Kuau Bayview Retention Basin Maintenance Plan (Draft) by Tom Atkins

Explanation and Justification for the Basin:

The explanation for the existence and maintenance of the Retention Basin as an essential common element of the KB Subdivision is given in the following statement:

When a new neighborhood or office building is constructed, the natural flow of the land is disturbed. Most of the trees, natural grass, and soil are destroyed and replaced with concrete, pavement, sidewalks, and other unnatural structures. The topography of the land is likely altered and the former natural flow of water has now been dramatically changed.

The direct result of all the changes is that rainwater that used to be soaked up by the natural land will now flow off the developed land at a much faster rate. The amount of water flowing out of gutters, down driveways, streets, and parking lots is much larger than the land can handle. In order to handle the rapid rate of water runoff, both residential and commercial properties are required to establish and maintain retention or detention ponds.


COMPLIANCE REQUIREMENTS:

Kuau Bayview HOA will make a good faith effort to be in compliance with the requirements stated in the following documents:

  1. STATE OF HAWAII: Storm Water Permanent Best Management Practices Manual, Wet Extended Detention Pond, Chapter 7, page 33
  2. A Handbook for Stormwater Reclamation and Reuse Best Management Practices in Hawaii
  3. COUNTY OF MAUI: Title MC-15, Department of Public works and Waste Management, Chapter 4
  4. Maui County Planting Plan
  5. KUAU BAYVIEW DCC&R: Section 3. ADMINISTRATION OF COMMON AREAS AND IMPROVEMENTS (a) Common Areas
  6. KUAU BAYVIEW Reserve Study: Review every two years.

Retention Basin Culverts

ORIGINAL CONSTRUCTION FIRM:

Sato & Associates Inc   2115 Wells St, Wailuku, HI 96793   Phone: (808) 244-9265

BASIN SCHEMATIC:

Unfortunately, there are no "As Built" drawings for the Retention Basin. To the right is the pre-construction "Grading Plan Map" drawing which accurately reflects most of the features of the Basin, including the locations of the Inlet and Outlet Culverts.

INLET - is located where the D24" is shown on the map.

OUTLET - is located on the 6' elevation contour at the end of the D30culvert line going to the Hana Hwy Manhole.

FENCE - consists of 982.86 linear feet, surrounding the 71,122 SqFt basin, with the following dimensions: 216.57' E x 275.54' S x 263.37' W x 227.38' N = 982.86 linear feet = 71,121 SqFt, with one gate, and a composition of galvanized chain link (11 gauge core wire with an extruded green vinyl finish).

OVERFLOW - If the basin were ever to overflow, the excess storm water would most likely flow up the outlet culvert and join with a County pipe under Hana Hwy then travel east and settle in the Kuau Beach Retention Basin located between Kuau Beach Place Road and the Blue Tile Roof Beach Access, as shown in the satellite view below:

Kuau Beach Retention Basin

The curbside drains and catchment basins are shown below in the locations marked in blue on the Subdivision map. The water from yard and impermeable surface run-off enters the curbside drains, and from there is conducted through the lateral and trunk-line storm water culverts to the Retention Basin where it enters the basin through the 24 inch Inlet Culvert in the NE corner.

31 curbside drains.pdf

STATEMENT OF GOALS and ACTIONS: The goal of the KB Retention Basin Maintenance Plan is to comply with the following provisions as stated in the DCC&R Section 3 (a) Adminstration of Common Areas:

"Without limiting the generality of the foregoing, the Association shall periodically pump and clean the retention basin located at the intersection of Lae Street and Hana Highway to prevent overflows, remove silt therefrom, inspect and maintain the basin and keep it free of trash, large over-growth and other debris, at all times maintain clear inlet/outlet drainage to and from the basin, monitor the basin water level during large storms, and provide a method to control basin overflow."

