Having a lot of variations and claims in project happen because of?

This happens in a Lumpsum EPC Contract because of lacuna in Front end engineering stage and also because the needs and expectations of stakeholders  were not factored in 

Employer related Variations

Consultants related Variations

Contractors related Variations

Change of plans or scope by Employer

Change in design by Consultants

Lack of Contractor's involvement in design

Change of schedule by Employer

Errors and omissions in design

Unavailability of equipment

Employer's financial problem

Conflict between contract documents

Unavailability of skills

Inadequate project objective

Inadequate scope of work for contractor

Contractor's financial difficulties

Replacement of materials/procedure

Technology change

Contractor's desired profitability

Impediment in prompt decision making process

Value engineering

Differing site conditions

Obstinate nature of Employer

Lack of coordination

Defective workmanship

Change in specifications by Employer

Design complexity

Unfamiliarity with local conditions

Inadequate working drawing details

Lack of specialized construction manager

Inadequate shop drawing details

Fast track construction

Consultant lack of judgment and experience

Poor procurement process

Lack of consultant's knowledge of available materials and equipment

Lack of communication

Honest wrong belief of consultant

Contractor's lack of judgement &experience

Consultant's lack of required data

Long lead procurement

Obstinate nature of consultant

Honest wrong belief of contractor

Ambiguous design details

Complex design and technology

Design discrepancies (inadequate design)

Lack of strategic planning

Non-compliance design with govt. regulation

Contractor's lack of required data

Non-compliance design with owner's requirement

Contractor's obstinate nature

Change in specifications by Consultant

Improper understanding of specifications at the planning stage or inept execution in execution stage.

Delivery gaps created due tto llack of expertise, change of personnel while execution and unforeseen delays also contribute to this.

VO's are majorly caused because of unavailability of equipment, poor workmanship, and design complexity

Also, improved design and avoiding frequent design changes will be very effective in controlling the problem of variations.