Overpumping Solution at Dover Ports

Faced with essential maintenance works on existing pumping infrastructure, the Port of Dover required a high-capacity, reliable, and long-term overpumping solution. Willow Pumps was commissioned to design and deliver a turnkey system to ensure uninterrupted wastewater management while the permanent systems were offline. The original enquiry covered an 18-month hire period; this was later revised to a 12-month fixed-cost solution following detailed on-site assessments.

The original proposal outlined a budgetary quotation based on limited initial data. This included:

• Overpumping capacity of 600 litres per second, distributed across four manholes.
• 65m pipe runs per pump with a 5m suction lift and open-air discharge.
• Equipment based on Flygt NZ3301LT submersible solids handling pumps, each with a 37kW motor.

A full site survey was proposed to confirm:

• Actual flow rates per manhole,
• Agreement on discharge points (either tanks or manholes),
• Optimal pipe runs and equipment access.

Following on-site discussions and a revised project scope, a more efficient and cost-effective solution was agreed for a 12-month duration. Key changes and final design details included:

• Flow Requirement: Reduced to 165 litres/second total, delivered by four pumps (approx. 41.25l/s per pump).
• Pipework: Reduced delivery distance to 24 metres per pump.
• Pumps: Upgraded to Flygt NZ3153HT horizontal submersible pumps, each driven by a 9kW motor.
• Pipework & Controls: All 6” suction and delivery pipework (now purchased), along with electrical distribution boards and connection cables, were permanently supplied.
• Discharge: Each line directed into a settlement tank with gravity outfall 400m away.
• Settlement Tanks: Four 40,000-litre tanks (12m x 2.4m x 3m) with 4x 6” inlets and 1x 12”outlet.Optional Alternative – Tank Trailer Solution An alternative considered was the provision of a pre-mounted tank on a trailer, allowing for delivery and removal as a complete unit, offering ease of installation and relocation if required.

The original proposal included 300kVA generators with float switch auto start, 3000-litre fuel tanks, and onsite telemetry and control boards. However, the final agreed solution excluded generators and fuel systems, assuming permanent electrical connections instead.

• Availability: Equipment was ready for deployment within 1–3 days. – Craneage & Lifting:
• Provided by Emerson Cranes.

• Flow Rate Uncertainty: Initial data lacked confirmed flow rates, complicating pump selection. As a solution, we conducted full manhole surveys and flow assessments to right-size the pump specification.
• Space Constraints and Ground Conditions: Uneven terrain and limited space at the port required flexible setup. We used compact Flygt submersible horizontal pumps with flexible hose arrangements and minimal footprint to mitigate this.
• Power Supply Management: Original plan relied on generator-based systems, which had logistical and fuel cost implications. To resolve this, we shifted to permanent electrical infrastructure with purchased distribution boards and controls.
• Tank Discharge and Gravity Flow: Required coordination with other contractors to ensure effective tank discharge over 400m. We ensured collaborative site coordination and use of optimally sized settlement tanks.

Willow Pumps provided a robust, reliable, and scalable overpumping solution tailored to the evolving needs of the Port of Dover. By shifting key infrastructure elements from hire to purchase, long-term cost efficiencies were also delivered to the client.

Willow Pumps continues to support the Port of Dover and Dover District Council as a trusted partner in wastewater and pumping infrastructure, offering both technical resilience and responsive service delivery.

• Pumping Duration: 12 Months
• Total Flow Managed: Approx. 165 litres/second
• Number of Pumps: 4 Flygt NZ3153HT Submersible Pumps
• Pipe Length per Pump: 24 metres
• Settlement Capacity: 160,000 litres (4 x 40,000L tanks)
• Motor Power: 9kW per pump
• Pump Suction/Delivery Size: 6” Bauer connections