Information for File # KAL

Transcription

1 Information for File # KAL Applicant Corps Contact Enbridge Energy, Limited Partnership Kristoffer A. Laman Address 600 South Lake Avenue, Suite 211, Duluth, MN Kristoffer.A.Laman@usace.army.mil Phone Primary County St. Louis County Section 26 Township Range 50N 19W Information Complete On October 13, 2016 Posting Expires On November 26, 2016 Authorization Type LOP-10-FDL This application is being reviewed in accordance with current practices for documenting Corps jurisdiction under Section 404 of the Clean Water Act. We have made a preliminary determination that the aquatic resources that would be impacted by the proposed project are subject to Corps of Engineers jurisdiction Section 404 of the Clean Water Act. If an approved jurisdictional determination is completed as part of the review process for this application, a copy will be posted on the St. Paul District web page at the following link: Project: The purpose of the work is to excavate, inspect, and if necessary, perform maintenance repairs on a section of the Enbridge pipeline across wetlands within the external reservation boundary of the Fond du Lac (FDL) Band of Lake Superior Chippewa (Fond du Lac Band). The overall project would result in temporary disturbance of 17,100 square feet (0.39 acres) of shallow marsh and wet meadow wetlands adjacent to an unnamed tributary to Stoney Brook. PROJECT DESCRIPTION AND PURPOSE: Access to the maintenance location would be from Arrowhead State Forest Road onto the Enbridge right-of-way (ROW), traveling northwest along the ROW to the maintenance site. A portion of the access route is located in a wetland. Enbridge plans to generate frost roads to facilitate access through wetland, as weather conditions allow, using caution not to disturb any soil in the process of creating and utilizing them. Temporary timber mats would be utilized where necessary to ensure no rutting or mixing of wetland soils occurs and where frost roads are not feasible due to weather conditions. The area around the specific section identified for pipeline maintenance would be excavated, visually and physically inspected, and repaired as needed. The excavation would be approximately 30 to 40 feet wide, 60 to 80 feet long and up to 10 feet deep. Equipment used 1

2 would include a backhoe or similar excavator, trucks to transport personnel, equipment and soil, timber mats for equipment to work off of within wetland and trench boxes to minimize the excavation width. Erosion control measures, such as silt fence and straw bales, would be installed as needed prior to soil disturbance in accordance with Enbridge s Environmental Mitigation Plan. Enbridge may temporarily place rock in the bottom of the excavation to create a safe and dry surface to complete pipeline inspection and repair maintenance work. Within wetlands, Enbridge would install a physical barrier, such as geotextile fabric, below the rock to separate the rock and native soils. The rock and any physical barrier would be removed from the excavation prior to backfilling of the excavation. Enbridge anticipates that dewatering activities (using pumps) would be necessary at the maintenance location. The dewatering structure would be located within a well vegetated upland area east of the maintenance location. Dewatering discharges would be directed to a filtration sediment bag placed within a straw bale dewatering structure lined with a geotextile fabric. NAME, AREA AND TYPES OF WATERS (INCLUDING WETLANDS) SUBJECT TO LOSS: The overall project would result in temporary disturbance of 17,100 square feet (0.39 acres) of shallow marsh and wet meadow wetlands adjacent to an unnamed tributary to Stoney Brook. The work for this project would include the construction of a 16-foot-wide access route through wetlands, accounting for 15,700 square feet of temporary wetland impacts. The work for this project would also include excavation and temporary stockpiling of excavated material from a 30 to 40 feet wide, 60 to 80 feet long and up to 10 feet deep inspection and maintenance area, accounting for 1,400 square feet of wetland impacts. Temporary timber mats would be used where necessary to ensure rutting or mixing of wetland soils does not occur. ALTERNATIVES CONSIDERED: The pipeline anomaly indication is located within a wetland; therefore temporary disturbance to wetland is unavoidable. Enbridge did evaluate an alternative access route to this maintenance site that would reduce wetland impact. However, landowner approval was not granted. The no inspection/maintenance alternative was abandoned due to the need to promote safe operations and reliable delivery of energy to customers. The maintenance project would be conducted on an existing pipeline structure, no off-site alternatives exist. COMPENSATORY MITIGATION: As no permanent wetland impacts would result from the project, the applicant has proposed that no required compensatory mitigation be required. All disturbed areas across wetlands, including the approach to the work site, would be restored, seeded, and mulched as necessary to restore the site to pre-construction conditions. Drawings See attached. 2

