A.5 Gerisch High School- Parking Lot Improvements.pdf

June 2, 2025 Project No.: 23-0981.14

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

RE: Geotechnical Investigation Southgate Community Schools Gerisch Middle School Parking Lot Improvements 12601 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 Gerisch Middle School. The district is interested in having the existing asphalt parking lots and tennis court 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 32 and 34 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 1 April 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 to 4.5 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 aggregate base consisting of asphalt millings or crushed limestone and underlain by clay. Sand was encountered below the asphalt millings at one location and underlain by clay. Water was not encountered at any of the locations. The approximate thickness of the aggregate base ranged between 4 and 24 inches.

At the location of C-1, the aggregate base extended beyond 28 inches. The hand augering was terminated within the thick aggregate base at this location.

23-0981.14 June 2, 2025 Gerisch Middle School Parking Lot Improvement Page 2

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”.

Dynamic Cone Penetrometer was used to determine the strength of the subgrade strength at three (3) coring locations, C-1, C-2 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:

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

Gerisch Middle School Parking Lot Improvement Page 3

Figure 1 – Coring Locations

C-1

C-5

C-3

C-4

C-2

Gerisch Middle School Parking Lot Improvement Page 4

Table 1 – Summary of Subsurface Conditions Encountered

CORE # DEPTH

(Inches) DESCRIPTION REMARKS

C-1

0 – 4

4 – 28+

Asphalt

Crushed Limestone

DCP test conducted at this location

Hand Augering was terminated in crushed limestone

C-2

0 – 2

2 – 8

8 - 33

33 - 35

Asphalt Millings

Brown Sand

Gray Clay

DCP test conducted at this

C-3

0 – 4.5

4.5 – 8.5

8.5 – 18.5

18.5 – 24

Asphalt Millings

C-4

0 – 4

4 – 16

16 - 26

C-5

0 – 3.5

3.5 – 16.5

16.5 - 28

DCP conducted at this