Attachment 01 - Building 201 Floor Evaluation.pdf

14 York Street, Suite 201 | Portland ME 04101-7408 | T 207.245.6060 | F 207.245.6061 | www.ThorntonTomasetti.com

July 22, 2021

Seth Bickford

Lead Engineer

VA MAINE HEALTHCARE SYSTEM

1 VA Center

Augusta, Maine 04330

RE: VA Togus Medical Center – Building 201 Maintenance Floor Evaluation

Dear Seth, We are writing this letter report to inform you of our evaluation of the maintenance floor structure and mezzanine at Building 201, located on the VA Togus Medical Center campus in Augusta, Maine. The purpose of our evaluation was to perform a conditions assessment of the existing structure, suggest concept level repairs where needed, and provide a load rating of the structure once repaired to sufficient condition.

We believe Building 201 was constructed circa the 1930s, and had originally served as the boiler house for the hospital. The original construction was a single story structure, with the base floor slab constructed approximately 13 feet below grade. The roof is comprised of a cast-in-place slab spanning to steel trusses. At some time after the original construction was completed, the boilers were removed and a new floor was added at grade level. The floor is constructed from steel framing supporting a concrete slab on metal deck. The frame is supported by steel columns, presumably bearing on concrete footings below the basement slab.

We estimate the maintenance floor was constructed circa the 1980s.

The building now serves as a maintenance garage for the grounds equipment. Several large pieces of equipment (front-end loaders, tractors, etc.) are parked in this garage. There are also hoists mounted to the garage floor that are used to lift some of the equipment for servicing. As a result, the first floor structure and columns below are required to support large loads from the vehicles, hoists and other equipment in the garage. There are also some small offices located at the north end of the building. The ceiling of these offices is framed to create a mezzanine floor that is used for light storage. The ceiling structure is comprised of steel bar joists supporting plywood sheathing.

Please refer to the attached Appendix A for photos of Building 201, which are referenced in this report.

VA Togus Medical Center

Building 201 Maintenance Floor Evaluation

July 22, 2021 Page 2 of 7

Observations and Testing

Thornton Tomasetti (TT) performed a site investigation of Building 201 on April 6, 2021 to observe and document the existing conditions, as well as assess the level of deterioration in the floor structure. TT performed non-destructive testing on the top surface of the garage floor to determine the extent of delaminated concrete. This was done by sounding the concrete with a hammer and by dragging chains across the deck surface. TT also took small concrete samples from the existing slab at several locations, and these samples were sent to an independent testing laboratory to determine the extent of chloride penetration into the slab. Finally, TT performed visual observations of the underside of the first floor slab to assess damage to the structure and document existing framing.

We were able to gain access to the slab structure via a floor hatch that accesses the basement level. Based on our observations in this area, we believe the floor is comprised of an 8 inch thick structural slab supporting a cast-in-place topping. We were not able to definitively determine the slab reinforcement while on site, as there was no sufficient access to observe the reinforcement within the slab. Overlying the structural slab is a concrete topping that appears to be of varying thickness. Our opinion is that this topping slab was placed after the structural slab and was used to create a sloping surface for drainage. Attached photo 2 shows the slab construction.

July 22, 2021 Page 3 of 7

Based on our observations and testing, we believe the garage has been subjected to large amounts of moisture and de-icing salts from the vehicles that are parked and serviced in it. Our initial observations noted visible surface scaling, cracking and delaminations in the top concrete surface (refer to photo 3). After sounding the concrete, the extent of deteriorated concrete was found to encompass approximately 50% of the garage floor area, with the heaviest damage observed at locations where vehicles were parked. Figure 1 on the preceding page shows the approximate extent of delaminated concrete in the building.

While on site, TT took four sets of concrete samples that were sent to an independent testing laboratory for chloride testing. Determining the level of chlorides in the concrete, which are often a result of the concrete’s exposure to moisture and de-icing salts, provide an approximate representation of the depth of corrosion penetration into the slab. Samples CL-1 and CL-2 were taken within the topping layer, while samples CL-3 and CL-4 were advanced through the topping and into the structural slab. In all cases, with the exception of sample CL-4, the maximum recommended chloride threshold per the American Concrete Institute (ACI) was exceeded. In the case of sample CL-4, the allowable chloride threshold was not exceeded between 2” and 4”. A summary of the chloride test results is provided in Table 1 below (the approximate location of each chloride sample is shown in Figure 1).

Table 1

Sample Depth

(in)

Chloride Content Threshold

% Sample Weight lbs/cy*

CL-1

0-1 0.161 6.3 1.1 Exceeds

1-2 0.275 10.8 1.1 Exceeds

CL-2

0-1 0.171 6.7 1.1 Exceeds

1-2 0.186 7.3 1.1 Exceeds

2-3 0.158 6.2 1.1 Exceeds

CL-3

0-1 0.125 4.9 1.1 Exceeds

1-2 0.106 4.1 1.1 Exceeds

2-3 0.118 4.6 1.1 Exceeds

4-4.75 0.097 3.8 1.1 Exceeds

CL-4

0-1 0.190 7.4 1.1 Exceeds

1-2 0.030 1.2 1.1 Exceeds

2-3 0.016 0.6 1.1 OK

3-4 0.024 0.9 1.1 OK

4-5 0.033 1.3 1.1 Exceeds

*Assumed Unit Weight 145 lbs/cf

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From the underside of the maintenance floor, we noted large areas of corroding metal deck, typically located beneath where vehicles are parked. The deck corrosion was significant in some areas, leading to the deck delaminating from the bottom of the concrete slab. Photo 4 shows some of the corroding metal deck that was observed. We generally observed the beams and columns supporting the slab to be in good condition, with no concerning signs of corrosion.

