Best Management Practice (BMP)

Oct 05 , 2012
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A growing concern among municipalities and other governing agencies is urban runoff. Urban runoff is water that gets into the storm-drain system and ends up in the lakes, streams or ocean. Two objectives seem to drive this concern:
To reduce the pollutants that wash into the lakes and oceans, especially the concentrations that occur in the first rains after a dry spell.
To conserve water by retaining it on the land where it can eventually percolate back down into the water table.

Programs to mitigate urban runoff are often in conflict with concerns of builders and home-owners, especially on compact city lots. Mitigation usually requires the construction of large seepage or “infiltration” pits to allow site water to percolate into the soil on site. Retaining water on site can threaten the stability of structures and the health of occupants as bogs are created around and under structures.

At Hammer Company we are actively keeping abreast of current mitigation requirements and practices and seeking to balance the needs and objectives of mitigation requirements with home-owner objectives.

If you live in the City of Santa Monica and have an urban mitigation pit as part of your drainage system, you may be required to have an annual inspection for Best Management Practice (BMP) on an infiltration pit or depression basin. You might receive a letter from the City of Santa Monica that starts out like this:

“Your property has participated in the City’s Urban Runoff Management Program through the installation of a Best Management Practice (BMP) device, such as an Infiltration Pit or Depression Basin, when construction work was performed in the recent past (since 1999.) The City’s Urban Runoff Pollution Ordinance, SMMC 7.10, requires that most major development or construction projects install a physical structure within the property, in the landscape or under the garage (some commercial and multi-family buildings) or driveway, to capture precipitation from roofs and other hardscapes for infiltration or treatment and release to the street. This program seeks to keep small background levels of pollution found in urban runoff off City streets, where it flows untreated into the Santa Monica Bay, and can cause beach postings and closures. This program also seeks to harvest a local water resource and infiltrate it into the ground for groundwater recharge and potential future extraction as a local water supply, reducing dependence on expensive imported water or to harvest into a cistern for reuse.”

What does this mean for you, the property owner? You may be required to have an annual visual inspection of your urban runoff mitigation or infiltration system, and turn in paperwork stating that you have done so. We can perform this visual inspection for you.

Our minimum Stormwater Mitigation System Inspection typically consists of:

1. Visual inspection of first-story gutters and any gutters visible from stair-case accessible upper story rooms or stair-case accessible flat roof. This inspection does not include putting our men on a slopping roof, or on a ladder extending beyond one story. If you want gutters inspected that exceed these limitations, we recommend contacting a gutter-cleaning company with appropriate workers compensation coverage for that work.

2. Where practical and accessible as provided in #1 above, hose-water test first-story downspouts to see if water flows through the spouts.

3. Visual inspection of deck and yard drain-inlets so see if they are clear of debris and silt.

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