FROM: Stan Zemler, Town Manager
Greg Hall, Public Works Director
Chad Salli, Project Engineer
Dwight Henninger, Police Chief
SUBJECT: I-70 Noise Mitigation Study Update
Since April 2004, Hankard Environmental has been under contract with the Town of Vail to provide consulting services as part of a comprehensive effort to reduce the impact of traffic noise on I-70. Mike Hankard and Ralph Trapani, representing the consultant team, have prepared a presentation outlining a series of mitigation actions in the categories of "source," "path" and "receiver" controls. Their observations and recommendations, along with proposed next steps by Town of Vail staff, are presented below.
2. OVERVIEW BY HANKARD ENVIRONMENTAL
This overview summarizes noise mitigation recommendations based on the work, to date, by Hankard Environmental. Recommendations are broken down into source, receiver, and path controls. A brief description of the key differences in these types of controls is provided first, followed by a description of each recommended noise mitigation measure.
Source controls benefit everyone. For example, reducing speeds and/or putting down quiet pavement reduces noise at ALL homes and businesses in town, versus a wall that benefits only those directly behind it or thicker windows that affect only an individual property. Therefore, the number of people that benefit from source measures is large. The cons of source controls are that each measure is costly, speed reduction requires cooperation from almost the entire motoring public, pavement changes require significant CDOT coordination, and covering the roadway has complex engineering, logistical, and political hurdles.
Path controls, i.e. barriers, benefit a given area such as a neighborhood. The extent of the benefited area depends on the height and length of the barriers and on topography. Barriers can consist of earthen berms, vertical walls, or some combination thereof. Barriers are typically 15 feet tall, can be hundreds to thousands of feet long, and provide 5 to 10 dB of noise reduction to those located within 300 feet of the barrier. Barriers are not very effective for receptors that are elevated above the roadway, such as houses on a hillside or the upper floors of a high-rise building. The cons of barriers, particularly walls, are aesthetics, cost, and the rigors of CDOT coordination.
Receiver controls, such as the construction of solid fences on individual properties and the installation of better windows are effective, but only benefit individual properties. Such measures are the responsibility of the property owner/developer. There are no significant cons to receiver controls, other than moderate cost.
Hankard recommends the Town of Vail consider each of the noise mitigation measures described below. None are simple and straightforward. This is not surprising, as the problem of I-70 noise has slowly evolved over the past three decades. Traffic volumes and speeds have increased slowly but steadily, and property development has continued in relatively close proximity to the highway. Back in the 1970’s, we estimate that daytime loudest hour highway noise levels were in the 55 dBA range. Generally speaking, this is a tolerable level to most people. Levels are now in the 65 to 70 dBA range, which are levels that begin to annoy people. Therefore, reversing the problem will take time, effort, money, and will come about only through the application of a variety of mitigation measures.
3. PRELIMINARY RECOMMENDATIONS BY HANKARD ENVIRONMENTAL
A. Continue Speed Reduction Campaign
B. Investigate Quiet Pavements
·Meet with or somehow consult with CDOT to ensure that any work done by the Town is in concert with CDOT’s and FHWA’s pavement approval process.
·Review the Statewide Transportation Plan (STIP) for other Mountain Communities to see if any comparable roads are due to be rehabilitated prior to 2007, with the thought that Vail could help fund a quiet pavement pilot project somewhere else to provide timely noise reduction and durability data.
·Consult with the I-70 Mountain Corridor Project and related groups to see if Vail could serve as a test case for quiet pavements for that project, as community noise is a significant issue along the entire I-70 Mountain Corridor.
·Hire CTL Thompson to develop a quiet pavement mix design for Vail, and conduct accelerated testing on the resulting pavement at a cost of $25k to $50k.
·Construct a test strip IF the results of mix design testing are favorable, and CDOT indicates that a test strip would be beneficial to their decision making process. The construction and testing of a 1,000 foot-long test strip is estimated to cost between $200k and $300k.
C. Cover I-70
According to Hankard this alternative should always be considered, because it offers the best noise reduction of any recommended measure. Placing I-70 in a cut-and-cover tunnel through all or part of Town would certainly be a significant, complex, expensive project. It should be noted that tunnels require full-time staff and equipment, thus have a high recurring cost. If the proposed I-70 Dowd Canyon tunnel comes to fruition, the challenge of providing full time staff and equipment may be eased by the proximity of that tunnel facility to one in Vail.
