October 7, 2016 Continental Country Club Home Owners · PDF filePotential Lake Draining...

Terracon Consul tants, Inc. 4685 South Ash Avenue, Suite H-4, Tempe, Ar izona 85282P [480] 897-8200 F [480]-897-1133 terracon.com

October 7, 2016

Continental Country Club Home Owners Association2380 North Oakmont DriveFlagstaff, Arizona 86004

Attn: Vicki DuncanPresident

Re: Potential Lake Draining AlternativesLake Elaine Restoration – Phase 1Continental Country ClubFlagstaff, ArizonaTerracon Project No. 65165238

Dear Ms. Duncan:

Terracon Consultants, Inc. (Terracon) has prepared this initial report to outline potentialalternatives that have been considered for planning purposes to drain Lake Elaine as part of thePhase 1 restoration process. The purpose of this report is to present potential alternatives thathave been developed to drain the lake and outline the expected additional engineering and duediligence efforts that will be required to further validate each alternative. This report also presentsour recommendation of the preferred alternative based on engineering considerations. However,we will wait board approval of the preferred alternative before proceeding with the additionalengineering and due diligence efforts that will be required.

We understand there has been some concern expressed by HOA members that this phase of theproject, including draining the lake and conducting the engineering evaluations of the existingconditions of the liner, subgrade and other features at the lake bottom cannot be completed duringthe coming winter months. From an engineering perspective and provided there are no regulatoryprohibitions against it, there is no reason that the lake draining operations cannot be completedduring the coming winter months. Provided that constant flows are maintained during the drainingoperations, sub-freezing temperatures should not necessarily be a prohibiting factor. In theadditional due diligence efforts and engineering evaluations outlined in this report, we willascertain any regulatory requirements that may further affect or impact the timing for the Phase1 work. Once the lake is drained, the engineering evaluations of the Phase 1 work can proceedas planned regardless of climatic conditions at that time.

In an effort to aid the project schedule for this phase of the project, we are proceeding concurrentlywith the preparation of contract documents for the Phase 1 work. These contract documents will

Potential Lake Draining AlternativesLake Elaine Restoration – Phase 1 ■ Flagstaff, ArizonaOctober 7, 2016 ■ Terracon Project No. 65165238

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be supplemented with a set of technical specifications and plans pending the final selection of thealternative for this phase.

Project Understanding

To date, Terracon has completed two field visits to the project site (along with our civil engineeringconsultant) and we have reviewed various documentation concerning Lake Elaine that has beenprovided to us with background information concerning this project. As a result of our evaluationsto date, we understand that both Humphrey Lake and Lake Elaine are supplied with treated wastewater that is purchased from the City of Flagstaff. The delivery of this water is first through asupply line to Humphrey Lake. Topographically, Humphrey Lake is located at a lower elevationthan Lake Elaine; therefore, the water is pumped uphill from Humphrey Lake to Lake Elaine. Mostof the water impounded within Lake Elaine is delivered from Humphrey Lake by an existing 8- to10-inch supply line, where the remaining balance of impounded water is the result of precipitationand runoff in the relatively small watershed upstream of the lake.

Based on our understanding of the project and the information gathered during our field visits, wehave identified three concept level alternatives which are being considered to drain Lake Elaineat the present time. These alternatives are summarized below and are subsequently discussedin more detail in the following sections of this report:

n Alternative 1: Utilize the existing supply lines to pump into Humphrey Laken Alternative 2: Open the outlet works of Lake Elaine and drain through eastern fairwaysn Alternative 3: Pump water to adjacent forest land to the east

