Statement_of_Work.pdf

Restoration of Stone Masonry August 26, 2019 US Forest Service, Grey Towers National Historic Site

Restoration of the Stone Masonry

Grey Towers National Historic Site Milford, Pennsylvania

Pike County, Pennsylvania.

Project Brief

The work to be performed in this contract is to be executed on stone masonry features at Grey Towers National Historic Site which is located at 151 Grey Towers Drive, Milford PA, 18337.

Grey Towers Drive entrance is approximately a quarter mile west of the town of Milford PA on Old Owego Drive. The other entrance onto Old Owego Turnpike is approximately one mile east of Milford exist off interstate 84. GPS point for entrance drive is: 41-328482, -74.814573.

The major components to the scope of work include:

Documenting the existing bonding, rhythm, and patterns for the purpose of matching the mason’s craftsmanship when replicating their mason work.

Disassembly of the deteriorating masonry walls and features including the stone walls, coping stones and footings. This work will be identified on a provided site map and/or during the pre-bid site meeting.

Retain all stone for reuse in the new specified masonry work.

Create new subsurface footings where required for new masonry walls. These footings will be created using crushed stone footing design utilized in 2009 masonry restorative work, unless Forest Service Contracting Officer requires otherwise.

Restore the original historic appearance (bonding, rhythm, and patterns) of the stone structures and other masonry components of those structures, utilizing the COR approved mortar formulas in this project.

Install specific masonry details (i.e., coping stone) to the same placement and sequence as removed or as specified in any change.

Coordinate & sequence the work with the Forest Service for their installation of a new or additional work.

The project is one component in the restoration of the Grey Towers National Historic Site (GTNHS) which is designated a National Historic Landmark. All work will comply with the Secretary of the Interior’s “Standards for the Restoration of Historic Structures” which can be further explained by the Contracting Officer or the Contract’s specified COR/inspector. The contractor shall familiarize themselves with those “Standards” as they apply to the work required. Assure that the contractor’s employees and subcontractors have the knowledge and skills required in complying with these standards since they will be a requisite to performing the work properly. Please supply information with your bid that key staff have this experience. If further information is needed please ask the COR for further information.

SCOPE OF WORK:

Record (document by photos and field sketches) the appearance, bonding, and rhythm of the stonework of the walls and their component stone features which illustrates the historic construction. This information will be required to rebuild the masonry and is the responsibility of the contractor. During the demolition phase, disassemble the stonework in a manner that allows to further record the conditions that may have caused the deterioration or might effect the new work to be installed. Provide this information to the Forest Service CO$R/inspector.

Prevent further damage to the historic stone or other masonry features that will be retained.

Carefully disassemble the designated stonework and their features using hand tools or pre-approved power tools. The designated person from the Forest Service (COR/inspector) at Grey Towers NHS must provide approval for the use of machinery or jackhammers prior to use.

Disassemble the stonework (coping stone, rubble bluestone and sandstone) removing all deterioration which will include most of the specified walls and footings. Where new stonework is to be joined to the historic wall, the contractor should assure that the new work is joined/bonded to sound masonry, creating a mend with stone and mortar, creating a mechanical bond. If pertinent to this contact, retaining wall backer-work (loose laid stonework hidden behind the dressed face wall) will be required to retain earth fill by thickening the wall mass

Construct footing 3 ½ feet wide and 2 feet deep where none currently exist, or where deterioration was caused by lack of proper footing for the local frost zone, or undermining by tree root systems. New footings will be created using crushed, modified stone (2A) laid into a filter fabric wrap, then mechanically tamped firm and solid before closing the wrap.

Relay new work masonry units (walls, stone corners, coping stones) assuring a match to the original pattern & rhythm of the stonework with the prepared and approved test panel.

If in addition to the existing stone more material is necessary to complete the project the contractor will be responsible to purchase matching stone. The dressed coping stone and walls stones are to match (or as near as quarrying operations allow) the existing face stones in color, quality, texture, and dressing technique. All of these stones are hand split with a “pitched rock face” finish. Pennsylvania bluestones are all natural cleft with pitched edges. This will be necessary at least for the coping stones but in some instances in the stone walls. The new material that will require “dressing” will be ordered appropriately sized to allow for “pitching” the face to match the “rock-faced” appearance.

In areas where stone will not be re-laid but re-pointing is necessary, deeply re-point the stone walls (1” minimum) where mortar is missing or has been removed during the project. Finish the face of the mortar joint with the tooling detail approved by NPS in the test panel prepared by the contractor.

Prepare surface and re-lay coping stone on all piers and retaining walls. Pitch the surface to drain water toward the front of the walls & piers.

Clean and restore landscape to the previous appearance. Re-establish the gravel trail along the inside (south side) the stone boundary wall in the lower field.

Additional Notes:

• The scope of work is as follows: [Attached specifications are included to provide standard masonry practices & materials testing information] Create an exact matching mortar that will used to re-create the mortar joints. The following steps can be followed to accomplish this.

Take sample of mortar and create a mortar match in color, texture, appearance. The key to matching is in the color of sand selected.

The mortar formula will be between a type “M” & type “S” compressive strength mortar

(2500-1800 psi) The mix will be:

Unit = particular capacity, not weight) unit of measure (i.e., quart gallon)

1. 1 portion Portland cement. [White or gray Portland should both be considered in combination with the available aggregates (sands) trying to approximate the color of original mortar]

2. ¼ portion hydrated lime [Type “N” hydrated lime]

3. 3 - 4 of masonry sand

Pre-mixed bagged, mortar (sak-crete types) will NOT be acceptable. Variations in the proportions of bagged mixes are unreliable and consequently should not be used in historic preservation projects.]

(Note: The sand used in the construction of the masonry features was probably a local source.

A test panel will be created by the contractor prior to beginning work on site. This test panel will demonstrate the ability of the contractor’s masonry to recreate the appearance of the mortar and the tooling finished created when tooling the historic stonework.

• Clean all masonry tools and equipment, during day to day operations, in an area prepared by the contractor prior to the beginning of the project. This area should be an absorbent material piled in a confined space that will be removed off site at the end of the project.

• Any efflorescence that appears on the masonry as a result of the contractual work shall be removed the following year on the anniversary of the completed project site work.

DIRECTIONS ON PREPARING TEST PANELS

1. After the submission of bids, but prior to the beginning of work, the contractor will prepare a two foot square, “test panel”. This panel will exhibit mortar joints prepared to match the appearance of the original (extant) mortar joints that are in good condition on the exterior walls of the structure and the brick deck of the masonry stoops.

The test panel will be prepared to simulate the cured mortar joint color, texture, and tooled finish of the stone walls & piers. The contractor shall prepare this test panel using the appropriate aggregate type and color in combination with the specified proportions of hydrated lime and Portland cement, to create the original’s mortar joint’s appearance.

This approved test panel will, upon Forest Service acceptance, serve both the contractor and Contracting Officer (CO) as the reference point for the finish mortar joint appearance.