Moraga Municipal Code § 1 Findings Regarding Local

The California Building Standards Commission has adopted and published the 2007 Building Standards Code, which is comprised of the 2007 California Building Mechanical, Plumbing and Electrical Codes. These Statewide Codes became effective January 1, 2008. These codes are enforced in the Town of Moraga by the Contra Costa County Building Department under the Joint Exercise of Powers Agreement entered into on June 17, 1975 between the Town and Contra Costa County.

Although these codes apply statewide, Health and Safety Code Sections 17958.5 and 18941.5 authorize a local jurisdiction to modify or change these codes and establish more restrictive building standards if the jurisdiction finds that the modifications and changes are reasonably necessary because of local climatic, geological or topographical conditions.

This Ordinance adopts the Statewide Codes by reference to County Ordinance No. 2007-54 and amends them to address local climatic, geological and topographical conditions. Pursuant to Health and Safety Code section 17958.7, the Town of Moraga finds that the more restrictive standards contained in this Ordinance are reasonably necessary because of the local climatic, geological, and topographic conditions that are described below.

I. Local Conditions

A. Geological and Topographic

Seismicity

(a) Conditions

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 damage to electrical transmission facilities and to gas and electrical lines in buildings, which in turn start can fires throughout the County, including in the Town of Moraga. The occurrence of multiple fires will quickly deplete existing fire department resources; thereby reducing and/or delaying their response to any given fire.

(b) Impact

A major earthquake could severely restrict the response of all Contra Costa County Fire Districts, including the Moraga-Orinda Fire District, and their capability to control fires involving buildings of wood frame construction, with ordinary roofing materials and flammable exteriors, or with large interior areas not provided with automatic smoke and fire control systems. Also, when buildings not equipped with earthquake structural support move off their foundations, gas pipes may rupture. Fires develop from line ruptures and spread from house to house, causing an extreme demand for fire protection resources. The proximity of large areas within the County to fault traces, including the Town of Moraga, necessitates adopting stricter structural construction standards.

(2) Soils

(a) Conditions

The area is replete with various soils, which are unstable, 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.

Throughout Contra Costa County, including the Town of Moraga, the topography and development growth has created a network of older, narrow roads. These roads vary in percent of slope, some exceeding twenty (20) percent. Some of these roads are private with no established maintenance program. During inclement weather, these roads are subject to rock and mudslides, as well as down trees, obstructing all vehicle traffic. It is anticipated that during an earthquake, several of these roads would be unpassable so as to prevent fire protection resources from reaching fires cause by gas line ruptures or other sources.

Topographic

(a) Conditions

(i) Vegetation

Highly combustible dry grass, weeds, and brush are common in the hilly and open space areas adjacent to built-up locations six (6) to eight (8) months of each year. Many of these areas frequently experience wildland fires, which threaten nearby buildings, particularly those with wood roofs, or sidings. This condition can be found throughout Contra Costa County, including the Town of Moraga. Earthquake gas fires due to gas line ruptures can ignite grasslands and stress fire district resources.

(ii) Surface Features

The arrangement and location of natural and manmade surface features, including hills, creeks, canals, roads, housing tracts, commercial development, fire stations, streets and roads, combine to limit feasible response routes for Fire District resources in and to District areas.

(iii) Buildings, Landscaping and Terrain

Many of the newer large buildings and building complexes have building access and landscaping features and designs, which preclude or greatly limit any approach or operational access to them by Fire District vehicles, In addition, the presence of security gates and roads of inadequate width and grades that are too steep for Fire District vehicles adversely effect fire suppression efforts.

When Fire District vehicles cannot gain access to buildings involved with fire, there is potential for complete loss.

Difficulty reaching a fire site often impacts fire personnel response both in terms of the numbers of that can reach the site and in the stamina of those fighting the fire. Access problems often result in severely delaying, misdirecting or making impossible fire and smoke control efforts in existing structures where pitch roofs have been built over an existing roof, smoke detectors should be required to warn residents of smoke and fire before the arrival of fire personnel.

(b) Impact

The above local geological and topographical conditions increase the magnitude, exposure, accessibility problems, and fire hazards presented to the Town fire resources. Fire following an earthquake has the potential of causing greater loss of life and damage than the earthquake itself. Most earthquake fires are created by natural gas developed from gas line ruptures. Hazardous materials, particularly toxic gases, could pose the greatest threat to the largest number, should a significant seismic event occur. Public safety resources would have to, be prioritized to mitigate the greatest threat, and may likely be unavailable for smaller single dwellings that were caused by broken gas lines.

Other variables may tend to intensify the situation:

The extent of damage to the water system.
The extent of isolation due to bridge and/or freeway overpass collapse.
The extent of roadway damage and/or amount of debris blocking the roadways.
Climatic condition (hot, dry weather with high winds).
Time of day will influence the amount of traffic on roadways and could intensify the risk to life during normal business hours.
The availability of timely mutual aid or military assistance.
The large portion of dwellings with wood shake or shingle coverings (both on the roof diaphragm and sides of the dwellings) could result in conflagrations.
The large number of dwellings that slip off their foundations and rupture gas lines and electrical systems resulting in further conflagrations.

