DETAILED ENGINEERING DESIGN FOR PORT SAID
ROAD TUNNELS UNDER SUEZ CANAL - EGYPT
Hydrocarbon Separator
4.2.1 Hydrocarbon Separator function and characteristics
When it is not expected that water contains hazardous liquids the diversion chamber will allow carrying effluent
into the oil separator before discharging into a water course or a public sewer to prevent environmental
pollution. Removal of small oil, fuel or grease spillages that may be spilt in a tunnel will take place.
There will be one oil separator at west side of tunnels and another one at east side.
Two cases are considered to define the maximum inlet flow at the oil separator:
1. Case 1. 10 minutes rain event with a return period of 10 years and a firefighting water discharge with 40
m3 of spillage in only one tunnel.
2. Case 2. A storm of 10 minutes of duration with a return period of 100 years.
The maximum inlet flow to the oil separator is during Case 1. This maximum inlet flow is 75 l/s, 50 l/s from one
tunnel plus 25 l/s from the other tunnel.
This equipment shall have the following functions / objectives:
Separation of sands by settlement.
Separation of oils and fats of a mineral nature and water hydrocarbons, by methods of coalescence and
density difference, without separating emulsified oils and hydrocarbons.
A regulatory system to divert any excess flow (shunt device). The excess of water collected in the
separator shall be taken directly to the discharge side in such a way that the separator shall only treat
the volume for which it is nominally designed.
The features of the oil separator are:
The hydrocarbon separator is Class I according to European Standard EN 858, high efficiency separation
system that, in standardized trial conditions, separates the light phase to obtain an effluent with
maximum hydrocarbon concentration of 5 mg/l. Coalescing lamellae are fitted inside the equipment
to achieve higher separation performance. This filler favours contact with hydrocarbon droplets to
form larger drops through grouping. The larger-size drops are more easily separated.
It includes a desander designed according to the guidelines of the EN 858 standard. The volume of the
desander is determined by the nominal flow.
It is provided with one manhole to the desander area and another one to the oil removal area.
Regulating System of water flow and by-pass with water spillway to overflow the excess.
It will also incorporate a safety device that prevents hydrocarbon from being released when the
equipment is full and a level control device.
The oil separator is leak-tight and fabricated from GRP with ortoftalics resins or similar approved.
Mechanical skimmer for separated oils extraction
Underground water table is below the oil separator therefore only a concrete slab 300 mm thick with a
steel reinforcement to anchor and protect the separator is required.
No vehicle traffic is expected above the separator.
4.2.2 Conditions for works execution and installation
4.2.2.1 Controls before the installation
The equipment shall have followed the manufacturers’ quality controls and shall be delivered with a
manufacturers guarantee in favor of the buyer. The equipment shall be inspected on delivery and in case any
visible damage is found it shall be returned to the manufacturer or tagged, marked and segregated pending
investigation by the Engineer.
4.2.2.2 Transport and handling
The equipment shall be transported and stored on suitable beds to ensure that damage is not caused due to
uneven support. During storage the equipment shall be firmly tied down in accordance with the manufacturer’s
instructions.
The equipment shall only be lifted through the eyebolts or lugs provided by the manufacturer for this purpose.
Lifting shall only be with straps or chains that form an angle of 60º to 90º with the axis of the equipment.
Equipment shall not be lifted with cables or chains around the equipment, nor shall any weight (person or
object) be placed on the same, during the lifting operation.
4.2.2.3 Excavation and filling
The equipment shall be installed strictly to the tolerances and in accordance with the manufacturer’s
instructions and to the levels shown on the Drawings. Excavation and backfilling shall be in accordance with the
manufacturer’s instructions.
4.2.2.4 Manholes
Manholes shall be installed as required to provide access in accordance with the Drawings and the
manufacturer’s requirements.
4.2.3 Admission into work Site
This equipment shall only be admitted into work Site when accompanied by detailed transport documentation,
as well as the documentation that shall allow the Engineer to verify the tests undertaken in the factory and the
conditions of transport.
4.2.4 Minimum tests for the acceptance of works
4.2.4.1 Request for additional testing
If the results of the tests either static or functioning are a reason for rejection of the equipment by the
Engineer, he may require further tests on the unit in question or replacement with an identical piece of
equipment, at the provider’s cost.
4.2.4.2 Commissioning
After installation and before the acceptance by the Engineer, the installed equipment shall be commissioned
and tests specified by the manufacturer shall be carried out to the satisfaction of the Engineer. Tests shall
include but not be limited to, checking the correct flow of water in the manholes as well as verifying the supply
of water is entering the tank as expected and the correct operation of the bypass system, alarms and
instrumentation.