Fort Pitt Park Improvements GMI Project No. 25012 Pittsburgh, Allegheny County, PA Page 1

TECHNICAL SPECIFICATIONS – MINE STABILIZATION

A. General

1. Contractor’s Design Experience Requirements: The Contractor bidding for this work shall submit proof of at least five (5) projects successfully completed in the last three

(3) years involving mine stabilization. A brief description of each project with the

Owner’s name and current phone number shall be included.

2. Purpose: The purpose is to effectively stabilize the subsurface strata by grouting at mine level such that differential settlements and/or extensive subsidence due to the future collapse of mined-out coal seam in the area of the proposed construction is minimized or eliminated.

3. Scope of Work: The work covered by these Specifications consists of furnishing of all labor, plant, power equipment and performing all operations in connection with drilling grout holes, handling, transporting, storing, mixing, and injecting the grouting materi-als, care and disposal of drill cuttings, waste water and waste grout, clean-up of the area upon completion of the work and all such other operations as are incidental to grouting as specified herein. The purchase and delivery of materials to the site will be the re-sponsibility of the Contractor.

4. General Program: The tentative sequence for carrying out the work is broken down into the following consecutive phases:

a. Drill and case, if necessary, all grout holes at the location shown on the attached

Grout Hole Location Plan.

b. Grout the holes using the grouting method specified.

c. Complete all grout holes by grouting under adequate pressure the rock overburden existing between the roof of the mine and the top of bedrock.

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5. Site Cleanup and Restoration:

a. The contractor must leave the site in a safe condition after grouting. After complet-ing field operations, promptly remove all equipment mobilized and material brought to the site and restore the site to its original condition, filling any holes, ruts etc., as described in the following bullet b. The work will not be considered complete until site cleanup has been accepted by the owner.

b. Restore ground areas disturbed by personnel and equipment as nearly as possible to their original condition, or to the satisfaction of the owner. Prior to starting the work, submit repair methods for the project to the Owner. Exercise particular care in the restoration of shrubs, lawns, fences, walls, gardens, pavements, etc., which are damaged and ascertain that all property is restored to its original condition be-fore leaving the site. No additional payments will be made for restoration of the disturbed areas.

6. Limitations: The total extent of the grouting program will be determined by the condi-tions encountered during the drilling and grouting operations. All work shall be done by using grout pressure which would achieve the desired penetration. The grout mix(es) and grouting method to be used at each location may vary depending upon the condi-tions encountered at the level of the mined-out coal seam and in the overlying rock strata. The extent of the drilling and grouting required under any scheduled item is approximate and the Contractor shall be entitled to no extra compensation above the unit prices stated in his Proposal for this Specification by reason of increased or de-creased quantities of drilling or grouting work required, the time required, the quantities of clean-up or by reason of the location, depth, type or nature of the required stabiliza-tion operations.

B. Air Rotary Grout Hole Drilling

1. Drill Rig: The drill rig will be capable of drilling 6-inch diameter holes (without sam-ples or core) with cuttings removed by air and/or water to a maximum depth of about

140 feet. The rig shall be equipped with an air gauge to indicate decreases and increases in air pressure. Drilling mud may not be used during the drilling process.

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2. Grout Hole Depth: Each 6-inch diameter hole will be carried to a depth of two (2) feet below mine level and, if necessary, casing may be installed to ensure that the hole does not cave. The location of the grout holes shall be survey-located and staked by the

Contractor prior to drilling as their orientation to the proposed structures are of critical importance. Any deviation from the pattern will only be permitted with the approval of the Geotechnical Engineer. It will be the responsibility of the Contractor to replace any grout hole stakes destroyed prior to the drilling of a hole.

3. Protection of Holes: It shall be the responsibility of the Contractor to protect all drilled and cleaned-out holes from debris until the completion of the grouting of the hole. Any required cleaning of the grout hole after initial drilling and cleaning shall be at the Con-tractor's expense.

4. Metal Pipe and Fittings for Grouting: All metal pipe and fittings required for grouting shall be furnished, cut, threaded, fabricated and placed by the Contractor. The minimum inside diameter of the grout supply pipe is two and one-half inches (2.5”). The Con-tractor shall take all necessary precautions to prevent any pipe from becoming clogged or obstructed from any cause, and any pipe which becomes clogged shall be cleaned out in a manner satisfactory to the Geotechnical Engineer at the Contractor's expense.

