Outlet Works, Gates, & Valves

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Demolition and removal of 5’x7’ bonneted slide gate and liner, 62” 38,000 lb Larner-Johnson needle valve and liner, and associated accessory structures. Install new jet flow gate and liner. Backfill grout upstream liner pipe in 3 stages. Install new FRP system. Decommission seven 42” gate valves. Drive new access tunnels through 30,000 psi granite using jack legs, rock splitters, chipping hammers, and other manual tools. Total rock and concrete hand demo’d = 361 CYs. Install new 42” access bulkheads. Abandon access shaft and air vent shaft with concrete fill. Install new standpipe vent system. Install new washdown system, air valves & related piping, and all electrical and I&C components. 

Demolition of existing concrete dam outlet works. Construction of new concrete outlet works. Work was at a remote mountain lake with only an 8-mile, two-track road. All materials were transported to the site via a custom, shortened trailer to negotiate the tight mountain switchbacks. A portable concrete batch plant was transported up the mountain and used to mix the concrete. Concrete was pre-mixed dry, transported in Super Sacks, and mixed on-site. A man-camp was set up to house workers at the site.

Inspection, testing, and repairs on a 54” and a 60” butterfly valves on the dam outlet works. Repairs included rebuild of the hydraulic operating cylinders, grating, painting, and electrical work. Testing and adjusting the HPU 

Engineering support, scheduling services, and submittal review for an outlet replacement project on privately owned dam near Farmington, NM 

One 100 cy diversion structure and head wall at end of 10’ diameter outlet works pipe located 11,500 ft elevation.  

 Concrete repairs and grouting of sluice gate bay outlet works. W

Dome Lake: Install a new 24” sluice gate in the existing outlet work. Grout the frame and make miscellaneous concrete repairs.   Willow Reservoir: Concrete repairs and grouting of sluice gate bay outlet works.  Work occurred above 10,000 ft elevation in extremely remote sites in the Big Horn Mountains. Required careful planning and staging to ensure all materials, equipment, tools, and crew provisions were correct, as getting back to civilization required hours of travel over barely existent roads 

Remove existing damaged or deteriorated concrete in the  sluiceway chute and stilling basin. Furnish and place cast-in-place concrete for concrete repairs in sluiceway and stilling basin. Remove existing damaged or deteriorated grout adjacent to existing sluice gate frames and replace with new grouting mortar. Rehabilitation of five each slide gates and frames and five each 30 ft. x 13.5 ft radial gates required: removal & disposal of existing coatings containing heavy metals, repairs, replacement seals, surface preparation, and recoating. Furnish and install galvanic anode cathodic protection systems for spillway radial gates. Diversion & care of Big Horn River with coffer dams up to 30’ tall. Furnish & place riprap underwater. Rehabilitate existing T-bar guides. Wire rope-related repairs to overflow radial gates 

Removed the failed steel lining in the outlet conduit downstream of the control gates.  Installed and welded 9-part, 48” square-to-round steel transition. All welds by certified welders and inspected. Backfill grouted (60 bags) between liner and excavated rock. Due to site conditions, group pump was located 90’ above liner, which required special grouting procedures. Dewatering provisions needed due to leaking upstream slide gate 

Disassemble, inspect, and reassemble 2 each 2’9” x 2’9” high pressure slide gates located in gate chamber at end of 300’ long tunnel. Revise hydraulic system. Dewatering provisions needed due to leaking upstream slide gate. 

Remove & dispose of the existing 3/16” steel plate, steel angles and concrete expansion anchors on the slope of the stilling basin. Furnish & install approximately 1,280 SF of 1/2” steel plate, fasteners & welding; furnish & install end, side, & top of slope treatments; and furnish & install over 300 gallons of Sikadur 52 epoxy injection adhesive under the steel plates. 

Demolition & removal of 2 each 20,000 lb. tractor-style slide gates. Installation of two new 7’ x 13’ x 12000 lb. slide gates, hydraulic operators, & associated equipment for the 80’ tall intake tower for the reservoir outlet works located on Sutherland Reservoir. Access to the work area was via a 900’ long outlet works tunnel.

Hydraulic system removal & replacement for 2 outlet works high pressure slide gates 

Remove piping and grout the existing water line and install blind flanges. Pressure grouting was performed against 200’ of lake head—surface preparation and painting of all steel surfaces of the metalwork. 

Remove two 10,000 gpm vertical turbine pumps, hand excavate & dispose of 100 cy of concrete & rock using rock splitter and hand tools.  Furnish & install 20 cy of reinforced concrete per sump, furnish & install two 300 hp 10,000 gpm 2-stage vertical turbine pumps, furnish & install steel piping and valves to connect existing piping to the new suction barrels for new turbine pumps.

Replace existing radial gate, place reinforced concrete trunnion blocks, replace wire ropes, spools, seals, and coatings. 

Replace existing outlet timber bulkheads with fabricated steel on the upstream face of the dam. All work rope supported.

Dewater outlet, disassembly and removal of emergency and regulating gates, repair cavitation damage and recoat emergency and regulating gate frames and transitions, replace seats on regulating and emergency gates frames and leafs, repair cavitation damage to emergency and regulating gate sills and regulating gate leafs, recoat emergency and regulating gate leafs, repair or replace bent extension stem on regulating gate, recoat cylinders, bonnet covers and gate hangers on emergency and regulating gates, and reassemble and test gates.