Alternative 1: Utilize the existing supply lines to pump into Humphrey LakeAlternative 1 would entail pumping water from Lake Elaine back into the existing supply line fordischarge by gravity means into Humphrey Lake. Utilizing the existing spillways and outlet worksat Humphrey Lake, the water would then be discharged to areas downstream ultimatelydischarging into Rio de Flag. Since the existing water supply system is configured to pump waterfrom Humphrey Lake to Lake Elaine, minor modifications would be necessary to configure andreverse the system for implementation of this alternative. The following photograph shows thesupply line at Humphrey Lake that is exposed above the ground surface at the pump house.Modifications to the system would include disconnecting the pipe at this location and connectinga temporary above ground line that discharges into Humphrey Lake. At Lake Elaine,modifications would include connecting a temporary pump and intake line at the existingdischarge point. However, the location of the supply line discharge point at Lake Elaine iscurrently unknown, so further investigation at this location will be necessary to fully validate thisalternative.



Photo 1: Lake Elaine supply line at Humphrey Lake pump house

Based on our visual observations of the supply line as shown in the above photo, the existingsupply line is an 8 to 10-inch cast iron pipe. Considering the pipe size and anticipated capacity,we estimate water can be pumped through this pipe at a rate of 1,000 gallons per minute. Basedon this estimated pumping rate, the pump(s) running 24 hours per day, and an approximate watervolume of 300 acre feet in Lake Elaine, we estimate approximately 60 to 75 days will be necessaryto drain the lake using this alternative.

Water discharged through the Humphrey Lake outlet works or spillway would flow by gravitydownstream of the Humphrey Lake Dam, which will traverse Continental Golf Club (CGC) Holes11, 10, between Holes 1 and 9 and discharge into the Rio de Flag channel just south of the Hole2 green. Refer to the Humphrey Lake Discharge Path shown on the Alternatives Exhibit attachedfor the anticipated drainage path for this alternative. Prior to undertaking this alternative, existinginfrastructure downstream of Humphrey Lake may need some improvement to accommodate thedischarge water, examples of which are shown in the follow photos.



Photo 2: Degraded channel along the drainage path

Photo 3: Blocked storm drain inlet near the maintenance yard



Alternative 2: Open the outlet works of Lake Elaine drain through eastern fairways

We understand that the Lake Elaine Dam was constructed with outlet works that could be usedto drain the lake. Based on our discussion with you, we understand these outlet works have notbeen operated in recent times and may be in need of repair. Assuming the outlet works at LakeElaine could be repaired, this alternative proposes to use this existing infrastructure to drain thelake through existing golf course fairways to the northeast. As an alternative, or in addition tousing the outlet works, lake water could be pumped into the emergency spillway for Lake Elainewhich discharges near the outlet works.

Water discharged through the Lake Elaine outlet works or spillway would flow by gravity alongthe golf course downstream of the Lake Elaine Dam along the established drainage path, whichtraverses Aspen Valley Golf Club (AVGC) Holes 4, 5 and 6 and discharges into an existing pondadjacent to the green at AVGC Hole 5. It is unclear, at this time, where excess water from thispond would flow, but an established channel exists along the east side of Continental Golf Course(CGC) Hole 15 which is located across Country Club Drive to the north of AVGC Hole 5. If noconnection exists between these two locations, a temporary above ground pipe could be installedover Country Club Drive to pump water from this pond and into the channel along the east sideof CGC Hole 15. From this point, the discharged water would flow north and into the existinginterconnected ponds along the west side of CGC Hole 18. It is unclear, at this time, whereexcess water would flow from these ponds, although the general topography suggests the waterwould sheet flow to the northeast through the existing townhome development, across CountryClub Drive and ultimately outlet into the Rio de Flag. Refer to the Lake Elaine Discharge Pathshown on the Alternatives Exhibit attached for the anticipated drainage path for this option.

The limitation of this alternative are locations within the downstream drainage route that are“blocked” by existing townhome developments and baseball fields that could be impacted as aresult of surface flows, as shown in the following photo:



Photo 4: Drainage path through townhome development

On its own, this alternative is not particularly attractive if the flows would have to be reduced to alevel to minimize impact to those developments located downstream. However, this option couldbe potentially utilized along with Alternative 1 in order to provide a more rapid means to drain thelake.

