Notice of Application for State Water Quality Certification

Public Notice (PN) Date: May 24, 2024          PN Reference Number: POA-2024-00143 v1.0
PN Expiration Date: June 24, 2024          Waterway: Unnamed Tributary Stream to Cook Inlet (Cottonwood Creek)

Any applicant for a federal license or permit to conduct an activity that might result in a discharge into waters of the United States, in accordance with Section 401 of the Clean Water Act (CWA), must also apply for and obtain certification from the Alaska Department of Environmental Conservation that the discharge will comply with the CWA and the Alaska Water Quality Standards (18 AAC 70). The scope of certification is limited to the water quality-related impacts from the activity subject to the Federal license or permit (40 CFR 121.3, 18 AAC 15.180).

Notice is hereby given that a request for a CWA §401 Water Quality Certification of a Department of the Army Permit application, Corps of Engineers’ PN Reference Number indicated above has been received0F0F[1] for the discharge of dredged and/or fill materials into waters of the United States (WOTUS), including wetlands, as described below, and shown on the project figures/drawings. The public notice and related project figures/drawings are accessible from the DEC website at https://dec.alaska.gov/water/wastewater/.

To comment on the project or request for a public hearing with respect to water quality, submit comments via email to the DEC email address: DEC-401Cert@alaska.gov with the subject line referencing Public Notice Reference Number: POA-2024-00143 v1.0 on or before the public notice expiration date listed above.

Applicant: City of Wasilla, Erich Schaal, 290 E. Herning Ave, Wasilla, AK 99654, (907) 373-9018; eschaal@cityofwasilla.gov

Agent: Stantec, John Marshall, 725 E. Fireweed Lane Suite 200, Anchorage, AK 99503; (907) 266-1108; john.marshall@stantec.com.

Project Name: Wasilla Wastewater Treatment Plant

Dates of the proposed activity is planned to begin and end: 08/15/2024 to 06/30/2025.

Location: The proposed activity is located within Section S13, T. T17N, R. R1W, Seward Meridian, in Matanuska-Susitna Borough, Alaska.  Project Site (Latitude, Longitude): 61.565080, -149.38537.

Purpose: The applicant’s stated purpose is to construct a Wastewater Treatment System utilizing natural wetlands to improve wastewater treatment and expand treatment capacity.

Description of Proposed Work: The applicant proposes to place up to 8,926 cubic yards of fill in 1.6 acres of wetlands to construct separation, diversion, and impoundment dikes and access roads in order to utilize the wetlands for a Waste Treatment System for the disposal of municipal treated wastewater.

Proposed Construction Activity: The proposed project is designed to construct and permit a Waste Treatment System. The construction activities include leveling and stabilizing the existing gravel trail/separation dike, constructing two surface hydrology diversion dikes, constructing a Waste Treatment System terminus impoundment dike (with culverts in the stream feature to create an outfall), constructing new access roads, and constructing Waste Treatment System boundary signage as detailed below. This design of the Waste Treatment System also takes advantage of the steep surrounding topography, namely the upland bluffs to the north and south, to completely contain the area for surface water treatment.

• Gravel Trail/Separation Dike Stabilization – The current gravel trail/separation dike was originally permitted for 1,313 CY of material (POA-2016-00140), with an additional 750 CY of material permitted (NWP 3) to maintain the structure above the height of the natural water level, as material settled into the soft wetland, allowing surface water to breach it. This project will permit an additional 3,040 CY of clean gravel to relevel the dike at 3 feet above water level and stabilize the dike by increasing the side slopes to 3:1 and placing organic clearing debris such as branches, stumps, and root wads from the project on the gravel slopes and toe (Sheet 4), widening the total wetland footprint to 0.26 acres. Although the dike acts as a semipermeable gravel barrier, this size increase and stabilization promotes flow south through the Waste Treatment System and designed outfall, which is the natural flow path. It also provides access for maintenance and monitoring.

• Diversion Dikes – Two, 250-foot by 10-foot diversion dikes are proposed to extend from the eastern edge of the system boundary. The diversion dikes will be constructed with a combination of plastic geocells (i.e., Permavoid, ABT), geofabric, coir logs, and a base of filter rock (Sheet 4). These structures are specifically located to extend into preferential surface water flow paths identified during the pilot study. The intention is not to construct an impermeable dike but rather a structure that slows and spreads flow. Slowing and spreading surface water flow will increase the overall area involved in treatment and increase hydrologic retention time to optimize efficacy. In addition, the diversions dikes will provide monitoring access.

