308Cement Treated Courses

308.01 Description . This work consists of constructing one or more courses of a

mixture of cement, soil or soil aggregat e, and water in accordance with these specifications and in reasonably close conform ity with the lines, grades, and typical cross sections shown on the plans or established by the Engineer.

308.02 Materials .

308.02.1 Materials to be Treated . The materials to be treated shall consist of materials

in place or placed under this contract. 308.02.2--Water . Water shall conform to the requirements of Subsection 714.01.3.

308.02.3 Cement . Cement shall conform to the requirements of Section 701.

When bulk cement is used, the Contractor shall provide means suitable to the Engineer for applying. The Engineer shall weigh shipments at random for verification of bulk cement quantities. When bag cement is furnished, the bag shall bear the manufacturer's certified weight. Bags varying more than five percent from the certified weight will be rejected, and the average weight of bags in any shipment, determined by weighing 50 bags taken at random, shall not be less than the certified weight. Cement shall be stored and handled in closed, weatherproof containers until distribution to the section of road being processed. If storage bins are used, they shall be completely enclosed.

308.02.4 Curing Seals . Curing seal shall be Emulsified Asphalt, Grade EA-1, EPR-1,

AE-P, CSS-1, SS-1, CMS-2h, or MS-2h meeting the applicable requirements of Section 702.

308.02.5 Soil-Cement Design . The design of soil-cement co urses shall be performed by

the Central Laboratory.

308.03 Construction Requirements .

308.03.1 General . The intent of these specifications is to provide for a cement treated

course of designated thickness consisting of a uniform mixture of cement, soil or soil aggregate, and water; constructed at the requ ired moisture content to the required density; free of laminations, construction cracks, ridges, or loose material; and with a smooth, closely knit surface meeting the requir ements set out in Section 321. A course whose compacted thickness is designated to be more than eight inches, shall be constructed in two or more layers of ap proximately equal thickness. The maximum compacted thickness of any one laye r shall not exceed eight inches. Immediately prior to placement of a course to be cement tr eated on an in place cement treated course, the in place course shall be thoroughly moistened. Except as necessary to provide the required curing and maintenance of traffic, all equipment and traffic shall be kept off each completed cement treated course until it is thoroughly cured. Unless otherwise specified, the curing period shall be seven days exclusive of days during which the temperature falls below 35°F. Prior to joining a previous day's work, or work more than two hours old, a vertical construction joint, normal to the centerline of the roadbed, shall be made in the old work. The joint shall be moistened if dry. Additional processing shall not be started until the construction joint has been approved by the Engineer. When vertical longitudinal joints are specified or permitted, the joints shall be constructed parallel to the centerline by cutti ng into the existing edge for a sufficient distance to provide a vertical face for the dept h of the course. The material cut away may be disposed of by spreading in a thin layer on the adjacent lane to be constructed, or otherwise disposed of in a satisfactory manner. If dry, cut joints shall be moistened immediately in advance of placing fresh mixture adjacent to them. On multi-lane construction, the Contractor may construct temporary crossovers at locations approved by the Engineer between roadway lanes to facilitate construction operations. The crossovers shall be built, removed, the median restored to section, and all erosion control items completed in accordance with the re quirements of the specifications without extra cost to the State. The first section of each cement treated course constructed will serve as a test section. The length of the test section will be determined by the capability of the equipment provided to perform the work, but not less than 350 linear feet nor more than 500 linear feet for the designated width. The Engineer and the Contractor will evaluate results of the test section in relation to contract require ments. In case the Engineer determines the work is not satisfactory, the Contractor shall revise procedures and augment or replace equipment as necessary to assure work comp leted in accordance with the contract, and shall correct all deficient work at no additional cost to the State.

308.03.2 Equipment .

308.03.2 1--General . Equipment necessary for the proper prosecution of the work shall

be on the project and approved by the Engineer prior to its use. Approval of cement spreaders will be contingent upon their known or demonstrated ability to make distribution of cem ent within allowable tolerances. Watering equipment shall be pressurized, ha ve one or more spray bars with suitable nozzle openings, and have positive controls for applying varying quantities of water. Mixing shall be performed with multiple pass mixers, single pass mixers, traveling mixing plants, or central mixing plan ts, as specified in the contract. Mixing and scarifying equipment for the road mix methods shall be capable of positive depth control. Rollers shall be of sufficient number, type , size, and weight to accomplish the required compaction. Leakage of water, oil, grease, or other liq uids from equipment shall be immediately corrected, or the leaking equipment removed from the work and replaced with satisfactory equipment.