3 S22 S23 S24! S27 S26 S25! Maintenance Location Arrowhead Township Saint Louis County! S34 S35 S36!;N 0 2,000 4,000 Feet 1 Inch = 2,000 Feet S33 S4 S3 S2 Carlton County Barr Footer: ArcGIS 10.4, :09 File: I:\Client\Enbridge_Energy\Work_Orders\Digs\ \Maps\Line_3\041516\L3_1059_6880.mxd User: jrv S1 North Carlton Unorganized Territory EXCAVATION SITE LOCATION Milepost

4 ! S26! Arrowhead Township Saint Louis County! Maintenance Location Field Observed Swale (2016) Field Delineated Wetland Boundary (2016) Field Delineated Wetland (2016) Arrowhead Forrest Road!;N S Feet 1 Inch = 350 Feet Imagery: 2015 NAIP via MnGeo WMS Service ACCESS ROUTE Milepost Barr Footer: ArcGIS 10.4, :40 File: I:\Client\Enbridge_Energy\Work_Orders\Digs\ \Maps\Line_3\041516\L3_1059_6880_Special\L3_1059_6880_AccessRouteWetlands.mxd User: mak3

5 ! Excavation Area 40' x 80'! Maintenance Location Erosion Control Barrier! Soil Stockpile Erosion Control Barrier Field Observed Swale (2016) Field Delineated Wetland Boundary (2016) Field Delineated Wetland (2016) Dewatering Area Soil Stockpile Excavation Extent Temporary Workspace 80' x 250' Temporary Workspace Dewatering Area!;N via Ice Road or Mats Feet 1 Inch = 100 Feet Imagery: 2011 UC-G High Resolution Via Esri Basemaps SITE PLAN Milepost Service Layer Credits: Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Barr Footer: ArcGIS 10.4, :51 File: I:\Client\Enbridge_Energy\Work_Orders\Digs\ \Maps\Line_3\041516\L3_1059_6880_Special\L3_1059_6880_SitePlanWetlands.mxd User: mak3

6 Dewatering Area (If Necessary) PLACE EROSION CONTROL DEVICES, AS NECESSARY EROSION CONTROL DEVICES WILL BE PLACED AROUND THE DISTURBED WORK AREA, AS NECESSARY Pipeline EROSION CONTROL DEVICES WILL BE PLACED ACROSS OPENING AT END OF THE DAY 30' - 40' EXCAVATED AREA 60' - 80' Subsoil Topsoil EXCAVATED SUBSOIL WILL BE STOCKPILED NEAR THE EXCAVATION WITHIN ECD S, AS NECESSARY MINIMUM ONE FOOT SEPARATION MUST BE MAINTAINED BETWEEN TOPSOILANDSUBSOILORA PHYSICAL BARRIER SHOULD BE USED. STOCKPILE TOPSOIL SEPARATELY FROM SUBSOIL WORKSPACE Pipeline Figure 1 Environmental Mitigation Plan Typical Maintenance Excavation Plan View For environmental review purposes only. DATE: 3/23/2015 REVISED: 4/8/2015 SCALE: NTS DRAWN BY: JEBAKKEN an ERM Group company K:\_CLIENT_PROJECTS\D-F\EEL\BARR\ 2015\04\REVISED_TYPICALS\ FIG_01_MAINT_EXCAVATION.VSD

7 NOTE: TRENCH BOXES CONSIST OF TWO STEEL PLATES THAT HOLD UP THE SIDES OF AN EXCAVATION. THE PLATES ARE HELD IN PLACE BY STEEL BRACES. PIPELINE TRENCH BOX TRENCHBOX EXCAVATION Excavation Apprx. 10' PIPELINE PLAN: TRENCH BOX PROFILE: TRENCH BOX SUBSOIL TOPSOIL EXISTING PIPELINE TO BE REPAIRED CONSTRUCTION MATS (AS REQUIRED) TRENCH BOX Topsoil Subsoil PROFILE: TRENCH BOX Figure 2 Environmental Mitigation Plan Typical Trench Box For environmental review purposes only. DATE: 3/23/2015 REVISED: 4/8/2015 SCALE: NTS DRAWN BY: JEBAKKEN an ERM Group company K:\_CLIENT_PROJECTS\D-F\EEL\BARR\ 2015\04\REVISED_TYPICALS\ FIG_02_TRENCH_BOX.VSD