Rehabilitation of the existing 64 foot diameter by 12 foot high floating ring gate located at the top of the Morning Glory Spillway. The work included disassembling the existing seals, associated curb angles and seal clamp bars and disposing of these parts. Modified and installed Government-furnished seals and new rolled curb angles along with the associated fasteners. Oversaw a subcontractor performing the sandblasting and painting of the exterior and interior of the ring gate which was covered by paint contaminated by lead and chrome. This work required a unique “doughnut” style access platform and containment structure to protect the work from the weather and contain the contaminants during sandblasting e 

Dewater, position bulkhead gates and control leakage, repair of two 72” diameter ring follower gates, surface preparation and coating of water bearing ferrous metal surfaces of two 72” ring follower gates, and surface preparation and coating interior surface of two 72” conduits from the upstream bulkhead gate to 10 ft. downstream of the ring follower gate, (170’ each).  

Furnished and installed a 30" Jet Flow valve, 60" butterfly valve, hydraulic system for the valves, 48"and 60" steel piping, a 10' x 17' x 22,000 lb. bulkhead gate, gate seals and guides down a 200' deep shaft, cable hoist and control system, deactivated 4 ea high pressure gates, and designed and installed new ventilation system. All work performed in shaft and intersecting tunnel. A major component of the work involved controlling upstream gate leakage (4400 g.p.m.) in the tunnel. New concrete and rock interface was pressure grouted. All material and personnel access via the shaft using a crane and contractor installed elevator. 

Construct galvanized steel walkway/handrails on penstocks. Replace 10" sump and penstock drain line and components. Replace two 8" pressure supply lines and components. Plug 8" tunnel drain line and components. Replace two 6" lower bonnet drain lines and components. Required hot tapping and grouting of various lines under lake pressure.e 

We designed and constructed a 700' long tunnel and intake structure through an existing rock fill and earthen dam to be used as a low outlet works. The 6' wide x 7.5' high tunnel was excavated through rock using an Alpine continuous mining machine. This tunnel excavation proceeded upstream through a rock outcropping within the earthen dam and terminated inside a sheet pile cofferdam located in the lake. Timing and coordination were critical items due to rising lake levels. The intake structure was cast in place. Welded bell and spigot pipe was installed in the tunnel and backfill concrete was placed. New concrete and rock interface was pressure grouted, using 1274 bags.  Other work included installation of a downstream valve vault, cathodic protection, grouting, and piezometers 

We subcontracted to Chicago Bridge & Iron to remove the following: 1600 CY penstock gallery overburden: 144 CY reinforced concrete roof deck; 850 CY concrete and 180 ton riveted steel plate trifurcation; 170 tons of cast steel in three each 14 ft x 14 ft x 12 ft tees; 140 CY concrete floor slab; 420 ton riveted steel plate 16' diameter penstocks; and two 16 ft and one 12 ft butterfly valves with operators. Placed 1800 CY reinforced concrete for new trifurcation. Replaced roof deck and overburden. 

Demolition included removal of concrete-embedded 10 ft diameter cylinder gate valve and 500 CY reinforced concrete from within a gate chamber located 200 ft underground. Also removed two 48" needle valves. Excavated, through controlled blasting technique, a 30' x 30' x 40' valve chamber in downstream face of existing concrete dam. Constructed energy dissipation / hydroelectric power plant structure (3400 CY structural concrete) requiring removal of 18,000 CY of shot granite and sandstone. Drilled, shot, and concrete-lined one 12' horseshoe x 800 LF free flow tunnel in sandstone to connect power plant structure with existing tunnel network. Drilled and shot 70 LF tunnel in granite for 126" penstock to within 10 ft of existing high-pressure gate. Drilled and shot 8' x 8' tunnel in granite. Constructed 12' x 12' x 48' high access shaft and adits in granite. Constructed gantry crane. Extensive dewatering required throughout project. Several river bottom excavations required diverting and pumping the Shoshone River (approximately 20-40 c.f.s.) away from the work area. 

Surface preparation & painting for all exposed surfaces of three fixed-wheel penstock gates and refurbishing twenty-four fixed-wheel assemblies per gate. (Each penstock gate is 26 ft wide x 38 ft tall.) Work on a fourth gate limited to spot repair and recoating. Work includes removal of the seal bars and seal bar clamps and repair/recoating of corrosion areas and/or failed coating areas. Work self-performed by Moltz forces: fabricating gate support structure, working with BOR and crane service provider to move gates across work site, removing and placing back the wheel assemblies and seals. Coatings removal and recoating performed by Hartman Walsh, subcontractor  

Removed 2 each 52,000 lb. 60" differential pressure needle valves and associated 72" piping from the interior of the power plant. Installed government-furnished jet flow valves and connected 72" piping. Work also included designing and installing the hydraulic control system and associated electrical work. 

Advise on 4' x 6' high-pressure gate options & procurement, develop project schedules, monthly progress calls, and oversight of gate installation. 

Prep, Welding, Belzona, & Coating of extensive cavitation reapirs to the downstream gate thinble.