308.03.2 2--Multiple Pass Mixers. Multiple pass mixers shall be the rotary-type with sufficient tines and so constructed and oper able as to obtain by multiple passes uniform

mixture of the cement, soil-aggregate, and water for the full depth of the course. 308.03.2.3--Single Pass Mixers . Single pass mixers shall be the pugmill type so constructed and operable as to meter the re quired quantity of water through a pressurized spray and obtain by a single pass a uniform mixture of the cement, soil or soil-aggregate, and water for the full depth of the course.

308.03.2 4--Traveling Plant Mixers . Traveling mixing plants shall be either of the type

that will pulverize the material to be treated and mix it and cement with the proper quantity of water without picking the materials up from the roadway, or of the pugmill type that elevates the materials into a pugm ill for mixing. The plant shall be equipped with a device that will accurately control and measure the quantity of water used. Worn scarifying and mixing parts shall be replaced , and extra parts shall be available for replacements.

308.03.2 5--Central Plant Mixers . Central mixing plants shall be either the batch type

using revolving blade or rotary drum mixers or the continuous mixing type. The cement, soil or soil-aggregate, and water may be proportioned either by weight or by volume. There shall be means by which the Engineer can readily verify the proportions in each batch or the rate of flow for continuous mixing. The charge and mixing time in a batch mixer, or the rate of feed to a continuous mixer, shall be such as to obtain complete mixing of all the material. Dead areas in the mixer, in which the material does not move or is not sufficiently agitated, shall be corrected. The plant shall deliver a uniform mixture meeting all specified requirements.

308.03.3 Road Mix Method . When the road mix method is used, no hauling of

materials for a subsequent course will be permitted directly on a completed cement treated course. Placing of material for a higher course shall be accomplished as outlined in Subsection 321.03. Materials for a higher course shall be kept bladed down as it is placed, and hauled over with truck traffi c being distributed ove r its entire width. Where reconstruction is required, it shall be for the full depth and width of the deficient section. The adding of a thin layer or strip of cement treated material will not be permitted. All sections to be reconstructed later than the two-hour period allowed for initial compaction shall have additional cement. When reconstruction is to be performed within 48 hours after the initial application of cement, 50 percent of the original quantity of cement shall be added. When reconstruction is to be later than 48 hours after the initial application of cement, an engineering study will be made, and the Engineer will specify the additional quantity of cement to be added, or the Engineer may require the total removal of the deficient work. If removal is required, a course meeting the requirements of the contract shall be constructed with new materials. In all cases where reconstruction is performed by the addition of cement, the cement, in place materials, and water shall be thoroughly mixed, processed, compacted, and finished in accordance with the requirements of the contract. Where deficient work is removed, the removal and disposal shall be performed in a manner satisfactory to the Engineer, and all ma terials shall be replaced and a new course constructed in accordance with the requirements of the contract. The furnishing of all materials for and all reconstruction shall be performed by the Contractor at no additional cost to the State.

308.03.4 Central Plant Mix Method . When the central plant mix method is used,

material for a higher course may be hauled directly on a completed and properly cured cement treated course for the minimum dist ance necessary as referenced in Subsection

321.03 The Contractor shall be fully responsible for all damages to the course.

Prior to placement of a course processed by the plant mix method, the Contractor shall have made satisfactory provisions for completing the section to specified requirements. To comply with these requirements, the Cont ractor shall, if necessary, use material(s) specified for contiguous shoulder construction. The mixture shall be hauled to the roadway in trucks equipped with protective covers. The mixture shall be uniformly placed on a moistened foundation by full-width spreader, or partial-width spreaders working in echelo n and spaced close enough together to place the entire course in one operation. The el apsed time between the start of moist mixing and the start of compaction on the roadway shall not exceed 60 minutes. The elapsed time between placement of ceme nt treated material in adjacent lanes shall not exceed 30 minutes, except where longitudinal construction joints are specified, or when joints are permitted by the Engineer in case of emergency. In the latter case longitudinal joints conforming to the requirements of these specifications will be permitted only to allow placement of material in transit at the time of the emergency. The material shall be placed, shaped, and compacted so that the completed course will be uniform, smooth, and conform to all of the requirements specified. Dumping of the mixture in piles or windrows and spreading with a motor grader or similar equipment will not be permitted except where the Engineer determines that such spreading is reasonable, as in the case of small areas inaccessible to mechanical spreaders. In all cases where reconstruction is required, the deficient work shall be removed, disposed of, and replaced with materials meeti ng the requirements of these specifications. Reconstruction shall be for the full depth and width of the deficient section, except where the Engineer determines that partial reconstruction will be sufficient, the Engineer may authorize in writing that reconstruction may be made on the defined partial section in accordance with the provisions and requirements for reconstruction under Subsection

