Patillas Dam Constructability Questions.pdf

Patillas Dam – Industry Outreach Questions

The Government requests input on potential constructability concerns and limitations for the Patillas Dam Seismic Modification Project. Contractors are encouraged to discuss the following questions during one-on-one breakout sessions, to be scheduled virtually following the site visit. Contractors are also voluntarily encouraged to provide written responses to these questions by June 30, 2026. Written responses may be emailed to USACE Contracting POCs Angel Martinez at angel.j.martinez@usace.army.mil or M. Renee Booth at meranda.r.booth@usace.army.mil. If you are submitting information that is proprietary in nature, please clearly mark the applicable documents or sections as "Proprietary." The Government will protect properly marked proprietary information and will not share it with other contractors or suppliers.

Embankment Work Work includes approximately 60,000 cubic yards of excavation and placement of up to approximately 670,000 cubic yards of imported zoned embankment fill. Embankment fill is generally required to be placed in loose horizontal lifts between 6 and 12 inches thick with stringent compaction control. The embankment work will be limited by the construction of the underlying outlet works extension along the western abutment.

What approaches would you propose for phased embankment construction to allow for early embankment construction while the outlet works extension is still being constructed? Is there suƯicient schedule or cost benefit to allow this option?

Given haul route limitations and expected production constraints, what realistic daily production rates do you anticipate for embankment fill?

Are the proposed limits of disturbance suƯicient for the embankment construction?

How would you protect the existing embankment concrete crest leveling wall throughout construction while minimizing impacts to earthwork operations?

Bulkhead and Bypass Operations The project requires continuous water deliveries from the reservoir at a rate of up to 25 cfs, with limited outage duration. However, flows will not be able to pass through the outlet works conduit while it is being modified. To maintain deliveries, bypass flows are anticipated to be conducted by pumping water from the reservoir, over the right abutment, and into the downstream canal. Bypass design and installation will be performed by the Contractor. Bulkhead design and installation to isolate flows in the tunnel will be by the Contractor. Unwatering of the upstream portion of the tunnel is not allowable due to depressurization concerns on the existing upstream tunnel stability near the inlet.

Based on the gate leakage shown in the presented video, what methods would you recommend for installing an isolation bulkhead, particularly methods which do not require underwater work with diving?

Continued operation of Patillas Canal is critical for the project. What bypass configuration would you propose and what redundancies would you incorporate? How would you plan for conflicts with the earthwork activities on the abutments? Are there alternate locations and details for connecting to the buried canal section? How would you connect the Canal Stilling Basin to the existing 72” RCP?

Is there a preference on fuel type for the canal bypass pumps (electric vs diesel, for example). What are the requirements for electrical service for the pumps?

Site Access The Government anticipates securing a temporary deed/easement with the landowner downstream of the Patillas Dam to allow for staging, borrow storage and construction access. What complications do you anticipate if the Government does not secure this access?

Is the proposed Contractor Use Area suƯicient for staging or would its limits negatively impact production? Should the Government consider arranging additional staging areas such as across from Highway 799?

What improvements or modifications would you expect to be necessary along the access routes, considering narrow roads, tight turning radii, unknown culvert capacity, and encroachments?

How would you document and avoid impacts to existing infrastructure, including deteriorated retaining walls and utilities, during haul activities?

Are there constructability concerns in establishing abutment access ramps, and is the currently assumed disturbance area adequate?

Outlet Works & Mechanical Work What constructability challenges do you anticipate when performing demolition of the existing outlet works conduit and construction of the new conduit in the tunnel, especially regarding limited space, equipment and material access, ventilation, and lighting?

What issues do you anticipate with contact grouting or CLSM backfill in the outlet tunnel? Would a switch to cellular concrete be beneficial?

What is the minimum constructible space beneath the 54-inch outlet works pipe within the tunnel in order to install, weld, and place concrete?

What techniques and equipment would you use to perform limited rock excavation under the steel conduit in the existing to provide additional clearance for concrete and steel pipe connections?

Construction Schedule The Government anticipates a four-year construction duration. The general sequence consists of pre-mobilization, submittals, procurement activities, followed by installation of canal delivery bypass and tunnel bulkhead, demolition of the existing pipe, and installation and testing of new outlet works pipe. Dewatering and excavation of the key trench can be performed in parallel with the outlet works demolition and reconstruction. Placement of embankment materials above the key trench cannot continue until outlet works conduit extension is completed. The Gate and Canal Valve house can be constructed in parallel with the embankment work. Due to typical rainy season, no embankment work is assumed August 1 to October 31.

Based on the identified constraints, is a four-year construction schedule realistic? What activities would be schedule drivers and risks?

Are there specific early-work activities that should be advanced to reduce schedule risk, such as the bulkhead and canal bypass?

How would seasonal restrictions during the rainy season impact productivity, access, and risk? What are your typical scheduling assumptions for weather delays that may impact earthwork in Puerto Rico’s tropical environment?

General Construction Logistics What restrictions or logistical challenges do you foresee in establishing Government

Use Areas and contractor staging areas on the limited available area?

What type of site power (voltage, amperage) for construction would you like to be available and where? Power can be made available along the western abutment but note that Puerto Rico experiences relatively frequent outages.

Does the existing reservoir access (adjacent to the right/western abutment) appear to be adequate, including the existing road conditions?

Any current concerns regarding equipment or materials availability either on the island or shipping to the island?