MEMORANDUM. Norm Evenstad, Water Resources Program Coordinator, Natural Resources Conservation Service (NRCS), Salt Lake City, Utah

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1 MEMORANDUM To: From: Norm Evenstad, Water Resources Program Coordinator, Natural Resources Conservation Service (NRCS), Salt Lake City, Utah Dennis Hawkins, PN Regional Diving Officer (PN-3425), Boise, Idaho Subject: Underwater Examination Report, Millsite Dam, Outlet Works Intake Structure (Riser) Examination with Sediment Sampling, November 7, 2006, Ferron, Utah NCRS, Salt Lake City, Utah GENERAL NCRS from Salt Lake City, Utah requested an inspection be performed on the outlet works intake structure and basin sediment samples be taken from the general vicinity of the intake structure located at Millsite Dam, Ferron, Utah. No other facilities were examined during this time period. Mr. Norm Evenstad, Water Resources Program Coordinator, NCRS, Salt Lake City, Utah requested the underwater examination of the outlet works intake structure and the procurement of basin sediment samples from the general vicinity of the structure. Staff from NCRS and the dam tender provided topside assistance during the examination. The purpose of the November 7, 2006 examination was to document and evaluate the underwater condition of the outlet works intake structure and to take basin sediment samples for further testing for pollutants. Following the underwater examination, the diver s observations were discussed with onsite representatives of NCRS. Bureau of Reclamation divers participating in the examination were: Jerry Sharman ( ), Dave Godaire ( ), Kevin Kelly ( ), and Jeff Peterson (PN-6438), all except Jeff Peterson are from the Technical Service Center, Denver, Colorado and Jeff Peterson is from the Pacific-Northwest Regional Office located in Boise, Idaho. Jerry Sharman was the Divemaster and author of this report. Topside assistance was provided by Messrs. Norm Evenstad (NCRS Salt Lake City, Utah), Ken Dastrup (NCRS Salt Lake City, Utah), and Lamond Smith (Dam Tender Ferron, Utah). Chip Royce (Salt Lake City, Utah) served as a sign language interpreter. BACKGROUND

2 Millsite Dam is owned by the Ferron Canal and Reservoir Company located in Ferron, Utah and was constructed and completed in The dam is located about 3 miles upstream from the town of Ferron, Utah and is fed by Ferron Creek (Figure 1). The reservoir covers a drainage basin area of approximately 157 square miles with a reservoir surface area at the spillway crest of 435 acres. This is equivalent to a reservoir storage of about 18,000 acre-feet. The dam has a structural height of 115 feet and a hydraulic height of 107 feet. The dam crest elevation is 6225 feet at mean sea level. The crest of the dam is 26 feet wide and 4150 feet in length. The spillway for the dam has a maximum discharge rate of 5450 ft 3 /s and the 54-inch diameter outlet works conduit has a maximum discharge rate of 480 ft 3 /s. The outlet works intake (riser) structure that was examined by the divers is submerged and is located about 100 to 150 feet upstream from the embankment (Figure 2). The steel reinforced concrete structure is approximately 47.8 feet tall. The base of the structure is about 34 feet long by 13.5 feet high by feet wide (Figures 3 and 4). The base of the structure was buried in sediment during this examination. Above the base, (Figures 5 and 6) the structure stands about 33.5 feet high and is about 10.5 feet wide by 16.5 feet long from about elevation 961 to about elevation 974 (elevations are based on survey datum on the drawings). From here the structure slopes up to about a 13 foot deep by 23 foot wide by 16.5 feet long trashrack structure. The upstream face of the riser has 8 foot wide by 30 inch high metal plates covering a total of 6 concrete portals. The top four of the six plates were exposed during this examination and the lower two plates were buried in sediment. The trashracks on both sides of the riser structure are comprised of metal I-beams set into concrete portals with 8 inch by 5/8 inch bolts through both ends of the I-beams to prevent movement. The I-beams are located horizontally across both the sloping bottom of the trashrack structure and up both sides of the structure. The top of the structure was constructed of a 23 foot wide by 16.5 foot long steel reinforced concrete slab. The drawing (Figure 2) shows 5-inch-diameter rubber bumpers located on each side of the top with a lift pedestal located about in the middle top of the structure. The weather during the inspection was slightly overcast and warm. Ambient temperature was about 70 o Fahrenheit or higher. The maximum diver depth was 60 feet (actual depth) to the sediment at the base of the structure. Water temperature was approximately 47 o Fahrenheit. Lockout/tagout procedures were implemented on the outlet works prior to the inspection dives. All gates controlled from within the outlet works control house were locked in the closed position. No previous underwater inspections of Millsite Dam outlet works have been conducted. EXAMINATION RESULTS Underwater visibility varied from about 10 feet near the reservoir surface to zero visibility at the bottom of the outlet works intake structure or reservoir basin. The divers inspected the outlet works intake riser and took samples of the basin sediments within the immediate area of the structure. 2