308.03.3 at no additional cost to the State.

308.03.5 Preparation of Grade . Prior to construction or reconstruction, the foundation

shall be prepared in accordance with the requirements of Section 321. The tolerance from design grade immediately prior to sp reading cement shall be minus one inch for design soils and plus or minus one-half inch for bases.

308.03.6 Preparation of Materials . Particles of aggregates larger than those passing a

three-inch sieve and deleterious substances, such as roots, sticks, grass turfs, or other vegetable matter shall be removed.

308.03.7 Application of Cement .

308.03.7 1--General . The percentages of cement shown on the plans are based on

preliminary soil investigation and are approxim ate. Before construction is started, the Department will make the necessary tests to determine the percentages of cement required. The quantity of cement spread on a section or added through a central plant shall not vary more than five percent of the quantity ordered. When the quantity spread is deficient by more than five percent, an additional application of cement shall be uniformly spread over the entire section to correct the defici ency prior to mixing operation. Cement, including that applied to correct deficiency, in excess of the allowable plus tolerance will be deducted from measured quantities. When the quantity of cement added through a central plant is deficient by more than the allowable tolerance, all mixtures produced with deficient cement will be considered unacceptable. When the quantity of cement added through a central plant is in excess of the allowable tolerance, the excess will be computed by the Engineer and deducted from measured quantities.

308.03.7 2--Weather Limitations . No cement or cement treated material shall be

applied or placed when the temp erature is below 40°F nor wh en the Engineer determines, based on the latest information available fr om the National Weather Service, that the forecast temperature will fall below 40°F within the next three (3) days in the area in which the project is located. For anticipat ed mixing operations on a Monday, a Friday forecast that runs through th e following Wednesday shall be used to determine if conditions will allow the application of cement on Monday. No cement or cement treated material shall be placed on a frozen fo undation or mixed with frozen material.

308.03.7 3--Road Mix Method . After preparation of the gr ade, the required quantity of

cement shall be spread uniformly over the grade. Cement lost or damaged from any cause shall be replaced without additional compensation before mixing is started. The cement spreader shall be positioned by stri ng lines or other approved methods during spreading to ensure proper application of ceme nt. All cement deposited into the spreader shall be weighed so that the pay quantity and the rate of spread can be determined. In small areas, bag distribution in an approved manner will be permitted. When bag distribution is made, a spike-toothed harrow or other equipment, that will not drag or blade the cement out of desired position but will strike it off at a uniform height, may be used. A motor grader, or other blade-type equipment, shall not be used to spread the cement. Except for final finishing, all processing shall be completed within three hours after spreading. Except by written permission of the Engineer, no cement shall be spread on an area that cannot be completely processed, including all final surface finishing, during the same day. No cement shall be applied when the moisture content of the material to be processed exceeds the optimum for the soil- cement mixture by more than two percentage points. No cement shall be spread when free wa ter is on the surface of the roadbed. No equipment except that used in spreading or mixing shall be allowed to pass over the freshly spread cement until mixed with the material to be treated.

308.03.7 4--Central Plant Mix Method . The cement shall be uniformly metered into

the soil or soil-aggregate in the specified pr oportions and at the time and in the manner that the application of water will not cause formation of cement balls.

