Assuming the lots are not contiguous to your principal residence, the sale will be treated as the sale of a capital asset with any gains subject to applicable taxation.
The best way to minimize your tax hit is to maximize your cost basis. Make sure that you include along with your purchase price all non-recurring closing costs (acquisition and refi's) and improvements including permit, architechural costs, and any other pre-construction costs you have incurred.
The difference between your net sales price and your cost basis (adjusted for improvements and depreciation) is your capital gain.
Your cost basis is determined by taking your original purchase price (plus any non-recurring closing costs) and adding the cost of any improvements made during ownership and then subtracting any allowable depreciation or amortization (whether claimed or not).
Your net sales price is the contract selling price less any selling costs (i.e. broker commissions and other transaction costs as well as fix-up expenses if real property is involved).
If you own the property for more then one year, then the gain will be treated as a long-term gain and will be taxed up to a maximum capital gain rate of 15% (5% if the gain would otherwise be taxable in the 10% and 15% brackets). Otherwise the gain is treated as a short-term capital gain and to the extent not offset by other capital losses will be considered as ordinary income the same as wages and interest subject to whatever your marginal tax rate is. Don't forget state taxes.
Accordingly, if you can hold onto the property for at least another month, you will get much more favorable tax treatment. As a short-term term capital gain, your $12,000 per lot gain may result in an additional $4,800 per lot in Federal and CA tax. If long-term, capital gains rates apply you tax liability may decrease to abot $2,600 per lot.
Because it is impossible for me to identify and consider ALL the relevant facts, this advice is not intended or written to be used for the purpose of avoiding penalties, and cannot be used for that purpose.