Twenty developments in various stages include enough approved housing units to increase Manteca’s population by upwards of 31,400 people.Some 38.7 percent of the 10,828 housing projects are tied up in the 1,049-acre Austin Road Business Park that saddles Austin Road in southeast Manteca. The housing portion of that project - some 456 acres - won’t be built until after the business park portion is well underway. In any case it is 2.5 times larger than any other housing project approved for Manteca.The housing slowdown triggered by the foreclosure mess spurred by creative loans didn’t slow new home building in Manteca down to a trickle as it did in many other Northern San Joaquin Valley locations.