308.03.8 Mixing.

308.03.8 1--General . Unless otherwise indicated, cement treated materials may be

processed by any one or combination of the mixing equipment described in Subsection 308.03.2. Where the bid schedule indicates single pass mixers, traveling plant mixers or central plant mixers will also be permitted. Where the bid schedule indicates traveling plant mixers, central plant mixers will also be permitted. Preliminary scarifying shall be carefully controlled and the undisturbed foundation shall have a crown conforming as nearly as practicable to that of the finished course. Subject to the moisture limitations prior to spreading cement as referenced in Subsection 308.03.7.3, soil to be processed may be pre-wet prior to spreading cement. All additional water required to bring the section being processed to the required moisture content shall be applied within one hour after the beginning of mixing. Mixing shall be carefully controlled so that the bottom of the course will conform as closely as possible to the design grade and cross section. When the plans indicate multiple courses to be constructed, the material for each course shall be mixed separately. Multiple courses shall be constructed so that each course is in direct contact with the underlying course, and an unmixed cushion of material between layers will not be permitted. Each increment of water added during mixing shall be incorporated into the mixture for the full depth, and no portion of the mixture shall remain undisturbed for more than 30 minutes prior to compaction. Mixing and water application shall be continued as necessary to produce a completed mixture of un iform moisture content. Particular care shall be exercised to ensure satisfactory mo isture distribution along the edges of the section, and to avoid the addition of excess water. The soil-cement mixture for subgrade and base construction shall be pulverized to the extent that 100 percent of the material, exclusive of gravel and stone, by dry weight will pass a 1-inch sieve and a minimum of 75 percent will pass a No. 4 sieve. The soil-cement mixture for design soils shall be pulverized to the extent that 100 percent of the material, exclusive of gravel and stone, by dry weight will pass a 1-inch sieve and a minimum of 60 percent will pass No. 4 sieve. When the un-compacted mixture is wetted by rain to the extent the average moisture content at the time for final compaction exceeds optimum by more than two percent, or if any of the operations after the start of mixing are interrupted continuously for more than 30 minutes, the entire area affected shall be reconstructed in accordance with these specifications at no additional cost to the State.

308.03.8 2--Road Mix Methods .

308.03.8 2.1--Multiple Pass Mixing . After the cement has been spread, it shall be mixed

with the material to be treated without th e addition of water. Immediately after the preliminary mixing of cement and soil or so il-aggregate, water as necessary shall be applied in the quantity required and incorporated uniformly into the mixture for the full depth. After the last increment of water has been applied, mixing shall continue as necessary until a uniform mixture of cement, soil or soil- aggregate, and water for the full depth of the course has been obtained. 308.03.8.2.2--Single Pass Mixing . After the cement has been spread, it shall be mixed by a mixer that applies water and mixes in one simultaneous and continuous operation. The mixer shall be operated at a speed that will produce a uniform mixture meeting all specified requirements for th e full depth of the course.

308.03.8 2.3--Traveling Plant Mixing . After the cement has been spread, it shall be

mixed with a traveling plant mixer that will apply the proper quantity of water and produce in one simultaneous and continuous operation a mixture meeting all the requirements of the contract.

308.03.8 3--Central Plant Method . Mixing in a central plant shall continue until a

homogeneous mixture meeting specified requirements is obtained, and no varying appearance is evident. The mixing time may be adjusted by the Engineer as necessary.

308.03.9 Shaping, Compacting, and Finishing .

308.03.9 1--General . The mixed material shall be sh aped as required immediately after

mixing, or delivery to the roadbed in the case of central plant mixed material. Initial compaction shall begin immediately, and machining and compacting shall continue until the entire depth and width of the course is compacted to the required density within two hours of the time of beginning mixing. Compaction shall be by equipment and methods that do not result in lamination. Areas inaccessible to rollers shall be compacted to the required density by other approved methods. The addition of thin layers of cement-treated material in order to conform to cross sectional or grade requirements will not be permitted. Compaction by vibration shall not be performed after the cement has taken its initial set. Vibratory compaction of a section sh all be completed within one hour. During compaction, a spike-tooth harrow or other suitable equipment shall be used as required to prevent lamination. After the mixture, except the top mulch, is compacted, water shall be added as required to the mulch, and thoroughly mixed with a spike-tooth harrow or its equivalent to bring the mulch to the needed moisture content. The surface shall then be reshaped to the requi red lines, grades, and cr oss section, and if necessary shall be lightly scarified to remove imprints left by the compacting or shaping equipment. The surface shall then be sprink led as necessary and thoroughly rolled with a pneumatic roller, and if the mixture contains plus No. 4 aggregate, at least one complete coverage of the section shall be made with a steel-wheel tandem roller. Surface compaction and finishing for the entire section shall be performed in a manner that will produce a smooth, closely knit su rface, free from laminations, construction cracks, ridges, or loose materi al, and conforming to the crown, grade, and lines stipulated within four hours after the beginning of mixing. Upon completion of compaction, testi ng will be performed in accordance with Subsections 700.03 and 700.04.

