Installation Specifications

1. Clearing

Where the lines are to be constructed in wooded areas, permanent easements shall be fully cleared. Cleared materials shall be disposed of off of the construction site. Disposal shall be made in accordance with all local and state laws. Trees cut down on the construction site will be hauled away from the site for proper disposal. Stumps of all trees cut down outside of the excavation area shall be removed. Ground surfaces shall be graded so as to promote proper drainage and allow mowing by vehicular equipment.


2. Site Grading

a. All rough grading shall be completed prior to the installation of the sewers and appurtenances.


3. Earthwork

 

3a. Explosives and Blasting

a. Explosives for blasting shall be stored, handled, and used in accordance with the North Carolina Department of Transportation Standard Specifications - latest revision, all local regulations, and practices outlined in the "Blaster's Handbook" published by E.I. DuPont de Nemours and Company, Inc. Blasting shall be conducted so as not to endanger persons or property, and shall be covered or otherwise satisfactorily confined. The blaster shall be responsible for, and shall make good, any damage of whatever nature caused by blasting or accidental explosions.

3b. Removal of Water

a. The bottom of all excavations shall be free from water when pipe is laid in the excavation, when concrete is placed and until work is carried above the groundwater level and is safe from flotation.

b. If any of the subgrade or underlying materials is disturbed by movement of groundwater, surface water, or any other reason, it shall be replaced with crushed stone or gravel.

 


4. Clean-Up of Site

a. At the completion of the work, all debris and excess construction materials shall be removed and the right-of-way shall be left clean and presentable.

5. Materials

a. Select Backfill

a1. Select backfill material shall contain no man-made or organic material or clay pockets and shall be free of rocks, clods, or other materials larger than 2 inches in nominal diameter. Materials from on-site excavations may be used for select backfill provided they meet the specified requirements and contain optimum moisture content for proper compaction. Water saturated material shall not be used as select material. If sufficient on-site select backfill material is not available, acceptable material from an off-site borrow area shall be secured.

b. Backfill

b1. Backfill shall be free of all organic materials and shall not contain any rocks larger than 4 inches in diameter, or be in a water saturated condition.

c. Crushed Stone or Screened Gravel

c1. Crushed stone or screened gravel shall meet the requirements of the North Carolina Department of Transportation Standard Specifications latest revision.

c2. Crushed stone or screened gravel shall conform to standard size No. 5. Any rock excavated on site which meets this gradation may be used. Specifically the stone shall meet the following gradation:

Sieve Size

Percentage Dry Weight
Passing Designated Sieve Size

1-1/2 inch

1 inch

3/4 inch

1/2 inch

3/8 inch

No. 200

100
90-100
20-55
0-10
0-5
0-0.6

d. Pipe Bedding

d.1 All material used for pipe bedding shall conform to North Carolina Department of Transportation Standard Specification latest revision for standard size 67 material. Any rock, run- of-bank sand, or gravel excavated on site which meets the following gradation may be used.

Sieve Size

Percentage Dry Weight

Passing Designated Sieve Size

1 inch

3/4 inch

3/8 inch

No. 4

No. 8

No. 200

100

90-100

20-35

0-10

0-5

0-0.6

e. Riprap

e.1 The stone for riprap shall consist of field stone or rough unhewn quarry stone. The stone shall be sound, tough, dense, and resistant to the action of air and water. The riprap shall be Class I as specified in the NCDOT Standard Specifications. The stone shall vary in weight from 5 to 200 pounds. At least 30 percent of the total weight of the riprap shall be in individual pieces weighing a minimum of 60 pounds each. Not more than 10 percent Riprap total weight of the riprap may be in individual pieces weighing less than each.

e.2 During placing, the stone shall be graded so that the smaller stones are uniformly distributed through the mass. The stone may be placed by mechanical methods, augmented by hand placing where necessary. The placed riprap shall form, a properly graded, dense, neat layer of stone. The placed riprap shall have a minimum depth of 12 inches.


