The Seven Stars Road Site is approximately 8km west of Birmingham City Centre. The site is mostly flat and covers circa 2.5ha and is accessed from Seven Stars Road from the East and is bound by the Birmingham Canal to the South, around 100m from the M5 on the West and bound by residential properties to the North.
The site itself has been occupied since 1904 with various historic land uses, all leaving extensive industrial damage to the natural environment. These include a canal wharf, commercial/industrial properties and a railway embankment. Most notably a tank farm and the Albright & Wilson Chemical works were present from 1938-1971 famed for the production of Match Phosphate as well as a raft of strontium and chromium based chemicals. Following the company’s closure, the site was used as a scrap metal recycling yard and then as an illegal waste site with various dilapidated buildings remaining on site.
The site was covered in hardstanding with a combination of fly tipped materials, skips and stockpiles of various materials including an extensive amount of Asbestos Containing Materials (ACMs).
The site was complicated further due to a known UXO risk.
Sanctus were engaged in 2019 to enable the regeneration of the site for a large commercial property. The development is expected to generate over 125 jobs with associated parking, offices, warehousing and service yard suitable for heavy goods vehicles with prominent soft landscaping.
Sanctus had an extensive remit to resolve all issues presenting ground risk, including removal/handpick of ACMs, removing all areas of Japanese knotweed, removal or treatment of scrap yard residues, removal and crushing of surface obstructions and hardstanding, demolish relict structures, identify and remove all subsurface obstructions and re-engineer the made ground to provide a development platform.
Sustainability was fundamental to the financial viability of the project as well as a key part of planning and the environmental impact of the project, therefore maximising material reuse was a key philosophy throughout design, planning and operational delivery.
The site overlies extensive made ground extending over 10m deep, alluvium and mudstone. Groundwater is shallow around 2mbgl in secondary aquifers.
This project was challenging on every level and as such required input from Sanctus, Ecologists, Conservation Architects, Archaeologists, UXO specialists, Canals and Rivers Trust, the West Midlands Combined Authority, Highways England, Environment Agency and Police to regenerate this most challenging of brownfield locations.
Technical Challenges & Solutions
During the works a number of additional challenges became prevalent: the southern boundary was formed by a series of lean-to buildings with large quantities of stacked and broken asbestos sheeting in the surrounding area. The former railway embankment was backfilled with oil-drums, tyres, wheels, cabling and general waste and 80% of its surface area was covered by deeply rooted Japanese Knotweed (JKW).
Sanctus employed the Definition of Waste Code of Practice to sustainably re-use materials on site to achieve the required formation level.
Enabling Works and Site Clearance
Works were completed in phases to allow individual disciplines the access and space to work. One of the earliest tasks was a thorough vegetation clearance to allow assessment of the surface contamination and to prevent nesting birds from occupying the site. Prior to the main works, the JKW infestation was delineated and treated with a glyphosate-based herbicide three times over a period of 6-months.
JKW was removed and placed into a lined designated 40-yard skip and sealed. 6,500m3 of soils from the area were carefully excavated and passed over a screener-conveyor system to remove oversized and deleterious materials. The soil was then handpicked and processed to remove rhizomes which were sealed in the JKW skip. This rigorous process allowed valued soils to remain on site. These were encapsulated in barrier membrane and placed at depth at recorded locations beneath soft landscaping areas. Levels were brought to formation with site won materials and finished with 600mm clean cover using recovered topsoil.
The area comprised various concrete slabs with steel frame structures containing ACMs and a number of stockpiles of various materials with Asbestos Insulation Board (AIB) fragments.
Sanctus deployed their unconditional 3 year asbestos licence to safely remove various ACM products which were segregated under controls with all the asbestos encountered sealed and removed to a suitably licensed offsite disposal facility. The entire works were carried out under specialist asbestos controls.
Sanctus identified 4no. different types of asbestos on site including Chrysotile, Amosite, Crocidolite and Anthophyllite. Over 120t of ACM was removed from site in total.
Sanctus undertook breaking-out and removal of former floor slabs and sub-surface obstructions to 2mbgl across the site using various combinations of 20 and 50t excavators and breakers, munchers, shears, and bucket attachments.
In reality, the site had so many unusual obstructions at varying depths, the majority of the site was cleared up to 5m in deep.
An obstruction was discovered in the north-east of the site that extended over 10mbgl associated with a former railway line. Sanctus considered it fundamental to the engineered integrity of the site to remove it.
A key aim for the regeneration was to minimise the need for imported/virgin aggregates onsite. All concrete and brick structures removed along with the stockpiles from demolition were screened, crushed and engineered for reuse, saving 12,000m3 of aggregate, all of which was successfully reused on site.
6No. Environmental Monitoring Stations were set up on the perimeter of the site and monitored daily, the results of which were independently verified to ensure we were only having a positive impact on the environment.
Materials Management and Treatment
Approximately 114,000m3 of materials were excavated and processed across the site, comprising 12,000m3 of brick and concrete and 102,000m3 of soils which were improved and re-engineered. Sanctus were able to retain 99.7%. of materials excavated and processed on site.
