Legal Compliances In Engagement Of Labour Contract?

Statutory obligations regarding engagement of contract labour
i am attached to pvt ltd. Company engaged in construction of govt, projects in bihar , jharkhand and west bengal. To carry on construction works, we are to engage contract labour .
What are the statutory obligations we will have to comply with?
Dear friends, if kindly highlight the obligations , it will be of immense help to me.
Thank u.

Ensure following compliance while engaging Contract Labour in any firm / project .
1) Principal Employer ( Your Organization) must having registration under CLRA.
2) Your Orgnisation must having registration under PF & ESI coverage.
3) Try to engage only those contractors who have earlier registration under CLRA othervise issue FORM V to all and fix their manpower which are required to be engaged daily at your site. In any case it should not cross the threshold limit as approved under license.
4) Take coverage under insurance for PLI and employees compensation act in case of any causality at site.
5) Maintain Canteen and welfare facilities at site as per norms.

If principal employer has only 15 person including CMD & all employees on regular roles and every one salary is above Rs 20,000/- and they give 100 % back to back work to other agencies and in this case the principal employer should have CLRA registration..?
Please advise..