24327 Geotech Report Ref.pdf

McDowell & Associates Geotechnical, Environmental & Hydrogeological Services ���� Materials Testing & Inspection

3730 James Savage Road ���� Midland, MI 48642

Phone (989) 496-3610 ���� Fax (989) 496-3190

Southeast Michigan Office 21355 Hatcher Avenue � Ferndale, MI 48220

Phone: (248) 399-2066 � Fax: (248) 399-2157

May 2, 2016

Beckett & Raeder, Inc.

535 West William Street

Suite 101

Ann Arbor, Michigan 48103

Attention: Mr. Kristofer Enlow, P.E.

Subject: Pavement Investigation

MDOC Saginaw-Parking/Access Roads/Walkway Paving Replacement

Main Parking Lots and Driveways

MDOC Saginaw Correctional Facility

9625 Pierce Road

Freeland, Michigan

M&A Job #16-64348

Dear Mr. Enlow, In accordance with your request, we have completed a Pavement Investigation at the subject project.

You indicated the purpose of this pavement investigation is to evaluate the in-place soil conditions so that a determination of methodology for the replacement and/or fixing of the associated pavements can be determined. McDowell and Associates was onsite March 22, 2016 and April 1, 2016 to complete the field work associated with this project. Nine (9) soil borings, designated as

1 through 9, were performed in the main parking lots and driveways and eleven (11) soil borings, designated as 10 through 20, were performed in the warehouse parking lot and perimeter road.

The approximate locations of the borings are shown on the Soil Boring Location Plan which accompanies this report.

The borings were advanced to a depth of five feet (5’) below the existing ground surface at the requested locations. The borings generally encountered three to six inches (3” to 6”) of asphalt pavement, twelve to thirty-one inches (12” to 31”) of gravel, followed by a variegated clay with sand and pebbles which was found throughout the remainder of the boring. The average cross-sections of the major areas is as follows:

Main Parking Lots – 4” of asphalt, 14” of a gravel base, clay subgrade with an estimated

CBR of 3

Main Driveway – 6” of asphalt, 16” of a gravel base, clay subgrade with an estimated

CBR of 3

Perimeter Road – 3” of asphalt, 18” of a gravel base, clay subgrade with an estimated

CBR of 3

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16-64348

5-2-2016

Soil descriptions and depths shown on the boring logs are approximate indications of change from one soil type to another and are not intended to represent an area of exact geological change or stratification.

Water was encountered in several of the borings at the time the field work was completed and ranged in depth below ground surface from ten to forty-two inches (10” to 42”). It should be noted that short-term ground water observations as noted on the Log of Soil Test Boring sheets may not provide a reliable indication of the depth of the water table. Water levels in granular soils could fluctuate with seasonal and climatic changes and/or rainfall in the area immediately prior to the measurements. In cohesive soils, lenses or seams of water-bearing sands or silts could be found within the various clay strata at the site that were not observed at the time the borings were completed.

During field work, Standard Penetration Tests using an automatic hammer were made during sampling and indicate that the gravel base has fair to good densities and the underlying native clay subgrade soils have good strengths and densities. Tests taken in the pavement cross-section soils gave results of seven (7) to sixteen (16) blows per foot. Tests taken in the native soils gave results ranging from seven (7) to twenty-four (24) blows per foot. The Standard Penetration Tests indicate that the base and subgrade materials appear to be compact and stable.

Laboratory testing results indicate that the gravel base is roughly graded to MDOT 23A specifications. The moisture content on the clay subgrade samples ranged from 7.1% to 21.2% with the majority being 13% to 15%. These moisture contents would suggest water observed in the borings at the time of completion was most likely the result of trapped water in the gravel base material.

Based on the supplied drawings, it would appear that the pavement at the MDOC Saginaw facility was originally installed in approximately 1990, thus making the parking lot approximately twenty-five (25) years old. There does appear that some maintenance and repairs have been done to the parking lot (re-sealing, coating or crack repairing). Typical asphalt pavement has a life cycle of approximately twenty to twenty-five (20 to 25) years depending on the maintenance that is completed. Due to the way the asphalt was breaking at the time of our field work and its age, we feel the asphalt has deteriorated past the point of repair.

It was planned for another two (2) borings for the warehouse parking and Sallyport and three (3) hand auger borings for the interior sidewalks, but due to underground utilities, the need to be escorted and the observed soil characteristics of the subgrade these borings and hand auger borings were omitted. You indicated that the typical traffic consists of approximately 600 cars in and out of the main parking lot, 1 semi-truck per day to the warehouse and 2 buses per week through the

Sallyport.

