Friend E.R.,RJH Consultants |
Weldon J.H.,Denver Water |
Olsen J.A.,RJH Consultants
Environmental and Engineering Geoscience | Year: 2010
Miller Reservoir and Dam is a 43-ft-high (13-m-high), 5,000-ft-long (1,524-m-long) dam located along the South Platte River north of Denver, CO. The reservoir is located at the site of a previous gravel mine. The capacity of the original gravel pit reservoir was about 800 acre-feet (986,800 m 3). By constructing a perimeter embankment and soil-bentonite cutoff wall and mining material within the limits of the reservoir, the storage was increased to over 2,000 acre-feet (2,467,000 m 3). This additional storage is an integral part of the water management system of Denver Water, which services 1.3 million customers and is Colorado's oldest and largest water supplier. Because of site constraints and property boundary limitations, the seepage barrier for the dam foundation included the combination of about 6,600 ft (2,012 m) of soil-bentonite cutoff wall with about 1,400 ft (427 m) of core trench extending into bedrock. The embankment consisted of three different typical dam sections that made use of available onsite materials for construction. Four distinct methods to connect the clay core of the embankment with the different seepage-control measures were designed and incorporated into the project. Vertical connections between the clay core, soil-bentonite cutoff wall, and bedrock were also designed and installed adjacent to the outlet works tower. This paper will present the different types of seepage control, incorporation of the embankment internal zoning with the seepage-control methods, and material utilization for dams with multiple seepage barriers.
Bambei Jr. J.H.,Denver Water |
Keil B.,Northwest Pipe Company
Pipelines 2013: Pipelines and Trenchless Construction and Renewals - A Global Perspective - Proceedings of the Pipelines 2013 Conference | Year: 2013
AWWA C200 Steel Water Pipe, 6 Inch and Larger, is an industry consensus standard that is recognized throughout the world and is the preeminent guide for the manufacture of steel pipe for water and wastewater applications in North America. The first AWWA steel water pipe standard (7A.3 and 7A.4) were published in 1940. In 1949, 7A.3 was replaced with C201 and 7A.4 was replaced with C202. These two standards were later combined into the C200 standard in 1975. Since then, the document has undergone six revisions, each iteration marked by improvements to the manufacturing process as well as associated quality control procedures. The most recent revision, incorporating a number of significant updates, was approved by the AWWA Board of Directors on June 22, 2012 and became effective on September 1, 2012. This paper will provide a historical perspective of AWWA steel water pipe standards, followed by a discussion of some substantial improvements made in the latest revision of C200. Topics discussed will include considerations for the Charpy toughness or impact testing, new testing requirements for gasket materials, allowable steel grades and or characteristics, manufacturing test requirements, weld procedures and weld testing. © 2013 American Society of Civil Engineers.
Good B.,Denver Water
AWWA Sustainable Water Management Conference and Exposition 2010 | Year: 2010
• Not all water can be reused in Colorado • The last 10 years have introduced many new challenges • Denver Water is expanding its thinking and pace of reuse • Milk stools hold the key!. © 2010 American Water Works Association.
Yates D.N.,U.S. National Center for Atmospheric Research |
Miller K.A.,U.S. National Center for Atmospheric Research |
Wilby R.L.,Loughborough University |
Kaatz L.,Denver Water
Climate Risk Management | Year: 2015
A multi-step decision support process was developed and applied to the physically and legally complex case of water diversions from the Upper Colorado River across the Continental Divide to serve cities and farms along Colorado's Front Range. We illustrate our approach by simulating the performance of an existing drought-response measure, the Shoshone Call Relaxation Agreement (SCRA) [the adaptation measure], using the Water Evaluation and Planning (WEAP) tool [the hydrologic cycle and water systems model]; and the Statistical DownScaling Model (SDSM-DC) [the stochastic climate scenario generator]. Scenarios relevant to the decision community were analyzed and results indicate that this drought management measure would provide only a small storage benefit in offsetting the impacts of a shift to a warmer and drier future climate coupled with related environmental changes. The analysis demonstrates the importance of engaging water managers in the development of credible and computationally efficient decision support tools that accurately capture the physical, legal and contractual dimensions of their climate risk management problems. © 2015 The Authors.
Turney M.S.,Denver Water
Pipelines 2010: Climbing New Peaks to Infrastructure Reliability - Renew, Rehab, and Reinvest - Proc. of the Pipelines 2010 Conference | Year: 2010
In 2008 Denver Water deployed the Sahara® (The Pressure Pipe Inspection Company) and SmartBall (Pure Technologies) leak detection systems into an 11.7 mile, 60 and 66-inch diameter potable water transmission main. Leaks unknown to the contractors were simulated by the owner during the testing. This paper compares the preparation required, implementation, and inspection results for each system as experienced by Denver Water. © 2010 ASCE.
