rfp-des-2026-19-addendum-6.pdf

Murphy Dam Outlet Works Improvements Project, Pittsburg, NH

ADDENDUM NO. 6

To: All Prospective Bidders Murphy Dam Outlet Works Improvements Project

Location: Pittsburg, NH

From: Charlie Krautmann – NHDES Dam Bureau Josh Paquet – GFT

Re: Addendum No. 6

Date: June 18th, 2026

Please find the following ADDENDUM NO. 6 for the Murphy Dam Outlet Works Improvements Project which is to be included as part of the Contract Documents thereof.

As per Specification Section 00200, Article 13.09 the bid shall contain an acknowledgment of receipt of this Addendum No. 6, (and all addenda). The addendum number and date shall be entered in the space provided in Section 00301 – Bid Form, Article 3 – 3.01A

Please note bids are now due on Friday, June 26th, 2026 at 1300 (EST). Hard copy bids may be received as stipulated in the Contract Documents.

This Addendum has been issued to include clarifications to a few questions which include:

Item #1 – Clarification

Question – How do you access the section of the existing penstock pipe where the exterior mounted flowmeters are to be installed?

Response –The exterior of the penstocks can be accessed within concrete pits located in the sub-basement described on sheet S-4. Note on the Sub-basement plan view (manhole grating) which depicts the access locations for each of the penstock pits.

Item #2 – Clarification

Question – Is there sufficient access for crew to get around the existing penstock where the flow meters are to be mounted?

Response – Yes

Item #3 – Clarification

Question – There are four boxes that represent the flow meter transducers on the plans. Since the Flexim FLUXUS ultrasonic clamp-on flow meter utilizes 2 transducers per flow meter system, it is assumed that the 4 boxes represent 2 complete systems (1 system for each penstock).

Please confirm that 1 complete Flexim FLUXUS ultrasonic clamp-on flow meter system per pipe is what is required.

Response – Yes, 1 complete flow meter system is required on each of the two penstocks (2 complete flow meter systems).

Item #4 – Clarification

Question – What elevation are the bottom of the penstock extension pipes required to be at?

Will demolition of the existing concrete floor be needed to achieve the required elevation of the bottom of the penstock extension pipes?

Response – Concrete demolition along the base of the pipe extension is not anticipated. The bottom elevation of the proposed extension pipe will match the existing penstock invert at each of the tie-in locations. The existing penstock invert at the transition to the new extension is approximately 5 inches above the stilling basin floor.

Item #5 – Clarification

Question – A permanent fence and permanent handrail are shown to be installed along the concrete stilling basin. Please confirm both are required and the system is meant to be redundant.

Response – Yes, both are required for redundancy.

Item #6 – Clarification

Question – In the Project Plans, both hand railings are shown to be aluminum pipe, but in Specifications Payment and measurement Section Part N. Bid Item 13a-b, Miscellaneous states that “Installation of new galvanized or stainless-steel handrail systems mounted to the top of concrete walls and platforms.” Please clarify desired material type and coating for both concrete and platform railings.

Response – The hand rail is to be composed of aluminum pipe and the specification will be revised accordingly.

Item #7 – Clarification

Question – Please provide details for how the jib crane is to be powered.

Response – The jib crane is to be manually rotated as well as manually operated with use of a chain fall trolley

Item #8 – Clarification

Question – Concrete subcontractor just raised a question about the quantity of the concrete in item 01200-9c cast in place concrete for liner extension encapsulation. We are coming up with approx. 175-180 CY for this scope of work, but the bid form shows 340 CY. Can you please confirm the quantity or revise, so that it avoids having unbalanced bid items?

Response – Yes, the quantity within the encasement area should approximately 180 CY, will revise the bid form.

Item #9 – Clarification

Question – There are multiple references to a 72” orifice in the JFG, but the inlet spool is 72”.

Please confirm a 60” orifice is the acceptable size.

Response – A 60-inch seal-ring orifice is acceptable for the Jet-Flow Gate, provided the gate maintains the 72-inch inlet/flange connection shown on the Contract Drawings and otherwise satisfies the dimensional, structural, operational, coating, testing, and commissioning requirements of the Contract Documents.

The Contract Specifications will be revised by addendum to clarify that the Jet-Flow Gate shall have a 72-inch inlet connection and a 60-inch seal-ring orifice. References in Section 35222 to a

72-inch seal-ring orifice will be revised accordingly. The Contractor shall submit manufacturer’s hydraulic performance data, operating-force calculations, and shop drawings demonstrating compliance with the revised requirements for Engineer review.

Item #10 – Clarification

Question – There are multiple references indicating the use of a wheel gate for the leaf (wheels, axles, wheel bushings, tracks, etc.) Please confirm acceptability of a bronze guided slide gate arrangement that’s otherwise compliant with the performance requirements.

Response – Section 35222 currently includes requirements for a wheel-supported gate leaf system, including wheels, wheel axles, wheel bushings, tracks, associated tolerances, and operating-force calculations. A bronze-guided slide gate arrangement is therefore not strictly compliant with the prescriptive requirements of the current specification. However, the Engineer will consider a bronze-guided slide gate arrangement as an acceptable alternative provided the Contractor demonstrates that the proposed design satisfies all hydraulic, structural, operational, actuator sizing, wear, service-life, alignment, and performance requirements of Section 35222. Any proposed bronze-guided arrangement shall be submitted with supporting calculations, operating-force analyses, material data, and manufacturer's experience demonstrating equivalent or superior performance to the specified wheel-guided arrangement.

Item #11 – Clarification

Question – Sections P-9-d-6 & e-2 reference a vertical orientation for assembly and testing.

Please confirm horizontal orientation is acceptable as long as all other pressure and operational test are conducted.

Response – Section 35222 requires assembly and operational testing with the Jet-Flow Gate positioned in the vertical orientation with the stem plumb, consistent with the final installed condition. The intent of this requirement is to verify proper alignment, wheel/track interaction, seal performance, stem operation, and actuator performance under conditions representative of field operation. Horizontal assembly or intermediate fabrication testing may be performed at the Contractor's option; however, the required operational testing, seal leakage testing, and performance verification specified in Section 35222 shall be completed with the gate in the vertical orientation unless an alternate test procedure is submitted and approved by the Engineer demonstrating equivalent verification of all specified performance requirements.

Murphy Dam Outlet Works Improvements Project, Pittsburg, NH