Item p-154 subbase course description 154 1




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PORT NOTE: This is a modified version of FAA Item P-154. At the end of this section are Construction Modifications denoting Port-specific changes. FAA and Port editing notes follow the text to which they refer.

For review: Use track changes when editing text. Turn off track changes when deleting FAA and Port editor’s notes. Cut and paste Construction Modifications to Engineer’s Design Report. Turn track changes back on and submit review documents in electronic and in hard copy to the Port with design edits showing.


For advertisement: Accept all changes. Submit to the Port in electronic and in hard copy.

ITEM P-154 SUBBASE COURSE

DESCRIPTION


154-1.1 This item shall consist of a subbase course composed of granular materials constructed on a prepared subgrade or underlying course in accordance with these specifications, and in conformity with the dimensions and typical cross section shown on the plans.
MATERIALS

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Recycled asphalt has been used in place of P-154 material. This is acceptable provided it is approved by the Airport District Office and no more than 50% is blended with new P-154 material. Excessive amounts, under heavy loads and heat, can settle. Although it can be compacted to a modified proctor it will bridge between coated particles and resist compactive effort. Recycled P-402 should not be used under any aircraft pavements since it is gap-graded, unless the virgin aggregate gradation is adjusted to meet the combined blend gradation.

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154-2.1 MATERIALS. The subbase material shall consist of hard durable particles or fragments of granular aggregates.  This material will be mixed or blended with fine sand, clay, stone dust, or other similar binding or filler materials produced from approved sources.  This mixture must be uniform and shall comply with the requirements of these specifications as to gradation soil constants, and shall be capable of being compacted into a dense and stable subbase.  The material shall be free from of clay, sod, grass, decayed vegetable matter, lumpsleaves, roots, organic debris, or excessive amounts of clay, and other objectionable or foreign substances.  Pit run material may be used, provided the material meets the requirements specified.
TABLE 1. GRADATION REQUIREMENTS


Sieve designation (square openings)

as per ASTM C 36 and ASTM D 422

Percentage by weight passing sieves
















3 inch (75.0 mm)

100




No. 10 (2.0 mm)

20 100




No. 40 (0.450 mm)

5 60

No. 200 (0.075 mm)

0 8



The portion of the material passing the No. 40 (0.450 mm) sieve shall have a liquid limit of not more than 25 and a plasticity index of not more than 6 when tested in accordance with ASTM D 4318.


The maximum amount of material finer than 0.02 mm in diameter shall be less than 3%.
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Include testing frequencies for the particle size distribution for preliminary and minimum of one per day during construction.

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PORT NOTE: The Port often uses Columbia River dredge sand. If that is what is desired, delete 2.1 above and replace with 2.1 below and Tables 1, 2 and 3 that follow.



154-2.1 MATERIALS. Subbase material shall be imported Columbia River dredged sand obtained from one of the following Port-tested and approved sources:
Glacier Northwest (Blue Lake Sand and Gravel)

20601 N.E. Marine Drive

Fairview, OR 97024
Morse Bros., Inc (Gresham Sand and Gravel)

1339 N.W. Eastwood Avenue

Gresham, OR 97030
Rinker Materials

5501 N.E. 223rd Avenue

Fairview, OR 97024
An alternate site may be utilized provided the Contractor submits documentation to the Port, prior to the preconstruction meeting, confirming that the proposed material will conform to the gradation requirements listed in Table 1, has been sampled and tested in accordance with the analytical methods listed in Table 2, and does not exceed the maximum concentration levels noted in Table 3. The analytical portion of the documentation shall indicate that the material has been sampled, evaluated, and tested by a Port-approved environmental consultant and/or testing laboratory, or pre-bid approved equal. Port-approved consultants include Hahn and Associates, Inc., Hart-Crowser, Inc., and URS Greiner. Port-approved testing laboratories include Columbia Analytical services, Inc. and North Creek Analytical, Inc.
TABLE 1. GRADATION REQUIREMENTS


Sieve Size

Percentage by Weight Passing Sieves

3/4 inch (19.0 mm)

3/8 inch (9.5 mm)

1/4 inch (6.35 mm)

No. 10 (2.0 mm)

No. 30 (0.6 mm)

No. 50 (0.3 mm)

No. 100 (0.15 mm)

No. 200 (0.07 mm)