Depperschmidt A.,Denver Water
Journal / American Water Works Association | Year: 2010
Denver Water's 'Use Only What You Need' campaign earns the utility a national award for humor and effectiveness. Hired talents drove the message around Denver in an old taxi that had been parted out and left with only what it needed to run. There were even towers of bright orange 50-gal drums stacked on top of each other throughout the city, helping people visualize the amount of water wasted from leaky toilets or broken sprinkler heads. The agency also encouraged people to take 2 minutes off their lawn-watering times with its 'Grass is Dumb' message. The campaign, displayed on billboards, TV commercials, bus tails, and other locations, told customers that 'Grass is Dumb. Water 2 minutes less. Your lawn won't notice.' Cutting 2 minutes is a small enough amount that lawns will stay healthy and green; if everyone did it. Denver Water plans to stick with its nontraditional advertising tactics to continue this water conservation momentum.
France J.W.,URS Corporation |
Martin J.,Denver Water
Association of State Dam Safety Officials - Dam Safety 2012 | Year: 2012
Antero Dam is a high hazard dam located near the headwaters of the South Fork of the South Platte River, near the Town of Hartsel, in Park County, Colorado. The dam was constructed between 1908 and 1909 by the Antero and Lost Park Reservoir Company. Denver Water purchased the dam in 1924 to provide raw water storage for municipal use. Significant seepage has been observed and noted at the dam since the reservoir's first filling in 1909, and seepage has continued to the present. For essentially its entire history of operation, the reservoir level has been restricted to various gauge heights (elevations) by the Colorado State Engineer (SEO), for a variety of reasons, including the observed seepage. Currently, the SEO's restriction on the reservoir level is Gauge Height (GH) 18 (El. 8941.9 feet). In 2011, Denver Water decided to further limit reservoir storage to GH 16 (El. 8939.9 feet), because of its concerns regarding safety of the dam. To provide guidance for future operation and other possible actions for the dam, Denver Water commissioned a quantitative dam safety risk analysis for the facility. The risk analysis was completed using facilitated expert elicitation procedures, which generally followed the best practices guidelines developed by the U.S. Department of the Interior, Bureau of Reclamation. The risk analysis team considered the full range of potential failure modes under static (normal), hydrologic (flood), and seismic (earthquake) loads. The results of the analysis indicated estimated risks of failure for operation under the current SEO restriction that were within the range of decreasing justification to take risk reduction actions, according to Reclamation's 2003 Public Protection Guidelines. However, the risk estimating team also observed that the relatively low estimated risks were principally the result of the low hydraulic head under current operating levels and the apparent foundation geology, and not because of any engineered features in the structure. Denver Water is now evaluating the results of the risk analysis to plan future actions, which may include modifications to the structure to provide engineered features that contribute to reduced risks. This paper will review the risk analysis procedures and results, highlighting the processes that were followed and the information sources that the team used in making its estimates.
Martin J.,Denver Water |
Johnson D.,Tetra Tech Inc.
Association of State Dam Safety Officials Annual Conference 2012, Dam Safety 2012 | Year: 2012
Ralston Reservoir is located northwest of Denver, Colorado in the foothills of the Rocky Mountains. A reservoir side slope failure occurred in 2008 and threatened one of the two inlet channels for the reservoir. The landslide was the third landslide to occur on the rim of this reservoir since filling in 1938. Worldwide, landslides occur along many reservoir side slopes, causing impacts to the reservoir and dam ranging from degradation of water quality, to structural damage, to wave generation that can impact the dam and spillway operation. The Ralston Dam was completed in 1937 as a storage reservoir for domestic water supply. The reservoir is on a small stream and is principally filled from a transmission canal and pipeline. The canal discharges into the reservoir by either a submerged box culvert flume in a small, steep sloped valley, or by a baffled chute drop structure. The box culvert discharges into a concrete channel that extends down the small valley to the main body of the reservoir, and is typically submerged. The massive landslide showed potential to undercut the box inlet flume, and reduce Denver Water's means to fill the reservoir and indicated a potential to impact water supply to portions of the City of Denver. Monitoring points were established and surveyed to develop an understanding of ongoing movement and preparations were made to perform field geologic and geotechnical investigation. Investigations, including geologic investigation and mapping, three borings/piezometers, and detailed inspection of the box conduit were made and summarized to prepare a model of the slide mass and the extent of movement. Stability analyses were performed and alternative methods of stabilization were developed and analyzed for benefits and costs. The data and analyses were used to develop a remediation approach that utilized Denver Water's internal forces and equipment, and took advantage of an onsite quarry for supply of buttress stabilization material. The partnering effort between the Owner and the Engineer developed a remediation plan that was (1) technically sound, (2) constructible by the Owner's own forces, and (3) cost effective. This project is an illustration of how an owner and engineering firm can work closely together to evaluate a failure, consider many options and implement a successful repair. © (2012) by Association of State Dam Safety Officials All rights reserved.
