I agree with all of the above solutions, but I have a few bits to add.
First, if you have already gotten a bronze medal on a level in survival using weapons, you will not be able to get this achievement on that level in 4 minutes (bronze medal). The idea behind that is you have already gotten the medal using weapons other than the melee weapons. So you can try for the seven minute mark for the silver medal with melee weapons only, but that will be much more difficult so keep this in mind.
Second, this achievement was much easier for me and my friends to achieve when there was 2 human survivors and two AI survivors. We tried with three humans and it was unreasonably difficult, 2 seemed to be much easier.
Third my strategy was on bus depot in the Parish. We started by setting up all of the gas and propane tanks in the narrow walkways between barriers parallel to the scaffolding with the button. This was in prep for the tanks, we could fall back around the 3.5 minute mark through these "hallways" firing on the cans and propane tanks creating a wall of fire and explosions to slow down and damage the tanks to make it to 4 minutes. We also setup the explosive and incendiary ammo (found at the entrance to the bus station) on either side of the bus which is parked perpendicular to the bus station. Each grab a molotov (for the tanks) and start it up.