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COLORADO DEPAR77~fENT OF 1 • , Water Quality Control Division • Rationale -Page 3, Permit No. CO-0029947 1 2. Ouahtuy. Acute and Chronic Low Flaws - The flows which are typically used to ca~ulare acute and chronic efjlucnt limitations are the one day in three year low flow (lE3J and the 30 day in three year low flow (30E3J, respectively. However, those flows have not been determined for either Logan Wash or Roan Creek by the Water Qualty Control Division. Therefore, the Division has derided to utilize the Qxro chronic low flow for Logan Wash from rlu previous permit. This flow was selected by Best Professional Judgrnunt as an estimation of the 30E3 (chronic) and the IE3 (acute) low flows since there are ro critical water quality standardbastd limier for slur permit that are q~icttd by the stream low flow value. Additionally. due to the ephemeral nature of Logan Wash, 6oth!the IE3 and 30E3 would also likely be 0.0 cfs. However, if future permit Umitr or water quality standards are changed, then the stream low flow values may need to be rtdettrnrined. 7hc stream !ow flows are as follows (all flows in cubic fed per second!: Table Ill - I - Chrome Low Flaw ,... Annual 0.0 0.0 IV. FAC/L%TY DESCRIPTION A. Industry Description The jaciUty is a research and development sire for the ecperimaual production of oil (kerogenJ from oil shale. Original plans called for production of 1,000 borreis per day of oil with associated process waters to be mechanically treated pear to discharge. However, due to economic reason, oil shale has never bete produced nor as expected to be pr~uced at the site any time in the near future. Therefore, the entire mine site currently remains idle m a maintenance only made. More derailed drscriptions of the mine site and its original operation plan are included in the 1983 and 1986 pmnrt rationales. 7tvo outfalis exist at the facility, OutfaU 001 is a mint dewntenng discharge located directly upstream from the oil/water separator and Outfall 002 is a mint dewntcring discha-ge from the portal of the Research mint adrt. Flow is monitored at Outfall 001 by a bucks acrd stopw>ztch and at Ou{raU 002 by a parshall flumes (.k~cidental, Inc. representatives stated that historically, OutfaU 002 has been the only outfaU with reported discharges primarily because the designated outfaU structure is located directly at the portal of the adit. 7lterefore, when inter is present, reported discharges occur. Conversely, the designated outfall structure for Gbl is located directly within Logan Wash some distance beneath the actual drainage hole. Therefore, altiwugh present, mine drainage typically percolates into the ground and rarely, rf ever, reaches the designated outfaU structure for Outfall 00I which redacts and/or eliminates actual discharger. Discharges correlate with periods of snow melt and wet weather with most discharges oocurring in the spring and summer months. Discharges from Outfall 002 occurred from May to November in 1993 and from April to May in 1994. Prior to 1993, neither outfaU had discharged for numerous years. Process iwnter is generated when soon activities are occurring, however, retort process waters art not allowed to be discharged through OutfaUs 001 or 002 at any time and art instead be directed to the evaporation ponds discussed below. ~7he facility conducted eight retorts m the mid 1980's but ro additional retorts have been conducted since. Prior to' 1991, EMRs Corporation was contracted to perform all on-site management of the Logan Wash mine site. Since rh'at trine, Dames Qc Moore has been contracted by Occidental, Inc. ro conduct the routine maintenance and perform the required environmental monitoring. A crew from Dames & Moor's Rife, Colorado, office visits the site on a weekly basis to check the outfaUs for discharges, leakage of the evaporation ponds, and for basic security reasons. There rs rro on-srte staff presem at the mrne site and the only remaining structures are the adrt, the outfal! structures, and the retort equipment and associated oil/water separator, piping system, evaporation ponds and leak collection system.