Alternative 3: Pump water to adjacent forest land to the eastA third alternative would include pumping the water into the forest area to the east of thedeveloped area and the lake, and allow the water to infiltrate naturally through the ground surface.Refer to the potential drainage areas shown on the Alternatives Exhibit attached. One majorconcern with this alternative is the presence of a housing development located on the west sideof Old Walnut Canyon Road downstream of the potential discharge areas. It is unclear at thispoint if the discharged water would infiltrate the ground before reaching this development.

This particular alternative would include the placement of some amount of temporaryinfrastructure including the installation of an 8 to 10-inch diameter pipe along the ground surface,roadways, etc. between the lake and the discharge area. A limitation to this particular plan is theunknown ground conditions located in the forest area and whether these conditions would allowfor the infiltration of surface water discharge. Geotechnical engineering evaluation to assessinfiltration characteristics of the ground conditions would be required to determine infiltration rates.Ground conditions could also be unfavorable for infiltration if bedrock is relatively shallow in thearea.



Additionally, the area over which the discharge would have to be spread is unknown. Thisparticular alternative may require more engineering than either of the other two in order to provethe technical viability but nevertheless could be considered for further evaluation.

This alternative could have the highest potential cost of all three. Additionally, because thisalternative would involve discharge onto forest service property, we would expect that regulatoryrequirements may be the most rigorous for implementation of this particular strategy.

Golf Course Drainage and Topographic Survey

Alternatives 1 and 2 involve discharging water through the existing golf courses in the immediatearea. It is unclear if the downstream fairways and greens can accept these additional flows, andif and where these additional flows could impact the surrounding residential developments androadways. Additionally, we anticipate that some amount of maintenance would be required to thegolf course to repair potential damage that may occur due to discharging water through the golfcourse.

To better assess the potential behavior of flows discharged through the golf courses, werecommend a topographic survey of the area be performed unless such topographic informationmight be available on plans for the golf course and surrounding development or in localgovernment files. The existence of such files will be part of additional due diligence andengineering efforts. In conjunction with this survey, the existing drainage culverts along thedrainage paths should be assessed to determine their flow capacity and condition. From thissurvey, the following information can be interpreted:

n The drainage path from each of the existing dam outlets to the Rio de Flagn Existing slopes/gradients along the potential drainage pathsn Anticipated flow velocitiesn The volume of the existing drainage channelsn Locations where the flows could be potentially restrictedn Depressions along the drainage path where water could pondn Locations where the flows could potentially impact the adjacent developmentsn Discharge attenuation benefits of existing ponds and depressions that could be

determined through hydraulic modeling

Regulatory RequirementsWith Alternatives 1 and 2 (and potentially Alternative 3), the treated waste water discharged fromLake Elaine will ultimately discharge into to Rio de Flag. However, based on the flows from thelake and the surface infiltration along the drainage path, the actual quantity of water that wouldreach the Rio de Flag is unknown.



Our team has discussed the potential regulatory requirements that may impact the selection ofany one of these potential alternatives. One of the main items that will need to be determined isthe limitations on discharging into the Rio de Flag wash, including both water quantity and waterquality. We understand that the Rio de Flag is considered a Jurisdictional Water of the UnitedStates, and at a minimum the following listed agencies will need to be consulted regardingdischarging the treated waste water into the Rio de Flag. It should be noted that the permittingprocess associated with draining treated waste water into the Rio de Flag may be extensive.

n Arizona Department of Environmental Qualityn The City of Flagstaffn The Army Corps of Engineersn Arizona Department of Water Resources

Fish

We understand that Lake Elaine is periodically stocked with fish to help control the insectpopulation associated with the lake. Regardless of which method is selected for draining the lake,the re-location and/or appropriate disposal of fish that currently exist within the lake will need tobe addressed. While we understand this lake is not under the jurisdiction of the Arizona Fish andGame Department, this agency may be a resource for procedures on how to accomplish fishharvesting and relocation.