308.03.9 2--Density . Determination of acceptance of compaction of cement treated

courses for required density will be performed on a lot to lot basis. Each lot will be each 2,500 linear feet per layer placed. At the discretion of the Engineer, a residual portion of a lot completed during a day's operation may be considered a separate lot or may be included in the previous or subsequent lot, except that any day's operation of less than one full lot will be considered a lot. Soil Cement Treatment of Subgrade. The lot will be divided into five approximately equal sublots with one density test taken at random in each sublot. The average of the five (5) density tests shall equal or exceed 96.0 percent with no single density test below 94.0 percent. Sublots with a density below 94.0 percent shall be corrected at no additional cost to the State and retested for acceptance. Each lot of work found not to meet the density requirement of 96.0% of maximum density, may remain in place with a reduction in payment as set out in the following table: PAYMENT SCHEDULE FOR COMPACTION Lot Density * Pay Factor % of Maximum Density 1.00 96.0 and above 0.90 95.0 - 95.9 0.50 94.0 - 94.9 * Any lot with a density less than 94.0% of maximum density shall be corrected at no additional cost to the State. The above Pay Factors shall be applied to th e square yards of treated area of each lot found not to meet the density requirement. Soil Cement Treatment of Base. The lot will be divided into five approximately equal sublots with one density test taken at random in each sublot. The average of the five (5) density tests shall equal or exceed 97.0 per cent with no single density test below 95.0 percent. Sublots with a density below 95.0 percent shall be corrected at no additional cost to the State and retested for acceptance. Each lot of work found not to meet the density requirement of 97.0% of maximum density, may remain in place with a reduction in payment as set out in the following table: PAYMENT SCHEDULE FOR COMPACTION Lot Density ** Pay Factor % of Maximum Density 1.02 98.0 and above 1.00 97.0 - 97.9 0.90 96.0 - 96.9 0.50 95.0 - 95.9 ** Any lot with a density less than 95.0% of maximum density shall be corrected at no additional cost to the State. The above Pay Factors shall be applied to th e square yards of treated area of each lot found not to meet the density requirement. Soil Cement Treatment of Irregular Areas. Density of irregular areas shall be rolled to highest stability. Irregular areas shall be defi ned as pre-leveling, wedging [less than fifty percent (50%) of width greater than minimum lift thickness], ramp pads, irregular shoulder areas, median crossovers, turnouts, and other areas where an established rolling pattern cannot be obtained. For cement treated materials other than for design soils and bases, the required density will be set out elsewhere in the contract.

308.03.9 3--Width, Thickness, and Surface Requirements . For the purpose of

determining reasonable conformity with the de signated width of a treated course, it shall be understood that the width of a treated course shall not vary from the designated edge lines by more than plus or minus one inch. For the purpose of determining reasonable conformance with the designated thickness of a treated course, it shall be understood that the depth of a treated course shall not vary from the designated thickness by more than plus or minus one inch. The finished surface of a treat ed course shall conform to the requirements shown on the plans, within the tolerances allowable under Section 321.

308.03.10 Protection and Curing . Each completed course shall be covered with a

bituminous curing seal as soon as possible but no later than 24 hours after completion. The surface shall be sealed w ith one of the specified bituminous materials applied by a pressure distributor at the rate of 0.10 to 0.25 gallon per square yard or as directed by the Engineer. The bituminous material shall be heated or otherwise prepared to ensure uniform distribution. Should the Contractor fail to seal the treated course within the time specified, the Engineer will suspend all othe r work and withhold payment of the current estimate(s) until all damages resulting there from is corrected and the treated course is sealed. When the treated course is th e subgrade, a subsequent course shall not be placed on the sealed course for at least seven (7) calendar days. During this 7-day period, the treated course shall not be subjected to an y type of traffic and equipment. When the treated course is the base, the Cont ractor shall use the mix design (7-day or 14- day) as specified on the Mix Design from the Central Laboratory. Depending on the specified mix design, a subsequent course shall not be placed on the sealed course for at least seven (7) or fourteen (14) calendar days. During this period, the treated course shall not be subjected to any type of traffic and equipment. The Contractor shall maintain the treated course and the curing seal in a satisfactory condition until covered by a subsequent course. Protection shall include immediate repairs of any surface irregularities or other def ects that may occur or develop. It shall be the Contractor's responsibility to control traffic and equipment loads to avoid damage and to guard against freezing of the treated material. All damage resulting from the Contractor's failure to protect and cure the treated course as specified herein or from freezing that may occur prior to being covered with the next course shall be corrected at no additional cost to the State. The Contractor shall submit, for approval of the Engineer, a method of correction that will restore the strength of the damaged material to that originally specified.

