SPECIFICATION 1.0 1.1.

PART 1 PRELIMINARIES Establishment on Site The pay item included in the bill of Quantities is provided to reimburse the Contractor for the cost of all operations necessary for and directly related to the establishment on site and any other operation necessary for establishment on site and to enable work to commence on the project. Payment The sum tendered for establishment on site will be paid 70% on completion of establishment on site to the satisfaction of the Engineer, but not before work has commenced on the project; and 30% to be paid on demobilization.

1.2.

Mobilization/demobilization of Plant and Equipment The contractor shall mobilize all plant and equipment necessary to carry the work not later than 15 days following the commencement date of the contract. The contractor shall demobilize all plant and equipment prior to issuing the final certificate. Pay item included in the bill of quantities is provided to reimburse the contractor for the cost of transporting his plant and equipment to the work site at the commencement of work and for demobilizing the plant and equipment after the works is completed. PART 2 ROADWORKS

2. 2.1

PART 2 ROADWORKS General Description The works described in the following sections of this part 2 refer to the construction of roadworks of District and Feeder roads and include site clearance, formingup of road formation, earthworks, sub-grade compaction and supply and construction of gravel wearing course in accordance with these specifications and in conformity with the lines, grades and dimensions shown on the drawings or directed by the engineer. No earthworks shall commence upon any portion of the construction until such time as ground levels have been taken by the contractor in an approved manner, and checked and accepted by the engineer to ensure that a firm basis has been established for measurement and setting out purposes. Should the contractor fail to comply with this requirement the Engineer reserves the right to base the final measurement on other survey data.

Before commencing work on any section of the road the contractor shall ensure that he has adequate instructions concerning the use of soils from cut. No claims for double handling will be considered. Excess excavation beyond the net outline detailed or directed shall be made good at the contractors expense in a manner acceptable to the Engineer. The Engineer reserves the right to control excavation and to direct where materials arising from cut shall be deposited and how and where it shall be used, and also to direct where borrow materials which may be essential for fill shall be obtained. The contractor shall take all risks from water, clean or foul, stream, river, surface, storm or ground water, whatever the source or sources may be. Water shall not be allowed to accumulate at any point in the earthworks. The contractor shall, at his own expense, affectively drain and keep dry all the works during the period of construction and shall take particular care to prevent surface water accumulating, soaking, soaking in, and softening the formation during construction. The contractor at his own expense shall rectify any loss of shape or compaction resulting from water affecting the earthworks. All side drains, sumps or temporary excavations for de-watering shall be formed, maintained and used outside and cleared of the main works and shall be properly filled in if so directed by the Engineer when their use ceases. The rates tendered must allow for all for all risks from de-watering of the earthworks during construction. No material should be left in the formation construction, which, if incorporated in the formation construction would adversely affect the stability of the compacted earthworks. Removed topsoil, humus, grass etc. shall be disposed of clear of the road in a manner such that drainage into the side drains or mitre drains or other drains is not impeded or it may be disposed of as waste as directed by the Engineer. Excavation of materials due to slips and falls in cuttings and banks attributable to carelessness of the contractor shall be made good at the contractors expenses in a manner acceptable to the Engineer. In general terms excavation shall be measured under two items. The first is a cut to fill item, which will be measured as compacted fill and the second is a cut to spoil item, which will be measured as an in-situ volume before excavation. Cut section and fill sections are defined as occurring where the finished sub-grade level is, for fill, more than 250mm above and for and for cut more that 250mm below existing ground level, measured on the carriageway center line before clearance. For cut or fill sections of road, the contractor will carry out a longitudinal profile and cross section survey at intervals of 50 meters or as directed by the Engineer and using

local datum. Two level pegs shall be set out at each cross section point, one in each side of the carriageway and clear of construction. These shall remain in position until the road construction is complete. Any pegs destroyed during construction shall be immediately replaced. Fills shall be constructed in layers of materials in loose thickness not exceeding 200mm and each layer shall be compacted as specified. Where possible the quality of materials used in fill construction shall improve with each successive layer upwards. Where embankments exceed 1.5 meter in height in side along ground the Engineer may direct the excavation of horizontal benches in bank foundation. Side drains emptying from cuts to embankments and all other drains shall be so constructed as avoid damage to embankment by erosion. The volume measured shall be the compacted volume between the ground profiles including the volume of excavation of benches and shall be computed by the method of average end areas from levelled cross section. The contractor must allow in his rates for any additional work, working space and the like, that he may require. 2.2 Definitions