100

95-100


80-100

60-98


25-90

10-60


2-15

0-6

The portion of material passing the No. 50 (0.3mm) sieve shall have a liquid limit of not more than 25 and a plasticity index of not more than 6 when tested in accordance with ASTM D 4318.
Sample and test material according to the analytical methods in Table 2:
TABLE 2. ANALYTICAL METHODS


Analysis


Method

Container
Size

Storage
Temperature

Maximum
Holding Time

Total Petroleum Hydrocarbons (TPH)

NWTPH-Dx

8-oz wide-mouth glass

4C

14 days

Polynuclear Aromatic Hydrocarbons (PAHs)

EPA 8270-SIM

8-oz wide-mouth glass

4C

Extract 14 days 40-day analysis

Polychlorinated Biphenyls (PCBs)/Organochlorine Pesticides

EPA 8081A/8082

4-oz wide mouth glass

4C

Extract 14 days 40-day analysis

Resource Conservation and Recovery Act (RCRA)
– 8 Metals

EPA 6010A/7471A

4-oz wide- mouth glass

4C

6 months
(Mercury 28 days)

The materials shall not exceed the following concentrations listed in Table 3 when tested according to the specified methods:


TABLE 3. MAXIMUM CONCENTRATION LEVELS

Analyte


Maximum Concentration Level
in mg//kg (ppm)

TPH as Diesel and Oil










Diesel

25

Oil

50







PAHs










Acenaphthene

3,700

Acenaphthylene

---

Anthracene

22,000

Benzo(a)anthracene

0.62

Benzo(a)pyrene

0.062

Benzo(b)fluoranthene

0.62

Benzo(g,h,i)perylene

---

Benzo(k)fluoranthene

6.2

Chrysene

62

Dibenzo(a,h)anthracene

0.062

Fluoranthene

2,300







Fluorene

2,600

Indeno(1,2,3-cd)pyrene

0.62

Naphthalene

56

Phenanthrene

---

Pyrene

2,300







PCBs/Organochlorine Pesticides










Aroclor 1016

3.9

Aroclor 1221

0.22

Aroclor 1232

0.22

Aroclor 1242

0.22

Aroclor 1248

0.22

Aroclor 1254

0.22

Aroclor 1260

0.22

Aldrin

0.029

alpha-BHC

0.09

beta-BHC

0.32

delta-BHC

---

gamma-BHC (Lindane)

0.44

alpha-Chlordane

---

Chlordane (tech)

1.6

Gamma-Chlordane

---

4,4’-DDD

2.4

4,4’-DDE

1.7

4,4’-DDT

1.7

Dieldrin

0.03

Endosulfan I

370

Endosulfan II

370

Endosulfan Sulfate

---

Endrin

18

Endrin Aldehyde

---

Endrin Ketone

---

Heptachlor

0.11

Heptachlor Epoxide

0.053

Methoxychlor

310

Toxaphene

0.44







RCRA 8 Metals










Arsenic

5.8

Cadmium

37

Chromium

210

Lead

400

Mercury

23

Selenium

390

Silver

390

During placement, the Port may elect to obtain samples of sand subbase to conduct material quality tests. Subbase material that fails to meet the Port standards shall be removed and replaced with acceptable material. Cost to remove and replace material will be paid for under the appropriate bid item unless the haul distance to the source of new material is 125 percent or greater than the distance to the original source, in which case the difference in haul distance will be paid for under the provisions for Change in the Work, as defined in the General Conditions.


CONSTRUCTION METHODS
154-3.1 GENERAL. The subbase course shall be placed where designated on the plans or as directed by the Port. The material shall be shaped and thoroughly compacted within the tolerances specified.
Granular subbases which, due to grain sizes or shapes, are not sufficiently stable to support without movement the construction equipment, shall be mechanically stabilized to the depth necessary to provide such stability as directed by the Port.  The mechanical stabilization shall principally include the addition of a fine grained medium to bind the particles of the subbase material sufficiently to furnish a bearing strength, so that the course will not deform under the traffic of the construction equipment.  The addition of the binding medium to the subbase material shall not increase the soil constants of that material above the limits specified.
154-3.2 OPERATION IN PITS.  All work involved in clearing and stripping pits and handling unsuitable material encountered shall be performed by the Contractor at his/her own expense.  The subbase material shall be obtained from pits or sources that have been approved.  The material in the pits shall be excavated and handled in such manner that a uniform and satisfactory product can be secured.
154-3.3 PREPARING UNDERLYING COURSE.  Before any subbase material is placed, the underlying course shall be prepared and conditioned as specified.  The course shall be checked and accepted by the Port before placing and spreading operations are started.
To protect the subgrade and to ensure proper drainage, the spreading of the subbase shall begin along the centerline of the pavement on a crowned section or on the high side of pavements with a one-way slope.
154-3.4 MATERIALS ACCEPTANCE IN EXISTING CONDITION.  When the entire subbase material is secured in a uniform and satisfactory condition and contains approximately the required moisture, such approved material may be moved directly to the spreading equipment for placing.  The material may be obtained from gravel pits, stockpiles, or may be produced from a crushing and screening plant with the proper blending.  The materials from these sources shall meet the requirements for gradation, quality, and consistency.  It is the intent of this section of the specifications to secure materials that will not require further mixing. The moisture content of the material shall be approximately that required to obtain maximum density. Any minor deficiency or excess of moisture may be corrected by surface sprinkling or by aeration. In such instances, some mixing or manipulation may be required, immediately preceding the rolling, to obtain the required moisture content. The final operation shall be blading or dragging, if necessary, to obtain a smooth uniform surface true to line and grade.