6. Excavation

a. General

a.1 All excavation shall be made in such a manner, and to such widths, as will give ample room for properly constructing and inspecting the structures they are to contain, and for such sheeting, timbering, pumping, and drainage as may be required within the limits shown in Standard STD-2.

a.2 Except where otherwise specified, excavation slopes shall be flat enough to avoid slides that will cause disturbance of the subgrade, or damage to adjacent areas. Intercept and collect surface runoff both at the top and bottom of cut slopes.

a.3 All excess excavated material and all excavated material which is unsuitable shall be removed from the site and replaced with suitable material.


b. Sheeting and Bracing

b.1 Place and maintain such sheeting and bracing as may be required to support the sides of the excavation, or to protect pipes and structures from possible damage, and to provide safe working conditions. The Contractor shall be responsible for the adequacy of all sheeting and bracing used, and for all damage resulting from sheeting and bracing failure or from placing, maintaining, and removing it. All sheeting and bracing shall be removed upon completion of the work. The County may permit sheeting to be left in place at the request and expense of others for the purpose of preventing injury to structures or property. Any sheeting or bracing left in place shall be cut off at least 2-feet below the finished ground surface.


c. Rock Excavation

c.1 All rock encountered within the limits of excavation shall be excavated. Rock shall be excavated so that generally there will be a clear space of at least 12-inches from the outside barrel of the pipe to the side of the trench. Isolated points of rock shall not come nearer than 6-inches to the pipe. At the trench bottom, the rock shall not come nearer than 6-inches to the pipe. In addition, sufficient rock shall be removed at joints to facilitate proper installation. Rock shall be fully removed at least 15-feet in advance of the laying of pipe.


d. Protection of Subgrade for all Excavations

d.1 To minimize the disturbance of the bearing materials and provide a firm foundation:

(a) Excavation shall be carried out below subgrade in limited areas, should disturbed soil or material with natural low bearing capacity be encountered. Stabilizing of these areas shall be done with select backfill or coarse aggregate as required. Soils disturbed through the operations shall be excavated and replaced with select backfill or coarse aggregate, as required.

(b) Provide positive protection against penetration of frost into materials below the bearing level during work in winter months.


riprap 0px; MARGIN-BOTTOM: 0px">7. Backfilling

a. Backfill shall be placed in maximum 8-inch lifts and compacted  to 95 percent of Standard Proctor AASHTO-T99 density, excepting backfill under structures,Riprap shall be compacted  of Standard Proctor Density. Backfill in the roadways shall be tamped to NCDOT requirement.

b. Pipe trenches shall be backfilled as soon as possible after pipe installations.

c. Where sheeting is used, use all reasonable measures to prevent the loss of support of the pipe or backfill when the sheeting is removed. If significant volumes of soil cannot be prevented from clinging to the extracted sheets, the voids shall be continuously backfilled as rapidly as possible. Thereafter limit the depth below subgrade that sheeting will be driven in similar soil conditions or employ other appropriate means to prevent a loss of pipe support. Sheeting embedded in granular fill or backfill materials shall be left in place.


8. Pipe Laying

a. Pipe laying shall in all instances be accomplished in a workman- like manner laid true to line and grade with bell ends facing (up-grade) in the direction of laying. The various pipes shall be handled, bell-up and laid in accordance with the manufacturer's requirements and good engineering practices.


9. Pipe Bedding

a. Shaped Bottom Bedding (STD-1): Shall be so the pipe bears uniformly upon undisturbed native earth. Soil is then back-filled and tamped by hand around the pipe (and completely under the pipe haunches) in uniform layers not exceeding six (6) inches in depth to 1'-0" above the top of pipe.

Each 6" layer shall then be placed, then carefully (so as not to disturb or damage the pipe) and uniformly tamped, eliminating the possibility of lateral movement.

b. Type II - Granular Material Embedment (STD-3): Shall be when the trench bottom is undercut a minimum of six (6) inches below the pipe barrel grade and filed with an approved stone as shown in the standard details.

c. Type III - Granular Material Embedment (STD-4): Shall be when the trench bottom is undercut a minimum of six (6) inches below the pipe barrel grade and filled with an approved stone to an elevation such that the pipe will be completely and uniformly bedded.

d. Concrete Encasement and Cradles (STD-5): Shall be as shown in the standard details.


10.Installation Limitations

a. The following are limitations and bedding requirements for supportive strength and shall be adhered to at all times:

 

(a) 6- & 8-Inch Pipe: Installation of 8-inch or PVC pipe with more than fourteen (14) feet of cover use Type II, Granular Embedment.