The upper mezzanine level was observed to be framed with 3/4" thick plywood spanning to 16” deep bar joists spaced approximately at 3’-9” on center. The bar joists are supported by 6” CMU bearing walls, which are likely unreinforced. The CMU appears to be supported by the steel beams at the maintenance level below. All framing at the mezzanine was observed to be in good condition.

Opinions and Probable Repairs

The topping slab, particularly in the areas where vehicles have been parking or serviced, is in poor condition. The corrosion is being driven by increased exposure to moisture and de-icing salts in these particular areas. The level of chlorides in the topping slab, particular in the top 1 to

3 inches, is very high and is indicative of significant corrosion potential. While some of the results show that the chloride levels begin to decrease with topping depth, the allowable ACI thresholds are still exceeded. Given that the chloride penetration is deep and widespread, we recommend that the extents of the delaminated concrete topping shown in Figure 1 be removed and replaced in their entirety. Areas not identified in Figure 1 as delaminated have not be exposed to the same levels of moisture. Our opinion is that these areas are in good condition and will not require any repairs.

Some higher chloride levels were found to have penetrated the structural slab, as evidenced by test samples CL-3 and CL-4. Our experience has shown that chloride levels will typically decrease with depth. Given that the chloride levels in sample CL-3 were still above the minimum

ACI threshold, it should be anticipated that some corrosion is occurring in the structural slab as well. Our opinion is that the extent of corrosion will be less significant than the topping slab.

However, in the planning of construction repairs for the slab, it should be anticipated that scattered areas of deeper repairs into the structural slab will be required. Based on our experience, our opinion is that most of these repairs will extend 1” to 3” into the structural slab, and full-depth removals will be unlikely. Repairs to the structural slab would consist of removing the delaminated concrete and replacing it with new.

Below the slab, the steel framing was found to be in good condition, and our opinion is that the framing will not require any structural repairs. The metal form deck was found corroded in several locations, particularly in areas where vehicles have repeatedly been parked or serviced.

Some of this corrosion was significant enough to delaminate the deck from the slab. We believe that moisture from the level above is penetrating through the voids and cracks in the concrete, eventually ponding on the top surface of the deck. The ponding moisture has accelerated the corrosion of the metal deck at these locations. Our opinion is that the metal deck was used as a

July 22, 2021 Page 5 of 7 form to place the concrete slab and is not contributing to the slab’s structural capacity. We recommend that the loose and heavily damaged pieces of the deck be removed to eliminate safety hazards. The remaining deck that is not significantly damaged can remain in place. We do recommend that the VA periodically monitor the remaining deck for further damages, as falling pieces of deck can create safety hazards for the spaces below.

In order to preserve the long-term durability of this floor structure, we recommend that a vehicular traffic membrane be applied throughout the spaces serving the garage use (the interior office spaces would not require the membrane). The membrane will prevent moisture from further infiltrating the topping and structural slabs, reducing the rate of corrosion in the structure. The membrane will also prevent moisture from infiltrating the slab and ponding on the metal deck, which will aid in mitigating further corrosion of the deck. Any traffic membrane that is applied will require periodic maintenance and repairs to keep it in good working condition. We are happy to work with the VA to develop a maintenance plan for this building to increase its long term durability.

The upper level mezzanine was found to be in good condition and will not require any structural repairs.

Structure Capacity

Structural drawings for the maintenance floor were not available. Based on our observations and dimensions from the site investigation, the steel structure supporting the mezzanine was found to have a capacity of 250 pounds per square foot (psf). Slab reinforcing could not be sufficiently verified on site, and therefore further destructive testing will be required to expose reinforcement and determine the slab’s capacity. Our opinion is that once the slab is restored to good working condition based on our recommended repairs, the capacity will be sufficient to handle most vehicular traffic. Large concentrated loads from heavy equipment will need to be carefully reviewed, and thus we plan to work with the VA to further evaluate the structure for such loads and determine the slab’s ultimate capacity.

The mezzanine bar joist framing was found to have a capacity of 68 psf, while the plywood sheathing was found to have a capacity of 24 psf. Plywood used in structural floors is recommended to be supported at a maximum distance of 24”. We would not recommend using this floor for storage unless the strength of the sheathing is increased. Options to increase strength would be to add additional layers of plywood sheathing, or remove the existing plywood and replace it with thicker sheathing or timber decking.

Conclusion

We trust the information in this report meets your needs at this time. Should the VA choose to move forward with repairs for the garage, we would be more than happy to provide construction documents for such repairs, as well as construction administration assistance and inspections

July 22, 2021 Page 6 of 7 as required. We’re also more than happy to work with the VA to develop a maintenance plan for the garage floor to increase its long-term durability.

Please do not hesitate to contact us if you have any questions.

Very truly yours, THORNTON TOMASETTI, INC.

Christopher G. Williams, P.E., S.E. Ethan A. Rhile, P.E.

Senior Associate Vice President

July 22, 2021 Page 7 of 7

APPENDIX A – BUILDING 201 PHOTOS

Photo 1 – East elevation of Building 201

Photo 2 – Maintenance floor slab construction

Photo 3 – Surface delaminations on floor slab

Photo 4 – Metal deck corrosion on underside of floor slab