21R1339 Note 5.pdf

Notice No. 5

31 August 2021

PRE-PROPOSAL QUESTIONS & ANSWERS

RFP N62742-21-R-1339

FY18 MCON P-103 WATER WELL FIELD US NAVSUPACT ANDERSEN, GUAM

NOTE: The following questions and answers are provided for INFORMATION ONLY. The RFP remains unchanged unless it is amended in writing on a Standard Form 30.

17. Ref. Section 1.2.4.1 and 1.2.4.3. The design of the well is to be based on various aspects including sieve analysis. Currently there is no drill rig on-island capable of collecting undisturbed “insitu” samples from the water-bearing zone depths (~500’) for these wells.

KTR Recommendation: Please waive the requirements of section 1.2.4.3.

ANSWER: Section 33 11 13 subpart 1.2.4.3 will be deleted. See forthcoming amendment.

18. Ref. Section 1.2.4.1, l. Description and discussion of geophysical techniques to be employed at the site. What geophysical techniques are being referred to?

ANSWER: Section 33 11 13 subpart 1.2.4.1 item 1 will be deleted. See forthcoming amendment.

19. Ref. Section 1.2.4.1, o. Description of plumbness and alignment testing. No on-island equipment capable of meeting the plumbness and alignment specs mentioned in section 3.3.2, a.

(150mm/5.9” deviation per 30m/98.43’lf) in Guam’s karst lithology.

KTR Recommendation: Please waive the plumbness and alignment requirement as it appears to pertain to line shaft turbine pumps rather than submersible type. The contractor will guarantee the successful installation/removal of the pump column.

ANSWER: The allowable deviation will be revised to 200 mm (7.9”), which is equivalent to 2/3 the inside diameter of the casing. This conforms with AWWA A100 and EPA’s Manual of Water Well Construction Practices. See forthcoming amendment.

20. Ref. Section 1.2.4.1, p. Description of specific methods employed to test for sand. Is sand content percentage testing during constant rate/final pump test being asked for? Will parameter measurements such as turbidity suffice?

DEPARTMENT OF THE NAVY

NAVAL FACILITIES ENGINEERING SYSTEMS COMMAND, PACIFIC

258 MAKALAPA DRIVE, SUITE 100

JOINT BASE PEARL HARBOR HICKAM, HAWAII 96860-3134

ANSWER: Section 33 11 13 subpart 1.2.4.1 will be revised to state that the test for sand content must be performed with a centrifugal sand sampler. The centrifugal sand sampler is referenced in AWWA A100 Appendix E. See forthcoming amendment.

21. Ref. Section 1.2.4.2. 100mm test well, upper aquiclude, case, grout and seal the boring, use test well to determine flow & water quality etc. The test well may be converted to the permanent well. There is no upper aquiclude at this site. Cannot case, grout and seal a test well that may be converted to a larger diameter permanent well. Drilling a 12” open (pilot) test hole for capacity testing has previously been done successfully.

ANSWER: Section 33 11 13 subpart 1.2.4.2 will be revised. The 100 mm diameter test well will be revised to a 200 mm test boring. A pump test in the open borehole will be performed to evaluate its potential as a production well. If appropriate based on the pump test, the borehole will be completed as a production well. If not, the borehole will be sealed and abandoned. See forthcoming amendment.

22. Ref. Section 2.1.5. Casing guides just below the double cement baskets and midway between the cement baskets and the ground surface. Installing casing guides above the screened water bearing zone is unnecessary and will prohibit the measurement of the filter pack and the well plug. Please refer to the filter pack & bentonite comment directly below.

ANSWER: The specifications require double cement baskets and no filter pack below the baskets. Section 33 11 13 subpart 2.1.5 will be revised to require casing guides at a minimum of two locations instead of three locations: one basket midway on the louvered casing, and one basket midway between the upper cement basket and the ground surface. See forthcoming amendment.

23. Ref. Section 2.1.7. Commercially made cement baskets, with all steel parts made of type 304 stainless steel. The use of cement baskets rather won’t provide a sufficient seal due to the high probability of borehole irregularities in the karst formation.

