Questions and Answers.docx

Mohawk DSM Additional Relief Wells & Collector System Upgrades IFB Pre-Bid Meeting – Contractor Questions

1. 3.1.5 Casing - Permanent Casing, 30 Inch Diameter. We need to know specified wall thickness on this material? Also, can this material be used?

USACE Response: No minimum thickness was specified for this A-36 steel casing as it is to be Contractor designed. The specifications state that “all casing shall have sufficient thickness to retain its shape and maintain a true section throughout its depth and may be in sections of any convenient length.” See paragraph 3.1.5 of SECTION 33 26 00.00 10 for additional requirements. For information only, 0.25 and 3/8-inch thick A-36 steel casings have been used for relief well installation at other Huntington District projects in Ohio with glacial outwash foundation soils and similar well depth.

2. Can you provide blow counts or other density information for the subsurface materials?

USACE Response: Blow counts for relevant (nearby) borings are provided on boring logs contained in SECTION 00 01 15 following the cover page with title “Boring Logs for select downstream berm piezometers.” Note the hammer weight, sampler size, drop height, etc. vary and often differ from the Standard Penetration Test (SPT) Method. Boring P-43A was completed by SPT Method; borings D-07-67, D-07-68 and D-07-69 were completed using a 3-inch diameter sampler and 300 lb. hammer. Note that the sonic drilling method was used to complete the relief well pilot holes and so blow counts are not applicable for these borings. However, the drilling time for each run is provided on the logs.

3. Is there an onsite location for disposal of the drilling and excavation spoils?

USACE Response: Yes, its location is shown on drawing sheet CS104. Also, see paragraph 3.5 of SECTION 31 00 00 regarding utilization of excavated materials.

4. Are there compaction requirements for the No. 9 Sand?

USACE Response: Compaction of the No. 9 Filter Material and Seepage Berm Material shall be in accordance with paragraphs 1.5 and 1.5.1 of SECTION 31 00 00 EARTHWORK. Vibratory compactors shall be used on material placed under and around pipes and manholes in accordance with paragraph 1.5.1. For fill above the pipes, material shall be compacted by making at least 4 passes with spreading equipment as described in paragraph 1.5.

5. What are the discharge criteria for the development and pump test water?

USACE Response: As per paragraph 3.4 DEVELOPMENT of SECTION 33 26 00.00 10, “all water discharged during the development process shall meet all county, state, and Federal water quality regulation requirements. See the aforementioned paragraph and other portions of SECTION 33 26 00.00 10 for additional requirements. All work shall be performed in accordance with all applicable Federal, state, county, and local requirements – see paragraph 1.3.1 of SECTION 01 57 20.00 10.

6. What is the desired wall thickness for the permanent 30” casing of the relief wells?

USACE Response: No minimum thickness was specified for this A-36 steel casing as it is to be Contractor designed. The specifications state that “all casing shall have sufficient thickness to retain its shape and maintain a true section throughout its depth and may be in sections of any convenient length.” See paragraph 3.1.5 of SECTION 33 26 00.00 10 for additional requirements. For information only, 0.25 and 3/8-inch thick A-36 steel casings have been used for relief well installation at other Huntington District projects in Ohio with glacial outwash foundation soils and similar well depth.

7. Specifications state that “the relief well riser pipe and any blank sections required shall be 11.8 inch inside diameter stainless steel pipe and shall be a minimum of Schedule 10 (0.148-inch) in wall thickness.” Schedule 10 12” pipe has 0.180” wall thickness, Is 0.180” the intended minimum wall thickness?

USACE Response: The 0.148-inch wall thickness is a typographic error and should be 0.180-inch instead. This correction has been included in Amendment 0002.

8. Is the contractor responsible for upgrades/ repairs to bathhouse for government use?

USACE Response: The Contractor is required to provide restroom facilities for Government personnel. Per paragraph 1.14.2, 2. of SECTION 01 50 00, the Contractor supplied Government office trailer is “located within a previous campground area, which is now closed. The trailer is located directly adjacent to the campground bathhouse, which shall be for Government personnel use. The Contractor shall ensure functioning power, heat, water, and restroom (sewer) facilities in the bathhouse.” Also see paragraph 1.4.4 of SECTION 01 50 00.

9. Is there any list of plan holders or known bidders formal or informal for this project. We wish to share our scope of work and final estimate for well drilling with all prime bidders.