We’re incredibly proud to say that only 0.3% of the entire material processed left site as waste. The material was minimised by a combination of initial screening, mechanical removal and/or handpicking. This material comprised 120 tonnes of ACMs; ~180 tonnes of unsuitable materials including various chemical drums, cabling, timber and plastics along with various car parts. Around 4 tonnes of JKW vegetation and rhizomes which were picked and separated from the soils; ~2000 tyres; and a single load of soil from a segregated area found to contain Blue Billy.
The southern boundary of the site backed onto the canal towpath. As a key element of planning and stakeholder liaison it was imperative this path remained open throughout the project. As part of the scheme the canal and assets were assessed by an Independent Historical Conservation Architect. Inspection of the towpath wall deemed it unsafe and it was necessary to dismantle and remove the wall by hand, brick by brick, with the bricks being retained for future restoration.
A former “dock” to the canal was identified with a “puddle clay” lining which had severely deteriorated, in addition to an old culvert. These features dated from before the 1890s and were in incredibly poor condition allowing water ingress into the site from the Canal, further impacting the poor-quality saturated soils. Following discussions with the client and the Canal and Rivers Trust an approved specialist lining/drainage contractor was appointed who infilled the culvert with a proprietary fast reacting foam that expanded and hardened on contact to water. The historic structure and boundary were thus preserved for the future.
Unexploded Ordnance (UXO)
The site is in a medium unexploded ordnance risk zone, thus presenting a heightened operational risk. All Sanctus staff are trained and have experience of undertaking watching briefs with UXO Awareness.
During the works, two items of suspected UXO were identified. Following our UXO procedure the areas were immediately segregated, and all works in the vicinity stopped. The first was later found not to be explosive in nature, however, the second was confirmed to be a World War II ordnance and as such the site was immediately closed as well as the construction project on an adjacent side of the canal, while the relevant authorities attended site to assess the UXO and remove it safely. Due to Sanctus’ efficient and effective excavation strategy, and the integrity of the item, the UXO was considered stable enough to be removed from site to negate the need for on-site denotation thus avoiding the closure of the M5 and surrounding infrastructure.
The legacy of chemical works left several unusual features including bricks inscribed with ‘Acid Proof’ and oxidising materials that would periodically and unpredictably self-ignite despite being submerged/saturated.
Our extensive background research allowed us to engage with former site workers, managers and regulators providing us with a better understanding of these challenges.
Toolbox talks and additional watching briefs were deployed, management ensured operatives on site were hyper aware of the materials they were excavating and crushing to make sure they were able to control/mitigate any reactions. Procedures were implemented including the use of the saturated soils as well as traditional fire control materials. In addition, odour controls were employed to avoid the generation of fumes.
Water, Water Everywhere!
The works were carried out throughout the wettest autumn & winter on record. Sanctus had to develop innovative solutions to prevent engineered materials from becoming saturated and risking undermining the stringent geotechnical criteria. Rainfall was exacerbated by relic water structures and culverts on site designed to replenish / manage the canal draining into the site. Therefore, Sanctus had to determine methods to drain soils alongside preventing further ingress of rain, providing the challenge of progressing work to schedule whilst allowing sufficient time for drying materials and draining those already placed.
Sanctus developed intricate movement schedules and actively tracked plant movements to minimise disturbance of placed materials. Reducing emissions, movement and handling of material in the process. The volume and intensity of water entering the site mobilised previously fixed contaminants including PAHs and TPH to the groundwater.
Sanctus deployed our bespoke water treatment (WTS) system after obtaining discharge consent from Severn Trent Water. Dewatering also protected the engineered platform and maintained productivity by draining the materials previously saturated and allowed further targeted material placement. The WTS removed up to 20,000 litres of water daily and discharged to the foul sewer. This was monitored via telemetry and sampled and analysed by an independent MCERTS accredited Laboratory.
Applying the Principles of the Circular Economy
The only materials that had been removed from site were those that were detrimental to the site, in particular, relic tyres, oil drums, ACMs from the structures and stockpiles, the Japanese Knotweed vegetation and picked rhizomes from the former railway embankment, and grossly impacted soils containing blue billy.
This allowed for 113,000m3 of material to be reused including soils, aggregates and site won materials (99.7%). Metals from the remaining structures and reinforcement from the obstructions as well as wood recovered from the Made Ground, along with the initial tree feeling, were segregated on site and sent offsite for recycling avoiding landfill and further increasing the sustainability of the project.
This incredibly challenging project successfully removed a significant legacy risk to the community, wildlife and the natural environment. Sanctus’ innovative approach, detailed material tracking, processing and segregation achieved savings of £12 million in disposal costs alone.
Sanctus had completed a complex earthworks project during the wettest autumn/winter on record and delivered the project in accordance with the client’s specification navigating an extensive array of previously known and unknown challenges. Whilst treating and improving nearly 900,000m3 of impacted groundwater.
The use of recycled aggregates/soils, reduced transportation and offsite disposal of impacted / engineered soils has offset 5,679t of CO2 (not including embedded carbon). We would have had to plant almost 1 million trees to offset the equivalent amount of carbon over our programme of work.