B. Climatic

Precipitation and Relative Humidity

(a) Conditions

Precipitation ranges from 15 to 24 inches per year with an average of approximately 20 inches per year. Ninety-six (96) percent falls during the months of October through April and four (4) percent from May through September. This is a dry period of at least five (5) months each year. Additionally, the area is subject to occasional drought. Relative humidity remains in the middle range most of the time it ranges from forty-five (45) to sixty-five (65) percent during spring, summer, fall, and from sixty (60) to ninety (90) percent in the winter. It occasionally falls as low as fifteen (15) percent.

(b) Impact

Locally experienced dry periods cause extreme dryness of untreated wood shakes and shingles on buildings and non-irrigated grass, brush and weeds, which are often near buildings with wood roofs and sidings. Such dryness causes these materials to ignite very readily and burn rapidly and intensely. Gas fires due to gas line ruptures can also spark and engulf a single family residence during these dry periods.

Because of dryness, a rapidly burning gas fire or exterior building fire can quickly transfer to other buildings by means of radiation or flying brands, sparks or embers. A small fire can rapidly grow to a magnitude beyond the control capabilities of the Fire District resulting in an excessive fire loss.

Temperature

(a) Conditions

Temperatures have been recorded as high as 114° F. Average summer highs are in the 75°-90° range in the Town of Moraga.

(b) Impact

High temperatures cause rapid fatigue and heat exhaustion of firefighters, thereby reducing their effectiveness and ability to control large building, wildland fires, and fires caused by gas line ruptures.

Another impact from high temperatures is that combustible building material and non-irrigated weeds, grass and brush are preheated, thus causing these materials to ignite more readily and burn more rapidly and intensely. Additionally, the resultant higher temperature of the atmosphere surrounding the materials reduces the effectiveness of the water being applied to the burning materials. This requires that more water be applied, which in turn requires more fire resources in order to control a fire on a hot day. High temperatures directly contribute to the rapid growth of fires to an intensity and magnitude beyond the control capabilities of the Fire Districts in Contra Costa County, including the Moraga-Orinda Fire District. The change of temperatures throughout the County between very low and extreme highs contributes to a voltage drop in conductors used for power pole lines. This necessitates that voltage drops be considered.

Winds

(a) Conditions

Winds are experienced from virtually every direction at one time or another. Velocities can reach fourteen (14) mph to twenty-three (23) mph ranges, gusting to twenty-five (25) to thirty-five (35) mph. Forty (40) mph winds are experienced occasionally and winds up to fifty-five (55) mph have been registered locally. During the winter half of the year, strong, dry, gusty winds from the north move through the area for several days, creating extremely dry conditions.

(b) Impact

Winds such as those experienced locally can and do exacerbate fires, both interior and exterior, to burn and spread rapidly. Fires involving non-irrigated weeds, grass, brush, and fires caused by gas line ruptures can grow to a magnitude and be fanned to an intensity beyond the control capabilities of the fire services very quickly even by relatively moderate winds. When such fires are not controlled; they can extend to nearby buildings, particularly those with untreated wood shakes or shingles.

Winds of the type experienced locally also reduce the effectiveness of exterior water streams used by all Contra Costa County Fire Districts, including the Moraga-Orinda Fire District, on fires involving large interior areas of buildings, fires which have vented through windows and roofs due to inadequate built-in fire protection and fires involving wood shake and shingle building exteriors. Local winds will continue to be a definite factor toward causing major fire losses to buildings not provided with fire resistive roof and siding materials and buildings with inadequately separated interior areas, or lacking automatic fire protection systems, or lacking proper gas shut-off devices to shut off gas when pipes are ruptured, or lacking proper electrical systems. National statistics frequently cite wind conditions, such as those experienced locally, as a major factor where conflagrations have occurred.

II. Necessity of More Restrictive Standards

Because of the conditions described above, the Town Council of the Town of Moraga finds that there are building and fire hazards unique to the Town of Moraga that require the increased fire protection and structural and design load requirements set forth in the County Ordinance, as adopted herein. The County Ordinance amends the Statewide Codes by increasing the minimum base shear in certain buildings to a level consistent with previous building codes (§ 74-4.002(e)). The County Ordinance addresses the need to prevent damage from pounding during an earthquake by providing increased separation between adjacent buildings on the same property and at property lines (§ 74-4.002(f)). The County Ordinance addresses a deficiency in the Statewide Codes' design provisions associated with the service load deflections of slender concrete shear walls by increasing the lateral stiffness of the shear wall (§ 74-4.002(j)). The County Ordinance amends the Statewide Codes by requiring an automatic sprinkler system to be installed in all buildings where the total floor area exceeds 10,000 square feet (§ 74-4.002(b)). The County Ordinance further amends the Statewide Codes by requiring the installation of a smoke detector in existing flat roof buildings when a pitch roof is added on top of the existing flat roof and the solid seating of the flat roof is not removed (§74-4.002(c)).