PORT NOTE: If using sand, add the following to 3.4: All existing sand materials encountered during excavation may be utilized for subbase provided materials meet requirements established by the Port for gradation, quality, and consistency.


154-3.5 PLANT MIXING.  When materials from several sources are to be blended and mixed, the subbase material shall be processed in a central or travel mixing plant.  The subbase material, together with any blended material, shall be thoroughly mixed with the required amount of water.  After the mixing is complete, the material shall be transported to and spread on the underlying course without undue loss of the moisture content.
154-3.5.1 MIXED IN PLACE.  When materials from different sources are to be proportioned and mixed or blended in place, the relative proportions of the components of the mixture shall be as designated by the Port.
The subbase material shall be deposited and spread evenly to a uniform thickness and width.  Then the binder, filler or other material shall be deposited and spread evenly over the first layer.  There shall be as many layers of materials added as the Port may direct to obtain the required subbase mixture.
When the required amount of materials have been placed, they shall be thoroughly mixed and blended by means of graders, discs, harrows, rotary tillers, supplemented by other suitable equipment if necessary.  The mixing shall continue until the mixture is uniform throughout.  Areas of segregated material shall be corrected by the addition of binder or filler material and by thorough remixing.  Water in the amount and as directed by the Port shall be uniformly applied prior to and during the mixing operations, if necessary, to maintain the material at its required moisture content.  When the mixing and blending has been completed, the material shall be spread in a uniform layer which, when compacted, will meet the requirements of thickness and typical cross section.

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If mixing in place will not provide a consistent subbase material, delete paragraph 154-3.5.1.

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154-3.6 GENERAL METHODS FOR PLACING. The subbase course shall be constructed in layers.  Any layer shall be not less than 3 inches (75 mm) nor more than 8 inches (200 mm) of compacted thickness.  The subbase material shall be deposited and spread evenly to a uniform thickness and width. The material, as spread, shall be of uniform gradation with no pockets of fine or coarse materials. The subbase, unless otherwise permitted by the Port, shall not be spread more than 2,000 square yards (1,700 square meters) in advance of the rolling. Any necessary sprinkling shall be kept within this limit. No material shall be placed in snow or on a soft, muddy, or frozen course.

PORT NOTE: When sand is used, replace first two sentences of 154-3.6 with the following: The subbase course shall be constructed in two or more approximately equal layers, each at least 12 inches (300 mm) and no more than 24 inches (600mm) thick, unless otherwise approved by the Port.


When more than one layer is required, the construction procedure described herein shall apply similarly to each layer.
During the placing and spreading, sufficient caution shall be exercised to prevent the incorporation of subgrade, shoulder, or foreign material in the subbase course mixture.
154-3.7 FINISHING AND COMPACTING. After spreading or mixing, the subbase material shall be thoroughly compacted by rolling and sprinkling, when necessary.  Sufficient rollers shall be furnished to adequately handle the rate of placing and spreading of the subbase course.
The field density of the compacted material shall be at least 100 percent of the maximum density of laboratory specimens prepared from samples of the subbase material delivered to the jobsite.  The laboratory specimens shall be compacted and tested in accordance with [ ].  The in place field density shall be determined in accordance with ASTM D 1556 or ASTM D 6938.  The moisture content of the material at the start of compaction shall not be below nor more than 2 percentage points above the optimum moisture content. All testing shall be done by a laboratory hired by the contractorPort. Density test results shall be furnished daily to the Engineer for acceptance determination.