5. Drilling Records: The Contractor shall keep, in the manner prescribed by and shall furnish to the Engineer, an accurate log of all grout holes including description of all materials of whatever character encountered in the drilling. The location of special fea-tures, such as mud seams, open cracks, soft or broken rocks, points of abnormal loss or gain of drill water or air occurring in any hole. The fact that an inspector will be present and keeping a record of the drilling shall not relieve the Contractor from the requirement for keeping an accurate log as described above to be delivered to the Geotechnical En-gineer on a daily basis.

6. Directives: The Geotechnical Engineer reserves the right to:

a. Direct the Contractor in the sequence of drilling or grouting; and also to make necessary adjustments in the design of mixes.

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b. Terminate the drilling of any of the holes at any level within the depth indicated on the schedule.

c. Order drilling of holes in addition to those shown on the Grout Hole Location Plan.

C. Exploratory Hole Drilling

1. Performance: The Contractor shall perform such exploratory drilling as may be re-quired to determine the effectiveness of the grouting operations after grouting. All ex-ploratory drilling shall be performed with rotary drilling equipment using coring type bits. Augering will be permitted in soil. The amount of and requirement for exploratory drilling will be directed by the Geotechnical Engineer. The NX or NQ holes will be required to be drilled to the bottom of the mine. The Contractor shall keep, in a manner satisfactory to the Engineer, and furnish to the Engineer an accurate Driller's Log of all exploratory holes drilled and shall not remove the core samples from the job site until directed to do so by the Engineer. Exploratory holes may be grouted under pressure, if conditions indicate, but in such cases the holes shall be grouted to full depth in one operation and the Contractor will not be required to remove the grout from part of the hole.

2. Payment: "Drilling of Exploratory Holes" will be measured for payment on the basis of the lineal feet of holes actually drilled in overburden or rock, as directed by the En-gineer. Payment for drilling exploratory holes will be made at the contract price per lineal foot for "Drilling NX or NQ Exploratory Holes".

D. Grout Plant

Prior to equipment mobilization, the Contractor shall submit a Site Plan for the proposed Batch

Plant location for review and approval. The grout plant shall provide all incidental equipment necessary to satisfy the design mix criteria and mixing process criteria, and transport of grout to injection holes.

1. Mixer: The mixer shall be equipped with a mechanically operated padded type agitator or equivalent and capable of mixing one hundred (100) cubic feet of grout per batch.

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2. Grout Pump: The grout pump shall be of the positive displacement variety with capacity of 250 GPM and up to 150 PSI pressure. The pump should be capable of handling a wide range of mix consistencies. Gauges must be present at the pump and point(s) of injection to allow for measurement of injection pressure.

3. Water Meter: A water meter shall be installed on the water line to permit accurate measurement of the quantity of water used in making the various mixes of grout.

4. Circulation: The arrangement of the grouting equipment shall be such as to provide continuous circulation of grout throughout the system, and permit accurate control of operation of a valve on the grout return line, regardless of how small the grout "take" may be. Adequate valves will be required at the pump and at each hole to insure control, by-pass and shut-off as required by the Engineer. The equipment and lines shall be prevented from becoming fouled by either constantly circulating the grout or periodi-cally flushing out the system with water. Flushing shall be done with the grout intake valve closed, the water supply valve open and the pump running at full speed.

5. Measurement: Facilities shall be provided to measure the proportions of water, flyash and cement required in the design mix.

E. Materials

1. Flyash: Flyash used shall conform to ASTM designation C 618-68T, but may not be required to meet the uniformity requirements of the specification.

a. Bulk or bagged flyash will be accepted, but is subject to the following conditions:

i) A bag of flyash containing 75 lbs. net will be considered equal to one (1) cubic foot.

ii) The flyash shall be stored so that it will not deteriorate from moisture, weather or other causes.

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iii) Bulk flyash shipment delivered in tank type trucks with a pneumatic un-loading system may be used if adequate storage facilities are provided. If bulk flyash shipments are delivered, the Contractor is to supply the Ge-otechnical Engineer with a list of equipment used for storage, handling, and disbursement of the flyash; such equipment must be approved by the

Geotechnical Engineer.

b. Sufficient quantity of flyash shall be stored at or near the site of the work to ensure that the grouting program will not be delayed.