The following definitions of Earthworks materials shall apply to this specification: (a) Topsoil shall mean the top layer of soil that contain humus material and can support vegetation. (b) Suitable material shall comprise all that which is acceptable in accordance with the Technical Specifications. (c) Unsuitable material or deleterious material shall mean other that suitable material and shall include material from swamps, marshes or bogs, peat, logs, stumps, perishable materials, susceptible to spontaneous combustion. (d) Rock shall mean that material which in the Engineers opinion, cannot be broken up or removed by means of crowbars and wedges and which is measuring not less that 0.20 cubic meters in volume. (e) Common excavation shall mean all other rock excavation. (f) Construction width shall mean the overall width of the works measured between the outer extremities of side drains, cuttings or embankment slopes, as the case may be. (g) Formation shall mean the top of construction immediately below the base course or the wearing course or the wearing course (If any). (h) Sub-grade shall mean the material in the top of construction immediately below the base course or the wearing course (if any).

(i) Sub-grade width or formation width shall mean the width of the roadway measured between the points of intersection of side drain or embankment slopes with the top of sub- grade level. (j) Formation level is synonymous with top of sub-grade level and shall mean the final compacted level of the surface of the sub-grade. (k) Wearing course shall mean the layer superimposed on the sub-grade or base course. (l) Free haul shall mean the distance which the fill or wearing course material must be transported on any trip before qualifying for overhaul payment and is 10 km for selected material, and 10km for wearing course material. (m) Overhaul is the total distance which material shall be hauled minus the respective free haul distance. 2.3 2.3.1 Site Clearance. Description of Work

Where the proposed alignment is in new alignment or where it follows an existing road and the existing clearance is too narrow, clearing shall be undertaken as shown on the drawings or to a width as directed by the Engineer. The clearing shall consist of clearing and removing from the designated areas of all trees, stumps, grass, debris, fences and other obstructions interfering with the proposed a work. The clearing shall include grubbing up or burning of all stumps, roots and vegetable matters. Where directed the excavations left by the removal of trees shall be backfilled and compacted. Timber and such materials as may be designated by the Engineer shall be salvaged. All vegetable debris shall be disposed of as directed by the Engineer. Care shall be taken in the lighting and control of fires to ensure that they do not spread. The contractor shall be solely responsible for fire damage resulting from this cause. Inside the area of the permanent works the standing and uninjured. Outside the area of the permanent works the contractor shall destroy only those threes directed by the Engineer. The contractors rate for site clearance should allow for felling and disposal of large trees as required within the designated areas. 2.3.2 Measurement.

Clearing for the road will be measured by the square meter and will be calculated by the length acceptably cleared multiplied by the final width of clearance as shown on the drawings or as directed less the actual cleared width of the existing roads or tracks. The contractor must allow for areas already cleared when pricing this item.

2.3.3

Payment

The rate offered under this item will include full compensation for all labor, equipment, tools, and incidentals necessary to complete the work described in this section or in any related sections. The contractor will have no claim for extra payment because he has been required to work round or leave undisturbed any trees in the cleared area. 2.4. Road Formation

2.4.1 (i) Grading: Light and Heavy. 2.4.2 (ii) Reshape Road: Light and Heavy. 2.4.1 (i) Description of Work 2.4.1 (i)a Light Grading This requires the blading of carriage way and side drains to re-establish the correct cross-section of the road. The graded section shall be proof rolled and all excessive graded loose material should be removed from the culverts inlet/outlet and side drains, where such work is expected to take between 1.5 and 2.5 hours per kilometre. Measurement in kilometers. Payment The rate offered under this item will include full compensation for all labor, equipment, tools and incidentals necessary to complete the work described in this section or in any related sections. 2.4.1(b) Heavy Grading

This requires the blading of carriage way and side drains to re-establish the correct cross-section of the road. The graded section shall be proof rolled and all excessive graded loose material should be removed from the culverts inlet/outlet and side drains, where such work is expected to take between 2.5 and 4.5 hours per kilometre. Measurement in kilometers. Payment The rate offered under this item will include full compensation for all Labour, equipment, tools and incidentals necessary to complete the work described in this section or in any related sections. 2.4.1(ii) Description of Work The term Reshape Road may in general be said to apply to those lengths of the road where the finished sub-grade level at the carriageway centerline is within +/- 250mm of existing ground level.