PORT NOTE: When sand is used, replace the first two sentences of the above paragraph with the following: Field density of the compacted material shall be at least 100 percent for the top 12 inches (300 mm) and the remaining to 95 percent of the maximum density of laboratory specimens prepared from samples of the subbase material delivered to the jobsite. The laboratory specimens shall be compacted and tested in accordance with ASTM D 1557.



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The Engineer shall specify ASTM D 698 for areas designated for aircraft with gross weights of 60,000 pounds (27 200 kg) or less and ASTM D 1557 for areas designated for aircraft with gross weights greater than 60,000 pounds (27 200 kg).

Include testing frequencies per square yard or cubic yard for density acceptance tests and moisture contents per lift of subbase course.

AASHTO T99 or T-180 (Moisture-Density) should be specified for soils that are expected to have more than 30% retained on the 3/4-inch sieve. The moisture-density relationship test procedures ASTM D 698 and D1557 are not applicable for materials with greater than 30 retained on the 3/4-inch sieve. A replacement procedure (ASTM D 4718) for the coarse material (greater than 3/4-inch) is used with ASTM methods but only until up to 30 percent is retained. Maximum density testing (ASTM D 4253) may be used but it also limits the material retained on the 1-1/2-inch sieve to 30 percent. The AASHTO T-99 and T-180 are similar to ASTM D 698 and D 1557, except they do not limit the replacement of the coarse material.

Material meeting the requirements of Item P-154 may be free-draining which may prevent the material from retaining sufficient moisture to meet the moisture at compaction requirements of this paragraph. If this situation occurs during field operations, minimum moisture content should be established for placement of the material.

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When nuclear density gages are to be used for density determination, testing shall be in accordance with Section Item GP-120. The calibration checks of both the density and moisture gages shall be made at the beginning of a job and at intervals as required to maintain consistency and as determined by the Port.
The course shall not be rolled when the underlying course is soft or yielding or when the rolling causes undulation in the subbase.  When the rolling develops irregularities that exceed 1/2 inch (1213 mm) when tested with a 16 foot (4.8 m) straightedge, the irregular surface shall be loosened and then refilled with the same kind of material as that used in constructing the course and again rolled as required above.
Along places inaccessible to rollers, the subbase material shall be tamped thoroughly with mechanical or hand tampers.
Sprinkling during rolling, if necessary, shall be in the amount and by equipment approved by the Port. Water shall not be added in such a manner or quantity that free water will reach the underlying layer and cause it to become soft.
154-3.8 SURFACE TEST.  After the course is completely compacted, the surface shall be tested for smoothness and accuracy of grade and crown; any portion found to lack the required smoothness or to fail in accuracy of grade or crown shall be scarified, reshaped, recompacted, and otherwise manipulated as the Port may direct until the required smoothness and accuracy reobtained. The finished surface shall not vary more than 1/2 inch (1213 mm) when tested with a Contractor-furnished 16 foot (4.8 m) straightedge applied parallel with, and at right angles to, the centerline. The finished surface shall be within 0.04 foot (12 mm) of specified grade.
154-3.9 THICKNESS. The Port uses survey to determine thickness of the completed subbase course. the thickness shall be determined by depth tests or sample holes taken at intervals so each test shall represent no more than 500 square yards (420 square meters).  When the deficiency in thickness is more than 1/2 inch (12 mm), the Contractor shall correct such areas by scarifying, adding satisfactory mixture, rolling, sprinkling, reshaping, and finishing in accordance with these specifications.  The Contractor shall replace at his/her expense the subbase material where borings are taken for test purposes.

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The use of survey for thickness determination is permitted.

