After dealing with Erebos your team must enter Apollo and reach Dr. Bergmann's laboratory. You can either proceed around the city and activate the generators, or proceed in the direct way through the scrapyard gates. Although the scrapyard is the direct approach, an ambush of banelings lies in wait and must be dealt with, usually they spawn on high ground so can be hard to deal with. Reactive Armor, Sonic Traps, or even simple flares will work wonders. After arriving at the labs Bergmann will inform you of his plans to cleanse the infestation. He will provide you two Laser Rifles to do so. After 30 seconds he will open up the Bio-Domes.