Abstract: A remedially deployable subsurface valve assembly is provided including a first tubing string, a first safety valve positioned in the first tubing string, a second tubing string, and a second safety valve positioned in the second tubing string. The first tubing string is a rigid production tubing string deployed in a hydrocarbon production wellbore extending beneath an earthen surface. The second tubing string is a flexible coiled tubing string remedially deployed in the interior of the first tubing string when the first safety valve fails. The second safety valve, which is located at the end of the second tubing string, is nested within the first safety valve to render the first safety valve inoperably fixed in the opened position. A seal, which is positioned in the annulus formed between the first and second tubing strings, defines a pressurizable segment of the annulus in pressure communication with the second safety valve.