  1. "to prevent overflows"
    Action:
    Routine clearing of debris from the Inlet Culvert and Outlet Culvert to allow the storm water to flow freely into the basin and upon reaching a depth of about 5 feet, to flow out of the basin.
  2. "remove silt therefrom"
    Action:
    Determine depth of silt by the distance the deposit of silt has infringed on the access road. Do this determination by scraping a trough in the sediment, from the highest level of the sediment on the access road, to the bottom edge of the access road, and measure the vertical depth of the silt, at that lowest point. When the silt deposit has reached a depth of 10% of the depth of the pond (12 inches), the silt should be excavated and removed.
  3. "inspect and maintain the basin"
    Action:
    Inspect the Basin at least twice a year and after major storms of more than 2 inches of precipitation. Record the results of the inspection on the Retention Basin Inspection Checklist, and file the form in the Retention Basin Inspection Checklist folder in the records office. (see exhibit E: Retention Basin Checklist).

    Take note of cracked culverts, signs of erosion, hollowed areas, caving in or slumping berms, and all indications that the basin structures may be unstable and not sound.

  4. "keep it free of trash"
    Action:
    Maintain a 4 foot wide open path through the Cane Grass to the Inlet Culvert to allow inspection of the culvert and removal of toys and trash carried into the basin by storm water.
  5. "keep it free of large over-growth"
    Action:
    Evaluate annually and, when needed, create a plan for the removal of any large over-growth.
  6. "keep it free of other debris"
    Action:
    Inspect the basin on a yearly basis, and remove debris which has been deposited by storm water transport, and by individuals dumping trash over the fencing, into the basin.
  7. "maintain clear inlet/outlet drainage to and from the basin"
    Action:
    Maintain an open path to the Inlet Culvert to allow inspection of the culvert and removal of trash carried into the basin by storm water.
  8. "monitor the basin water level during large storms"
    Action:
    Measure and record the depth of water at the bottom of the access road immediately after large storms (one inch of rainfall in a 24 hour period), as judged by the rain gauge at the National Weather Service for precipitation at Kahului, Maui. Example shown below:
    Screen shot 2012-12-13 at 11.05.01 AM.png
  9. "provide a method to control basin overflow"
    Action:
    Maintain a clear Emergency Spillway located at the entrance road to allow overflow to Hana Hwy.
  10. "maintain the 6 foot fence surrounding the basin"
    Action:
    Inspect and repair breaks in the fence on a routine monthly basis. Replace or repair (as needed) the "No Trespassing" signs on the gate and on the West side fencing adjacent to the Paia Community Center playground.
  11. "prevention of health hazard"
    Action:
    Routinely inspect for the presence of rodents, insects, pests, and vermin. Respond to complaints from residents about possible health hazards. Contact Maui District Health Office when consultation is required.
  12. "control of invasive species of plants"
    Action:
    * Identify species ( see exhibit C: Invasive Species/Noxious Weeds)
    *Cut stem or trunk off close to the ground
    *Dig out the roots
    *For the stumps that will be allowed to remain for the purpose of stabilization of the berm on steep slopes, immediately apply the appropriate herbicide to the circumference of the freshly cut stump just inside the layer of bark (cambium layer) using a brush or applicator squeeze bottle. ( see exhibit B: Herbicide Application Technique)
    Contact: CTAHR Cooperative Extension Office when consultation is required.
  13. "evaluate the need for 'trash rack' grate cover for OUTLET Culvert"
    Action:
    (see exhibit D: Trash Rack Evaluation)
  14. "Rodent control and Insect vector control"
    Action:
    Pesticides will not be used in the Basin.

    Mosquitos will begin to breed in standing water within 72 hours and can then become a problem. Mosquito monitoring will begin at day 3 following the storm water event. If a severe mosquito hatch occurs, an expert will be consulted, following a recommendation by the Department of Health for a determination of the need for treatment of the problem.

    Identification of Rodent Population: Rodent infestation to be investigated by visual observation of rat signs such as droppings, tracks, runs, or burrows and rub marks.

  15. "Ground cover"
    Action:
    Grass and vegetation with a stabilizing root structure will be maintained on the slopes to control erosion. Chemical Fertilizers will not be used in the Basin.

References:

Only native or non-invasive plants should be used as approved by a licensed landscape architect. Suitable plant types for the specific BMP areas can be found by consulting an arborist, licensed landscape architect, or referring to various online sources such as:

  • VegSpec - a web-based decision support system that assists land managers in the planning and design of vegetative establishment practices.
  • USDA Plants Database - an extensive database of native and non-native plants of the United States with over 100 plant characteristics.