KTR Recommendation: Well construction utilizing a closed bottom shoe, a coarse filter pack, followed by a 2-foot layer of fine sand and a 5-foot hydrated bentonite plug then grouting to ground surface is standard local industry practice and has resulted in many successful supply well installations.

ANSWER: Cement basket location will be selected based on video logs that identify locations in the borehole that are sufficiently smooth. If sufficiently smooth sections do not exist at appropriate depths based on the video logs, an alternative to the use of cement baskets will be considered.

24. Ref. Section 2.4.3. Cored Rock Samples. Is the intention to do rock coring on this project?

And if so what quantity and for what purpose?

ANSWER: Section 33 11 13 subparts 2.4.3 and 2.4.4 will be revised to delete references to cored rock samples. See forthcoming amendment.

25. Ref. Section 3.2.1. The diameter of the borehole for the well shall provide a minimum of 75 mm all around the outside diameter of the casing. A 12-inch casing plus welding collar has an outer diameter of 13.25-inches and shoe outer diameter of 14.121-inches. This necessitates a borehole diameter greater than 19 inches to over 500’ bgs. An 18-inch diameter hole will still exceed the GEPA requirement for sealing the annular space, however an 18-inch hole is extremely risky in this karst lithology and the risk increases substantially with a larger diameter borehole.

ANSWER: Provide borehole in accordance with the specifications to ensure that the grouting of the annular space can be performed with a tremie pipe.

26. Ref. Section 3.2.2, d. DTW measurements shall be taken immediately after water is encountered and thereafter at the beginning of each work shift. Not feasible to collect DTW measurements immediately after encountering water due to the presence of the drilling foam.

Drilling foam normally takes approximately 48 hours to settle.

ANSWER: Section 33 11 13 subpart 3.2.2 item d will be revised to limit the depth to water measurement to at the start of the next day’s shift after water is first encountered. An approved defoamer may be used if necessary. The requirement to continue water level measurements at the start of each day will be deleted. See forthcoming amendment.

27. Ref. Section 3.2.5, c. The casing shall be temporarily secured and the well initially developed and cleaned by bailing. When the well has been cleaned of drilling muds, drill cuttings, cave-in materials, etc., the casing shall then be lowered to its final position.

Developing, bailing and cleaning the well while the casing is temporarily suspended above its final position runs the risk of sloughing materials from the sidewalls and not being able to set the casing/screen at the proper elevation. Additionally, if these wells were completed with filter pack and a bentonite plug (filter pack well) this process would not be needed.

ANSWER: Section 33 11 13 subpart 3.2.5 item c will be revised to state that the casing should initially be lowered to its final depth instead of temporarily secured above the final depth. See forthcoming amendment.

28. Ref. Section 3.2.7.2, b. Grout placed in the annulus shall be installed by tremie pipe. Use of a 2” OR 3” tremie would require an ~ 22" to 24" dia borehole that is perfectly straight. Tremie has always been waived by GEPA and calculations of the annular materials to show there was no bridging is local standard industry practice.

KTR Recommendation: Waive the tremie requirement, as it will be hard to find a drilling contractor willing to drill a 24" diameter hole to over 500' bgs. In Guam’s karst lithology?

ANSWER: Grout placed in annulus must be installed by tremie pipe in accordance with the specifications.

29. Ref. Section 3.3.1.1. Pump tests shall be conducted in the open borehole…… This statement contradicts section 1.2.4.2 that asks to case, grout and seal the test well. Please advise.

ANSWER: Section 33 11 13 subpart 1.2.4.2 will be revised. The open borehole will not be cased or grouted prior to the pump test. A pump test will be performed in the open borehole to determine viability as a production well. See forthcoming amendment.

30. Ref. Section 3.3.2, a. The maximum deviation from the vertical shall not be more than 150mm/5.9” deviation per any 30m/98.43’lf of depth for the plumbness test. There is no on-island equipment capable of meeting these specs in Guam’s karst lithology. Please waive the plumbness and alignment requirement as it appears to pertain to line shaft turbine pumps rather than submersible type.