• Impoundment Dike – A single, 230-foot by 11-foot impoundment dike is proposed at the end of the Waste Treatment System. The permeable impoundment dike will be constructed similar to the diversion dikes and be a combination of geocells (i.e., Permavoid, ABT), geofabric, coir logs, and filter rock base (204 CY), only larger in size (Sheet 3). This structure will span the unnamed stream feature that originates on the property and include three 48-inch culverts to create an outfall with predictable year-round flow (Sheet 3). The purpose of the Impoundment dike is to define the eastern limit of the Waste Treatment System and establish a physical point of compliance for discharge permitting, while maintain existing surface hydrology. The pilot study determined that almost the entire surface flow of water enters the stream prior to the proposed impoundment dike location. Maintaining existing hydrology and vegetation is an important component of the design. This impoundment dike will extend south/southwest from the toe of the infiltration beds to an elevation above surface water to capture surface water flow, if any, outside the stream.

• Access Road – A gravel access road will be constructed along the eastern/northern edge of the Waste Treatment System, along with improving an existing access along the west side of infiltration Bed 9 (Sheet 5). The access road has a 15-foot-wide drive surface with approximately an 18-inch thickness of clean fill over geofabric. The road alignment is constrained by the slope stability of the infiltration beds, as well as the wetland boundary and has been designed to minimize impacts to the wetlands. This access road will facilitate construction and access for maintenance and water sampling activities.

• System Boundary and Signage – The boundary of the Waste Treatment System will be marked by the installment of facility signs every 50 feet along the northern, western, and southern boundaries (Sheet 2) of the facility where there isn’t an existing facility fence. This signage is intended to notify surrounding property owners of the extent of the Waste Treatment System, inclusive of City of Wasilla WWTP property. Signs on driven posts are planned to minimize disturbance of wildlife that use the wetland corridor. The spacing on signage may increase and total length of perimeter posted reduced based on project needs.

During construction, erosion control BMPs will be implemented to minimize sedimentation into the wetland and stream feature during construction.

Applicant Proposed Mitigation: The applicant proposes the following mitigation measures to avoid, minimize, and compensate for impacts to waters of the United States from activities involving discharges of dredged or fill material.

1. Avoidance: The No Action alternative was considered, which consists of not constructing the above-described features to create a WOTUS-excluded Waste Treatment System.Without the construction of a Waste Treatment System the existing wetlands are WOTUS, therefore the WWTP cannot discharge effluent to them for additional wastewater treatment and effluent disposal (18 AAC 70).Without additional effluent disposal capacity, the existing subsurface discharge will continue to overload the percolation beds resulting in excess nitrate in the groundwater, effluent leakage from the percolation beds to the surface, and negatively impact surface water quality.Furthermore, without an increase in the WWTP’s effluent disposal capacity the City will be forced to truncate or even eliminate expansion of wastewater treatment services for the City of Wasilla.Therefore, the No Action alternative was rejected.
2. Minimization: The preferred alternative is to design and construct an environmentally responsible Waste Treatment System that maintains the functional integrity of the existing wetland complex to greatest extent practicable while also meeting the goals of surface water isolation from the surrounding landscape, maximum effluent treatment, sustainable effluent disposal, and meet or exceed the most stringent applicable water quality standards.

   During the preliminary and final design planning process, the city evaluated designs to identify the least environmentally damaging design that still meets the minimum requirements to be a Waste Treatment System and meet the needs of the current and future effluent treatment and disposal volumes. During the process, the city made efforts to reduce and avoid impacts to wetlands, both within the Waste Treatment System and in the surrounding area. These avoidance and minimization measures were incorporated in the preferred alternative (i.e., the design presented in this application).

3. Mitigation: There is no upland alternative for this project. Wetlands and waters impacts are unavoidable for the project. The fill footprint was minimized to the greatest extent practicable while still constructing a Waste Treatment System that meets WWTP facility goals.In addition, this Waste Treatment System almost entirely preserves the current WOTUS functions, including hydrologic functions, carbon sequestration, and wildlife habitat. No compensatory mitigation is proposed for the following reasons:

•     Relatively small quantities of fill in wetlands and streams

•     The project preserves the natural functions of the existing wetlands

•     The project is the publics best interest relative to the No Action alternative.

After reviewing the application, the Department will evaluate whether the activity will comply with applicable water quality requirements (any limitation, standard, or other requirement under sections 301, 302, 306, and 307 of the CWA, any Federal and state laws or regulations implementing those sections, and any other water quality-related requirement of state law). The Department may certify (or certify with conditions) with reasonable assurance the activity and any discharge that might result will comply with water quality requirements. The Department also may deny or waive certification.

The permit application and associated documents are available for review. For inquires or to request copies of the documents, contact dec-401cert@alaska.gov, or call 907-269-6285.

Disability Reasonable Accommodation Notice

The State of Alaska, Department of Environmental Conservation complies with Title II of the Americans with Disabilities Act (ADA) of 1990. If you are a person with a disability who may need special accommodation in order to participate in this public process, please contact ADA Coordinator Megan Kohler at 907-269-4198 or TDD Relay Service 1-800-770-8973/TTY or dial 711 prior to the expiration date of this public notice to ensure that any necessary accommodations can be provided.