Temporary drainage during construction

Temporary drainage keeps excavations, formations, and working areas manageable during construction — diverting surface water, collecting seepage, and pumping where needed until permanent systems are live. It is part of enabling and groundworks sequencing, not a substitute for the permanent SuDS or sewer design.

This process page covers planning, installing, maintaining, and removing temporary drainage so permanent works are not undermined by uncontrolled water.

Temporary drainage should appear on the enabling programme with owners and removal dates. If it only exists as a verbal plan, it will be missing on the first wet Monday.

review Groundworks Contractors in Wandsworth and Groundworks Contractors in Kingston.

When sequence matters

When digs sit wet; when stripped sites shed silt-laden runoff; when foundation formations must stay dry for inspection and pour; or when permanent outfalls are not yet available.

It also appears when planning conditions require silt management and the site would otherwise discharge dirty water off-plot.

Typical sequence

Step 1: Plan catchments and discharge
What this step delivers: Temporary route and legal discharge path agreed.
Step 2: Install sumps and runs
What this step delivers: Water controlled ahead of critical digs.
Step 3: Maintain through works
What this step delivers: Pumps and silt controls kept working.
Step 4: Remove or hand over
What this step delivers: Temporary system cleared when permanent drainage lives.

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What each stage delivers

Typical measures include temporary ditches or piped runs, sumps, pumps, settlement tanks or bunds for silt, and staged connections into permanent systems only when allowed.

Design of temporary works should consider where water will go without flooding neighbours or polluting watercourses. HSE/CDM duties apply to pump fuel, cables, and open excavations.

Remove or hand over temporary systems at the agreed stage so they do not become accidental permanent features that bypass designed treatment.

Link temporary drainage to the wider enabling plan: haul roads, stockpiles, and compound runoff all generate water that needs a managed path. If permanent SuDS features exist early, fence them off from temporary dirty water or accept that they will need cleaning before adoption or handover.

Where temporary drains cross public footways or shared access, plan lighting, signing, and covers to CDM expectations; temporary does not mean informal from a safety perspective.

Programme risks and hold points

Wet excavations or standing water on stripped platforms
Silt risk to roads or watercourses
Permanent outfall not yet built
Pour and inspection windows needing dry formation
Planning conditions on construction runoff

Pre-start and handover checklist

Temporary drainage sketch aligned to programme
Discharge / silt management method agreed
Pump maintenance and out-of-hours response
Protection of permanent soakaways/attenuation from silt
Removal date written into the programme

Keeping trades coordinated

Install temporary routes early, maintain them through the critical dig/pour window, then remove or integrate as permanent drainage comes online.

At demobilisation, remove temporary pipes and sumps that could short-circuit permanent SuDS or leave trip hazards in soft landscape areas.

Where time and cost usually escalate

Pump hire duration, silt treatment, and weather-driven downtime dominate. Under-scoping temporary drainage is a common cause of foundation delay. Enabling-works and excavation cost pages provide related commercial context. Silt settlement before any permitted discharge protects both consents and neighbour relations. Fuelled pumps need bunding and spill kits; electric pumps need RCD protection and cable management away from dig edges. Extended wet seasons multiply pump-hire weeks; treat duration risk explicitly in enabling allowances rather than assuming a short dry spell. Review temporary drainage after each major storm and adjust sump positions before the next dig phase.

Stage overview

Aspect	Temporary	Permanent
Purpose	Keep works dry / control silt	Long-term designed system
Lifespan	Programme window	Design life / adoption
Risk if left	Bypass of SuDS / pollution	N/A if correctly commissioned

Temporary vs permanent drainage.

Where this sequence is commonly used

Foundation digs on wet sites
Stripped housing parcels before permanent SuDS
Basement and deep excavation dewatering support
Silt control beside watercourses

Frequently asked questions

Can temporary pumps discharge to the foul sewer?

Only if specifically permitted. Uncontrolled discharge of silt-laden water to sewers or watercourses can breach consents. Agree the discharge route first.

Is temporary drainage part of enabling works?

Often yes. See enabling-works guidance for the wider package; this page focuses on the drainage sequence itself.

Who maintains temporary pumps overnight and weekends?

Agree responsibility in the package. Unattended pumps that fail in a storm are a common cause of flooded formations and delayed pours.

Can temporary drains stay as permanent land drains?

Only if the designer adopts them into the permanent detail with correct materials and outfalls. Most temporary runs should be removed or formally redesignated.

How This Issue Is Normally Diagnosed and Repaired

Follow the typical path from problem identification through to resolution:

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