2. Cement: The cement used shall conform to ASTM Designation C 150-56 for Portland

Cement. Bagged or bulk cement will be accepted.

a. Bagged cement shall be delivered in approved paper bags with name brand, type and manufacturer clearly marked thereon. Similar information shall be provided on shipping notices accompanying each bulk shipment.

b. A bag of cement shall contain 94 lbs. net and will be considered equal to one (1) cubic foot.

3. Sand: Sand for grout shall consist of hard, tough, durable, uncoated particles. It may be composed of natural sand, manufactured sand or a combination of natural and man-ufactured sand. The shape of the particles shall be generally rounded or cubical and shall not contain more than 15 percent of flat or elongated pieces having a maximum dimension in excess of five times the minimum dimension. The sand shall be well-graded from fine to coarse and the gradation shall conform to PennDOT's Bituminous

Concrete Sand Type B.

4. Water: The Contractor should define the source of water. The water used in the grout shall be fresh, clean and free from injurious amounts of sewage, oil, acid, alkali, salts or organic matter. Whenever the outside temperature is below 20°F, heat the water to be used in the ground to a temperature of 70°F to avoid freezing in the lines.

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5. Concrete: Concrete must correspond to Type C and must provide a minimum 1000 PSI

7-day strength. Whenever the outside temperature is below 20°F, heat the concrete to be pumped to a temperature of 40°F to avoid freezing in the lines.

F. General Conduct of Contractor's Operations

In addition to other provisions of this specifications, accomplish the specified work in accord-ance with the following:

1. The locations of injection holes are indicated. Depending upon conditions disclosed during the drilling and injection operations, additional holes may be required as deter-mined by the Geotechnical Engineer. Extend the holes through the rock strata to the base of the mined coal seam. If subsurface conditions, as revealed by the drilling oper-ation, indicate that injection to greater depths is necessary, drill holes to the necessary depth as determined by the Geotechnical Engineer.

2. Accomplish the specified work under continuous monitoring by the Geotechnical Engi-neer. Adjustments to grout mixes, pumping rates, zones and stages of grouting, and the sequence in which holes are drilled and injected will be determined in the field by the

Geotechnical Engineer.

3. The Contractor has the option of preparing injection materials at the site or delivering them ready-mixed. Attention is called to the fact that space at the work area may be limited and much of the available space may be needed for other work operations. Sub-mit layout sketches and descriptions of all proposed plant and equipment for approval.

4. Replace any injection hole that is lost or damaged due to mechanical failure of equip-ment or inadequacy of grout supply by another hole drilled by the Contractor at his own expense.

5. Conduct all work so that it is consistent and orderly not to adversely affect the other work. Periodic clean-up will be required when requested by the Geotechnical Engineer.

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Clean up and remove all waste immediately upon completion of drilling and injection operations.

6. The project site shall be delivered back to the Developer at the same condition as deliv-ered at rough grade. Pads and Batch Plant area shall be clean and free of any waste material. Contractor shall take precautions not to damage the pad or mix area with ex-cess water during mixing and cleanup.

7. The contractor shall have a Registered Surveyor to perform stakeout of injection holes and exploratory boring locations for approval by the Geotechnical Engineer.

G. General Grouting Procedures

1. Injection of grout mix into the holes involves, in general, either one or two stages. In some cases, depending on field conditions, more than two stages in a hole may be re-quired. The number of holes injected in two or more stages depends upon the extent of voids encountered and grout "take". Where large voids are encountered, injection may require two or more stages.

2. In no case will a subsequent stage of injection in a given hole be permitted to commence before a minimum period of 16 hours has elapsed since completion of the previous stage of grouting in that hole.

3. The water-solids ratio (by volume) of the grout may be varied as approved by the Ge-otechnical Engineer to meet the characteristics of each hole as revealed by the drilling and injection operations. Provide all admixtures with a minimum compressive strength of 300 PSI at 7 days.