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154-3.10 PROTECTION. Work on subbase course shall not be conducted during freezing temperature nor when the subgrade is wet.  When the subbase material contains frozen material or when the underlying course is frozen, the construction shall be stopped.
154-3.11 MAINTENANCE. Following the final shaping of the material, the subbase shall be maintained throughout its entire length by the use of standard motor graders and rollers until, in the judgment of the Port, the subbase meets all requirements and is acceptable for the construction of the next course.
METHOD OF MEASUREMENT
154-4.1 SUBBASE. The quantity of subbase material shall be measured in final position to the nearest 0.01 foot (3 mm) and computed by means of the composite method.  The resulting volume is that bound by the original ground line established by field cross sections and the final theoretical pay line established by the final subbase surface indicated on the plans, subject to verification by the Port.  Subbase materials shall not be included in any other quantities.The yardage of subbase course to be paid for shall be the number of cubic yards (cubic meters) of subbase course material placed, compacted, and accepted in the completed course.  The quantity of subbase course material shall be measured in final position based upon depth tests or cores taken as directed by the Engineer, or at the rate of 1 depth test for each 500 square yards (420 square meters) of subbase course, or by means of average end areas on the complete work computed from elevations to the nearest 0.01 foot (3 mm).  On individual depth measurements, thicknesses more than 1/2 inch (12 mm) in excess of that shown on the plans shall be considered as the specified thickness plus 1/2 inch (12 mm) in computing the yardage for payment.  Subbase materials shall not be included in any other excavation quantities.
BASIS OF PAYMENT
154-5.1 SUBBASE.  Payment shall be made at the contract unit price per cubic yard (cubic meter) for subbase course. The quantity of subbase to be paid for shall be the number of cubic yards of approved material imported, placed, compacted, and accepted. Payment will be made at the contract unit price per cubic yard for imported subbase. No payment will be made for existing sand or aggregate material reused as subbase; however, the processing (grading and compacting) of reused sand or aggregate material will be paid for at one-third the amount paid for new imported sand subbase. This price will be full compensation for furnishing all materials; for all preparation, hauling, and placing of these materials; and for all labor, equipment, tools, and incidentals necessary to complete the item.
Payment will be made under:
Item P 154 5.1 Subbase Course—per cubic yard (cubic meter)
TESTING REQUIREMENTS
ASTM C 136 Sieve or Screen Analysis of Fine and Coarse Aggregates
ASTM D 1556422 Particle Size Analysis Density of SoilsSoil In-Place by the Sand-Cone Method
ASTM D 1557 698 Moisture -Density Relations of Soils and Soil -Aggregate Mixtures Using 10-pound (4.5.5 lb (2.49 kg) Rammer and 12 in (305 mm18-inch (45 cm) Drop
ASTM D 29226938 Density of Soil in and Soil-Aggregate In-Place by the Nuclear Density Method Methods

ASTM D 4318 Liquid Limit, Plastic Limit, and Plasticity Index of Soils


END OF ITEM P-154

CONSTRUCTION MODIFICATIONS

154-2.1 Materials (Only if requiring Columbia River dredged sand)
Modification: Requires the use of imported Columbia River dredged sand obtained from one of 3 designated sources pre-approved by the Port. It also allows a supplier to have his source of this material approved prior to the pre-construction meeting.
Justification: The vast majority of structural fill placed at PDX is Columbia River dredged sand. Because of the proximity of the river to the airport this is a relatively available material. This one-sized material (gradation defined by its name) maintains good structural capabilities through a wide range of load conditions, readily compacts with water and vibratory equipment, has excellent drainage properties, and is relatively inexpensive.
Although the Port wants to use dredged sand and other similar materials, it has been forced to adopt a policy regulating the materials imported onto its property. The Port found that many times imported materials do not meet current environmental standards – i.e., some of the dredged sands encountered have been found to contain high levels of arsenic and other types of heavy metals. The suppliers listed have had their materials tested and meet Port environmental quality requirements.
154-3.7 Finishing and Compacting– Northwest Mountain Region Addition to Second Paragraph
Modification: Deleted the requirement for all testing to be performed by a contractor-hired laboratory. All testing will be accomplished by a Port-supplied independent testing firm.
Justification: Several times in recent years the Port has attempted to rely on contractor-supplied testing results. These attempts have met with limited success. The Port believes that, based on past experiences, the risks are too great, especially when working on the runway, to trust testing to the contractor. The little that the Port may save on testing can easily be overshadowed should a conflict arise. The Port has experienced this situation (conflict over testing results) and did not fare well in the legal system.
154-3.8 Surface Tests
Modification: Added a requirement that the finished surface be within 0.04 feet (12 mm) of design grade.
Justification: The Port believes that by maintaining control of the elevation of each layer it will have better control of the final surface.
154-5.1 Basis of Payment
Modification: Added a method of paying for the processing of salvaged sand subbase or aggregate base material being reused as subbase while not paying for the material itself.
Justification: The Port continually looks at ways to reuse existing materials. The Port believes that such reuse is not only environmentally sound it also can be a cost saving to the project. The Port has been quite successful in this endeavor and encourages the contractor to participate by offering a way of paying for the work involved to reuse these materials.




4/16/16

SUBBASE COURSE



P-154-





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