If you have additional time in your training schedule—in this scenario, more than three months until your target race—and you wish to add another mini-cycle to the base building phase, feel free to do so.  I recommend repeating the last four-week mini-cycle.  Race walk all of the same workouts, but increase your pace by 10 seconds a mile.  For example, in this schedule, walk at 9:50 per mile during the added weeks, as follows:

Alternatively, try increasing your weekly mileage to 50 miles without increasing intensity.  Consider this option:

Do not simultaneously increase intensity and mileage!  It causes injuries.