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HomeMy WebLinkAboutMINUTES - 01162007 - SD.5 TO: BOARD OF SUPERVISORS contra FROM: CARLOS BALTODANO, DIRECTOR Costa BUILDING INSPECTION DEPARTMENT, '' �A��`� County DENNIS BARRY, DIRECTOR COMMUNITY DEVELOPMENT DEPARTMENT, MAURICE SHIU, DIRECTOR f �` PUBLIC WORKS DEPARTMENT y S DATE: January 16, 2007 SUBJECT: Water Drainage Plans Ordinance SPECIFIC REQUEST(S)OR RECOMMENDATION(S)& BACKGROUND AND JUSTIFICATION RECOMMENDATIONS 1 . INTRODUCE Ordinance Number 2007-01 requiring drainage plans and improvements for certain development projects in the unincorporated area; WAIVE reading and FIX January 23, 2007 for adoption. FISCAL IMPACT None. t� CONTINUED ON ATTACHMENT: YES SIGNATURE RECOMMENDATION OF COUNTY ADMINISTRATOR RECOMMENWT19FN OF BOARD COMMITTEE APPROV OTHER SIGNATURE(S): ACTION OF BOAR, ON APPROVED AS RECOMMENDED _�L O HER VOTE OF SUPERVISORS I HEREBY CERTIFY THAT THIS IS A TRUE UNANIMOUS (ABSENT ) AND CORRECT COPY OF AN ACTION TAKEN AYES: NOES: AND ENTERED ON THE MINUTES OF THE ABSENT: ABSTAIN: BOARD OF SUPERVISORS ON THE DATE SHOWN. Contact: Carlos Baltodano (33[5]-1108) r ATTESTEelerk �L✓ cc: Building Inspection John Cullef th oard fSupervisors County Administrator and Counttrat County Counsel Community Development Public Works BY c ,DEPUTY CB:nr BACKGROUND/REASONS FOR RECOMMENDATIONS On July 25, 2006, the Board of Supervisors directed the Building Inspection, Community Development and Public Works Departments to work with County Counsel and the District II Supervisor to draft ordinance amendments to address the possible impacts from single family residential building permits on natural or repaired landslide areas. It had come to the attention of the District II Supervisor that building permits had been issued for three single family residential additions in the same incorporated area without consideration of the cumulative impacts of the drainage from these additions on a repaired landslide. Approving permits for these additions caused the drainage from each lot to be taken to a previously repaired landslide area. This raised the concern of what would happen if other properties in the area made similar improvements and did not consider the impacts by the additional drainage run-off in a repaired landslide or areas with inadequate existing drainage facilities. At the request of the Board, the three departments have been meeting to identify ways to alert staff of unstable soils areas during the review of permits and how future cumulative impacts from drainage could be tracked over time. After several meetings, it was determined that it would be more prudent to require drainage plans in order to track the cumulative drainage impacts on adjacent properties. Construction of drainage improvements is required if specified in a drainage plan that has been approved by the County Building Official. Attached is a drainage plan ordinance that adds section 74-6.012 to Title 7 (Building Regulations) of the County Ordinance Code. Also, attached are the findings of local conditions to justify construction standards. The Drainage Plan Ordinance describes when the plans are required and specifies the exact content and information needed on the plans to be submitted. The basic requirement is to indicate the location of all proposed natural and man-made drainage facilities for the storage or conveyance of runoff including drainage swales, ditches, culverts and berms, sumps, sediment basins, channels, ponds, storm drains and drop inlets. This will show where and how the water is being conveyed and where it travels through the site and where it finally is discharged. The construction of drainage improvements will be required if they are specified in a drainage plan that has been approved by the County Building Official. The Drainage Plan Ordinance will require that the drainage plan shall be prepared by a registered civil engineer if construction is proposed for land where the slope exceeds 20 percent or if the land is identified by the County Building Official as having a history of unstable soil or landslide. This determination will be based using the most current USGS seven and one- half minute quadruple map or other published sources. Staff has determined that adoption of the attached ordinance is exempt from the California Environmental Quality Act (CEQA) under Section 15061(b)(3) of the State CEQA guidelines. This ordinance can be seen with certainty to have no effect on the environment. Water Drainage Plans Ordinance 2007-01 Page 2 of 2 (Intro 01/16/07) ADDENDUM TO ITEM SD.5 January 16, 2007 Supervisor Uilkema congratulated the Building Inspection, Community Development and Pulbic Works departments on their cooperative efforts compiling the Ordinance. She confirmed the whole purpose of this Ordinance is to properly control and to route surface water run-off. Carlos Baltodano, Director, Building Inspection thanked Supervisor Uilkema for the introduction and her kind words. Mr. Baltodano noted this was a joint effort by three departments, Building Inspection (BI), Community Development(CDD) and Public Works (PW)who refer to themselves as the Land Development departments, more so the three department heads, Dennis Barry CDD, Maurice Shiu PW and himself. Mr. Baltodano stated the three had met numerous times to develop this ordinance. This ordinance amends and adds a new section to the building code and it was crucial that the amendment was in concert and agreement with other ordinances and procedures within CDD as well as PW. Homeowners and developers, if they fit the threshold as specified in the ordinance will be required to submit a drainage plan indicating exactly how the run off of the water is going to be conveyed to a proper source. Mr. Boltadano stated the departments would have this information up front rather than once the permit is