Additional_Questions_11_May_2015.docx

M67001-15-Q-0048 Additional Questions

The below questions were a direct result from questions that arose from the original questions and responses.

Question:

We have reviewed the UFC 3-575-01 code for grounding. It appears 25ohms is required. This requirement also required a counter poise system to be installed 30" below grade. In lieu of the 30" below grade we could tie the system into the bases flight line tie downs.

Are the existing tie downs grounded and can they be used to meet this requirement?

Answer:

The vendor can use existing grounding points as long as they do not interfere with the ingress/egress of the aircraft and do not present a trip hazard to Marines on the deck. When final dimensions of shelters are known (at award), the customer and vendor will coordinate to produce a scale drawing of the final layout. At that time, we can align the layout to the existing grounding points and make any required layout adjustments and hazard mitigation plans.

Question:

The Government’s response to questions stated that contractors are to design the grounding system per UFC 3-575-01.

The issue with this code is that you have to have a counter poise system installed at 30" below the dirt surface. To do this per that code we would have to cut the concrete around the perimeter of each shelter, dig down 30" below the base of the concrete then install the counter poise system and reapply the concrete to grade.

The alternative to trenching would be to use the tie-downs. Aircraft tie downs should be tied together inside the concrete to create your grid layout. The catch to this is that the contract says we can only use the tie downs if they meet the requirements. You cannot determine if the tie downs meet the requirement with a simple site visit. The magic is inside the concrete. You have to make sure the tie down are tied together to create the grid. You cannot see the grid with the naked eye as it is inside or below the concrete. We would need your engineering that base engineering has so we can integrate our system with your current system.

Without the grid layout drawings and information I don't believe that anyone with 100% surety can design a grounding system per UFC 3-575-01 and the trenching option will cost more than the shelters.

Answer:

There is no available drawing of the tie-down grid layout. The vendor can use existing grounding points as long as they do not interfere with the ingress/egress of the aircraft and do not present a trip hazard to Marines on the deck. When final dimensions of shelters are known (at award), the customer and vendor will coordinate to produce a scale drawing of the final layout. At that time, we can align the layout to the existing grounding points and make any required layout adjustments and hazard mitigation plans.

Question: This code also covers Lightning Protection. Do we just design a grounding system or do you want lightning protection and the grounding?

Answer: Per the NAVSEA OP 5, lighting protection is not required for shelters used for our purposes. We do not request lighting protection.