Environmental geology is a multidisciplinary field that is closely related to engineering, geology, and environmental geography. Each of these fields involves the study of the interaction of humans with the geologic environment. One of environmental geology goals is the application of geological information to minimize possible adverse environmental degradation and maximize possible advantageous conditions resulting from the use of natural and modified environment.
Urban runoff: Excess urban water becomes contaminated while running down various impervious surfaces before entering the drainage systems. Water running off these surfaces tends to pick up gasoline, motor oil, heavy metals, biological waste, trash and other pollutants from roadways and parking lots, as well as fertilizers and pesticides from lawns.
Reducing runoff water impact: Runoff into storm drains and sewers can be minimized by including low impact development or green infrastructure practices into municipal plans. These unlined ditches are often referred to as swales, bioswales, or biofilters. Biofiltration swales are artificial wetlands that act as storm water collection facilities that allow suspended solids to settle. These contaminants are immobilized and/or decomposed by plants and microbes. The biofiltration swales direct water from urban runoff through a system of natural vegetation and filtration that removes sediment, nitrogen, harmful bacteria and other contaminants and prevents them from reaching the harbors and beaches. In effect, bioswales use nature as technology. To perform as an effective treatment, the Biofiltration Swale must meet certain design criteria. These design factors are calculated in a complex formula to measure the expected performance.
The Newport Boulevard bioswale was constructed in 2007. This bioswale is at the lowest elevation a large urban area and collects water from about 400 acres of nearby businesses and residences. The bioswale was converted from a half century old concrete storm channel that discharged untreated water directly into the Newport bay. The following geologic factors were studied by CalTrans and the city of Newport Beach prior to authorization of the conversion.
- Geology and Soils - The existing geology and soils setting and potential effects from project implementation on the site and its surrounding area. Related studies included existing water flow and quality monitoring.
- Newport Beach is located in the region which contains several active faults, including the nearby Newport-Inglewood Fault. The effects of following factors were studied:
- Ground Shaking
- Slope Stability
- Seismic Shaking
- Soils and Subsurface Conditions
- Seismic Settlement
- The following questions were analyzed and evaluated to determine whether impacts to geology and soils are significant environmental effects. Would the project expose people or structures to potential substantial adverse effects, including the risk of loss including injury, or death involving:
- Rupture of a known earthquake fault?
- Strong seismic ground shaking?
- Seismic-related ground failure?
- Landslides?
- Result in substantial soil erosion or the loss of topsoil?
Here is an excerpt from the completed project from the 2007 Newport Beach State Water Resources Control Board Report:
- The third project for implementation with our State Water Resources Control Board Clean Beaches Initiative grant is the bioswale construction along Newport Boulevard.
- The V-Ditch receives an estimated 30,000 gpd of urban runoff and the functioning bioswale filters urban runoff before entering Newport Bay. Based on flow and water quality monitoring at this location, it was determined that the high measured bacterial loads could be contributing to beach advisory posting at the Turning Basin as well as within the Newport Island Channels. While source control within the tributary watershed is the ultimate goal, the City saw an opportunity to redesign and reconstruct a flood conveyance channel ideal for treatment for bacteria filtration in dry weather flows.
- A filtration bioswale was designed to replace a 300-foot concrete V-ditch along Newport Boulevard. The City worked with CalTrans, to design the bioswale such that the flood conveyance function of the channel would be maintained. The graded channel includes a bed composed of layered sand, gravel and river rock. Each layer is separated by geo-textile fabric to increase the efficiency and stability of the engineered filter. The finished bioswale was then planted with native plants and hydro-seeded with a native seed mix.
It is not necessary to go on the bioswale property to log this Earthcache. Questions can be answered by parking nearby and taking a short walk along Newport Boulevard to view the area. Logging Requirements: Do not post answers online. Send me an email with the following:
1. The text "Newport Boulevard Bioswale" on the first line.
2. The number of people in your group.
3. If there was a landslide here what kind of damage, if any, would you expect?
4. How deep do you estimate the bioswale is at the approximate midpoint?
5. Please post a picture with your face or geocaching device showing the area. This is a suggestion from Earthcache HQ to prevent armchair caching, plus pictures are always fun!