Based on a visual observation of the pavement in the MDOC Saginaw facility, the soil borings and the results of laboratory tests, the pavement distress does not appear to be related to a problem with the subsurface conditions at the site but more likely just the age of the pavement. If you were satisfied with the serviceability of the existing Main Parking Lots, Main Driveway, Perimeter Road and Sidewalks, then removal of the existing asphalt/concrete, proof rolling the existing base

Page -3- MDOC Saginaw Pavements material and replacement with a similar thickness of asphalt/concrete should yield a similar life cycle to that of the current pavements.

You have provided several options that you think will be used for the repairs, the following are our comments to the options that you proposed.

Main Parking Lot Option 1 – Remove existing 4-inches of asphalt, proof roll base, undercut as necessary, pave 4-inches: This would be a cost effective option. The 4” of asphalt could consist of a 2” base of 3C or 13A and a 2” top of 36A.

Main Parking Lot Option 2 – Same as above, but add in underdrains to the existing storm structures: Anything done to lower/remove water is beneficial to the pavement section and would potentially extend pavement life and possible reduce maintenance costs.

Main Parking Lot Option 3 – Remove asphalt, base, and over excavate to allow for a total new cross section: This option would provide the better end results, but with additional costs. A complete new cross-section could consist of, 12” MDOT Class II sand sub-base with drainage, 8”

MDOT 21AA, and 4” of pavement as noted above.

Main Driveway Option 1 – Mill and pave two or three inches: This is not a viable option as the pavement too far deteriorated. We would recommend replacing the complete 6” of asphalt at a minimum.

Main Driveway Option 2 – Remove existing 6-inches of asphalt, proof roll base, undercut as necessary, pave 6-inches (two-inches of 2C, 3C, 4C mixes?): This would be a cost effective option.

The use of the “C” asphalt mixes is good choice because the high percent of crushed aggregate will provide a more stable section. Due to Asphalt Institute recommendations of using layer thickness of 3-4 times the nominal maximum aggregate size, we would suggest a 4” base of 3C and top with 2” of 4C.

Main Driveway Option 3 – Same as Main Driveway Option 2, but add in underdrains to the existing storm structures: Same as Main Parking Lot Option 2.

Main Driveway Option 4 – Remove asphalt, base, and over excavate to allow for a total new cross section: This option would provide the better end results, but with additional costs. A complete new cross-section could consist of, 12” MDOT Class II sand sub-base with drainage, 8” MDOT

21AA, and 6” of pavement as noted in Main Driveway Option 2.

Perimeter Road Option 1 – Mill and pave two or three inches: There was only approximately 3” of asphalt on the perimeter road. We feel that trying to mill off 2” will not work well and the remaining 1” would not hold together, therefore, this is not a viable option.

Perimeter Road Option 2 – Pulverize and pave three or four inches: This is a good option, due to the traffic (golf carts and occasional vehicle) we would suggest a single 3” layer of asphalt be placed for the perimeter road. The asphalt mix could be 13A or 3C.

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Additional Geogrid – Could we remove the asphalt and a portion of the base, add geogrid, add

21AA and pave: This could be used with any of the above mentioned options. If you removed the asphalt and 8” of existing gravel, then placed a TX-5 geogrid, 8” new 21AA and 4”/6” of asphalt the estimated calculated traffic the pavement could handle based on Tensar’s Spectrapave 4-Pro

Software would increase on the order of 3 to 4 times. We are not sure if this would actually be seen because the pavement its self may break down prior to seeing that amount of traffic volume.

During reconstruction of the Main Parking Lot, Main Driveway and Perimeter Road, we would suggest that McDowell & Associates be on site to proof roll and verify compaction on the aggregate base before asphalt is placed. These activities should be done in accordance with, at a minimum, MDOT standards set forth in the Density Testing and Inspection Manual or any local agency specifications. This will help to ensure the aggregate base conditions are similar to those found in the soil borings. While the asphalt is being placed, we should again be on-site to verify asphalt temperature, compaction and roll pattern. These tests will help to ensure the best possible end product with the selected materials.

McDowell & Associates is not responsible for independent conclusions, opinions or recommendations made by others based upon information presented in this report. Our experience indicates that the actual subsoil conditions at the site could vary from those found at twenty (20) test borings made at specific locations. It is, therefore, essential that McDowell & Associates be notified of any variation of soil conditions to determine their effects on the recommendations presented in this report.

If you have any questions regarding the information contained in this report, please do not hesitate to call.

Respectfully Submitted, McDOWELL & ASSOCIATES

Michael S. Keenan, P.E.

Project Engineer