4. If, in the opinion of the Geotechnical Engineer, the volume of grout being injected or placed into a hole is excessive, thicken the mixture. Quantities of such materials added to the grout mix will be determined by the Geotechnical Engineer. If the desired result is still not obtained, temporarily discontinue injection in the hole. Allow the injected

Pittsburgh, Allegheny County, PA Page 9 material to attain initial set (minimum 16 hours). Perform additional drilling and/or in-jection in an adjacent area as directed by the Geotechnical Engineer and injection oper-ations resumed later in the previous hole. Repeat such procedures until injection into the hole has been completed to the required final elevation. Admixtures used to accel-erate the setting of the grout must be approved by the Geotechnical Engineer.

5. Arrange the grouting equipment to permit accurate control of injection volume regard-less of how small the grout "take" may be. Prevent the equipment and lines from be-coming fouled by either constantly circulating the grout or periodically flushing out the system with water (not discharging into the grout hole). Flush with the grout intake valve closed, the water supply valve open and the pump running at full speed. Measure grout going to each hole, using equipment specified herein and procedures acceptable to the Geotechnical Engineer.

6. Prepare grout test cylinders for 20 percent of the batches placed in accordance with

PTM 611, except that the Geotechnical Engineer reserves the right to require preparation of test cylinders from any batch. Have cylinders tested and results reportedly promptly.

H. Specific Grouting Methods

1. Open Void in Mine Workings - Place grout supply pipe to bottom of boring and inject up to 10 cubic yards of grout to consolidate any mine gob on the bottom of void. Remove grout pipe and allow grout to set for 16 hours. Place concrete supply pipe to within three

(3) feet of bottom of hole and inject concrete through pipe under gravity flow while slowly raising pipe tip to top of void. Maintain the tip of the pipe in the fluid concrete.

Once the concrete level has reached the top of the void, discontinue concreting, raise pipe above concrete level in hole and allow concrete to set for 16 hours. Measure con-crete level in hole and if level has fallen below top of void, continue concrete injection.

If the level has not fallen below the top of the void, begin grouting operations as noted in Section H-7.

2. Partially Gob-Filled, Partially Open Void Mine Workings or Gob-Filled Mine Workings

With Void in Mine Roof - Place grout pipe on bottom of hole and inject 10 cubic yards of grout into the mine, discontinue grouting, remove pipe and allow grout to set for 16

Pittsburgh, Allegheny County, PA Page 10 hours. If grout level is determined to be above the void after 16 hours set, grout the hole as indicated in Section H-7. If the grout level is found to be below in the mine workings or mine roof noted during drilling, then place concrete as described in Section H-1 for open voids. However, where the remaining voids are less than two feet high, place fine aggregate in them.

3. Gob-Filled Mine Workings, Solid Coal or Mine Workings Not Found (Mine Roof or

Mine Floor) - Place the grout supply pipe on the bottom of the boring and inject grout mix. If the grout level rises quickly above the mine roof, grout the hole as per Section

H-7. However, if grout takes occur within 15 feet above the mine floor, then inject up to 10 cubic yards of grout into the boring, grouting discontinued, the grout pipe raised and the grout permitted to set for 16 hours. After set, conduct grouting as noted in Sec-tion H-7.

4. Non-Void Holes - Grout all non-void holes (with in-place coal or with existing fill) by inserting grout pipe into the hole and the hole is backfilled with a volume of ce-ment/flyash grout to about 3 feet above the roof of the mine.

5. Fractured Roof Overburden - After the mine level has been adequately grouted, place a packer at the top of rock and inject the grout mix under sufficient pressure into the rock fractures of the rock strata surrounding the hole as the grout supply pipe is withdrawn.

6. Interior Holes – Grout all interior holes by inserting grout supply pipe into the hole ex-tending to the base of the void. The grout mix is then pumped into the void until a firm contact with the roof of the voids occurs.

7. Remainder of the Hole (above the roof) - Once the mine workings have been grouted as required, then the remainder of the hole is to be grouted. To accomplish this, follow the following steps:

a. The grout pipe is always placed at the bottom of the boring and then slowly with-drawn while grout is injected into the hole. Maintain the tip of the injection pipe within the grout being placed.