USACE Response: A list of all pre-bid attendees is attached at the bottom of these questions and answers. Also, located at https://beta.sam.gov/ there is a list of interested vendors.

10. Section 33 26 00.00 10 page 12 paragraph 3.4 outlines DEVELOPMENT. Paragraph 3.4.1 outlines DEVELOPMENT Chemicals. Paragraph 3.4.2 outlines Surging and Pumping. All of these are variations of developmental processes. It is our experience that well development on similar wells to produce satisfactory results takes as much as 50 hrs. or more per well. The question is about items 26 and 27 of the bid form. Item 26 allows 30 hours for surging and item 27 allows 60 hours of pumping. The total development time for 10 wells can easily approach 500 hours. Even when combining line items 26 and 27 on the bid form, total development time allotted is 90 hours or only 9 hours per well. We ask for additional guidance.

USACE Response: Quantities for Bid Items 26 and 27 have been increased, and these changes are included in Amendment 0002.

11. Sheet CS203 talks of Temporary Well Closures. Are these required on existing wells only or are they required on each well as completed? May we use an MJ cap to seal the well rather than a coupling and riser pipe?

USACE Response: Reference paragraph 1.6.1 of SECTION 31 00 00. The temporary well closures are a means for the wells to be temporarily taken out of service so their flows do not interrupt construction. It is anticipated that they would be needed for existing wells which will be modified or temporarily lose their exits during replacement of their outlets. It is expected that in sections of the existing system that are not to be modified, the end stub of the collection system pipe (to remain) will be bulk headed and then those wells in other sections would not need temporary well closures and could continue to function. It would be the Contractor’s discretion if the temporary closures are necessary for the new wells. They may be needed to prevent the new wells from flowing during certain construction processes – see paragraph 1.6 of SECTION 33 26 00.00 10. There must be a means of safely removing existing well closure devices during an extreme flood event if there is question on dam stability with them in place. The connection method must also not damage the existing fiber glass well risers.

A MJ cap could be used as a temporary well closure if it could be installed in such a manner as not to damage the existing fiber glass well risers and so long as it could be safely removed in the event of an extreme flood event where the COR may call for the wells to be allowed to flow.

12. 30” Temporary outer well casings. We are experiencing confusion concerning outer casing length and bottom elevation placement. We are trying to calculate total footage of 30” outer casing required for the bid. While collecting material bids, we were required to provide HDPE vault/T Head total lengths to our vendor. There is a table on sheet CU502 with lengths and elevations. Column G represents the top of the filter pack. The drawing leads us to believe this is also the bottom of the concrete and bottom elevation of the 30” casing. I have attached a table with my own elevation and length calculations. The column in yellow represents what we feel is the correct concrete base elevation which should also be the bottom of the 30” surface casing elevation. I have added the column from your table on sheet CU502 which provides gravel pack elevations. Can you please verify what the correct elevation and surface casing length should be?

USACE Response: On drawing CU502, the TOP OF WELL SCREEN ELEVATION, listed in Column F, is set. There is to be a minimum of 3 feet of filter pack above it, but it can be more to make up for elevation fluctuations based on the depth of top of screen and bottom of well vault. This means that Column G (TOP OF FILTER PACK) is in error, as it was calculated using the minimum top elevation of the filter pack which was measured 3 feet above the top of well screen. This elevation should extend to the bottom of the 30” permanent casing and concrete. The bottom of the 30” permanent casing should be 5’ (6” + 18” + 3’) below the floor of the well vault. Based on this, the TOP OF FILTER PACK for each well has been revised, and these changes to column G are shown in amended drawing CU502 included in Amendment 0002.

Additional Questions:

13. Where can We obtain the plans, specs, proposal for the project?

USACE Response: All documents including synopsis, solicitation, specifications, drawings, amendments and question & answers can be found at https://beta.sam.gov/ by typing in W9123720B0001 in the search bar.

14. Was there a pre-bid meeting?

USACE Response: Yes a pre-bid meeting took place on May 19, 2020.

15. Do we need to be registered to bid?

USACE Response: See solicitation W9123720B0001 under Additional Instructions for complete details.

16. What is required to be returned when bidding?

USACE Response: See Section 00 20 00 – Instructions to Bidders in solicitation W9123720B0001.

17. What hours will the contractor be allowed to work?

USACE Response: See solicitation Section 01 20 00, Paragraph 1.13.3, which states that “The Contractor’s work hours with this contract shall be at the discretion of the Contractor as approved by the Contracting Officer.”