Preferred Alternative

At this time, it is our team’s collective opinion that Alternative 1 is the most technically feasibleand least invasive alternative to the community and will allow existing infrastructure to be utilizedwith only certain modifications. However, as previously discussed, we could potentially combineAlternative 1 with a “partial” Alternative 2. Either of these alternatives would also allow for certainamount of the discharge water to be used and infiltrate into the existing golf course fairways inthe area once golfing season is concluded (which we understand will be on or about November1).

At a minimum, the following is a summary of the expected due diligence and engineering effortsthat we consider applicable to confirmation of this as the preferred alternative:

n An agreement must be negotiated between the Continental Country Club HOA and theowners of Humphrey Lake to allow this alternative to go forward and in order for the HOA’sselected contractor to make certain modifications to the existing infrastructure at the pumphouse and lake, namely pipeline modifications, spillway repairs, etc.

n An engineering evaluation needs to be made of the existing culverts that are located withinthe drainage path near the maintenance yard along Hole C10 to determine the capacity



for flow discharge and any temporary or permanent improvements which will be requiredfor this alternative.

n An engineering evaluation of the existing channels flow capacities located downstream ofHumphrey Lake and any modifications that may be necessary.

n Identification of any private or public properties beyond the golf course that could besubjected to the flows during discharge and agreements/approvals for those owners.

n Identification of any jurisdictional agencies and approval for discharge into Rio de Flag.

n Development of a plan for fish relocation/harvesting during the drainage process.

n Preliminary Geotechnical Investigation to determine infiltration rates, potential soil erosionalong alternative drainage corridors, and sub-surface soil formations.

General Comments

The intent of this document is to expand on the alternatives that we presented to you in previousemail correspondence concerning this project. This document presents the results of our duediligence efforts to date and may not necessarily reflect all requirements that may be necessaryto undertake draining the lake. We expect that a more comprehensive list of requirements will bedeveloped as due diligence efforts are further completed during the course of our work on thisproject. Additionally, more alternatives than those listed in this document, or modifications to thealternatives listed may surface as further engineering and due diligence efforts are completed.

This report present certain alternatives that should be considered by the HOA for this project.We are available to expand on these alternatives if necessary. We await your concurrence anddirection to proceed with finalizing the preferred alternative for this project as outlined in thisreport. As previously stated, we are proceeding with the preparation of contract documents thatwill be combined with the technical specifications and plans of the preferred alternative once theyare fully developed. We would anticipate that counsel for the HOA would provide an independentreview of the contract documents before they are finalized and issued for bid by potentialcontractors.

As a final comment, we believe that a design build delivery method may be a better approach forthis project to engage with and receive council from reputable and knowledgeable contractorswho can speak to specific dewatering, infrastructure, and constructability questions in the field.This delivery method could also accelerate the project schedule. Our civil engineering consultantshave project history with a contractor who has lake experience, who could provide advice forvarious implementation aspects of this project.



We appreciate the opportunity to be of service to you on this project. If you have any questionsconcerning this report, or if we may be of further service, please contact us.

Sincerely,Terracon Consultants, Inc.

Jesse R. Huston, P.E. Donald R. Clark, P.E.Senior Project Manager Senior Principal

Attachments: Alternatives Exhibit (Sheet 1 of 1)

Copies to: Addressee (1 via email)

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LEGEND:

Alternative 1: Humphrey Lake Discharge Flow Path

Alternative 2: Lake Elaine Discharge Flow Path

Alternative 3: Adjacent Forest Discharge Flow Path

Aspen (A) Valley Golf Club and Hole Number

Continental (C) Golf Club and Hole Number

Rio de Flag Channel

Lake Elaine Supply Line

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Lake Elaine Supply Line

Continental Holes

Aspen Valley Holes

Conceptual Pipeline Location

Potentially ImpactedDevelopment



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