum of the existing level of flood protection must be maintained at the end of this phase of construction so similar lengths of berm removal and construction are required. A future phase of construction will take place to complete the full floodplain restoration upstream to Brooklyn Bridge. Work tasks will generally involve placement and maintenance of necessary sediment and erosion control treatments, clearing and grubbing, earth/rock berm excavation, local transport of excavated material to new berm construction location, temporary stockpiling of boulders, placement of fill and construction of scour-proofed berm, final grading, and seeding and mulching. 3.0 Project Supervision Engineering oversight of the project will be conducted by the VT DEC River Management Program and its designated Project Engineer. The contractor will be obligated to comply with directives from the Project Engineer for the purpose of ensuring the contractor meets all contract provisions and design specifications while complying with permit requirements. Initial field staking of grades, berm location, and project limits will be provided by the Project Engineer. 4.0 Construction Access Construction access has been initially determined for the site (See designated access locations #1 and #2 in the construction plans in Attachment A). The primary entrance to the project site will take place from the Town-owned dirt road located adjacent to the State Highway Garage. The construction area is commonly used by local residents for recreation so adequate warning of construction activities and safety signage and fencing is required. The contractor may suggest additional access points to the Project Engineer and Town for approval. Any town or private drives utilized by the contractor for access and egress will be restored to pre-project conditions upon completion of the project. 5.0 Construction Details and Specifications Construction plans, details, sequence, and additional specifications are attached (Attachment A). The following general sequence applies to this construction phase. The selected contractor may suggest adjustments to this sequence or a different sequence of events to the Project Engineer for approval. All excavation work will be conducted within the footprint of the existing and proposed berms, or the channel during sediment removal. The majority of work will be performed on Town Roaring Branch Restoration RFP Page 2

3 lands. Some private parcels are located at the project site (Table 1 and Attachment A). These landowners have been contacted about the project, and the contractor will work with the Project Engineer and Town to accommodate landowners as needed. The Project Engineer or Town will establish contact with landowners prior to the beginning of construction. Table 1. Local Landowners Lanowner Address Notes Caroline Greene 403 Park Street Crosses main berm where fortification is planned Bennington Little League 83 Little League Road New berm adjacent to ball fields Mount Anthony Union High School 246 S Stream Road New berm crosses corner of land Berm Rehabilitation Construction will begin with the rehabilitation of the existing armor on approximately 150 feet of berm adjacent to the right bank (facing downstream) of the Roaring Branch just upstream of Park Street (Proposed berm station 0+00 to 1+50). This activity will maintain the structural stability of the berm in place while holding its base width and side slope constant. Rock additions cannot project into the active river channel. Excavation of the top of the berm (depth ~ 1-2 feet) is anticipated to match the top elevation of the berms and USACE levee on the south side of the Roaring Branch, per design specifications, that will improve access to the armor rehabilitation site and upstream locations. Approximately 800 cubic yards of waste quarry rock and large riprap meeting design specifications (diameter ~ 4 feet) exist at the berm rehabilitation site and will be re-worked to improve scour protection. Riprap will be tied into the existing channel edge at or below the toe of the bank. The objective of the berm rehabilitation is to have a continuous rock face that is approximately 6 feet thick and extends approximately 15 feet up the bank from the channel. It is estimated that 100 cubic yards of graded 4-foot stone will be required to haul to the site for the berm rehabilitation to supplement on-site materials. Berm Excavation and Construction Continuing directly upstream, portions of approximately 550 feet of existing berm will be removed and a new berm will be constructed at the nearby edge of the available floodplain (Proposed berm station 1+50 to 7+00). Based on cross sections of the existing berm obtained from LIDAR and ground survey, the estimated volume of earth to be excavated during this phase of work is approximately 20,000 cubic yards. Excavated material from the existing berm will be hauled via approved access locations and placed on-site in the currently wooded area east of the capped remediation site on the former Jard property and west of the Town-owned access road (See attachment A). This area (~ 1.5 acres) will be cleared and grubbed prior to fill placement. Old roads and paths exist in the construction area that will allow for hauling with minimal removal of existing floodplain vegetation. Excavation, disposal, and access areas will be marked in the field by the Project Engineer and reviewed with the selected contractor prior to the start of construction. Roaring Branch Restoration RFP Page 3

