It must be a nice time to own a business that rents temporary construction fencing.  Last week, a couple of Downtown parking lots were closed off, making way for new mixed-use projects on 9th Street and Olympic Boulevard.  We can now add a third surface lot to that tally, as the phase one site of South Park's G12 development is now fenced off in preparation for construction.  Designed by locally-based TCA Architects, phase one will rise seven stories at the southeast corner of 12th Street and Grand Avenue. The low-rise building is being developed by a partnership between the Wolff Company and Sonny Astani, and will contain 347 apartments above 18,500 square feet of ground floor retail space.  G12 will offer its residents 24-hour concierge and valet service, in addition to standard amenities such as a pool and a fitness room.  The project has gained some praise for its relative lack of automobile parking (at least by LA standards), as well as its ample bicycle accommodations.  Although the project's current surroundings are a mixture of parking lots and forgettable one-story buildings, this section of South Park is slated for explosive growth in the immediate future.  A second phase of G12 is planned for an adjacent parking lot, although a timeline for that half of the project has yet to be announced.  Developer Mack Urban also intends to construct multiple residential and hotel towers nearby, the first of which could break ground late this year.