The reshaping of the road is essentially a side haul or grading operation with a maximum longitudinal haulage of 50m. Reshaping shall include the following: Removal of grass roots, humus topsoil and general any unsuitable material present in the full construction width between the outside of the side drains. No. Material should be left in the formation construction, which, if incorporated in the formation construction would adversely affect the stability of the compacted earthworks. Removed topsoil, humus, grass, etc. shall be disposed of clear of the road in a manner such that drainage into the side drains or mitre drains is not impeded or it may be disposed of as waste as directed by the Engineer. Carry out earthworks necessary to produce the completed profiles of side drains and formation to the specified standards, lines and levels, grades and dimensions as detailed or directed. This will include the scarification of the existing roadway surface to a minimum depth of 100mm, excavation of material from side drains, and the transverse or longitudinal movement up to 50m. Of this material to fill or waste. The operation will provide a completed side drain and formation as detailed and specified. The full width of the sub-grade material between the outside edges of the shoulder shall be watered formed according the drawings and compacted up to the 95% of maximum Dry Density of BS Heavy1.

The classification into light and heavy reshaping will be decided by the Engineer and is based on the following quantities of material scarified moved, displaced and re-placed per meter of road. Rural Roads Light reshaping Heavy reshaping Maximum 1.5 m3 Maximum 3 m3

2.4.1 Measurement Measurement shall be by the linear kilometer of road formation prepared to the horizontal and vertical alignments, cross-falls, cambers, super elevations, etc. for the typical cross section types as detailed on the drawings and shall include for side drain construction. 2.4.2 Payment The rates offered under these items shall allow and include: removal of deleterious materials, scarification, excavating and forming side drains, movement of material over a longitudinal distance of 50m, watering and compaction to achieve the desired road profile. Excavation of rocks or boulders occurring within carriageway will be paid for under an extra over item.

According with Article 5.7 of the Pavement and Materials Design Manual 1999 adopted by the Ministry of Works of The United Reputed Republic of Tanzania

PART 3 DRAINAGE WORKS 3. 3.1 DRAINAGE WORKS General

The drainage work consists of excavation of roadside drains in the preparation of the formation, excavation of mitre drains, catch water drains and outfall drains, excavation for and the construction of culverts and vented drifts, concrete and masonry works, stone pitching, gabions, erosion checks and such other ancillary works necessary for the construction and completion of the works. In the layout and construction of the drainage systems particular care shall be taken to avoid conditions, which may create soil erosion. 3.1.1 Open Drains.

3.1.1.1 Description of work 3.2.1.i. Side Drains Side drains shall generally be constructed simultaneously with the road formation, and be excavated to a minimum invert gradient of 2 percent, if possible. The completed drainage system must be freely operating and trimmed to a neat workmanlike finish with no high points or low points, which would cause pounding to occur. As the invert must follow the road grade as closely as possible, conditions may arise in soft material or on a steep grade that could cause erosion. The Engineer may, under such conditions, direct that erosion checks be constructed across the drain to reduce the effective grade of the drain invert to about 4% for highly erodable natural soils. Excavation of side drains is not measured separately but is included in the forming up operation and paid for under pay item Road Formation 2.4.1(i) Grading: Light and Heavy and under pay item pavement re-formation. 3.2.1.ii. Mitre Drains

Mitre drains shall be considered as drains constructed at an angle to the centerline of the road to divert water from the side drains. Mitre drains will be located as directed. The size shape and frequency of mitre drains are as shown on the drawing or as directed by Engineer.

As a general rule, mitre drains shall be shallow and wide and constructed to the flattest grades consistent with efficient discharge of water. Mitre drains shall normally discharge freely on natural ground surface or into natural drainage or culvert outlet or inlet channels. Care must be taken in choice of the route of the drain so as avoid excessive earthworks. Where necessary mitre drains shall be continued beyond the limits of the road reserve provided the consent of the land owner/occupier is obtained through the correct channels. 3.2.1. iii. Mitre Banks Mitre Banks shall be considered as the barrier in the normal side drain, which diverts the flow of water from the side drain into the mitre drain. Mitre banks shall be of adequate size and shape to be effective at all times, and shall be constructed of approved soil or gravel compacted in layers not exceeding 150mm in thickness, true to lines, levels and cross sections shown on the drawings or as directed by the Engineer. Mitre banks may also be constructed of hand packed stone covered with a layer soil. The cost of construction of mitre banks shall be include in the rate of mitre drains. Measurement For measurement purposes mitre drains are classified into two categories: Category one are those drains whose construction or reshaping require an excavation of an amount less than 0.5m3 per linear meter run of drain. This category is measured in linear meters of existing drains reshaped and the meter of new drains excavated to the typical cross sections shown on the drawings or as directed. Category two are those drains whose construction or reshaping require an excavation of an amount greater than 0.5m3 per linear meter run of drain. This category is measured in cubic meters of existing drains reshaped and the meter of new drains excavated to the typical cross sections shown on the drawings or as directed.

The provision of diversion banks shall be included in the rate tendered for mitre drains.