USIBWC Amendment 4 -D5_27_25.pdf

Upper Brownsville Levee and Floodplain Failure

RFP 191BWC25R0010

All questions and answers will be incorporated into the Technical Specification in Section 00.91.16.

1. Section 31.32.13 of the Project Specifications contain “Dry Soil Mixing” specifications. Section

1.7 – General states: “The intent of the dry soil mixing program specified herein is to provide soil improvement within the limits indicated on the Contract Drawings and to achieve the required degree of soil improvement to meet the performance criteria in Subsection 1.9.”

Drawing sheet 27813-000-01 “Project Layout Soil Mix and Stone Columns” calls for 72” (6-ft) diameter interconnected soil mix columns to create soil mix panels. In practice the typical diameter of a dry mixing tool is 36 inches; slightly larger tools have been used in very soft shallow soils. A review of the borings near the soil mix work zone, DP-201 and DP-202, show the subsurface soils are stiff to very stiff, fat clays with water content at or below the plastic limit of the soil. Dry soil mixing of any diameter would be extremely difficult in these soil conditions and dry soil mixing with a 72-inch diameter tool would be impossible. Will the owner allow wet soil mixing to be used providing all passing criteria are satisfied?

Response 1: The critical "factor" in the design is the area replacement ratio (ar). Contractors can use any size soil mix columns as long as they maintain that ratio based on the current design and meet the performance criteria in Technical Specification Section 31.32.13 1.9. The Contractor is allowed to modify the design shown in the drawings or change the ar if they can prove it will meet the design requirements. The Contractor's plan to meet these criteria shall be provided to the COR per Section 31.32.13 1.11.

2. When does the government anticipate Soil Mixing and Stone Column construction will begin? If not a specific date, a timeframe will be helpful.

Response 2: The schedule for starting and sequencing work will be up to the Contractor. We estimate award of this Contractor in August 2025 with the Notice to Proceed being issued within a month after that.

3. Addendum # 1 , drawing no. 27822-000-01, specifies soil mix column of 72” diameter. Please confirm alternative column diameters of 36” ~ 60” may be utilized, provided Area Replacement Ratio(ARR) remains consistent with the design intent (ARR ~ 27%), and specification requirements are satisfied.

Response 3: See the response to Question 1.

4. Specification Section 31.32.13: Can Wet Soil Mixing be allowed in lieu of Dry Soil Mixing?

Response 4: If the Contractor can show that the performance criteria in Technical Specification Section 31.32.13 1.9. are met with this method, then yes, wet soil mixing will be allowed.

5. Tentative schedule when it is going to start?

Response 5: See response to Question 2.

6. Section 01.52.13-Field Offices and Sheds - Is there an area identified adjacent to the project limits for contractor's staging yard?

Response 6: Possibly. There is an area east of the project owned by the Government that could be utilize as a staging and/or storage area. However, all areas available are subject to flooding and are impacted by the Government's and Texas' border security operations. The specific area will need to coordinate with the COR and compliance confirmed prior to use by the Contractor. Use of such areas shall be at Contractor’s risk.

7. Section 00.31.19 Existing Conditions - Is the expectation to relocate and maintain the existing temporary barbed wire fencing within the project limits?

Response 7: No. The Texas National Guard will remove, maintain, and relocate temporary fencing.

8. Section 01.55.26 Traffic Control and Project Signage - What is the agreed upon access route through the project limits? Can a turn-around be built outside of project limits, or is it IBWC's intention for the route to pass straight through? If intended access is as shown on plans, has an agreement been reached with CBP for Border Fence gate access?

Response 8: It is the Contractor’s sole responsibility to coordinate with Border Patrol and utility owners who are affected by the Contractor’s construction activities for access, construction schedule, and progression of work throughout the project duration in order to provide continuous access to the affected owners and obtain uninterrupted access within the project area (01.31.00 1.4.B.3). Any turn-arounds outside of the project limits but on USIBWC controlled property require COR approval, a pre-disturbance topographic survey, and restoration of the site after use to include revegetation.