PubMed | Denver Water and Southern Nevada Water Authority
Type: | Journal: The Science of the total environment | Year: 2015
Nitrosamines are considered to pose greater health risks than currently regulated DBPs and are subsequently listed as a priority pollutant by the EPA, with potential for future regulation. Denver Water, as part of the EPAs Unregulated Contaminant Monitoring Rule 2 (UCMR2) monitoring campaign, found detectable levels of N-nitrosodimethylamine (NDMA) at all sites of maximum residency within the distribution system. To better understand the occurrence of nitrosamines and nitrosamine precursors, Denver Water undertook a comprehensive year-long monitoring campaign. Samples were taken every two weeks to monitor for NDMA in the distribution system, and quarterly sampling events further examined 9 nitrosamines and nitrosamine precursors throughout the treatment and distribution systems. NDMA levels within the distribution system were typically low (>1.3 to 7.2 ng/L) with a remote distribution site (frequently >200 h of residency) experiencing the highest concentrations found. Eight other nitrosamines (N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitroso-di-n-propylamine, N-nitroso-di-n-butylamine, N-nitroso-di-phenylamine, N-nitrosopyrrolidine, N-nitrosopiperidine, N-nitrosomorpholine) were also monitored but none of these 8, or precursors of these 8 [as estimated with formation potential (FP) tests], were detected anywhere in raw, partially-treated or distribution samples. Throughout the year, there was evidence that seasonality may impact NDMA formation, such that lower temperatures (~5-10C) produced greater NDMA than during warmer months. The year of sampling further provided evidence that water quality and weather events may impact NDMA precursor loads. Precursor loading estimates demonstrated that NDMA precursors increased during treatment (potentially from cationic polymer coagulant aids). The precursor analysis also provided evidence that precursors may have increased further within the distribution system itself. This comprehensive study of a large-scale drinking water system provides insight into the variability of NDMA occurrence in a chloraminated system, which may be impacted by seasonality, water quality changes and/or the varied origins of NDMA precursors within a given system.
News Article | December 17, 2015
DENVER (AP) — Colorado's top environmental official is stepping down, months after he clashed with federal authorities over a massive spill of toxic wastewater from an inactive mine in southwest Colorado. Mike King's resignation was announced Thursday and takes effect Dec. 31. The executive director of the Colorado Department of Natural Resources had led the agency since 2010. His departure comes on the heels of the resignation of Hickenlooper's lieutenant governor and appears part of the regular string of exits of veteran officials as the administration moves into its final years. King clashed with the U.S. Environmental Protection Agency earlier this year over the Aug. 5 Gold King Mine disaster. The spill polluted rivers in Colorado, New Mexico and Utah, including on the Southern Ute Reservation and the Navajo Nation. The EPA came under intense criticism from Congress and from state and local officials for causing the blowout and for the way it responded. The EPA said after the spill that that Colorado officials endorsed its cleanup operation at the mine and that state experts were at the Gold King Mine on the day of the spill in a supporting role for the cleanup operation. But in a September letter to the EPA, King raised nine objections to the EPA's account. He said that Colorado officials neither approved nor disapproved of the operation. King's letter was a blow to the EPA's contention that outside technical experts supported its plan to push a drainage pipe through debris covering the entrance to the Gold King Mine. The letter also raised questions about an investigation of the spill by the federal Bureau of Reclamation, which said two mining experts from the state approved of the project "The investigation's conclusions into the events surrounding the discharge were not consistent with our staff's involvement and we felt it important to make sure the investigators were aware of our perspective," King said in a statement about his letter. The director did not immediately respond to a request from The Associated Press for additional comment Thursday. A statement from Gov. John Hickenlooper on Thursday said that King plans to take a new job as director of planning with Denver Water. Hickenlooper praised King as "wicked smart" with a " casual charm," and credited King for overseeing Colorado's first statewide water plan, which came out earlier this year. The governor gave no timeline for replacing King. The governor has another notable vacancy to fill in his cabinet, Lt. Gov. Joe Garcia. Garcia announced last month that he is resigning to run the Western Interstate Commission for Higher Education.