The minimum design gradient for a SID is 3.3%, from a minimum of 35 feet over the Departure End of the Runway (aka the DER) until the point at which the SID ends. If the end point impinges on your 2nd segment, which is invariably the case, you have to be able to maintain at least 3.3% net climb or there's a chance that you will not clear an obstacle. OS is right, as usual, in that if your aeroplane will not climb at or above 3.3% in the OEI case, under any specific conditions, your company really should provide an emergency escape route procedure.