Publish by: Dakini Engineering General Contracting
This article is to help home owners understand proper slope maintenance, BMP's (Best management Practices), erosion control and what is an erosion retaining gravity wall.
In my photo albums under erosion control are a set of pictures that compliment this article.
Proper erosion control and maintenance requires the following:
Site or building pad or roof waters of a home or patio slab should never be allowed to free flow over a slope. This type of uncontoled drainage over a slope is refered to as sheet flow. This condition weakens the slope surface and creates erosion which destabilizes the slope over time.
All slopes should be uniformily irrigated and planted with deep rooting, drought resistant plants, such as Ficus trees, Red Apple or Disney Land ice plants. Red Apple is the lowest maintenace ice plant. If your current slope has an ice plant that is typically referred to as Pickle weed, it can cause superficial surface slides to your slope. The reason for this, is this type of ice plant is very leaf heavy with shallow roots. It typically grows wild in San Diego.
For a greater range of plant options, consult a landscape expert, landscape architect or go to the Cal Trans web site for recommended plants for slope stability and erosion control.
To properly replant a new slope or recently striped slope, one must ensure there are no soft spots or minor weakness's in the slope. Properly run a UV light, PVC, Sched. 40, pipe system with heads on 15 to 20 centers on an electronic timer system to come on 1 hour prior to sun rise and during the high heat summer months a second time at noon. Both times should be set between 5 to 8 minutes long. No more time is required to maintain healthy plant growth. Over water can destroy the integrity of the slope over time.
Place landscapers Jute fabric over the soils of the slope to retain the surface silts of the soils on the slope until new plants have taken over. Every 15 foot of vertical slope should have a Straw waddle placed across the slope and at the toe of the slope properly wood staked to the slope to prevent heavier erosion during rain fall. Additionally, it may be a good idea to add a Silt fence product at the toe of the slope to ensure there will be no silt contamination of propert beyond the slope being planted.
Next on larger slopes, we recommend spraying the slope with a product called Hydroseed with a design mix appropriate to your site that are drought resistant. This is a straw, fertilizer, seed mix with a binder (glue) to hold the slope during the maturation of the designer landscape planting.
Next plant the slope with your designer plants along with a ground cover like Red Apple or equal. When planting Red Apple ice plant, it should be placed on 8 inch centers in all directions for reasonable maturation and cover time.
After the plant life have become established, you can remove the lower straw waddle and silt fence.
The irrigation system should be viewed during operation at least twice a year to ensure it is functioning properly.
If you desire a patio or wall at the top of your slope, the most economical is Keystone Concrete gravity block walls with a fiber glass grid placed as per manufactures design recommendations. If the wall is designed to be under 3 feet tall, there is no building permit required. Any patio concrete slab or pavers should be designed not to sheet flow over the slope. Best design is to place 6 inch Diameter area drains on Approx. 20 foot centers in the middle of the slab or paver system with a non-perforated, 4 inch Dia., SDR35 pipe system which discharges to the front street or to the bottom of the slope in the same type of pipe system to a legal water coarse. If there are rood eaves with a gutter system and downspouts, they should also be connected to this pipe system. If the roof eave is absent of an eave gutter system, it's wise to install a seamless aluminium gutter system. All eave gutter systems should be installed level and tight to the roofing materail. Never hang gutters with s skew or slope. They will not function properly if they do slope. The majority of the eave gutter contractors do not install eave gutters properly.
I hope you find this information helpful in caring for your slope.
Dana Ansell, Forensic investigator and CEO of Dakini Engineering General Contracting.