4 PCB contamination exists in the proposed excavation and berm construction locations adjacent to the former Jard site that now has a capped remediation site. The cap and surrounding swale will be avoided during this project. Past sampling has revealed concentrations in the range of 0 to 1.8 ppm in surface soils, and concentrations have been shown to generally decrease with depth. Note that 1 ppm is the typical limit for residential sites and 10 ppm is considered the upper allowable range for industrial sites. Given the soil contamination, the excavated material cannot be moved from the current parcel of land. The contractor will need to draft and follow a Health and Safety Plan (VOSHA/OSHA 29CFR ) throughout the duration of work due to the presence of the soil contamination. Samples will be provided to the selected contractor upon request. VOSHA/OSHA Hazardous Waste Operations and Emergency Response (HAZWOPER) training is recommended for the contractor (VOSHA/OSHA 29CFR ). Two groundwater monitoring wells exist in the berm excavation area and are to be maintained in place. Excavation will take place around the wells and then the well casings will be cut down to grade as excavation proceeds. The wells will be location by the Project Engineer before construction begins. Large stone (D > 1 foot) encountered during excavation of the existing berm can be used for riprap. Investigation of surface materials of the berms suggests that a portion of a previous riprap installation exists (volume ~ 500 cubic yards) at the upstream limit of excavation that may be used for riprap protection on the new berm. Approximately 2,700 cubic yards of large stone (diameter ~ 4 feet) is needed for scour protection of the proposed berm, and thus 2,200 cubic yards of rock is required to be hauled to the site. Berm construction will include shaping deposited fill, excavating existing historic fill in some locations, and installing riprap armor on the side closest to the Roaring Branch (See construction plans and details in Attachment A). The top elevation of the berm will match the top elevation of the USACE levee across the channel on the south side of the river in all locations. Fill material for the berm should be well-graded, homogenous fill consisting of mixed boulder, cobble, gravel and sand found on the site. Riprap material should also be graded so that void size is reduced. The Project Engineer will stake out the southern base of the entire berm (the side where armor is to be applied). Small tree and sapling removal and grubbing will be performed on the berm excavation and construction sites (1.7 acres), the fill disposal area to the east of the former Jard property (1.5 acres) and other access ways (0.3 acres). The total project disturbance area is thus anticipated to be 3.5 acres, and all of this land area will be seeded and mulched to stabilize soils within the required time frame (See Sediment and Erosion Control Notes in Attachment A). Sediment Excavation Approximately 4,100 cubic yards of channel sediment removal is proposed in the Park Street Bridge area to remove built up sediment bars. This excavation will remove sediment to approximately the 2-year flood elevation. All sediment must be removed during low flow where Roaring Branch Restoration RFP Page 4

5 machinery will largely be kept on the bars and out of the water. Sediment must be directly loaded with an excavator and not pushed up and piled with a bulldozer to remain in compliance with US Army Corps of Engineer s regulations. No stockpiling of material, even temporarily, is allowed below the ordinary high water line (i.e., top of bank). Approximately 100 cubic yards of sediment is also proposed for removal from the sediment bar at the outfall location of the Congress Street flap gate. 6.0 Erosion & Sediment Control Under the Vermont Construction General Permit (2006) For Stormwater Runoff from Construction Sites, activities solicited under this RFP are subject to the authority of Vermont s construction discharge permit program. The permit indicates the requirements for low risk site work and for posting the permit on-site during construction activities. Once awarded the project, the contractor must fill out the Notice of Addition of Owners or Operators to Coverage to be added to the Vermont Construction General Permits (3-9020). The berm removal and construction is classified as a low-risk activity according to Appendix A of General Permit The linear nature of this floodplain restoration project has led to the request and approval of the following sediment and erosion control specifications by the State of Vermont that must be followed for the duration of the project. 1. Delineating site boundaries will be the responsibility of the Project Engineer. 2. Stabilized construction entrance already exists on site. If tracking of soils takes place the Project Engineer will request installation of a construction entrance. 3. Silt fence will not be required unless directed by the Project Engineer in specific areas. 4. There is no upland or channelized runoff potential to address. 5. All permanent erosion and sediment run-off controls are accomplished within the project earthworks design. 6. Final stabilization of all disturbed soil areas not treated with rock riprap will be accomplished with seed and mulch. No erosion matting is necessary. 7. No additional measures for winter stabilization are necessary. 8. No dewatering activities are necessary. 9. Daily inspections are the responsibility of the contractor, and to implement any necessary BMPs to address any discharges or potential for discharge noted, or as directed by the Project Engineer. Refer to the construction plans (Attachment A) for notes on erosion and sediment control. Activities solicited under this RFP are subject to a Vermont Stream Alteration Permit. The site has also been cleared for wetland and cultural resources. If during construction the contractor believes that wetland or cultural resources have been encountered, work should be stopped and the Project Engineer should be contacted. Roaring Branch Restoration RFP Page 5

6 7.0 Project Schedule Construction will begin spring 2010, or at the discretion of the selected contractor with approval from the Project Engineer. A Notice to Proceed will be issued by the Project Engineer prior to the start of work. Construction and site stabilization must be completed and approved by the Project Engineer no later than 10/1/10. Failure to complete the project on time may result in forfeiture of the performance bond. 8.0 Performance Bond Contractor shall provide performance bond of the amount of $10,000 that shall be filed with the Town of Bennington prior to issuance of a Notice to Proceed by the Project Engineer. 9.0 Bid Submittal Information & Format Contract bid proposals must be physically received at the Bennington Town Office by Dan Monks, Planning Director, 205 South Street Bennington, VT no later than 1:00 PM on Monday, March 15, A pre-bid site showing is not planned. Revised construction plans are available from the Project Engineer in electronic format only. Bids will be opened at 1:15 PM on Monday, March 15, 2010 at the Bennington Town Offices. Notice of contract award is anticipated by Friday March 19, Bids shall be presented on the enclosed bid sheet (Attachment B). Additional information supporting lump sum bids will be accepted. The Town of Bennington reserves the right to reject any or all bids on its own motion. Technical questions with regard to the preparation of bid proposals may be addressed to: Barry Cahoon, P.E., Vermont River Management Program at barry.cahoon@state.vt.us or or Roy Schiff, Ph.D., P.E., Milone & MacBroom, Inc. at roys@miloneandmacbroom.com or Attachments Attachment A: Revised Construction Plans Attachment B: Bid Sheet Roaring Branch Restoration RFP Page 6