approved. Once a permit is in place the department will be able to track development and improvements throughout the unincorporated areas of the County. Supervisor Bonilla asked how this ordinance compares with some of the cities ordinances. Mr. Boltadano responded at the beginning of the research for this ordinance they had done a survey only to find the City of Orinda was the only city that is doing something about drainage. Dennis Barry, Director, CDD clarified noted it important to emphasize when Carlos says nobody is monitoring drainage other than Orinda,this refers only to additions to single family homes or individual building permits for single family homes on existing lots certainly any discretionary reviews of sub-divisions or development plans for commercial uses do consider drainage and appropriate conditions for them. Supervisor Uilkema suggested in regards to Supervisor Bonilla's concerns that the matter be taken to City--County relations so that cities are aware of the ordinance in the event that they would like to incorporate the ordinance into their own processes. Supervisor Uilkema moved the item with a second by Supervisor Gioia. The item passed unanimously with all Board members present. On this day the Board of Supervisor's APPROVED introducing Ordinance No. 2007-01 requiring drainage plans and improvements for certain development projects in the unincorporated area,waiving reading, and fixing January 23, 2007 for adoption. ORDINANCE NO. 2007-01 WATER DRAINAGE PLANS The Contra Costa County Board of Supervisors ordains as follows (omitting the parenthetical footnotes from the official text of the enacted or amended provisions of the County Ordinance Code): SECTION I. SUMMARY. This ordinance adds section 74-6.012 to the County Ordinance Code to require a drainage plan to be prepared for certain development projects and to require construction of drainage improvements if the improvements are part of a drainage plan approved by the County Building Official. SECTION II. Section 74-6.012 is added to the County Ordinance Code, to read: 74-6.012 Drainage Plan. (a) When Required. A drainage plan is required for any building, structure or improvement that requires a building permit and falls within one of the following categories: (1) Results in an impervious surface of 1,000 square feet or more. (2) Involves grading, or removal of vegetation down to bare soil by any method, of more than 10,000 square feet. (3) Is subject to local ponding due to soil or topographic conditions. (4) Is located within a special flood hazard area, as defined in section 82-28.504. (5) Involves land disturbance or structure placement within 100 feet of the top bank of any watercourse shown with a blue line on the most current USGS seven and one-half minute quadrangle map. (6) Involves construction of 500 square feet or more on land where the slope exceeds 10 percent. (7) Is located in an area identified by the County Building Official as having a history of flooding or erosion that may be further aggravated by, or have a harmful effect on, the construction or adjoining properties. (b) Contents. (1) A drainage plan shall include the following site information: ORDINANCE NO. 2007-01 1 (A) Flow lines of surface and subsurface waters onto and off of the site. (B) Existing and finished contours, at two-foot intervals. (C) The location of any existing buildings, structures or improvements on the property where the work is to be performed and on adjacent lots. (D) Sufficient information to demonstrate compliance with chapters 816-4 and 816-6. (E) The location of all existing natural and man-made drainage facilities for the storage or conveyance of runoff, including drainage swales, ditches, culverts and berms, sumps, sediment basins, channels,ponds, storm drains and drop inlets serving the site. (2) A drainage plan shall include the following drainage information: (A) The location of all proposed natural and man-made drainage facilities for the storage or conveyance of runoff, including drainage swales, ditches, culverts and berms, sumps, sediment basins, channels,ponds, storm drains and drop inlets. (B) All surface and subsurface drainage devices, walls, cribbing, dams and other protective devices to be built with or as a part of the proposed construction. (C) Hydraulic calculations that show the flow-carrying capacities of proposed conveyance devices and justify the estimated runoff of the area served by any proposed conveyance device. (D) Discharges and velocities of proposed conveyance devices, and storage volumes of any sumps,ponds or sediment basins. (3) Engineered drainage plans. A drainage plan shall be prepared by a registered civil engineer if construction is proposed for land where the slope exceeds 20 percent or if the land is identified by the County Building Official,based on the most current USGS seven and one-half minute quadrangle map or other published sources, as having a history of unstable soil or landslides. An engineered drainage plan shall include estimates of existing and increased runoff resulting from proposed improvements and methods for reducing the velocity of any increased runoff, in addition to all other information required by this section. (4) Geotechnical reports. If a drainage plan shows that discharge resulting from the proposed construction will occur over land where the slope exceeds 20 percent or ORDINANCE NO. 2007-01 2 over land with a history of unstable soils, then a geotechnical report shall also be prepared. (c) Procedures. A drainage plan shall be submitted with the building permit application. Drainage plans shall be neatly and accurately drawn, at an appropriate scale that will enable ready identification and recognition of submitted information. Drainage plans shall be prepared in accordance with written standard specifications on file with the County Building