Fenstanton Roads, Groundworks and Sewers
At New Development of 84 Houses including Housing Authority properties JJMac limited was appointed as PC to undertake Archaeology, Roads and Sewers, Section 278 and Plots works.
Client Kier
Location Fenstanton Cambridgeshire
Key woks delivered Archaeology, Roads and Sewers, Section 278 and Plots works
Fenstanton Aerial Trial Hole Works undertaken using Vacuum Excavation and Hand Digging under the supervision of CADENT Gas Networks. All utilities located were recorded by JJMac site engineer using GPS for future records and the Section 278 works.
JJMac Fenstanton Trial Hole Works
JJMac Fenstanton Trial Hole Works
JJMac Fenstanton Trial Hole Works

Newt Licence & 3D pond design
A new Newt Pond was created to home the newts. It is expected that the newts will migrate over the summer time to the new pond.

Before the earthworks were undertaken, we used AutoCad Revit to draw up and measure the volumes of the excavations. This allows us to price and plan the works very accurately. This 3D data can be used in the earthworks equipment such as the Dozer which is Trimble enabled. This allows the setting out information to be programmed directly into the Dozer and Excavator for the operators to follow. This operation reduces the requirement for a site engineer and increases safety on site as the engineer will not be required to work amongst the heavy equipment.
JJMac Fenstanton Newt Licence & 3D pond design
JJMac Fenstanton Newt Licence & 3D pond design
JJMac Fenstanton Newt Licence & 3D pond design


Archaeology


JJMac Fenstanton Archaeology
The archaeology works were carried out in phases.

The earthworks were carefully planned to accommodate the archaeology digs and to minimise movement of soils around site.

The whole site had to be reduced by 1.0m where the archaeology teams started their works. Approx. 25,000m3 was excavated with approx. 10,000m3 of subsoil being disposed off site.

The Topsoil was stored on site for re-use and the remaining subsoil was re-engineered across the site to bring the site back up to formation level for roads and driveways etc.

There is a great deal of risk on the site with re-engineering the subsoil. If not engineered properly the subsoil can become water logged and will have to be excavated and disposed off site.


Section 278 – Highway works
Site crew hard at work laying Beany Kerbs. Beany kerbs are a combination of a drainage channel and a kerb. Root barrier had to be use to ensure no roots would enter the beany channels and block it or dislodge the kerbs.
JJMac Fenstanton Section 278 – Highway works
JJMac Fenstanton Section 278 – Highway works
JJMac Fenstanton Section 278 – Highway works


Drainage – Section 104
Drainage was set out with lines and pegs to identify centre of manhole. Next deep drainage was undertaken using proprietary earthwork support and manhole boxes. Drainage was laid using Laser levels to ensure line and level are as designed. Bottom of manhole was formed with concrete. All manhole rings were dropped onto concrete base and set to specification, clay channels were placed in manhole where clay drainage is used. Channels have been finished using Granno (sand and cement) to achieve smooth finish. Once manholes were constructed they must be surrounded with 150mm concrete. We used a shutter for this operation. Also manholes with cover slabs were placed to correct level and gullies have been connected to the main storm run with 1500mm clay pipe
JJMac Fenstanton Drainage – Section 104
Drainage laid using Laser levels to ensure line and level are as designed
JJMac Fenstanton Drainage – Section 104
Manholes must be surrounded with 150mm concrete.
JJMac Fenstanton Drainage – Section 104
Gullies being connected to the main storm run with 1500mm clay pipe


Air Testing Drainage
All adoptable Foul drainage laid on site must be air tested and witnessed by an Anglian Water or (local foul network owner) representative.
Air is pumped into the pipeline, usually via a hand-pump with a control valve, until the reading on the manometer is around 125-150mm. The set-up is then left for 5-10 minutes to allow for temperature stabilisation within the pipe before the pressure is reduced to exactly 100mm on the manometer scale.

The manometer is then monitored for a period of 5 minutes
The level of water in the manometer should not fall below the 75mm mark during this period. This is deemed to be a "pass" and the pipeline is declared satisfactory and can be backfilled.

However, if the level in the monometer does fall bellow the 75mm mark, then the equipment should be checked and cleaned and the pipeline examined for leaks or defects. If any problems are identified, they should be rectified before re-testing. If the air test is re-applied and is failed for a second time, a water test should me administered.
JJMac Fenstanton air test set-up
Idealised air test set-up
Section 38 – Adoptable Highway Construction
Cambridgeshire county council act as Highway Authority and adopt residential roads under Section 38 of the highways act 1980. As this development serves 86 individual dwelling units, the road has a highway function and must be constructed in accordance with their construction specification. Failure to comply with their construction specification would result in the road not being adopted by the Highway Authority.