(b) 10-Inch and 12-Inch Pipe: Installation of 10-inch and 12-inch PVC pipe with more than twelve (12) feet of cover, use Type II, Granular Embedment.

(c) Ductile Iron Pipe: Installation of Ductile Iron Pipe with more than twenty (20) feet of cover use Type II - Granular Embedment. More than thirty (30) feet of cover use Type III Granular Embedment. This is regardless of ground water and/or soil conditions.

b. In areas having 3.00 feet and less or 18.00 feet and more of cover, use Ductile Iron Pipe.


11. Portland Cement Concrete

a. Acceptance of Concrete: The County shall require all and as many tests as he deems necessary to insure the concrete acceptability. The cost of the test shall be at the suppliers or contractors expense.

b. Depositing: Concrete will not be used if it cannot be placed within ninety (90) minutes of the dispatch time. Concrete shall be deposited in such a manner so as to prevent contamination by foreign material and segregation due to rehandling or flowing. Segregated concrete and/or concrete consisting of foreign material will not be used. Depositing will not be done when temperature has not exceeded 35 degrees Fahrenheit and ring by 10:00 A.M. Concreting shall cease when the descending air temperature rise falls below 40 degrees Fahrenheit. It shall not resume until the ascending air temperature rises to 35 degrees Fahrenheit. All concrete shall be kept from freezing. Frozen concrete shall be replaced. Free fall shall not exceed 3 per case.

c. Forms: Forms may be made of wood, plywood, metal, or any other suitable material. Forms shall be mortar tight, of material strong enough to resist noticeable deflection or bulging between supports, and the interior dimensions of the forms shall be such that the finished concrete shall be of the proper form and dimensions. The design of the forms shall take into account the effect of vibration of concrete as it is placed and also the rate of speed at which the forms will be filled.

d. Mechanical vibrators, of an approved type, and continuous spading and/or rodding of concrete shall be used to produce proper contact of concrete with forms and reinforcing steel in piers and with forms and pipe in monolithic inverts insuring a compact, dense and impervious artificial stone of uniform texture.

e. Curing: All concrete shall be cured by one of the following methods:

 

e.1 Forms left in place for a period of seven (7) days. Exposed concrete shall be moist cured.

e.2 Moist curing performed when forms are removed before seven (7) days. All construction joints shall be moist cured.

e.3 Curing compound used immediately after forms are removed and all surface water has disappeared.

f. Finishing: The structure shall have a uniform and textured surface. All form marks exposed to view shall be rubbed off with a stone.


12. Testing

a. Testing is required on all lines and shall be done in the presence of the County or his representative. A minimum of 48 hours notice shall be given to the County before testing begins unless other schedules can arranged. All testing and disinfection shall be completed prior to connection to any existing line.

b. Sewer Line Testing (Shall be tested either by Water Testing or Air Testing)

b.1 Water Testing

  1. Water testing shall be either the infiltration or exfiltration type as specified herein.
  2. Infiltration – This testing method will only be allowed when it can be shown that the hydrostatic head outside the pipe is a minimum of 4 feet above the crown of the pipe for the entire length of the pipe being tested. If allowed, the test will be made by measuring the infiltration flow of water over an approved measuring weir set up in the invert of the sewer a known distance from a temporary bulkhead or limiting point of infiltration. If the sewer or sewers have been pumped out, no test shall be started until normal infiltration conditions are established in the line to be tested.

The quantity of the infiltration or leakage for any section of sewer shall not exceed 100 gallons per inch diameter per 24 hours per mile of sewer. The length of connections tributary to the sewer shall be included in determining the length of sewer under test.

Sewer lines which cross streams, large drainage ditches, etc., shall be tested and shall show a zero infiltration. If any infiltration is present, the line shall be either repaired or replaced and retested.

  1. Exfiltration – This testing method shall be used if the infiltration test cannot be used. This testing method cannot be used if the water table is to the top of the pipe at any point along the tested line. The sewer shall be tested for leakage by bulkheading the sewer at the manhole at the lower end of the section being tested and filling the sewer with water until it is 4 feet above the crown of the sewer or to the top of the upstream manhole whichever is lesser. Leakage will be the measured amount of water added to maintain the water at the starting level. Tests will be conducted for a minimum of 4 hours with readings at 30 minute intervals.