Official. A drainage plan is not considered approved until the County Building Official approves the plan in writing. (d) Violations. (1) The failure to submit a required drainage plan is a violation of this section. (2) The failure to comply with an approved drainage plan, including the failure to construct drainage improvements specified in an approved drainage plan, is a violation of this section. (Ord. 2007-01 §2.) SECTION III. EFFECTIVE DATE. This ordinance becomes effective 30 days after passage, and within 15 days after passage shall be published once with the names of supervisors voting for or against it in the Contra Costa Times, a newspaper published in this County. PASSED on uabtby the following vote: AYES: (?t0�0�., U. 1� eMQi, �OIld�Qi� dlGr' �GP 1t� NOES: 14glaS� ABSENT: ABSTAIN: NO&ICz ATTEST: JOHN CULLEN, Clerk of the Board of Supervisorsand Chair and County Administrator By: Cz [SEAL] Deputy TLG: HA2007\Building Inspection\drainage plan ord-final2.wpd ORDINANCE NO. 2007-01 3 CONTRA COSTA COUNTY FINDINGS IN SUPPORT OF ORDINANCE NO. 2007-01 The Board of Supervisors of Contra Costa County, in adopting Ordinance No. 2007-01 regarding water drainage plans and improvements, finds as follows. 1. Soils Contra Costa County is replete with various soils, many of which are unstable, with clay loam and alluvial fans being predominant. These soil conditions are moderately to severely prone to swelling and shrinking, are plastic, and tend to liquefy. 2. Hillside Development Due to technological engineering advances and scarcity of flat parcels of land, more and more development is occurring on hillsides. Within Contra Costa County there are hillside areas that are known to be prone to landslides or can be susceptible to unstable conditions. As new development creates new driveways, roof tops, and decks, it creates additional impervious surfaces. In addition, some prior hillside development activities resulted in oversteepened and improperly sloped or retained older cuts and excavations. Some of these also contribute to instability. 3. Roads Throughout Contra Costa County, the topography and development growth has created a network of older, narrow roads. These roads vary from gravel to asphalt surface and vary in percent of slope, many exceeding 20 percent. Several of these roads extend up through the winding passageways in the hills providing access to remote housing subdivisions. The majority of these roads are private with no established maintenance program. During inclement weather, these roads are subject to rockslides and mudslides, as well as downed trees, obstructing all vehicle traffic. 4. Seismicity Contra Costa County is located in Seismic Risk Zone 4, which is the worst earthquake area in the United States. Buildings and other structures in Zone 4 can experience major seismic damage. Contra Costa County is in close proximity to numerous earthquake faults including the San Andreas Fault and contains all or portions of the Hayward, Calaveras, Concord, Antioch, Mt. Diablo, and other lesser faults. A 4.1 earthquake with its epicenter in Concord occurred in 1958, and a 5.4 earthquake with its epicenter also in Concord occurred in 1955. The Concord and Antioch faults have a potential for a Richter 6 earthquake and the Hayward and Calaveras faults have the potential for a Richter 7 earthquake. Minor tremblers from seismic activity are not uncommon in the area. A study released in 1990 by the United States Geological Survey says that there is a 67% chance of another earthquake the size of Loma Prieta during the next 30 years, and that the quake could strike at any time, including today. Scientists, therefore, believe that an earthquake of a magnitude 7 or larger is now twice as likely to happen as to not happen. Earthquakes of the magnitude experienced locally can cause major hillside damage and landslides. 5. Need for Ordinance Ordinance No. 2007-01 is necessary to protect the public health, safety and welfare and to protect public and private property, because of the conditions described above. Without proper drainage control, soils become more unstable, and the potential for landslides increases. Improperly controlled drainage in hillside areas can contribute to landslides in several ways. When a hillside is saturated, a potential landslide block has more weight because of the water, which results in a larger driving force. Groundwater moving through the soil exerts seepage forces that further reduce stability, and the presence of groundwater reduces the strength of the soil on a potential slide plane. Improperly controlled surface water runoff can reduce slope stability by infiltrating into the near- surface soils at critical locations, and by causing erosion. Where groundwater emerges at the surface, resulting in a spring or seep, the runoff can cause surficial erosion that can undermine or oversteepen a slope. Undermining or oversteepening and the consequent loss of support at the toe of the slope can trigger a landslide. Furthermore, without proper drainage control, an increase in impervious surfaces results in an increase in the volume and velocity of runoff, which can result in flooding, erosion and alterations in natural streams. The purpose of Ordinance No. 2007-01 is to properly control and route surface water runoff. Under the ordinance, surface water runoff can be controlled and routed to existing natural and man-made drainage facilities for the storage or conveyance of runoff, including drainage swales, ditches, culverts and berms, sumps, sediment basins, channels, ponds, storm drains and drop inlets, or new improvements can be required, depending on the conditions of the property where development is proposed. In addition, the ordinance will allow the tracking and monitoring of projects and of the potential impacts to public and private property in hillside development.