KTR Recommendation: In lieu of the plumbness and alignment testing the contractor could guarantee the successful installation/removal of the pump column.

ANSWER: Section 33 11 13 subpart 3.3.2 item a will be revised to allow a deviation of 200 mm per 30.0 meters of depth. See forthcoming amendment.

31. Ref. Section 3.3.2, a. The alignment shall be tested by lowering a section of pipe or dummy 12.2 m/40’ long to the bottom of the well. The OD of the plumb shall be equivalent to the ID od the well casing. This appears to be a typo as it is impossible to accomplish.

ANSWER: Section 33 11 13 subpart 3.3.2 item b will be revised to state that the OD of the plumb should be equal to the casing inside diameter less 2 mm. See forthcoming amendment.

32. Ref. Section 3.5.1, a & b. A well shall be considered abandoned if the contractor does not complete the well to the depth ordered by the Contracting Officer, if the Contractor should abandon the well due to loss of tools or other cause. No payment shall be made for any work performed on an abandoned well. The statement “other cause” is very vague, open to interpretation and seems to put all the liability on the drilling subcontractor. What happens if a well cannot be completed to the depth ordered by the Contracting Officer due to the presence of large voids that cause a loss of circulation or borehole collapse through no fault of the driller?

ANSWER: Abandonment of the well must be performed in accordance with the specifications.

Completion of the well is the responsibility of the contractor.

33. Ref. Section 3.5.1, f. Well decommissioning or abandonment includes the removal of all materials left in the borehole or well, including backfill materials. Casing, screen and any other material placed into the hole before the decision was made to abandon the borehole or well. It is impossible to remove steel casing and screen in a 500’ well that has been backfilled. Please advise.

ANSWER: Section 33 11 13 subpart 3.5.1 item f will be revised to exclude removal of the casing if the casing has been grouted into place. See forthcoming amendment.

34. Ref. Section 3.5.2.1, j. & l. Indication of penetration resistance such as drive hammer blows given in blows per 150 mm of driven sample tubes. Information must include hammer weight and drop distance.

Description of material in accordance with ASTM D2488 or standard rock nomenclature in accordance with CED TR GL-85-3……USCS etc.

Is geotechnical drilling using a hollow stem auger rig required and if so, what are the sample intervals and to what depth? If hollow stem auger drilling is waived will all the requirements of section 3.5.2.1, l. still be applicable? The subsurface will be predominantly paleokarstic coralliferous limestone of a similar nature with heterogeneously occurring voids. All of the disturbed cuttings from Air-Rotary drilling will be mostly the same size and material type? And what type of "chemical field screening" is being referred to?

ANSWER: Section 33 11 13 subpart 3.5.2.1 items j and l will be revised to delete references to the use of hammer blows to indicate penetration resistance. Drilling with hollow stem auger will not be required. See ASTM D2488 for chemical field screening. See forthcoming amendment.

35. Ref. Section 3.5.2.3, c. Type and make of equipment, bailer and pump used during development. Is a submersible pump being required as part of well development?

ANSWER: Use of a pump for well development is not required by Section 33 11 13 subpart

3.5.2.3 item c, however, the use of a pump is desirable.

36. Ref. Section 3.5.2.3, m. Name and description of the disposal facility or area, for the waters removed during development. Could the development water be allowed to percolate into the nearby ground the same as the >1 million gallons of water from the 72 hr pump test? The development water could be run through filter material to remove the fines if necessary.

ANSWER: Section 33 11 13 subpart 3.5.2.3 item m will be revised to state that the pumped water could be conveyed to a location a minimum of 15.24 meters from the well where the pumped water will not flow back towards the well. See forthcoming amendment.

37. Ref. Section 3.6. Submit Well Operating Permit for each well to the Contracting Officer.

What is required by the KTR for the Well Operating Permit.

ANSWER: The well driller is responsible for submitting the Well Operation Permit in accordance with the Guam EPA requirements.

