function shockwaveTimer(primary, minutes_left)
    local key = primary and "primary" or "secondary"
    --Configurable alert intervals, key = current time, value = next alert
    local next_intervals = {}
    next_intervals[60] = 5
    next_intervals[5] = 3
    next_intervals[3] = 1

    send("shipt " .. key:title() .. " shockwave timer expires in " .. minutes_left .. " " .. (minutes_left == 1 and "MINUTE!" or "MINUTES."))


    if bwl.shockwaveTimers[key] then
        bwl.shockwaveTimers[key] = nil
    end

    if next_intervals[minutes_left] then
        bwl.shockwaveTimers[key] = tempTimer((minutes_left - next_intervals[minutes_left])*60, [[shockwaveTimer(]] .. (primary and "true" or "false") .. [[, ]] .. next_intervals[minutes_left].. [[)]])
    end
end