Revised Laws of Saint Lucia (2023)

PART 4
MANHOLES

14.   Manholes

1.  

   (1)   Manholes shall generally be provided at all points on a sewer, lateral drain or drain—

   1.  

      (a)     where the size, direction or gradient of a sewer, lateral drain or drain undergoes a change;

   1.  

      (b)     where a soil pipe or a waste water pipe connects to a drain or where a branch drain connects to a drain;

   1.  

      (c)     where a rainwater pipe connects to a rainwater drain either directly or through a gully trap or where a branch rainwater drain connects unless the Sewerage Authority agree otherwise;

   1.  

      (d)     and where the above-mentioned circumstances do not exist, at intervals not exceeding 300 feet from a manhole.

1.  

   (2)   The minimum internal dimensions of manhole chambers shall be as follows, except that for manholes less than 6 feet deep the Sewerage Authority may permit the use of smaller manholes at its discretion.

Rectangular Manhole

The minimum internal dimensions of the access shaft, that is, that portion of the manhole which connects the roof of the manhole chamber to the surface of the ground, shall be 2' 3”.

1.  

   (3)   Foundation. The foundation of the manhole shall be of concrete of thickness as follows:

   Depth of outgoing invert.	Minimum thickness of base slab
   Up to 6ft.	6 inches
   6 feet to 15 feet	9 inches
   over 15 feet	9 inches

1.  

   (4)   Walls. The walls of the manhole shall comply with the following requirements—

   1.  

      (a)     the area of the base slab shall extend over the external dimensions of the manhole chamber. Projecting footings need only be provided if the projection is necessary to protect against uplift;

   1.  

      (b)     the walls of the manhole may consist of—

      1.  

         (i)     brickwork, or

      1.  

         (ii)     in situ concrete not less than 9 inches thick, or

      1.  

         (iii)     precast concrete or reinforced concrete, or

      1.  

         (iv)     precast concrete pipes with in situ concrete surround;

   1.  

      (c)     the bricks used shall comply with British Standard 1301 clay engineering bricks Class B or be of such other quality as the Sewerage Authority shall approve and they shall be solidly built in English bond. They shall be rendered inside with mortar. Where the manhole is constructed of precast concrete pipes it shall be surrounded with concrete up to a height of 6 inches above the top of the highest opening or joint in the pipe forming the manhole chamber provided always that such concrete may be omitted where sufficient benching is laid inside the manholes to make the bottom of the manhole and pipes entering thereabout perfectly watertight.

1.  

   (5)   The roof of the manhole chamber may be constructed—

   1.  

      (a)     by means of a brick arch. The arch shall be constructed of not less than 2 rings of special radiused bricks set in mortar;

   1.  

      (b)     by means of a concrete slab suitably reinforced to carry the weight of the access shaft, ground and traffic above. The slab shall not be less than 6 inches in thickness. Precast concrete sections may be used such as taper pipes connecting circular manhole chambers with circular access shafts. Taper pipes so used shall not be less than 2 feet in length.

1.  

   (6)   The access shaft—

   1.  

      (a)     if rectangular, shall be corbelled inwards on 3 sides to reduce the size to that of the internal dimensions of the cover frame. All corbelled work shall be in whole bricks or blocks. The access shaft if circular shall be surmounted by a concrete slab 3 inches in thickness and the under surface of such slab shall, where it passes over the pipe forming the manhole shaft, be half an inch higher than the highest part of such pipe. The concrete slab shall be adequately supported around its perimeter with concrete or approved hard filling;

   1.  

      (b)     shall be surmounted with an approved manhole cover and frame in accordance with British Standard 497 for manhole covers, road gully gratings and frames or in accordance with British Standard 556 for concrete cylindrical pipes and fittings including manholes, inspection chambers and street gullies and shall be properly bedded in mortar.

1.  

   (7)   Where the manhole exceeds 4 feet in depth step irons shall be built vertically down one of the walls immediately under the manhole cover. The step irons shall have a vertical spacing of one foot, shall be staggered horizontally one foot each side of a vertical centre line. Step irons shall be galvanised malleable cast iron in accordance with British Standard 1247 for manhole step irons or may be constructed of reinforced concrete with the approval of the Sewerage Authority. All step irons shall be rigidly built into the side of a manhole.

1.  

   (8)   The floor of the manhole shall consist of suitable purpose made channels or concrete channels formed in situ with a perfectly smooth face and connecting the various pipes entering the manhole to the channel with easy bends discharging into the main channel in the direction of the flow. The manhole of the channel shall be brought up in concrete vertically to the height of the crown of the outgoing pipe and shall be benched at a slope of one in 3 to the walls of the manhole provided always that where a pipe enters through such wall the concrete shall be brought up to the level of the mid point of such pipe and channels as aforesaid shall be formed in the concrete to convey the discharge from the entering pipe into the main channel where practicable in such manner that the invert of the branch channel is at the same level as the crown of the outgoing pipe.