A retrievable and retrofittable subsea hydraulic dump valve assembly for a subsea oil and gas production system including at least one hydraulic selector valve including a solenoid and a spring. The hydraulic selector valve converts a first hydraulic pressure supply line into a primary hydraulic pressure supply line and a second hydraulic pressure supply line into a pilot line and a backup hydraulic pressure supply line. In a first operating configuration the hydraulic selector valve channels a first flow of hydraulic fluid from the first hydraulic pressure supply line to the critical control valve actuators to maintain the critical control valve actuators in the open configuration. In a second operating configuration the hydraulic selector valve channels the flow of hydraulic fluid to the subsea environment at a local venting location to reconfigure the critical control valve actuators into a closed configuration.