With a new promise of $125 million from Minnesota Twins owner Carl Pohlad in hand, Hennepin County will seek state permission to increase the local sales tax for a Warehouse District ballpark in downtown Minneapolis. Under the terms of the plan to be unveiled at a Metrodome press conference Monday, the Twins and the county would build a $360 million, 42,000-seat open-air stadium. The site is near the confluence of Interstate Hwy. 394, the end of the Hiawatha Light Rail line and the proposed Northstar commuter rail in downtown Minneapolis. The total cost of the ballpark project is projected to be $478 million, including bonding costs, site preparation and surrounding infrastructure, such as road and pedestrian improvements. No state money would be required.