DWQ-2024-007901

Mr. George Elliot
Project Manager
Washington County Water Conservancy District
533 East Waterworks Drive
St. George, Utah 84770
Dear Mr. Elliot:Subject:Chief Toquer Dam and Reservoir Construction Permit
On October 9, 2024, the Division of Water Quality (DWQ) received the engineering plans and specifications for the Chief Toquer Dam and Reservoir. Theseengineering plans and specifications
were prepared byRB&G Engineering and stamped by Utah Certified Professional Engineer (P.E.) Brandon D. Horrocks, P.E.The following is a summary of the proposed major construction projects:
Construction of an earthen dam;
To limit infiltration the reservoir area will be lined predominantly with a High Density Polyethylene (HDPE). There is a small are where Liner Low Density Polyethylene (LLDPE) will
be used. The HDPE and LLDPE will be welded together. The liner is also intended to limit the impact of the reservoir on local groundwater quality
The reservoir will cover over 100 acres of land and will store up to 3600 acre-feet of water.
The reservoir will include an emergency spillway to meet Dam Safety requirements, but this spillway will only be utilized under rare severe stormwater runoff conditions. The spillway
will be tied into the ephemeral wash that connects into Ash Creek.
The reservoir is located within an ephemeral wash that ties into Ash Creek. The primary flow into the reservoir will be reuse water from the Ash Creek Pipeline and excess water available
from Toquerville Springs. Flows from ephemeral washes will also enter the reservoir during storm events that generate runoff within the watershed.
Conditions: The specifications for the liners included Ethylene Propylene Diene Monomer (EPDM), Polyvinyl Chloride (PVC), Flexible Polypropylene (FPP) and Chlorinated Polyethylene (CPE).
These were not included on the engineering drawings and cannot be used in this project. The Nondestructive seam testing for the HDPE and LLDPE indicates that the air channel will be
pressurized to 25 to 30 pounds per square inch (psi) and after 5 minutes if the loss of pressure is greater than 4 psi then the seam fails. To be consistent with other pond projects,
DWQ requires that the initial pressure be a minimum pressure be 30 psi and after 5 minutes the loss can only be 3 psi. The plans and specifications, as submitted, comply with the Utah
Water Quality Rules, (R317, Utah Administrative Code). A Construction Permit is hereby issued as constituted by this letter, subject to the following conditions:Any revisions or modifications
to the approved plans and specifications must be submitted to DWQ for review and approval, before construction or implementation thereof. Please submit any changes for review and approval
directly to Woodrow Campbell, P.E., of the DWQ Ground Water Protection Section.A written operations and maintenance manual, containing a description of the functioning of the facilities,
an outline of routine maintenance procedures, and all checklists and maintenance logs needed for proper operation of the system, must be submitted and approved before the final inspection
and operation of the system.The approved facilities must not be placed in service unless DWQ has conducted a final inspection, reviewed and approved the As-Built Construction Certification
Report, and provided written authorization to place the constructed facilities in service.Construction activities that disturb one acre or more are required to obtain coverage under
the Utah Pollutant Discharge Elimination System (UPDES) Storm Water General Permit for Construction Activities. The permit requires the development of a storm water pollution prevention
plan (SWPPP) to be implemented and updated from the commencement of any soil disturbing activities at the site until final stabilization of the project. For more information, or to obtain
permit coverage on-line, please go to: http://www. waterquality. utah.gov/UPDES/stormwater. htm
The plans and specifications for this project have been stamped and signed by a Professional Engineer currently licensed to practice in the state of Utah. The construction design, inspection
supervision, and written construction certification of all work associated with this Construction Permit must be performed by a Professional Engineer licensed to practice in the state
of Utah.
This Construction Permit will expire one year from the date of its issuance, as evidenced by the date of this letter, unless substantial progress is made in constructing the approved
facilities or the plans and specifications have been resubmitted and the construction permit is reissued. This permit does not relieve you, in any way, of your obligations to comply
with other applicable local requirements. You may contact Jeremy Roberts, Southwest Utah Public Health Department at 435-986-2582, or Paul WrightDEQ District Engineer at 435-896-2590
for further assistance regarding local matters.
Please contact Mr. Campbell at the beginning of construction to allow periodic inspections to be scheduled. Upon completion of the project, a final inspection and approval of the As-Built
Construction Certification Report is required before the approval to operate the completed facilities can be issued. Please remain in contact with Mr. Campbell to schedule the final
inspection. The Construction Certification Report with final as-built drawings must include test results for the following construction quality assurance and quality control (CQA/QC)
elements:
Soil Subgrade
Proctor Curves,
Soil Classification,
Field Compaction Testing
Permeability, and
Subgrade Acceptance Certification.
Flexible Membrane Liner
Panel Placement Log,
Trial Seam Test Log,
Seaming Record,
Seam Test Record,
Repair Log,
As-Built Drawing,
Manufactures Certification including QA/QC Testing of the Rolls, and
Professional Engineer Certification.
ConcreteConcrete Mix Verification,Concrete ASTM Testing Method, Frequency, and Results,Concrete Testing Pass/Fail Criteria, andCrack Inspection and Repair.
If we can be of further assistance, please contact Mr. Woodrow Campbell at [e-mail] or [phone].
Sincerely,
John Mackey, P.E.

DirectorJKM/WWC/DJH:Attachments (2):Chief Toquer Dam and Reservoir Drawings (DWQ-2024-007254)Chief Toquer Dam and Reservoir Contract Documents and Specifications (DWQ-2024-007252)cc:w/o
AttachmentsPaul Wright, DEQ District EngineerJeremy Roberts, Southwest Utah Public Health DepartmentAaron Anderson, Bowens Collins Associates ([e-mail])Brandon Horrocks,
RB&G Engineering, ([e-mail])