Here's a thumbnail sketch on him taken from the American CW Research Database. I believe you will find a great deal of information on the regiment & companies Record of Events in the Broadfoot Volumes, Supplement to the Official Records, which may be found in most large city libraries and universities.

Alan has provided you with information on obtaining his service record file.

Washington L. Rivenbark

Residence New Hanover County NC; an 18 year-old Farmer.
Enlisted on 6/1/1861 at New Hanover County, NC as a Private.
On 6/1/1861 he mustered into "K" Co. NC 3rd Infantry
He was discharged for disability on 12/10/1862
(By reason of "gunshot wound of the forearm")
He was listed as:
* Wounded 7/1/1862 Malvern Hill, VA
* Returned 12/10/1862 (place not stated)
Promotions:
* Corpl 9/17/1862
Other Information:
born in New Hanover County, NC
Sources used by Historical Data Systems, Inc.:
- North Carolina Troops 1861-65, A Roster