3 Outlet Works Riser Structure The top of the outlet works intake structure was approximately 40 to 43 feet from the reservoir water surface and was covered by approximately 1.5 feet to 2 feet of very fine sediment. Therefore, it was difficult to determine the condition of the concrete slab. However, there was no apparent evidence of serious damage or deterioration of the slab. Two of the 5 inch diameter cylindrical rubber bumpers were found and one appeared to be in satisfactory condition with no signs of serious deterioration and the other was found to be broken at the midpoint. The lift pedestal on the top of the structure was also located and is covered in a thick layer of rust and appears to be non-functional. The bottom silt was located at approximately 60 feet in depth, which indicates that only about the top 20 feet of structure remains exposed. The remaining portions of exposed concrete on the riser structure are coated with a thin layer of algae, but appear to be in satisfactory condition with no signs of cracking, spalling, serious deterioration, or damage. The plates on the upstream face of the structure were measured to be about 1/4- to 3/8- inch thick steel and were held to the wall by four bolts per plate. The surfaces of some of the metal plates were clean (Photograph 1) and others were covered with a thin layer of algae with some minor surficial rust. The bolts on the exposed plates were more seriously rusted (Photographs 2 and 3). There were some rust nodules on the surface of the metal plates, but this was usually within or around the area of the bolts. The trashracks on the sides and sloping sides of the structure are horizontal I-beams (Photographs 4 through 6), set into slots in the concrete (Photos 7 and 8). Each beam was prevented from moving by pins set in the I-beams, on the inside of the portals the beams sat in (Photographs 9 through 12). There is a layer of algae and rust across the surfaces of the I-beams, with some rust nodules. The pins used to prevent movement of the I-beams are more seriously rusted with some loss of section. However, the I- beams appear to be in satisfactory structural condition and functioning as designed. Sampling Five samples of the basin sediment were taken from the outlet works intake riser area during this dive, per the request of Mr. Norm Evenstad (NRCS). Samples were collected using 1-liter poly bottles supplied by Ms. July Fahy, Bureau of Reclamation ( ), Denver Technical Service Center (TSC). One sample was collected from the top of the outlet works intake structure and the other four were taken from the reservoir floor near or against the riser. Samples were taken by driving the sampler deep (1 to 2 feet) into the sediment and by shoveling sediment into the sampler by hand. Basin sediment was too saturated with water and a representative sample could not be taken without pushing the sampler deeper and manually pushing it into the sampler. Samples were provided to Ms. Juli Fahy for analysis. 3

4 CONCLUSIONS AND RECOMMENDATIONS The outlet works intake structure appears to be in satisfactory condition. Due to infilling of sediment around the structure, only about 20 feet of the structure could be examined. The concrete of the structure is in satisfactory condition with no signs of serious damage or deterioration. The metal plates covering the portals on the upstream side of the structure and the I-beam trashracks on the sides of the structure exhibit surficial rust and the pins holding the I- beams in place are more seriously rusted with some loss of section. However, there is no sign of loss of structural integrity of these features and they appear to be functioning as designed. The outlet works intake structure should be re-examined on a regular basis as part of the Routine Operations and Maintenance schedule. Cc: Chief, Dam Safety Office, Denver CO Attention: D-1440 (w/o attachments) Director, Technical Service Center, Denver CO Attention: D-8470 (Veesaert) (w/attachments) (2 copies) NRCS, Salt Lake City Utah (Norm Evenstad, Ken Dastrup) D-8470 (Sharman) D-8010 (Dinneen) (w/o attachments) D-2230 (Archives/Official File Copy) 4

5 List of Figures Figure 1 - Drawing 7-E-18915, Millsite Dam Location Map & Reservoir Data Curves (Sheet No. 2) Figure 2 - Drawing 7-E-18915, Millsite Dam Riser Layout (Sheet No. 15) Figure 3 - Drawing 7-E-18915, Millsite Dam Steel Reinforcement Riser (Sheet No. 29) Figure 4 - Drawing 7-E-18915, Millsite Dam Steel Reinforcement Riser (Sheet No. 31) Figure 5 - Drawing 7-E-18915, Millsite Dam Riser Layout (Sheet No. 69) Figure 6 - Drawing 7-E-18915, Millsite Dam Steel Reinforcement Riser (Sheet No. 27) 5

6 Photo 1. Millsite Dam Metal plate over portals on the upstream face of the structure. 11/7/2006 Photo 2. Millsite Dam Corner of a metal plate covering portals on the upstream face of the structure. Arrow denotes rusted bolt holding the plate to the concrete face. 11/7/2006

7 Photo 3. Millsite Dam Arrow denotes rusted metal bolt holding the metal plate to a portal on the downstream face of the structure. 11/7/2006 Photo 4. Millsite Dam Metal I-beam used as trashracks on the intake sides of the riser structure. Buoy magnet was tied to the top I-beam. 11/7/2006

8 Photo 5. Millsite Dam Metal I-beam set into the concrete walls of the riser structure and used as trashracks. 11/7/2006 Photo 6. Millsite Dam Metal I-beam set into the concrete walls of the riser structure and used as trashracks. Arrow denotes one of the pins used to prevent movement of the I-beams. 11/7/2006

9 Photo 7. Millsite Dam Metal I-beam set into the concrete walls. Upstream or downstream face of the structure. 11/7/2006 Photo 8. Millsite Dam Metal I-beam set into the concrete walls. Upstream or downstream face of the structure. 11/7/2006

10 Photo 9. Millsite Dam Arrow denotes rusted bolt on end of I-beam trashrack. 11/7/2006 Photo 10. Millsite Dam Arrow denotes rusted bolt on end of I-beam trashrack. 11/7/2006

11 Photo 11. Millsite Dam Arrow denotes rusted bolt on end of I-beam trashrack. 11/7/2006 Photo 12. Millsite Dam End of I-beam inserted into concrete wall. Arrow denotes rusted bolt on end of I-beam trashrack. 11/7/2006