Complex Oracle SQL to sum data
I think you might be able to get the results you want with:

select j_title, k_title, l_title, sum(wrk_hr) from
(
  SELECT
   J.J_Title,
   K.K_Title,
   L.L_Title,
   L.Work_ID,
  SUM(CASE WHEN TRUNC(C.CHRG_DT) = TO_DATE('09/27/2013', 'mm/dd/yyyy') THEN C.WRK_HR END) AS WRK_HR
  FROM C, L, K, J
  WHERE J.Project_ID = 'ABC'
  AND K.Project_ID = J.Project_ID
  AND L.Project_ID = K.Project_ID
  AND C.Work_ID = L.Work_ID
  GROUP BY L.Work_ID, L.Project_ID, K.Project_ID, J.J_Title, K.K_Title, L.L_Title
)
group by j_title, k_title, l_title;