A.3 Allen Elementary School Parking Lot Improvements.pdf

June 2, 2025 Project No.: 23-0981.16

Mr. Jason Hardy Southgate Community Schools 13940 Leroy Southgate, MI 48195

RE: Geotechnical Investigation Southgate Community Schools Allen Elementary School Parking Lot Improvements 16500 McCann Avenue

City of Southgate, Wayne County, MI

Dear Mr. Hardy:

It is our understanding that the Southgate Community School District would like to make improvements to the parking lots at Allen Elementary School. The district is interested in having the existing asphalt parking lots milled and overlayed. To aid in this process, PEA Group has performed the following services:

• Core the asphalt pavement sections at five (5) locations (C-1 through C-5) across the parking lot to determine the thicknesses of the asphaltic concrete sections.

• Hand auger at the coring locations to approximate depths ranging between 26 and 32 inches below the base of the asphaltic concrete to determine the type and existing condition of the base and subgrade.

• Dynamic Cone Penetrometer testing at selected coring locations to evaluate the strength of the subgrade and estimating the CBR value of the subgrade.

PEA Group cored the asphalt pavement sections on 3 May 2025. The coring locations are shown in Figure 1 attached. The coring was performed with a 4-inch diameter diamond tipped pavement-coring bit driven by an electrical drill. The approximate thickness of the asphaltic concrete sections encountered at the coring locations ranged between 2.5 to 5 inches.

Pavement base and subgrade material were sampled with a 3.25-inch diameter bucket type hand auger.

The subgrade conditions encountered at the coring locations below the asphaltic concrete consisted of crushed limestone (aggregate base) and underlain by brown and gray clay. Water was not encountered at any locations. The approximate thickness of the aggregate base ranged between 8 and 10 inches.

The approximate thickness of asphaltic concrete sections and the condition of the gravel base and subgrade at each coring locations are summarized in Table 1 “Summary of Subsurface Conditions Encountered”.

23-0981.16 June 2, 2025 Allen Elementary School Parking Lot Improvement Page 2

Dynamic Cone Penetrometer was used to determine the strength of the subgrade strength at three (3) coring locations, C-1, C-3 and C-5. Based on the tests, the CBR value of the subgrade is estimated to be 3.

The scope of the present investigation was limited to evaluation of the thickness of the pavement materials, determining the existing subgrade conditions, and estimating the CBR of the existing subgrade. If you have any questions regarding this report, or if we may be of further assistance to you in any respect, please feel free to contact us. We appreciate the opportunity to have been of service to you.

Sincerely, PEA Group

Indranil (Neel) Deysarkar, PE D. Jack Sattelmeier, PE Project Engineer Director of Geotechnical Engineering

Attachments:

Fig 1 – Coring Locations Table 1 – Summary of Subsurface Conditions Encountered

Allen Elementary School Parking Lot Improvement Page 3

Figure 1 – Coring Locations

C-2

C-3

C-4 C-1

C-5

Allen Elementary School Parking Lot Improvement Page 4

Table 1 – Summary of Subsurface Conditions Encountered

CORE # DEPTH

(Inches) DESCRIPTION REMARKS

C-1

0 – 2.5

2.5 – 12.5

12.5 - 31.5

Asphalt

Aggregate Base: Crushed Limestone

Brown/Gray Clay

DCP test conducted at this location

C-2

0 – 4.5

4.5 – 12.5

12.5 - 32.5

Crushed Limestone

C-3

0 – 5

5 – 15

15 - 30

Brow/Gray Clay

DCP test conducted at this

C-4

0 – 4

4 – 14

14 - 26

C-5

0 – 4.5

4.5 – 12.5

12.5 - 32.5

Brow/Gray Clay

DCP conducted at this