21R5009 - Contractor Questions and Answers.pdf

Q&A for PL159/PS160 - 21R5009

Question Answer Are the storm sewer lines truly “stormwater only”? Do they have any process water tied to them? Are any known sump pumps tied to them?

The storm sewers are only storm water. There are some storm flows going to the sanitary that have yet to be moved to the storm sewers.

However, the contractor does not have to address these flows aside from calculation made using overall design drainage area.

Is the 50 yr, 24 hr storm a corp standard? The 50 yr, 24 hr storm is not a corps standard.

Is there a preliminary engineering report for this area? No, there is not a preliminary engineering report for this area.

Could pump station be placed at or closer to detention basin? The pump station placement is not constricted by the location indicated in Appendix B3 STR166 Conceptual Location.

Does the current storm sewer cut through a corps certified levee and will any permitting be required for replacement of pipe above or through levee or embankment near existing outlet structure?

The levee embankment is not a Corps certified levee. There are not permits required on account of the levee. Backfill repairs to the levee shall use best practices for levee work.

Will lowering of the parking lot create elevation issues with getting flow to proposed detention basin due to vertical depth constraints of detention basin?

If sheet flow is the only method considered then there may be concerns.

For storm sewer replacement, are both 36” and 48” storm sewer proposed to be replaced from River to Parking lot area? What pipes are part of the remove and replace in the 600 linear feet of pipe?

The designer may propose rebuilding the whole of the storm sewer, but that could drive up the cost. The 600 linear feet of pipe is an estimate removal used by the government for a likely design.

If design calcs indicate a pump size (large pumps) that are not available from a Buy American company, would exception be made for foreign pumps?

(Call to be made by the KO)

Are elevations of the existing storm sewer available (invert elevations and rim elevations)? Elevations of the existing ground available? Building elevations available?

Appendix D Boring depths Beck and East has BLDG159 elevation in 1912 adjusted datum. Appendix B1 Survey Limits will allow the balance of these unknown elevations to be gathered.

Is the existing sluice gate on the 36” RC to be replaced as part of this project, or can it be reused?

The existing sluice gate may be reused if used in its current location.

Is the location of the proposed pump station, the existing levee, the pavement replacement area, and storm sewer replacement areas have any contaminated soils that need to be addressed?

Please see Scope of Work paragraph

2.4.3.2. Asside from the PFAS/PFOA

there are no known contaminates.

Looking at the existing 48” RC, and not knowing rim elevations, the existing 48” RC currently does not have a sluice gate. In looking at Appendix A drawings, it appears manhole C36 has a 12” RC line that drains a low ground elevation area. Based on these drawings, if the 12” RC pipe was attached to the existing 27” RC line, the existing 48” line could be rehabilitated (lined or repair joints) of the pipe, the manholes could be lined and add bolt down castings to make this line accept pressure during a flood condition. A sluice gate with an automatic check valve could be added to this line as a precaution, but essentially not need to be part of the scope of the pump station. This is based on the drawings provided in Appendix A, and not knowing all the elevations. Sections of the 48” line could be replaced with pressure pipe if the condition of the existing is not conducive to rehabilitation.

The Garrison is not interested in a pressurized storm system that relies solely on gravity head to establish flow.

The Buy American clause 52.225 ( made in USA) requires the component from initial melting stage to end-product to be made in USA. We are not able to meet this clause with Sulzer submersible pumpsneither does any other submersible pump manufacturer in the US market. Can we request for a waiver of this clause for submersible pumps?

A waiver is possible if there is no US Manufacture

Can I please request to change the type of the pump to Vertical Axial Flow Pump?

(DPW can support this change to Vertical Axial flow pump, but wishes to dicuss with KO.)

Is it possible to get an estimated drainage capacity for this project?

DPW has not calculated this quantity.