Weather and Outside Forces (WOF)
Remediations and Geotechnical Repairs
The Solution
- DTP supports all key steps in your geohazard management to protect your pipelines from potentially adverse environment conditions and reduce risks.
- The experts at DTP understand the nature of WOF Threat types, we have developed appropriate mitigation strategies to prevent incidents and impacts to your pipelines, public and environment.
- DTP realized the importance to maintain a safe and reliable service. Our personnel have extensive experience in difficult terrains such as rock soil, steep slopes and high-water flow areas.
- Our specialized services supports the completion of your planned pipeline WOF remediation activities in a timely and efficient manner.
Activities
- Geohazard evaluation – Pre-engineering for the following WOF threats:
- Landslides, slips, subsidence & vertical/lateral scouring.
- Geohazard management – Temporary and permanent remediation (Repairs):
- Wash repair: Earth movement, soil stabilization and backfill, install rock shield, concrete mats and gabion baskets/walls.
- Ground cover: Backfill, re-seeding and apply stone/riprap
- River/Creek crossing maintenance: Install riprap stone, grout mats & weights.
CASE STUDY
- Client: TC Energy
- Date: 22/06/2023
- Piperline: Tuxpan-Tula (TXTL) pipeline system, NPS 36
- Location: KP 63+169 TXTL pipeline system
- Scope: Geohazard mitigation – Permanent Remediation.
1. Problem statement
Due to the intense rains, horizontal and vertical scouring was observed in the Tuxpan – Tula gas pipeline, KP 063+169. The pipe is not exposed, however, the coverage along the pipe is 0.88 m.
The width of the erosion is approximately 9 m within the Right of Way (RoW) of 33 m; Since the riverbed is diverted with respect to the axis of the gas pipeline, the affected length is approximately 35 m. The vertically eroded depth is at least 1.2 m
2. Solution
Uncover the pipe, carried out abrasive cleaning of the pipe in order to perform a 360° visual inspection and NDEs by TC Energy Integrity Field Services and conducted the necessary repairs to guarantee the integrity of the pipe. The rockshield was placed as additional protection layer.
Once the pipe has been repaired, a gabion protection was installed, anchored with rectangular gabions walls throughout the repair (except at the gas pipe crossing).
3. Procedure
EXCAVATION
- Site access road was improved for vehicle, material and machinery transportation.
- Site grading included vegetation cleaning, removal and disposal of topsoil.
- Delimitation of the entire área designated for the remediation.
- Topographic survey and location of line pipe, width of 30 m (15 m on each side of the axis) and a length of 60 m (20 m downstream of the pipe axis and 30 m upstream) to define elevations.
- Gas monitoring and line pipe detection in a regular basis.
- Excavation of a trench 3.5 m wide and of variable depth along four sections of up to 10 m in length and a total length of up to 35 m, in such a way that the pipeline is uncovered in its entire length of the section, placing supports every 8 m with pipe pillow.
- Manual excavation is carried out at compression station.
- The pipe must be free (uncovered) in a section of 10 meters with 1.50 m on both sides of the pipe.
Repair and coating
- Once the entire pipeline is uncovered, a 360º visual inspection of the coating must be carried out by TC Energy Integrity Field Services.
- Testing areas subject to abrasive cleaning and coating repair are determined by TC Integrity Field Services.
- Definition and preparation of areas to be repaired.
- Abrasive / mechanical cleaning with Black Beauty
- Recoating of the pipe in was accordance with TC Energy procedure “TES-CO-EPU-GL Field-Applied
- External Liquid Coatings for Steel Pipeline Systems (CAN-US-MEX)” and TC Energy’s inspection on Field.
- The following measurements are carried out during this stage:
- Chloride detection test in areas to be coated
- Measurement of environmental conditions (HR, Dew Point, TS, TA, Wind speed.
- Blotter test.
- Coating must be applied by NACE specialists.
- All equipment must be certified.
Curing, adhesion and dry film thickness tests are carried out. - Application of Rock Shield as additional protection layer.
Cover and Gabion Retaining Wall
- Pre-cover and cover of the pipe.
- Sand soil improvement with quality subgrade material.
- Installation of a 30cm tape on the top of the pipe as an additional protection measure.
- The filling to protect the pipe is formed in layers of 20 cm, compacted and improved with cement.
- Construction of a gabion quilt work, anchored with gabion walls and placement of a dentil and gabion wings at the entrance and exit of the gabion structure to prevent erosion of the reconstructed material.
- Placement of geotextile for the gabion dentil placement (downstream) and filling with stones, as well as for the gabion walls upstream and downstream.
- Measurement of the continuity of the cathodic protection cables using a multimeter and cleaning the coating of the cathodic protection cables to be spliced 25 mm (1 inch).
- Install the geotextile for the gabion quilt placement (central) and finally proceed to fill the gabion quilt.
