2017 9-28 Observ siderostat Conc slab Report.pdf

Department of Conservation and Recreation

Stoneham Field Laboratory

164 Pond Street

Stoneham, MA 02180

To: Barbara Farina

From: Anthony Crupi

Date: 9/28/17

Subject: Blue Hills Observatory existing footing inspection.

Scope of work:

The DCR Lab was asked to look at an existing footing at the Blue Hills Observatory and comment on its condition. The following observations and test results are listed for your review.

Observations:

1. The footing is 96” long by 96” wide. A test pit was dug on the side of the footing on the building side. The test pit showed the footing to be 22” deep and appears to be built directly on ledge.

2. The footing has a 51” round grout ring present in the center of the footing, the ring is roughly 1.5” above the top of the footing and 22” from the center of each side of the footing. The ring has 16 - 1” anchor bolts present, which have been cut off flush with the top of the ring.

3. Using this information, the weight of the footing would be roughly 8000 pounds or 4 tons.

This was determine by calculating the total cubic feet of the footing and multiplying by

140.0 (Average weight of concrete per cubic foot in this area.)

4. I was told the footing was built in 1960 which would make it 57 years old. The footing has no cracks or signs of distress present. The grout ring that held the previous tower, is of course cracked from the removal process.

Test Results:

1. The four corners of the footing were marked and tested using a Swiss Hammer by Humboldt MEG, Co. Model H-2975.

2. The test results indicate 3500 PSI, 4500 PSI, 4500 PSI AND 3500 PSI for an average of 4000 PSI.

See below Footing Sketch.

Co a) I...

C

Co

Sum mary:

Department of Conservation and Recreation

Stoneham Field Laboratory

164 Pond Street

Stoneham, MA 02180

Observation Building

The footing is in surprising good condition for its age. What we do not know is if it is pinned to the ledge below, or if it has rebar present in it, and if so what size or spacing. The above information was gathered to provide the Designing Engineer a look at this existing footing.

More testing, including cores could be done if desired. Please feel free to call me at any time with concerns or questions.

Respectfully submitted, Anthony Crupi Laboratory Supervisor DCR Lab 164 Pond Street Stoneham, MA 02180 Cell 617-719-0838 Email anthony.crupi@state.ma.us

L 8’-O” or 96” izTest Area 2 4500 PSI Average

N Test Area 1 3500 PSI Average

/51DIA.

Grout Ring

Area

Test Area 3 4500 PSI Average

Test Area 2 3500 PSI Average

1.5’ 1