9. Section 00.31.19 Existing Conditions - What method is to be used to inspect and verify the ACBM/Rock Rip Rap revetment limits installed into the Rio Grande River below water?

Response 9: It will be Contractor’s means and methods to inspect and verify existing conditions.

10. Section 01.55.26 Traffic Control and Project Signage - Is it expected that Contractor will maintain continued access through the site for CBP or other Stakeholders? This may cause complications under the International bridge where access has low overhead and is narrow.

Response 10: Contractor shall ensure that all roads used during construction are maintained throughout the duration of use and shall be restored to the preconstruction condition or the intended construction condition (01.55.26 3.3.A.). Roads serving the right-of-way, identified as such or not, owned by the USIBWC or CBP shall be clear and available to these agencies (01.11.00 3.2.C.). Limited full closures will be allowed but must be coordinated through the COR and CBP.

11. Section 00.31.19 Existing Conditions - What are the Monitoring Wells that have been identified and located in the excavation limits for the Soil Mix Columns? Is the requirement that these wells are to be removed or protected in place?

Response 11: Piezometers, or monitoring wells, were installed to measure the groundwater across the critical section near station 1900+13 (with coupled inclinometers) and assess the flow regime.

The piezometers and inclinometers are to be removed.

12. Section 31.32.13 Dry Soil Mixing - There are multiple methods for Soil Mixing Columns identified. IBWC Specifications outline "Dry Soil Mixing." Are other Soil Mixing Methods accepted, while still meeting all the technical requirements?

Response 12: The Contractor is allowed to modify the design or change if they can prove it will meet the design requirements.

13. H.17 Extended Warranties - The warranty period last for 2 years. Typically this include failure based on workmanship or material defects. Is adverse weather damage a warranty item?

Response 13:Any damage due to adverse weather will be responsibility of the Contractor.

However, damage from named storms is excluded (www.nhc.noaa.gov/aboutnames.shtml).

14. 52.236-27 Alt I Site Visit -Differing Site Condition clause will be included in the contact. Can a draft copy be provided for review.

Response 14: FAR 52.236-27 Site Visit Alt I is different than 52.236-2 Differing Site Conditions.

FAR 52.236-27 Alt I is located on page 79 of the solicitation. FAR 52.236-2 is located on page 22 of the solicitation. Since there is no clause named "Site Visit-Differing Site Conditions" and since both of those clauses are already within the solicitation, this question is not understood.

15. Section 00.73.63 Security Page 1-Who is responsible for Border Security within the project limits as it is not defined in Section 1.8. Please confirm that this will be assumed by others.

Response 15: The Contractor is responsible for site security as noted in Specification Section

00.73.63 1.6. Border security operations are not a Contractor responsibility.

16. The RIPRAP Schedule on page 27828-000-01 calls out for Nominal Thickness from station 1895+46 - 1896+82 to be 20 inches. On the Plan and Profile page 27819-00-01, the plan calls out for 18 inches of RIPRAP. Please clarify the correct Nominal Thickness and Maximum Rock Size for RIPRAP to be installed between said section.

Response 16: The schedule of 27828-000-01 calls our 20" nominal SIZE for the riprap with a thickness of 18". This is also consistent with Sections C and D on 27825-000-01.

17. Plan pages 27831-000-01 through 27836-000-01 show a horizontal scale of 1" = 20' and a vertical scale of 1" = 10', however, the grid in each cross-section shows 10' intervals both vertically and horizontally. Please clarify the correct scale.

Response 17: Will need to ask Arcadis. Response Pending.

18. The quantity of rip rap and ACBM calculated on plan view pages 27812-000-01, 27819-000-01, 27825-000-01 differs from the quantity calculated in the cross-section pages 27831-000-01 through 27836-000-01. Please clarify if we should utilize the plan view pages or the cross-sections for actual quantities.

Response 18: Contractors are responsible for determining the best way to make their own quantity estimates.

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