Lacking a Dowd Canyon tunnel, Hankard recommends consideration of shorter, multiple tunnels that may not require fully staffed tunnel facilities. This could be accomplished by placing developments over the highway consisting of one or more buildings along with some extended plaza-like space. These could be placed in critical noise areas. This would also provide a north-south connection for pedestrians. Care would need to be taken regarding noise from the portals. A full tunnel feasibility study evaluating short versus long tunnels, safety, and life cycle cost issues would be the next step if Vail wants to pursue covering I-70.
A. Continue to Exhaust Berming Opportunities
An initial field review of I-70 through Vail indicates that there are still areas where earthen berming would provide some noise reduction. We will identify these areas, and we advise Vail to continue working with CDOT to get these berms constructed.
Install Solid Safety Barriers
Much of the noise from vehicle traffic comes from the interaction of the tire and the pavement. Therefore, in certain areas, even a relatively short (height-wise) barrier would provide some noise reduction. CDOT’s 3-foot tall Type 7 Solid Safety Rail, which the Department uses regularly on its roadways, would be a logical choice as it meets current safety standards.
Preliminary modeling and a field survey of Town indicate that the Type 7 rail would provide 1 to 3 dB of noise reduction only in a few specific areas where the terrain conditions are appropriate. For those areas where open guardrail currently exists, the Town could consider petitioning CDOT to replace it with solid rail when it is due for major maintenance. Alternatively, the Town could petition CDOT to replace existing open rail with solid rail immediately, or install solid rail where none exists currently.
Hankard will provide a description of areas where the solid rail will provide at least 1 to 2 dBA of noise reduction at adjacent residences. In considering its options, both cost and aesthetics should be weighed. Type 7 barrier costs approximately $50 per foot (installed). Sites will require anywhere from 500 to 2,000 linear feet, at a resulting cost of $25k to $100k per site. Aesthetically speaking, Type 7 rail does tend to become chipped and marred over time.
C. Install Steepened Slope Berms
There may be some areas where a 5 to 10 foot tall barrier is needed to provide any significant noise reduction, yet there is not enough room for a berm with the standard slopes of 3:1 or even 2.5:1, and a concrete wall would be too obtrusive or otherwise infeasible. In these areas, a soil-reinforced steepened earth berm combined with a Type 7 barrier shape on the traffic-side (where necessary) provides a possible solution. A preferred site, a preliminary design, and a cost estimate will be prepared by Hankard for the Town’s consideration.
Analyze Preferred Noise Wall Location
CDOT responded to Vail’s request to construct a temporary noise barrier demonstration by requiring that any such barrier must meet all of the requirements of a permanent barrier. Therefore, a temporary barrier is not recommended, as it would cost almost as much as it would to construct a permanent barrier. Hankard recommends that one preferred site for a permanent barrier be identified. Either the Town can dictate a location, or Hankard can provide a list of three or so where acoustically a wall would be appropriate. The preferred site should then be analyzed according to CDOT noise guidelines, a cost estimate produced, and the issue of aesthetics discussed.
A. Advise Residents on Do-It-Yourself Noise Control Solution
Individual property owners can reduce noise at their homes and businesses by constructing small barriers (berms and/or walls), placing outdoor use areas such as patios in more quiet parts of their property, installing acoustic windows in select locations, and otherwise sealing the highway side of their homes. We recommend that Hankard Environmental develop a brief how-to document that can be made available to townspeople (i.e. distributed, placed on website, etc.)
B. Strengthen Design Review Process
Hankard recommends Vail require new developments and re-developments along I-70 to consider noise at the very earliest stages of design. Outside recreation areas should be somehow shielded from the highway. Inside areas should be specified with adequate windows. Exposed decks facing the highway should be avoided. Hankard will draft some guidelines for the Town’s consideration.
The list of recommendations from Hankard Environmental are comprehensive and, in some cases, will require additional research and review. However, staff recommends taking immediate action on the following next steps:
Direct staff to contract with CTL-Thompson, Inc., for up to $40,000 to develop a low noise asphalt mix that will meet CDOT’s approval for use during the I-70 overlay through Vail in 2007.
Direct staff to work with CDOT to facilitate use of "quiet" asphalt in all future asphalt work in Vail, including pursuit of a test strip.
Continue use of sand storage berms along I-70 in Vail and work to obtain approvals from private property owners to expand the sand storage berm project onto private properties, where feasible.
Direct staff to draft a policy resolution outlining Town of Vail support for concrete barrier use in place of the existing open rail barriers during future additions and replacements.
CDOT Letter, re: Temporary Noise Barriers