B09_Attachment_12_Q_A_Part_2_0002.pdf

Q&A Part 2 - 140P3026R0002 CHOH Repair to Inlet Lock 2

1. Is muck out required for the dam portion of work at the dry stack walls?

a. Sheet C12 includes profiles and sections of each cofferdam. Upstream cofferdam is required to be excavated down to minimum elevation 176.5’ or Bedrock and downstream cofferdam is required to be excavated 1’ below existing grade to set sandbags. Removal of any debris is also required in order to set the sandbags and key-into the substrate. See notes on Sheet C6 which require the contractor to use caution to avoid projected foundation of existing dry stack stone walls and riprap revetments. Key-in of the sandbag and/or impermeable membrane in accordance with bulk sandbag cofferdam detail on Sheet C10 to provide water resistant seal is part of the contractors means and methods and may extend beyond the minimums shown in the plans.

2. How would NPS like to address any underpinning of the Lock Gate walls if discovered?

a. This would be addressed as a differing site condition (FAR 52.236-2) or under changes (FAR 52.243-4).

3. Does NPS have specific company or person that we need to use for having paddles and frames made?

a. Per response to prior question, the government will furnish eight (8) new paddle assemblies (4 left and 4 right) with associated pieces (similar to Sheet S4.2), four (4) pivot components which include the two (2) pivot bearing plates (similar to Detail 3 - Sheet S4.3), and two (2) socket caps (similar to Detail 3 - Sheet S4.3).

4. What is the location of the sump?

a. Conceptual location of removable pumping station (RPS) is shown on Sheet

C6 for permitting purposes. See Notes 5 & 6 on Sheet C6 regarding if relocation or additional RPS’s are installed. The final configuration of the dewatering system, location of the RPS’s, and number of RPS’s is subject to the contractor’s means and methods for dewatering as required in Section 312319 of the specifications.

5. Are we designing the bottom of the miter at the gate as the stopping point for the muck out, approx. 2’ or can we include in our proposal a not to exceed depth of 2’?

a. As noted on sheet 1/S2.0 the intent is to “temporarily remove existing material to allow inspection and repair of courses at the base of the Lock” for void repair shown on detail 2/S2.0. Approximate sediment elevations can be found on sheet C5 and approximate base elevation of Lock is shown on 1/S2.0. Actual miter sill elevations will be verified in the field during excavation. At the upper lock gate, excavation to the bottom of the existing miter sill is required. Photos during partial dewatering of the upper lock gate area can be seen in the attached photos from 6/3/2014.

6. Are we required to remove stone after the project is complete or leave in place?

a. It is unclear what this question is directed towards.

i. If this is directed towards any cut stones discovered during excavation within the canal, See callout on sheet C5 in regards to salvaging of existing cut stones greater than 12” x 18” x 6” from the material excavated at the base of the inlet lock walls. These stones must be of comparable geology to the existing, in adequate structural condition, and not bear any character defining features. Any cut stones salvaged for potential reuse in stone masonry walls should be stockpiled onsite and reviewed with NPS for approval prior to reuse.

ii. If this is directed towards any stones removed from the historic structures as part of demolition, see paragraph 3.4.A of Section 024120 which addresses requirements for demolition debris.

iii. If this is directed towards the stone required for the stabilized construction entrances (SCE). Per MDE BMP details and their specifications shown on sheet C10, these are temporary structures to be removed upon completion of the project, and only with permission from the erosion and sediment control inspector. The resulting disturbed ground below the SCE must be brought back to existing grade and stabilized accordingly.

7. Will we be required to remove any vegetation where the matts are going? What does NPS want done with that area once the matts are pulled up?

a. It is assumed that this question is directed towards the timber crane mats shown across the canal prism at the downstream side of the Limit of Disturbance (LOD) on Sheet C2. Crane mats overlaid on non-woven geotextile may be installed directly on grade as shown on Sheet C2. Removal of existing vegetation is not prescriptively required by NPS below the timber crane mats, however some minor grading of the area within the canal at the downstream side of the LOD may be necessary to properly seat the crane mats to support access across them. Upon removal of the crane mats permanent stabilization is required in accordance with the contract.

8. Can we pull a crane up close to the edge of the first pier/bridge in order to move equipment into place at the lock gates? Crane is approx. 90 tons. Utilization of cranes has been allowed in the past with submitted crane plan. Using a crane would be the safest option for moving equipment over to the work area.

a. Per sheet C3 note 3 “the contractor is responsible for evaluating, designing, and constructing bridging/shoring/protection measures to sufficiently carry the intended loads from construction activities over the bridges and historic masonry walls. The design shall be signed and sealed by a PE in the state of Maryland and be submitted for approval.” The use of a crane can be considered by NPS subject to the submitted plan meeting the contract requirements for protection of historic features.