For a road to preform satisfactory, the road must be constructed on an adequate foundation. A poor subbase would lead to insufficient support to the layers above, leading to a rapidly deteriorating road. For Road construction, the subgrade is accessed in terms of California Bearing Ratio (CBR) value. The CBR value can be determined either by Plasticity test or plate test to determine the CBR value. Cambridgeshire County Council recommended using plasticity tests to be undertaken on the Fenstanton site. Samples of soil were taken at road formation level to ensure moisture content relates to equilibrium conditions at depth. Samples were taken every 30 meters along the centre line of the proposed roads to ensure on overall average site CBR value can be obtained. Fenstanton obtained a 4% CBR value, meaning the depth of subbase was 315mm.

The road was set out by JJMac’s setting out engineer to enable the commencement of the road to be cut. Profiles were set out along chainages every 5 meters and 1 metre offset from the curb line to enable machine movement when cutting to formation level. A level offset 1 metre from finished road level was also given to ensure the road was then cut to formation level following the speciation as laid out below. On site levels were ‘boned in’ using a ‘traveller’ using the profiles set out.
Sub-Base 315mm Type 1 supplied via GRS
Binder course 190mm Thick AC 20 DBM supplied & laid by Phoenix Surfacing
Surface Course 40mm Thick AC10 DBM – To be laid once plot works are complete
JJMac Fenstanton Section 38 – Adoptable Highway Construction
Drainage laid using Laser levels to ensure line and level are as designed
JJMac Fenstanton Section 38 – Adoptable Highway Construction
Road Trimmed and ready for Tarmac.
In order to comply with the requirements of the Highway Authority the test results for the Foundation Surface Modulus shall be the rolling mean of six results and must be grater than 80MPa. For the avoidance of doubt: 80MPa is the lowest limit that the Highway Authority will accept and any measurement bellow this figure will have failed the test. No individual results is to be less than 50MPa.

Once the road is cut to formation level sub base can be laid. A layer of geotextile is required between the clay formation and fill material to facilitate construction. The type 1 was spread evenly in layers of 150mm and compacted with the use of a Hamm HD 140 Roller Fenstanton roads achieved well above the required MPa levels with average 87MPa with 120MPa in places.

The sub base is only approved by Cambridgeshire County Council after a performance test is undertaken on the material. JJMac Ltd were required to undertake lightweight reflectometer testing (LWD) to ensure a minimum surface stiffness / compaction is achieved before the place of the remaining asphalt layers.

Prior to surfacing, the tarmacing contractor and Cambridgeshire County Council representative and JJMac site manager take ‘Dips’ of the tarmac thicknesses that will be laid. The dips are taken from the string lines at each side of the road. The top and bottom lines are set out to enable the crews that are ‘trimming’ the roads to install the camber or cross falls. Top line to oposing bottom line will give the camber. The tarmac contractor will set the laying levels on the Barber Green and follow the road.

Once the tarmac is laid, there are numerous tests that will be carried out to ensure compliance with material specification and workmanship.

Compaction is critical for tarmac as this will provide the strength and durability of the road. If the tarmac is not compacted properly, it will inevitably allow water penetration and quickly break up.
JJMac Fenstanton Section 38 – Adoptable Highway Construction
Setting out string lines
JJMac Fenstanton Section 38 – Adoptable Highway Construction
Density Testing machine
JJMac Fenstanton Section 38 – Adoptable Highway Construction
During construction

Service, Utilities and Substation
One of the most important elements of the Roads and Sewers works is co-ordination of the off site and on site utilities installation.

Numerous months of planning go into making sure all the utilities are called off and arrive on site in the correct order and in a timely manner as not to have trenches open for too long.

On fenstanton, we were very fortunate to have all the services come into site and be laid within a two week window. Water first as it is the deepest. Then Gas and Electric last. This way we can excavate the most efficient trench formation and backfill each utility as it is laid. BT and fibre ducts will be last to lay as they are most shallow.

It is very important to the construction programme that the utilities go in quickly as the trenches around the site not only create a hazard but they also cut off sections of the site and where we can’t get on certain elements of works that may be near the open trenches. All utilities are laid dead and will be made live in sections as and when required. Once the utilities become live, we have to adhere to Kier and JJmac policy of hand digging within 1.0m of a live service.
JJMac Fenstanton Service and Utilities
Utilities installation
JJMac Fenstanton Substation
Electrical substation construction
JJMac Fenstanton Substation
Electrical substation construction
The substation is critical to the site and essential that it is constructed and signed off by the electrical network provider in time for the electrical cables come into site. The sub station base is formed with Reinforced concrete poured into formwork to form the trough for the incoming cables and the electrical equipment to be housed and connected.