Deleting EBS volume manually.

1. login to AWS console.
2. Navigate to Services --> compute --> EC2 --> Volumes.
3. Select the unwanted volumes, From the Actions drop down --> Delete Volume.

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Note: 

By default, if any EC2 instance is terminated only root volumes are deleted for that particular EC2 instance. it depends on the settings made at the time of EC2 instance launch.

To delete the unwanted volumes need to follow above procedure.