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26 Sallwood Court Pinbarren- ESC inspection 15-10-2021 (1)
Attached to the e-mail Operational Works Application - DA Form 1 - Plan - Erosion & Sediment Control Inspection Report - 26 Sallwood Court Pinbarren.
Erosion and Sediment Control Inspection Report Purpose of Meeting Erosion and Sediment Control inspection Project 26 Sallwood Court, Pinbarren Prepared By Luke Hamilton Phone No 0412 739 706 Date 15-10-2021 Present Kathy Ford Email [email protected] Luke Hamilton Email [email protected] Introduction Aussie Environmental were engaged by Kathy Ford to review the current level of erosion and sediment control (ESC) on her property at 26 Sallwood Court, Pinbarren. Scope and Purpose Noosa Council as part of their Advisory e-mail requires - Action 2 “Make the site stable and immediately contact a Certified professional in Erosion and Sediment Control (CPESC) to put in place suitable erosion and sediment controls to prevent the runoff of sediment from the property” A site inspection was completed on site on 15 October 2021 by Certified Professional in Erosion and Sediment Control (CPESC) being Luke Hamilton (Operations Manager for Aussie Environmental). The advice identified herein will assist the land owner in demonstrating compliance with their General Environmental Duty. CPESC - site observations • The site is located on private land with some earthworks completed over the last 2 months, for: access to an existing dam; to clean out sediment build-up in an existing dam; remove and chip weed vegetation; re-profiling and provide surface protection (Geofabric and Rock) to the drainage line leading to the dam; and re-landscaping the property. The terrain is hilly surrounded by rural living property. The property is over 1 Ha, has a dwelling, drainage easement, dam and cleared grass areas and gardens. • Previously most of the land was used as horse paddocks with the new owners re-landscaping, removing the Camphor Laurels and improving drainage protections and improving the existing dam’s capacity. At the time of the inspection earthworks were under a stop works order from Council with the dam and part of drainage line cleaned out and reprofiled, geofabbed and rocked. Silt fence was in place and mulch and topsoil stockpiled. Sub-soil exposure was still evident around and within the dam, drainage lines and along the access areas. • The soil on site is a medium clay texture. The slopes are less than 8% grade, however the drainage easement’s catchment is quite steep resulting in rapid runoff and slow permeability. Slope stability would be considered good; however, any exposure would generate turbid runoff.
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• The one drainage line (partly Council drainage easement) is un-named tributary to Pinbarren
Creek.
• Due to the time of the year (High erosion risk based on average monthly rainfall), the large extent of
the uphill catchment and the proximity to a waterway, any exposure of any surface would have high
erosion risk.
• At the time of the inspection the sediment controls (dam and silt fence) were adequate for the
amount of exposure, however the level of erosion control is lacking and finalisation of the
earthworks needs to continue to remedy this issue.
• It was noted that the land-owner has a large supply of mulch on-site. This mulch is excellent for
erosion control (covering exposed soils) and a mulch berm correctly installed (refer attached
drawing) has a higher sediment control standard than silt fence.
CPESC – advice and corrective actions
Following is Best Practice for this sort of development with reference to the IECA Best Practice
Erosion and Sediment Control Guidelines (IECA Guidelines) document [2008, International Erosion
Control Association (Australasian Chapter)]
Table Book 2 -G3 - Best practice site clearing and rehabilitation requirements
Risk Best Practice Requirements
All Cases • All reasonable and practicable steps taken to apply best practice erosion
control measures to completed earth works, or otherwise stabilise such
works, prior to anticipated rainfall-including existing unstable, undisturbed,
soil surfaces. under the management or control of the
building/construction works.
High • Land clearing limited to maximum 4 weeks of work.
• Disturbed soil surfaces stabilised with minimum 75% cover within 10 days
of completion of works within any area of a work site.
• All planned garden beds protected with a minimum 75mm layer of organic
Mulching, heavy Erosion Control Blanket, Rock Mulching, or the
equivalent.
• Staged construction and stabilisation of earth batters (steeper than
6H:1V) in maximum 3m vertical increments wherever reasonable and
practicable.
• The use of turf to form grassed surfaces given appropriate consideration.
• Soil stockpiles and unfinished earthworks are suitably stabilised if
disturbance is expected to be suspended for a period exceeding 10 days.
Table Book 2 -G3 - Best practice channel clearing and stabilisation requirements
Risk Best Practice Requirements
All Cases • All reasonable and practicable steps taken to apply best practice erosion
control measures to completed channel works, or otherwise stabilise such
works, prior to an anticipated 1ncrease in stream flow.
High • Channel clearing limited to maximum 2 weeks of programmed work.
• Disturbed soil surfaces stablised with minimum 90% cover within 5 days
of completion of works within any constructed drainage channel or
waterway.
• Appropriate consideration given to the use of rock protection,
biodegradable Erosion Control Mesh or the equivalent, on all erodible
stream banks subject to high velocity flows.
• Non-completed channel works stabilised if exposed, or expected to be
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exposed, for a period exceeding 10 days.
Drainage Controls.
- Unfortunately, with steep slopes and the large extent of uphill catchments it is very important to
divert upslope runoff around any future soil disturbance. This cannot be achieved on this site.
- It appears that the channel protection has matched existing rip rap protection which would have
been hydraulically sized to the upstream catchment, slope and expected flows.
- The dam spillway (which was shaped but not protected) should also match the rock protection
upstream.
Erosion Controls
- All planned garden beds protected with a minimum 75mm layer of organic Mulching.
- The use of turf to form grassed surfaces given appropriate consideration or hydromulching (3T/ha
of mulch, 40kg/ha cover crop, 40kg/ha perennial grasses, 250kg/ha fertilizer, tackifier).
Sediment Controls-
- Site soils have a high clay content and any exposure would generate turbid runoff. Sediment
Controls such as silt fencing or mulch bunds should be in place (which they are). Do not remove
until there is 80% cover.
- The dam is acting as a sediment basin/trap at present. Use Superfine Gypsum broadcasted over
surface or preload the gypsum along the inlet channel. This will help settle the clay practical and
improve dam clarity/water quality.
Luke Hamilton, Operations Manager
Certified Professional in Erosion and Sediment Control (CPESC No. 9205)
Aussie Environmental
Phone: 07 5315 5431
Mob: 0412 739 706
Address: 19 Central Park Drive, Yandina, QLD 4561
Postal Address: P O Box 525, Yandina, QLD 4561
Email: [email protected]
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