Police believe the attack was targeted rather than the work of mindless vandals.
Hydraulic hoses were cut on eight machines including excavators and dumper trucks while sand was poured into fuel tanks and tyres let down
Thousands of pounds worth of damage was caused at the site at Crossgills Farm in Lancaster.
Sgt Lindsay Brown of Morecambe Police told the Lancaster Guardian: “Eight vehicles, including excavators and dumper trucks, were damaged to the tune of thousands of pounds at the weekend.
“Tyres have also been let down and sand put into fuel tanks.
“We are keeping an open mind as to who is responsible, however the vandals have made a concerted effort to cause criminal damage by using bolt croppers to cut the rubber hoses.
“There is also a serious risk to the operator of the machinery if they start it up.
“It’s pretty reckless.”
Andrew Langley, Costain Project Manager, said: “We’ve had several incidents of intruders entering our construction sites in the evening and weekends, causing significant damage to the plant and machinery.
“Whilst these incidents are both disruptive and costly to the project, the overwhelming issue is that a construction site is not a playground to intruders who may or may not be aware of the dangers that exist on a live construction site.
“The sites contain enough risks to the trained and qualified construction workers alone.
“The workers are briefed each day, and wear the correct protective clothing at all times.
“An intruder or child has no knowledge of where unstable ground conditions exist, what structures are incomplete or not secure, and what injuries can be sustained when tampering or vandalising machinery.”