38. Ref. Section Water Quality Analysis Table. Analytes listed in this table don’t appear to coincide with US EPA and Guam EPA drinking water standards. Please advise.

ANSWER: The water quality test will be conducted in accordance with Section 33 11 13 subpart 3.3.3. The Water Quality Analysis Table at the end of Section 33 11 13 will be deleted.

See forthcoming amendment.

39. Ref. Specification Section 33 11 13 and drawing CW501. Gravel packing around the well screen.

Comment:

Based on the drawing CW501 and specification section 33 11 13 there is no required gravel packing around the well screen, which may not work in Guam. The project site soil strata is underlain with coralline limestone where the fine particles of the limestone can easily break off and enter the screen slots without the gravel packing. Gravel packing is normally required on all water wells on Guam.

Question:

Please advise if gravel packing will be required on this project. If required, please provide specification and drawing.

ANSWER: Gravel packing is not required for this project.

40. Ref. Specification Section 33 11 13 sub part 1.2.4.2 & 1.2.4.3. Test Wells and sampling for geotechnical analysis

Comment:

Water well deep boring the air-foam rotary drill rig is normally used. This equipment is not equipped with drive hammer to collect undisturbed soil/rock samples and perform standard penetration test. The only soil/rock samples that can be collected are the drill spoils mixed with drill foam and water that comes out from the hole.

Question:

Please consider to waive the sampling requirement for the drilling.

ANSWER: Section 33 11 13 subpart 1.2.4.2 will be revised and subpart 1.2.4.3 will be deleted.

See forthcoming amendment.

41. Ref. Specification Section 33 11 13 sub part 2.1.5. Casing guide.

Comment:

Should gravel packing be required, the screen section of the well will have to be gravel pack.

The casing guide will impede the tagging of the gravel pack material.

Question:

Please consider to waive the casing guide requirement.

ANSWER: See response to Question 22.

42. Ref. Specification Section 33 11 13 sub part 2.1.7 & 3.2.6. Cement basket.

Comment:

Should gravel packing be required, the screen section of the well will have to be gravel pack.

The cement basket will not be necessary.

Question:

Please consider to waive the cement basket requirement

ANSWER: See response to Question 22.

43. Ref. Specification Section 33 11 13 sub part 2.4.1. Containers for drill cuttings. We would like to request if Ziploc bags can be used for drill cuttings in lieu of air tight liter container

ANSWER: Ziploc bags will not be allowed in lieu of air tight liter containers.

44. Ref. Specification Section 33 11 13. Depth of wells

a. Please provide estimated depth of each well

ANSWER: The depth of each well can be estimated based on the Typical Well Construction Detail on drawing CW501 and elevations shown on the well site plans.

b. Please provide the total dynamic head (TDH) for each well.

ANSWER: The total dynamic head for each well will not be provided. Minimum pump requirements are included in Section 43 24 27.

45. Ref. Specification Section 33 11 13 sub part 3.2.7.2 paragraph A & B. Cement grouting of annular space.

Comment:

The specification calls for water and cement grout mix only. Due to the porous characteristics of limestone the water cement grout will be easily absorb by the highly porous limestone and cavities encountered.

Questions:

a. Please advise if it is acceptable to add sand to the grout mixture, if added; please provide specification for sand.

ANSWER: Provide cement grout mix in accordance with the specifications. Adding sand to the grout mixture will not be allowed.

b. Since there is no water around the solid casing there will be no segregation expected and tremie method is not necessary. Besides the tremie pipe would not fit into the space between casing and the bore wall. We would like request to waive the tremie method and use direct pouring method for grouting.

ANSWER: Grout placed in annulus must be installed by tremie pipe in accordance with the specifications.

46. Ref. We respectfully request a 3-week time extension to the bid closing date for P-103 Water Well Field. This is needed to moderate the challenge of responding to three (3) NAVFAC request for price proposals over the 9-day period from Sept. 15 thru Sept. 23, 2021 and provide an opportunity to secure adequate vendor & subcontract price coverage.

ANSWER: Proposal due date was extended via Amendment No. 0001.

End of Notice