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b. Free fall of grout or concrete through the injection stage is prohibited.

c. If large grout takes are not encountered, fill the boring to a point five to ten feet below top of rock. If large grout takes occur at a particular level in the hole, inject ten (10) cubic yards of grout at this level and if no significant rise in the grout level occurs, discontinue grouting operations, the pipe raised out of the grout and the grout permitted to set for 16 hours. Once the grout has set, lower the pipe to the bottom of the hole and grouting resumed, using a thickened grout mix. If large grout takes persist (five cubic yards or more), shovel sand into the hole dur-ing grouting. If, after placing ten (10) cubic feet of sand, no significant rise in the grout level occurs, discontinue grouting operations, the grout pipe removed from the hole and the grout permitted to sit for 16 hours. Once the grout has set, lower concrete pipe to within two to three feet of the bottom of the hole and inject fine aggregate concrete into the hole.

d. Once the grout level has risen approximately 20 feet above the large take level, stop the grouting operation, remove the pipe and permit the grout to set for 16 hours. Grouting operations can then be continued to within five to ten feet below top of rock, the pipe removed and the grout be permitted to set for 16 hours.

e. After the grout has set for 16 hours at a depth of five to ten feet below top of rock, measure the grout depth. If the grout level has not dropped more than ten feet below the previously recorded level, fill the hole with grout to the ground surface and remove the casing. If the grout level has dropped in excess of ten feet, place the pipe at the bottom of the hole and continue grouting to within five to ten feet below top of rock, the pipe removed and the grout be permitted to set for 16 hours.

Continue grouting operations as specified.

I. Grout Mix

1. Use grout composed of a mixture of cement, flyash, sand and water or other admixtures.

Provide a grout mix consisting of 3 parts flyash to 1 part cement by loose volume and

2.7 parts water. Provide a water-cement-flyash ratio with a minimum compressive strength of 300 PSI at 7 days. The water to cement and flyash ratio may subsequently

Pittsburgh, Allegheny County, PA Page 12 be altered at the site to meet the characteristics of each hole as revealed by the drilling and grouting operations. The alternative cement and flyash ratios must have a minimum compressive strength of 300 PSI at 7 days.

2. All grout mix designs to be used will be subject to review and approval of the Geotech-nical Engineer. Submit proposed designs, with sufficient test data to verify strength, well in advance of use. If testing during the injection operations indicates that expected strengths are not being achieved due to mixing proportions, modify the mixing propor-tions to achieve satisfactory strengths.

3. Admixtures to accelerate set time, or to maintain grout temperatures or for other pur-poses will be subject to the approval of the Geotechnical Engineer. There will be no extra payment for admixtures used by the Contractor for his own convenience.

4. Furnish to the Geotechnical Engineer three (3) copies of the records specified above within 24 hours after drilling or injection of each hole is completed or each batch of grout is injected.

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Bidding Sheet

BIDDING SHEET

(Specimen)

The bidder agrees to perform all work under the grouting contract described in the specifica-tions and shown on the attached Grout Hole Location Plan for the following lump sum and unit prices. The total lineage footage of drilling quoted in the Bidding Sheet is based on the assumption that the drilling will be performed from the existing ground elevation at the project site.

SCHEDULE OF PRICES

Description

Quantity Payment

Unit Total

Bid Price

Base Bid

One

L.S.

Demobilization shall include all cost with restoring the pads and batch plant area back to original state.

3. Drilling of 143 six-inch diameter grout injection boreholes, 2 feet into bedrock below the bottom of the

Pittsburgh Coal seam, average depth 35± feet/hole (5,000± total L.F.). Placement of PVC casing to the top of rock in all 143 holes, average depth 15± feet/hole (2,145± total L.F.). Average injection volume of grout per hole is estimated to be approximately 10± cubic yards (1,430± cu. yds). Performing two

(2) exploratory borings (NX or NQ2 size) approximately 70 L.F. to evaluate the effectiveness of grout-ing.

Item Unit Unit Price

• Drilling of Grout Hole: _____ L.F. $__________

• Casing: _____ L.F. $__________

• Grout In-Place: _____ C.Y. $__________

• Concrete In-Place: _____ C.Y. $__________

• Exploratory Boring: _____ L.F. $__________

** Any adjustment in the above-mentioned quantities will be made on the unit rates provided.

Grout Hole Location Plan

Item