Consideration and Approval of Contract:  Cinder Lake Landfill Geotechnical Investigation Professional Services Contract RSOQ No. 2017-48

The City sought proposals to investigate both the quantity and quality of rock located below Cell E (115 acres) of the Cinder Lake Landfill (CLL). This geotechnical investigation (Project) would be completed through a comprehensive drilling, sampling and testing pattern. The Project would drill approximately 13 holes to depths ranging from 120 to 160 feet below ground surface. Rock samples will be taken at various depths within each hole and tested to determine suitability for use as an aggregate base material according to the engineering standards established by Arizona Department of Transportation (ADOT) and the Maricopa Association of Governments (MAG).

While the current approved design contains approximately 4 million cubic yards of rock and soil, a 2015 geophysical survey concluded that an additional 4 million cubic yards of rock and soil could be excavated below the design elevation.

If the City pursues revised design elevations, then it will need to request a permit revision from the Arizona Department of Environmental Quality (ADEQ).

While the current CLL closure date is projected to be 2054, proposing a revised design depth would extend the CLL operations by an additional seven (7) to ten (10) years. Additional financial benefits could also be realized through the sale of crushed rock from within Cell E.

While it is difficult to project solid waste trends in forty years, the additional landfill airspace will likely be of great value to future generations. In addition, the Project will assist in determining the value of crushed aggregate for regional infrastructure projects.

The City Council appropriated funds in the budget in account 211-06-165-0631-0-4433.

Public Infrastructure-Deliver quality community assets.
Environmental And Natural Resources-Actively manage and protect all environmental and natural resources.
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While there has not been a Council decision on this Project, previous geotechnical investigations have been approved by the City Council. This includes the approval of a similar drilling and sampling project in Cell D in 2013.

Option 1-Approve the Contract with Amec Foster Wheeler authorizing the company to drill, sample, test, and prepare reports for the Project.

Option 2-Direct City staff to conduct the solicitation of bids for drilling contractors. Meanwhile, Amec Foster Wheeler would be assigned to conduct soil sampling, testing and preparation of reports.

Option 3-Reject the contract.

The Cinder Lake Landfill Solid Waste Facility Plan acts as the guiding construction document, with approved excavation depths in Cell E as shown in Appendix A (115 Acres).  The depths established by the engineer of record were based on marginally rippable (extractable) rock as determined by previous soil boring logs. The engineer of record assumed that when it became time to excavate to the design elevations, the City’s only desirable method of excavation would be to rip the soil and rock with bulldozers with minimal blasting.    

In the summer of 2011, sonic drilling was performed in conjunction with the United States Geological Survey (USGS) to study subsurface conditions within the Cinder Lake basin. The mission of the project was to determine the quantity of soil and rock below the entire Cinder Lake Basin. Upon examination of the rock samples, Staff concluded that the basin potentially contained favorable sources of basalt which could possibly meet specifications as an aggregate base course. Staff compared the previous geotechnical reports with the new samples and determined that additional drilling and sampling of rock in the landfill footprint was justified.

In 2013, samples of rock and soil were extracted from Cell D (33 acres) to further assess the viability of subsurface rock for use as an aggregate to meet the standards of ADOT and MAG. Results proved favorable and staff concluded that approximately 1.3 million cubic yards of rock would be available within in Cell D. In addition, revising the excavation below the existing depths could extend the life of the landfill by an additional four years. Staff further recommended additional investigation was warranted in Cell E.

In 2015, the City contracted with Amec Foster Wheeler to conduct a geophysical survey (seismic refraction). The scope of the project involved identifying changes in strata densities below Cell E. The results from the survey indicate sizable quantities (approximately 4 million cubic yards) of rock exist below the existing design elevation. While the geophysical survey provided a snapshot of the changes in densities, the confidence in the data would be better qualified if actual rock samples are collected and tested for their engineering properties (strength, resistance to wear, absorption, et. al.).

The City's Purchasing Section issued a Request for Statement of Qualifications (RSOQ) on February 16, 2017, to competitively select a professional consulting team.  On March 21, 2017, four (4) Statement of Qualifications (SOQ's) were received.  An initial review of all four SOQ's to determine responsiveness to the requirements presented in the RSOQ was completed by the Senior Procurement Specialist assigned.  All four (4) responses were deemed responsive and were distributed to the evaluation committee for review.  The evaluation committee consisted of five (5) people; four (4) City Staff and one (1)  licensed general contractor.  The evaluation committee independently reviewed, evaluated and scored each submittal in accordance with the evaluative criteria established in the RSOQ.  The total resulting scores of the four submittals are as follows:

Firm                                                                 Total Score
Amec Foster Wheeler                                      480
Geosyntec                                                        425
Speedie & Associates                                      386
Four Corners Environmental                            361

Based on the numerical evaluation of the submittals received, Amec Foster Wheeler received the highest ranking. Immediately following the selection, Amec Foster Wheeler was asked to provide a scope of work and fee proposal.  After review and discussions between the City and Amec Foster Wheeler, a not to exceed fee of $242,570.00 was agreed upon.

According to the current approved design, Staff has calculated approximately 4 million cubic yards of soil and rock remain within Cell E. However, the 2015 geophysical survey concluded that the CLL could be excavated to a deeper elevation, and an additional 4 million cubic yards of soil and rock could be available. This Project will help to confirm not only the additional landfill airspace to be gained, but it will also help to qualify the quality and market value of the rock within Cell E. 

It will take two (2) to three (3) weeks from Notice To Proceed to mobilize. During this period, Amec Foster Wheeler will be developing a safety plan, getting Arizona Department of Water Resources permits for the borings, and scheduling logistics. Drilling and sampling will take eight (8) to ten (10) weeks. Testing will be conducted at Amec Foster Wheeler's geotechnical lab in Phoenix, and is likely to take an additional two (2) weeks to complete. In the meantime, Amec Foster Wheeler will be preparing the draft report for review, and an additional two (2) weeks will be needed to complete the draft report. Staff anticipates that the total project time will be fourteen (14) to seventeen (17) weeks. Approximately 1,000 gallons of non-potable water will be used daily for this work. 
 
Should the results of the Project prove favorable, and the City Council decides in favor of excavating deeper than the approved design elevations, then a revised excavation plan will need to be submitted to the ADEQ.

This Project will assist Staff to better determine the volume of sub-surface soil and rock available on-site. While the soil can be used as a viable means of covering trash, rock is not of great desire for the landfill operation.  However, there are potential financial benefits to be gained in realizing the rock as a resource for future infrastructure projects within the City.

The current closure year for the CLL is 2054. Expanding the CLL to a deeper elevation will provide the benefit of continuing to maintain affordable solid waste services for the community and the region for an additional seven (7) to ten (10)  years.

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