308.03.11 Maintenance . The Contractor shall maintain the cement treated course and

the curing seal in a satisfactory condition until covered by a subsequent course. Maintenance shall include immediate repairs of surface irregularities or other defects that may occur. It shall be the Contractor's re sponsibility to control traffic and equipment loads to avoid damage and to guard against fr eezing of the course. All maintenance shall be performed at the expense of the Contractor and repeated as necessary to keep the cement treated material a nd the curing seal intact.

308.04 Method of Measurement . Cement incorporated in the accepted work, subject

to the limitations set out in Subsection 308.03.7.1, will be measured by the ton, as designated, in accordance with the provisions of Section 109. Accepted soil-cement-water mixing will be m easured by the square yard or ton. Contractor furnished materials will be meas ured and paid for in accordance with the provisions for the governing pay items shown in the contract. Bituminous curing seal will be measured by the gallon as prescribed in Subsection

109.01 Unless otherwise specified, distributor tank measurements will be used. The volume of material over five percent above the allowed range for each shot will be

deducted from measured quantities, except that 15 percent will be allowed for irregular areas where hand spraying is necessary. The volume of all bituminous material lost, wasted, damaged, or rejected, or applied outside of designated areas, or in excess of the Engineer's directions and tolerances allowed, or contrary to the specifications, will be deducted from measured quantities. Water will not be measured for separate payment. Unauthorized wastage or us age of any materials, unused materials remaining in stockpiles, and additional materials required for reconstruction of unacceptable work will be deducted from measured quantities. Determination of quantities to be deducted will be made by the method the Engineer considers to be most practicable and equitable, and the Contractor’s decision as to the method used shall be final.

308.05 Basis of Payment . Cement will be paid for at the contract unit price per ton.

Soil-cement-water mixing will be paid for at the contract unit price per square yard or ton, as specified. The prices thus paid shall be full compensation for completing the work. Bituminous curing seal, measured as prescribed above, will be paid for at the contract unit price per gallon, which price shall be full compensation for furnishing, applying and reapplying if needed, protecting, maintaining; and all tools, equipment, labor and incidentals necessary to complete the work. Payment will be made under: 308-A: Cement - per ton 308-B: Soil-Cement-Water Mixing, Type* Mixers, Component - per square yard or ton** 308-S: Bituminous Curing Seal - per gallon * Optional, Single Pass, Multiple Pass, Traveling Plant, or Central Plant. ** Central Plant Mixers Only. SECTION 310 - MECHANICALLY STABILIZED COURSES

310.01 Description . This work consists of constructing one or more courses by the

incorporation of stabilizer aggregate in a ccordance with these specifications and in reasonably close conformity with the lines, grades, and typical cross sections shown on the plans or established by the Engineer.

310.02 Materials .

310.02.1 Materials to be Stabilized . The material to be stabilized shall consist of base

material placed under this contract or under a previous contract. General conditions governing the use of materials shall be as set out in Section 106.

310.02.2 Stabilizer Aggregates . Stabilizer aggregates of the kind and size specified

shall meet the requirements of Subsection 703.20.

310.02.3 Composite Mixture . The composite mixture of mechanically stabilized

courses shall be in accordance with the requirements and provisions of Subsection

703.08 In order to obtain the desirable composite mixture, the Engineer may vary the quantity of stabilizer aggregate shown on the plans by as much as 25 percent.

Acceptance of the composite mixture for co nformance to the specification requirements for gradation, liquid limit and plasticity index shall be based on samples obtained from the roadway. A minimum of one random sample shall be obtained for each 1000 linear