The quantity of the infiltration or leakage for any section of sewer shall not exceed 100 gallons per inch diameter per 24 hours per mile of sewer. The length of connections tributary to the sewer shall be included in determining the length of sewer under test.

Sewer lines which cross streams, large drainage ditches, etc., shall be tested and shall show a zero infiltration. If any infiltration is present, the line shall be either repaired or replaced and retested.

b.2 Air Test

 

(a) A low pressure air test shall be used to determine accept- ability of completed work. The Contractor shall furnish men, equipment and materials necessary to conduct the test. The Contractor shall perform the air test in the presence of the Engineer and County. The air test shall conform to UNI- B-6-79 or latest revision.

(b) All air used shall pass through a single control panel. Individual air hoses shall be used from control panel to pneumatic plugs, from control panel to sealed line for introducing low pressure air, and from sealed line to control panel for continually monitoring the air pressure rise in the sealed line. All monitoring gauges shall be subject to calibration as deemed necessary.

(c) Pneumatic plugs shall have a sealing length equal to or greater than the diameter of the pipe tested. The plugs shall resist internal test pressures without requiring external bracing or blocking. Plugs shall be tested prior to installation in the pipe run. A length of pipe shall be sealed at both ends with the plugs to be used in the sewer test. Air shall be introduced into the plugs to 25 psig. The sealed pipe shall then be pressurized to 5 psig. The plugs shall withstand this pressure without bracing or movement.

(d) The air test shall be performed when the sewer is complete with all structures in place, the trench backfilled and the lines clean and free of all debris.

(e) The test shall be performed on a reach-by-reach basis. Test plugs shall be placed in the line at each manhole, secure to the manhole to prevent movement, and inflated to 25 psi.In low-lying or poorly drained areas, the groundwater level shall be determined by the Contractor by a method acceptable to the Engineer. Low pressure air shall be introduced into the sealed line until the internal pressure reaches 4 psi plus water pressure from pressure from groundwater as determined by the Engineer. Low pressure air shall be introduced into the sealed line until the internal pressure reaches 4 psi plus water pressure from groundwater as determined by the Engineer. The air pressure shall then be allowed to stabilize at no less than 3.5 psi plus water pressure from groundwater as determined by the Engineer. After the stabilization period, the air test shall commence. The line shall be deemed acceptable if the pressure drop does not exceed 1 psi in the time prescribed for the test in the accompanying table. If the line tested fails to meet these requirements the Contractor shall, at his own expense, determine the source of leakage and shall repair or replace all faulty material and correct the workmanship.

TABLE 2

MANDREL SPECIFICATIONS

Nominal Diameter (inches)


PVC-SDR 35 ASTM D3034 L (inches)


 

D (inches)


 

8

10

12

15

18


 

8

10

12

15

18


 

8

10

12

15

18

16.60


 

L=Mandrel Arm Length

D=I.D. of Proving Ring


c. Vacuum Testing of Manholes

All sanitary sewer manholes constructed by the Contractor shall be vacuum tested for leakage in the presence of a County Inspector. The vacuum test will not apply to any existing manholes that have been converted to drop manholes by the Contractor.

The Contractor shall furnish all labor, equipment, and any appurtenant items necessary to satisfactorily perform the vacuum test. All testing equipment shall be approved for vacuum testing manholes.

Each manhole shall be tested after assembly and unless directed otherwise by the County prior to backfilling.

All lifting holes shall be plugged with an approved non-shrink grout.

All pipes entering the manhole shall be plugged. The contractor shall securely brace the plugs in order to keep them from being drawn into the manhole.

The test head shall be placed at the inside of the top of the cone section of the manhole and the seal inflated in accordance with the manufacturer's recommendations.

A vacuum of 10-inches of mercury shall be drawn and the vacuum pump shut off. With the valves closed, the time the vacuum to drop to

9-inches of mercury shall not be less than that shown in the table below.

       
       
       

       Rockingham County North Carolina
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      Rockingham County Government
      371 NC Hwy 65
      Reidsville NC 27320
      Phone: 336.342.8100
      Fax: 336.342.8105
       
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